Memory Distortion

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Question description

Consider eyewitness testimony, a facet of the judicial system that relies on the soundness of memory for its effectiveness. The following story demonstrates the grave consequences inherent in certain kinds of memory distortion.

In the days following Jennifer Thompson’s 1984 rape by an unknown assailant, law enforcement officials presented her with a “photographic lineup.” It was composed of local individuals who loosely fit Thompson’s description, including one man the police considered a likely suspect in the attack. Police and the prosecution relied on Thompson’s eyewitness testimony as a critical building block in the case against Ronald Cotton. Thompson’s memory-based selection of Cotton’s image eventually brought him to trial as a defendant.

Jennifer Thompson’s eyewitness testimony led to the conviction of Ronald Cotton for rape. Thompson described memorizing the details her attacker’s appearance that fateful night so that she might later help to catch him. Based on Thompson’s testimony, the prosecution won, and Cotton received a sentence of life plus 54 years in prison.

After serving nearly 11 years, Cotton was exonerated on the basis of DNA evidence. In the years since Cotton’s release from prison, he and Thompson have reconciled. They now travel together throughout the United States, speaking about the lack of reliability of eyewitness testimony in criminal cases. Unreliable eyewitness accounts of crimes serve as one example of memory distortion. Consider factors in the Cotton case that may have affected the accuracy of Thompson’s memory.

In this Discussion, you examine factors that might influence and create distortions of memory. You also explain potential consequences of memory distortion on eyewitness testimony.

With these thoughts in mind:

Post a brief description of at least 2 factors that might influence and create distortions of memory. Then explain how one of those factors might create a memory distortion. Provide a specific example to support your response. Finally, explain three consequences of memory distortion in the context of eyewitness testimony.

Support your response using at least scholarly 3 references. APA Format. 2-3 paragraphs.

The American Journal of Bioethics, 8(1): 9–20, 2008 c Taylor & Francis Group, LLC Copyright  ISSN: 1526-5161 print / 1536-0075 online DOI: 10.1080/15265160701842007 Target Article Neuroimaging Techniques for Memory Detection: Scientific, Ethical, and Legal Issues Daniel V. Meegan, University of Guelph There is considerable interest in the use of neuroimaging techniques for forensic purposes. Memory detection techniques, including the well-publicized Brain Fingerprinting technique (Brain Fingerprinting Laboratories, Inc., Seattle WA), exploit the fact that the brain responds differently to sensory stimuli to which it has been exposed before. When a stimulus is specifically associated with a crime, the resulting brain activity should differentiate between someone who was present at the crime and someone who was not. This article reviews the scientific literature on three such techniques: priming, old/new, and P300 effects. The forensic potential of these techniques is evaluated based on four criteria: specificity, automaticity, encoding flexibility, and longevity. This article concludes that none of the techniques are devoid of forensic potential, although much research is yet to be done. Ethical issues, including rights to privacy and against self-incrimination, are discussed. A discussion of legal issues concludes that current memory detection techniques do not yet meet United States standards of legal admissibility. Keywords: neuroethics, neuroimaging, memory, Brain Fingerprinting, lie detection, Daubert In the 2004 film Eternal Sunshine of the Spotless Mind, a neuroscientist invented a technique whereby specific memories can be erased from one’s brain. Although the ethical issues about the use and abuse of such technology were explored in the film, the film was not warning viewers of the imminent development of such technology. Indeed there are two characteristics of memory storage that make specific erasure difficult, if not impossible. First, memories are stored in a distributed fashion, and second, a memory network in one locus contains many memories. The first is a problem for erasure because to erase a memory trace in one locus leaves traces at other loci. The second is a problem for erasure because erasing a network erases more than just the desired memories.1 Specific memory erasure can be viewed as a two-stage process: in the first stage, the neural basis of the memory is identified, and in the second stage, the memory is erased. Although the second stage is science fiction, neuroimaging techniques that could accomplish something resembling the first stage are currently in development, and, in one case, actually being used. Thus it is not too early to begin discussing the ethical and legal ramifications of such techniques. Criminal investigation is the most obvious application of a technique that can identify the existence of a memory in the brain. If an individual is being investigated for the commission of a crime, then such a technique, it has been claimed, could identify them as guilty or innocent based on the presence or absence of a memory for the crime. Note that such a memory detection technique is different than lie detection because, in theory, the existence of a memory could be detected regardless of whether the examinee is lying. The development of neuroimaging techniques has made memory detection possible because existing behavioral techniques for the detection of memories rely on participant cooperation, which cannot be expected of the guilty person claiming innocence. Imagine a neuroimaging test that can detect the presence of a crime memory. A positive result on such a test would support the conclusion that the examinee was guilty, and a negative result would support the conclusion that the examinee was innocent. The test has neither perfect specificity nor perfect sensitivity, however. A positive test result for an innocent examinee is called a false positive, and a negative result for a guilty examinee is a false negative. Received 16 April 2007; accepted 19 September 2007. Address correspondence to Daniel V. Meegan, Department of Psychology, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada. E-mail: dmeegan@uoguelph.ca 1 Memory dampening techniques, which are pharmaceutical in nature (Brunet et al. 2007; Doyère et al. 2007; Pitman et al. 2002), are different than erasure techniques in that they are designed to reduce the emotional intensity of memories (e.g., for the treatment of post-traumatic stress disorder). Such techniques are not hindered by the distribution and network characteristics of memory storage because the emotional component of memories is handled by localized processes that specifically act on those memories that are currently active (i.e., new or reactivated). ajob 9 The American Journal of Bioethics The validity of the test for guilt detection relies on a low false-positive rate, and the validity of the test for innocence detection relies on a low false-negative rate. The next section reviews three memory detection techniques with an emphasis on their vulnerabilities to false positives and false negatives. NEUROIMAGING TECHNIQUES FOR MEMORY DETECTION The two most obvious neuroimaging methods for memory detection are event-related variants of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). EEG measures brain electrical activity that reaches scalp electrodes, and fMRI measures regional blood oxygenation in the brain, which is correlated with brain activity. Event-related refers to a specific sensory stimulus event rather than an entire event, such as a crime, that would have a multitude of sensory stimuli associated with it. Eventrelated neuroimaging presents an event to a participant, and then measures the resulting activity. Memory research using event-related EEG (called the event-related potential, or ERP, technique) or event-related fMRI has sought to identify characteristic activity that occurs when an event has been presented to the brain prior to the test, as is the case with crime-relevant events and the criminal’s brain. For all the effects described later in text, the activity resulting from old events (i.e., presented earlier) is quantitatively distinguishable from that resulting from new events (i.e., not presented earlier). Note that the utility of these effects are not compromised by the aforementioned characteristics of distributed memory networks. Even if a memory trace is distributed, a test need only find it in one place to demonstrate its existence; moreover, some of the effects described later in text indeed find distinguishable activity in multiple regions. The fact that many memories are stored in a single network is not a problem either, as long as the network is differentially active for old and new events. Each of the effects reviewed will be evaluated on the following four attributes that characterize the ideal memory detection test for criminal investigations: 1) Specificity: Everyone has seen knives before, but only the guilty examinee has seen the specific knife that was used in the crime. If an effect occurs for new events that merely resemble old events, then there is a real risk of false positives. On the other hand, if an effect is very specific, then false negatives could result if the event is an inaccurate portrayal of the crime stimulus. 2) Retrieval automaticity: One of the problems that limits the validity of the polygraph is its vulnerability to countermeasures (National Research Council 2003). The neuroimaging effects described here distinguish between old and new activity, and an effective countermeasure would use mental control to make old and new activity indistinguishable. Old/new differences can be eliminated by making old events look new or by making new events look old. A memory effect that has automatic- 10 ajob ity is resistant to the former type of countermeasure. In other words, there is nothing that an examinee can do to make an automatic memory effect produce new-like activity for old events. A non-automatic effect, on the other hand, is susceptible to countermeasures and thus prone to false negatives. The second type of countermeasure, in which new events are made to look old, is also a very real possibility, especially for tests that lack specificity. For example, if the new (crime-irrelevant) events include a tree, then the guilty examinee can attempt to recall a tree from the past, thereby producing old-like brain activity from which the brain activity produced by crime-relevant events will be indistinguishable. 3) Encoding flexibility: Encoding refers to the initial presentation of a stimulus. In the criminal investigation scenario, encoding occurred at the crime. All memory and neuroimaging research uses a prospective memory approach in which the encoding conditions are both known and controlled. This research has shown that the encoding conditions can have a profound impact on how a stimulus event is responded to on subsequent presentations. A criminal investigation necessitates a retrospective memory approach in which the encoding conditions are neither known nor controlled. For this reason, it must be assumed that the encoding conditions could have been poor. If a memory detection test is to ensure a low false-negative rate, then the effects must be robust in a variety of encoding conditions. 4) Longevity: Because considerable time might pass between the crime and the memory detection test, an ideal effect would remain measurable for long retention intervals. If an effect is known to decay to the point of immeasurability after a certain retention interval, then it should not be used for longer retention intervals. Otherwise the likelihood of false negatives is too high. Priming Effects The first effects I will describe are usually referred to as neural priming effects (Schacter et al. 2004) or repetition suppression effects (Grill-Spector et al. 2006). Just like priming a surface affects the way it receives paint, priming the brain with a stimulus affects the way it responds to the stimulus on subsequent presentations. Neuroimaging studies of priming have generally shown a reduction in activity for primed (old) events compared with unprimed (new) events, and the most consistent reductions are found in regions of the brain involved in the perceptual processing of sensory stimuli (Grill-Spector et al. 2006; Schacter et al. 2004). Specificity Priming effects are most robust when the event is perceptually identical to the prime stimulus (Koutstaal et al. 2001; Schacter et al. 2004). This has obvious implications for how priming effects might best be employed in criminal investigations. For example, if a knife was used in a crime, then a photograph of the actual knife would be more likely to elicit January, Volume 8, Number 1, 2008 Neuroimaging Techniques for Memory Detection a priming effect than a pictorial representation of the knife, a photograph of another knife, or the word knife. Priming effects can also be attenuated when the prime and event, although the same object, are shown from different viewpoints (Vuilleumier et al. 2002). If priming effects are to be used in criminal investigation, then the selection of events should thus consider the most likely viewpoint of the perpetrator. In summary, priming effects are very specific, and thus there seems a greater risk of false negatives than false positives. Retrieval Automaticity Priming effects are thought to occur automatically (Wiggs and Martin 1998). Most priming research has used experimental tasks, often called indirect memory tasks, in which participants are not told that they are participating in a memory experiment, and they are given a task to do that is not explicitly mnemonic. Researchers generally assume that participants are not aware that they have seen an old event earlier. It is easy to envision a criminal investigation scenario, however, in which a guilty examinee is aware that they have seen a particular crime-relevant event earlier. Thus it is useful to consider research that has examined whether priming effects occur for direct memory tasks in which participants are explicitly told that some events are old. Although some studies have shown similar priming effects for direct and indirect tasks, other studies have shown differences (Henson 2003; Henson et al. 2002). More research is clearly necessary to understand the test conditions under which automatic priming effects can be reliably measured. Encoding Flexibility The priming literature has examined the impact of attending to the prime stimulus at encoding. Attending to an object is not the same as looking directly at it; one can look at one object but attend to another. Several fMRI studies have found that visible but unattended primes produce smaller priming effects than attended primes (Eger et al. 2004; Vuilleumier et al. 2005; Yi and Chun 2005; Yi et al. 2006; although see Bentley et al. 2003). In criminal investigations, even if it can be assumed that the perpetrator viewed an object, it might be unsafe to assume that they attended to it. Imagine a murder investigation in which the shirt worn by the victim might seem an obvious choice for a prime because the perpetrator must have seen it. However, the shirt was likely irrelevant to the task at hand, and thus could have gone unattended. The selection of events for a memory detection test should thus consider the likelihood that an object received the attention of the perpetrator. Longevity Behavioral priming effects can last an impressively long time (Cave 1997; Mitchell 2006). The question remains, however, whether neural priming effects last as long as their behavioral correlates. The first studies to confirm the longevity of neural priming used modest retention intervals of days (van Turennout et al. 2000, 2003), but a more recent study (Meis- January, Volume 8, Number 1, 2008 ter et al. 2005) found lasting, albeit less distributed, priming effects after a six-week retention interval. Old/New Effects Old/new effects are similar to priming effects in that they are differences in neural activity for old and new events. The primary difference is that old/new effects are thought to reflect memory retrieval processing rather than perceptual processing. When an old event is presented, there are two distinct types of retrieval processes that might be initiated (Yonelinas 2002). One type, called familiarity, is relatively fast and automatic and results in knowing that an event is old without remembering the context in which it was seen. The other type, called recollection, is relatively slow and effortful and results in remembering the context in which an old event was seen. ERP research has led the way in identifying distinct old/new effects associated with familiarity and recollection (Friedman and Johnson 2000; Rugg and Yonelinas 2003). The mid-frontal old/new effect, associated with familiarity, is a negative potential occurring between 300 and 500 milliseconds after event onset that is less negative for old than new events at mid-frontal electrode sites. The parietal old/new effect, associated with recollection, is a positive potential occurring between 400 and 800 milliseconds after event onset that is more positive for old than new events at parietal electrode sites.2 More recently, fMRI research has also been successful at identifying brain activity uniquely associated with familiarity and recollection (e.g., Daselaar et al. 2006; Henson et al. 1999; Yonelinas et al. 2005). Specificity New events that are similar to old events are sometimes falsely recognized as old. Such false recognition is associated with the experience of familiarity (Yonelinas 2002), and mid-frontal old/new effects have shown old-like activity for similar-new events (Mecklinger 2006). Although this suggests a risk of false positives, there is reason to think that this problem is not as great as it may seem. False feelings of familiarity are a relatively rare occurrence in everyday life— it is not as if objects we encounter commonly elicit feelings of familiarity simply because of their resemblance to old objects. Scientists who wish to study familiarity in the laboratory thus create artificial situations in which participants are much more likely to experience familiarity and false recognition (e.g., Curran and Cleary 2003). Other research suggests that the mid-frontal old/new effect might be appropriately specific. For example, it is sensitive to study-to-test changes 2. Two hypotheses stated here are not without controversy among memory scientists. Namely that: 1) familiarity and recollection are supported by distinct retrieval processes, and 2) the mid-frontal and parietal old/new effects represent familiarity and recollection, respectively. Nevertheless, the application to memory detection is unaffected by these scientific controversies. In other words, as long as an old/new effect distinguishes old from new events, it does not matter whether that effect is uniquely associated with a particular mnemonic process or experience. ajob 11 The American Journal of Bioethics in stimulus format (Schloerscheidt and Rugg 2004) and context (Tsivilis et al. 2001). Retrieval Automaticity The automaticity of old/new effects has been assessed in studies that have used an exclusion methodology (Jacoby 1991). In exclusion tasks there are usually two types of old stimuli, one of which is to be classified as old (i.e., included) and the other as new (i.e., excluded). If brain activity associated with recognizing old events is automatic, then excluded events should show the same activity as included events. Existing studies suggest that this is the case for the mid-frontal old/new effect (Bridson et al. 2006; Czernochowski et al. 2005), but is not always the case for the parietal old/new effect (e.g., Dywan et al. 2002; Herron and Rugg 2003). These results are consistent with the suggestion that familiarity is automatic, but recollection is not (Jacoby 1991). Other results suggest that the parietal old/new effect might be immune to the types of deliberate misclassification that would be used by the guilty examinee trying to conceal his recognition of crime-relevant events (Johnson et al. 2003; Tardif et al. 2000). Encoding Flexibility ERP studies have examined two encoding manipulations: 1) divided attention, and 2) levels of processing. In divided attention studies (Curran 2004), optimal encoding is represented by a single-task condition in which items are studied for a later recognition test, and suboptimal encoding by a dual-task condition in which studying must be done simultaneously with a second task. In levels of processing studies (Rugg et al. 1998, 2000), optimal encoding is represented by a deep encoding condition in which semantic judgments are made about the items, and suboptimal encoding by a shallow encoding condition in which perceptual judgments are made. The results suggest that the mid-frontal effect is relatively insensitive to the encoding conditions, and that the parietal effect is relatively sensitive. Longevity ERP research has used retention intervals that are far too short to assess the practical longevity of old/new effects. In fact, the studies that have been designed to confirm that the mid-frontal old/new effect has longevity have used retention intervals of only one day (Curran and Friedman 2004; Wolk et al. 2006). P300 Effects Although related to the parietal old/new effect (Spencer et al. 2000), P300 effects have been used somewhat differently and thus will be treated separately here. The P300 is a positive ERP occurring between 300 and 1000 milliseconds after event onset that is maximal at mid-parietal electrode sites for events that are both infrequent and meaningful (Polich and Kok 1995). The classic P300 task, called the oddball task, requires participants to make one response to infrequent target events and another response to all other (non- 12 ajob target) events, thus producing a more robust P300 for targets than non-targets. Applications to memory detection were considered following the discovery that old non-targets could produce a target-like P300 (e.g., Allen et al. 1992; Farwell and Donchin 1991; Rosenfeld et al. 1988). In P300 memory detection tests, there are usually three types of events: targets and two types of non-targets. Irrelevants are frequent non-targets designed to be meaningless to all participants, and probes are infrequent non-targets designed to be meaningless to some participants and meaningful to others. In the crime investigation scenario, probes are crime-relevant events designed to be meaningless to innocent examinees and meaningful to guilty examinees. Studies employing this method have generally shown that probes elicit a target-like P300 for guilty examinees, and an irrelevant-like P300 for innocent examinees (e.g., Farwell and Donchin 1991). Specificity Most P300 studies have used words rather than pictures as events. Because words are recognizable stimuli to all literate examinees, it is only in the context of the test that targets, probes, and irrelevants take on their respective roles. Word stimuli thus make specificity a challenge. It is not so much a problem for targets and irrelevants because they are distinguished by frequency and task-relevance, which are known to be important factors in P300 generation. The task-irrelevance of probes, however, creates a risk that they could produce irrelevant-like effects for guilty examinees (i.e., false negatives). The solution to this problem is context provision. For example, in a recent PBS special featuring the Brain Fingerprinting test (Brain Fingerprinting Laboratories, Inc., Seattle WA),3 the examiner read the following statement to examinees: “In this test, you will see an item that one of the suspects was wearing when he was apprehended, an item that was in the possession of the suspects when they were apprehended, the item the suspects were stealing, and where the crime was committed (the kind of place, dwelling or establishment)” (Innovation: Brain Fingerprinting 2004). These statements referred to the probe stimuli; for example, the probe ‘flashlight’ was referenced by the statement concerning the item in possession of the suspects. This context provision was designed to increase the likelihood that ‘flashlight’ elicited a target-like P300 for guilty examinees. The context provision approach is vulnerable to countermeasures. For example, if the guilty examinee simply ignores the contextual information, the meaningfulness of the probe ‘flashlight’ is likely to be comparable for guilty and innocent examinees, as everyone has had some experience with flashlights. To be fair, some word probes, even without 3. The Brain Fingerprinting test is a P300 memory detection test originally developed by Farwell and Donchin (1991) and more recently commercialized by Brain Fingerprinting Laboratories, Inc., Seattle, WA (Rosenfeld 2005). The PBS special was part of the Innovation series, and originally aired in May 2004; available at: http://www.pbs.org/wnet/innovation/episode8.html (accessed December 7, 2007). January, Volume 8, Number 1, 2008 Neuroimaging Techniques for Memory Detection context provision, are uniquely meaningful to guilty examinees. Nevertheless, words are inferior to pictures in terms of their potential for meaningfulness, and a photograph of the specific flashlight used in the aforementioned crime would presumably have been less likely to require context provision in order to have elicited a target-like P300 in guilty examinees. Retrieval Automaticity The P300 memory detection task described previously is an indirect memory task that does not force guilty examinees to be deceptive concerning their recognition of probes. In other words, when the task requires a target/non-target classification, probes are honestly classified as non-targets. Others, though, have used an old/new classification that forces the guilty examinee to dishonestly classify probes as new. Several studies have shown that the deliberate misclassification of old events as new (Johnson et al. 2003; Miller et al. 2002; Rosenfeld et al. 2003), or the exclusion of old events (van Hooff et al. 1996; van Hooff and Golden 2002), tends to attenuate the P300. The most likely cause of P300 attenuation in these studies is not dishonest responding, per se, but rather the mental effort involved in a difficult classification (Johnson et al. 2003).4 In other words, it is more difficult to respond dishonestly than honestly. Because the probe P300 can be attenuated by dishonest responding to probe events, it is best to use an easy classification task that does not require examinees to be deceptive concerning their recognition of probes. There are two countermeasure strategies that could be attempted by the guilty examinee in a P300 memory detection test: 1) to produce an irrelevant-like P300 for probes, and 2) to produce a probe-like P300 for irrelevants. There is no existing evidence to suggest that the former strategy is likely to be successful, as long as the probes are appropriately meaningful (see previous discussion) and the task allows honest classification of probes (see previous discussion). In other words, it is difficult to treat something meaningful as meaningless. The latter strategy, in which events designed to be meaningless are made meaningful, seems more intuitively plausible, and one study has provided evidence supporting this intuition. Rosenfeld et al. (2004) trained guilty participants, who had committed a mock-crime, to employ a countermeasure in which irrelevants were treated as taskrelevant events. Although participants were still required to make an overt non-target response to irrelevants, they also made distinct covert responses to different categories of irrelevants, which resulted in a probe-like P300 for irrelevants. 4. The attenuation of the P300 under high mental effort conditions suggests another possible countermeasure strategy in which the guilty examinee increases task difficulty by covertly performing a second task during the memory detection test (Bashore and Rapp 1993). One limitation of this strategy is that the constant performance of the second task should affect the P300 for all stimuli (i.e., not just probes), and thus the probe P300 should still look targetlike. January, Volume 8, Number 1, 2008 The countermeasure strategy used by Rosenfeld et al. (2004) could be thwarted methodologically, however. The target, probe, and irrelevant events used by Rosenfeld et al. (2004), were organized into distinct categories. Countermeasure training involved informing guilty participants of the categorical nature of the test. They were then trained to make a particular covert response any time they saw an irrelevant from a particular event category. A simple way to prevent such a countermeasure is to eliminate the categorical nature of the test. Consider the following scenario. In preparation for a P300 memory detection test, a guilty suspect is being trained by a P300 countermeasure expert hired by his lawyer. The expert predicts that the weapon used in the crime will be used as a probe. If the test is known to have a categorical structure, then the expert can also predict that the target and irrelevants will be weapons. Thus the expert can train the suspect to use the countermeasure used by Rosenfeld et al. (2004); in other words, the suspect can be trained to make a distinct covert response every time he sees a weapon event. If, on the other hand, the test does not have a categorical structure, then advance training of this nature is impossible, and the only countermeasure available to the guilty examinee is to prepare to make covert responses to irrelevant events that cannot be predicted in advance. It is certainly possible that such a countermeasure strategy will result in a probe-like P300 for irrelevants, but this possibility has not yet been tested. Encoding Flexibility Farwell and Donchin (1991) provided a highly optimal encoding environment for probe stimuli. The participants were given detailed instructions before performing a mock act of espionage. The instructions included to-bememorized details that would later become the probe events in a memory detection test. To ensure that the details were memorized, the participants were repeatedly tested until they had responded correctly at least five times to questions regarding each of the probes. Although this type of memorization might be representative of some types of premeditated crimes, there are many crimes that have far less optimal encoding conditions. Several recent studies have examined the effect of suboptimal encoding on P300 memory detection (Rosenfeld et al. 2006; 2007; van Hooff 2005; van Hooff and Golden 2002). In these studies, suboptimal encoding was represented by an incidental encoding condition and optimal encoding by an intentional encoding condition. The results have been mixed—incidentally encoded information sometimes does (Rosenfeld et al. 2007) and sometimes does not (van Hooff and Golden 2002) elicit a P300. Given that in many crime situations the perpetrator is not intentionally memorizing crime details, these results suggest that one cannot assume that all crime details will be salient enough to later elicit a measurable P300. Longevity In their oft-cited mock espionage experiment, Farwell and Donchin (1991) used a one-day retention interval. In a ajob 13 The American Journal of Bioethics second experiment, they intended to test the efficacy of their procedure over longer retention intervals by using participants who had committed actual crimes sometime prior to the test. However, because the participants’ memories for the crimes were revisited in an effort to determine the appropriate probes for the memory detection test, this experiment should not be considered a longevity test. More research is necessary to assess the longevity of P300 memory detection tests. Other issues arise at retrieval (i.e., when the memory detection test is administered) rather than encoding. For example, the emotional state of the examinee at the time of the memory detection test must be considered, because such factors have been shown to affect brain activity (Polich and Kok 1995). Also, an uncooperative examinee could sabotage a test by not following task instructions or by preventing reliable brain measurement (e.g., moving the head during an fMRI scan). Forensic Potential SCIENTIFIC ISSUES Previous research was reviewed in the preceding section and is summarized in Table 1. This section reviews what still needs to be done before these techniques can be put to use in criminal investigations. It also discusses the likelihood that future research will find that the techniques meet the standards required by criminal investigations. Future Research All of the research reviewed in the previous discussion was conducted in laboratory environments, and field tests will be an important component of future research. Because the application of P300 effects to memory detection was first considered at least 20 years ago, P300 effects have been tested in situations designed to resemble criminal investigations. By comparison, priming and old/new effects have been tested in situations that lack ecological validity. This is most obvious when considering automaticity, because memory researchers who use priming and old/new effects have not considered situations in which participants are trying to conceal their recognition of old events. Whereas memory research typically reports the combined effects of many participants, criminal investigation requires an assessment of individual examinees. Although priming and old/new effects have occasionally been used at the individual level in cases of amnesia (e.g., Düzel et al. 2001), P300 memory detection tests have been developed with the individual in mind (e.g., Farwell and Donchin 1991). Allen (2002) has provided invaluable information concerning the best way to implement the individual approach in memory detection. Lastly, it would be interesting to see whether variables that influence P300 effects, such as the infrequency of old events, have similar influences on priming and old/new effects. Longevity and encoding flexibility have not been sufficiently tested for any of the effects reviewed in the previous discussion. Future tests of longevity require a lengthening of the retention interval so that it resembles that which is likely to occur in criminal investigations. As for encoding flexibility, there are many factors likely to affect encoding that have not yet been tested. These factors include the heightened emotional state of the perpetrator (something that cannot easily be reproduced in mock crimes), the possible presence of drugs (e.g., alcohol) in the nervous system of the perpetrator, and the age and health of the perpetrator. 14 ajob The existing research provides no conclusive evidence to suggest that any of the techniques are devoid of forensic potential. Nevertheless, much research is yet to be done. Some of the problems identified in the previous discussion, especially those related to specificity and automaticity, have the potential to be solved with methodological advancements. For problems associated with encoding flexibility and longevity, on the other hand, there is much less reason to be optimistic that methodological advancements will provide solutions. Among the sins of memory categorized by Schacter (2001), the sins of absent-mindedness and transience respectively describe the encoding flexibility and longevity problems. In other words, methodological advancements can do nothing about the fact that memory has a tendency to fail when the encoding conditions are poor and the retention interval is long. For this reason, it would not be at all surprising if further research using poor encoding conditions and long retention intervals provided evidence that false negatives were a genuine and insurmountable problem for memory detection. ETHICAL ISSUES Nothing was your own except the few cubic centimetres inside your skull. — George Orwell, Nineteen Eighty-Four (1949, 25) To those who live in free societies, Orwell’s Oceania was the ultimate dystopia in which the Thought Police possessed effective means for identifying what was going on inside the minds of individuals based on their overt behavior. As suggested by the quote, the Thought Police did not have neuroscientific techniques for extracting the thoughts out of the brains of individuals. It is not surprising, then, that modern society is extremely wary of the prospect that neuroscience research is attempting to develop, or has developed, such techniques (Sententia 2001). Although one would like to think that free societies could be trusted to use such techniques appropriately, recent events (e.g., the use of torture in interrogations and the increased invasiveness of domestic surveillance by the United States since 9/11) make it clear that such thinking would be naive. It is important to note that EEG- and MRI-based techniques are impractical for surveillance because the former require the attachment of electrodes to the scalp and the latter require that the head remain stationary inside a strong magnetic field. January, Volume 8, Number 1, 2008 Neuroimaging Techniques for Memory Detection Table 1. Technique Priming Effects Mid-Frontal Old/New Effects Manipulations False negative risk False positive risk Automaticity Stimulus specificity Viewpoint dependence Direct memory task Manageable Manageable Mixed results Low Low — Encoding flexibility Attention Manageable — Longevity 3 days Low — 6 weeks Low — False recognition Stimulus specificity — Manageable Manageable Low Contextual specificity Exclusion task Manageable Low Low — Longevity Divided attention Levels of processing 1 day Low Mixed results Low — — — Specificity Automaticity False recognition Exclusion task — Mixed results Low — Encoding flexibility Divided attention Levels of processing 1 day High High Low — — — Context provision Task-irrelevance of ‘probes’ Task-irrelevance of ‘irrelevants’ Dishonest classification High Manageable Manageable — Farwell & Donchin 1991 Farwell & Donchin 1991 — Low Farwell & Donchin 1991 High — Exclusion task High — Manageable — Encoding flexibility Countermeasure training Incidental encoding Miller et al. 2002; Rosenfeld et al. 2003; Johnson et al. 2003 van Hooff et al. 1996; van Hooff & Golden 2002 Rosenfeld et al. 2004 Mixed results — Longevity 1 day Low — Test attribute Specificity Specificity Automaticity Encoding flexibility Parietal Old/New Effects Longevity P300 Effects Specificity Automaticity January, Volume 8, Number 1, 2008 References Koutstall et al. 2001 Vuilleumier et al. 2002 Henson 2003; Henson et al. 2002 Bentley et al. 2003; Eger et al. 2004; Vuilleumier et al. 2005; Yi & Chun 2005; Yi et al. 2006 van Turennout et al. 2000, 2003 Meister et al. 2005 Curran & Cleary 2003 Schloerscheidt & Rugg 2004 Tsivilis et al. 2001 Bridson et al. 2006; Czernochowski et al. 2005 Curran 2004 Rugg et al. 1998, 2000 Curran & Friedman 2004; Wolk et al. 2006 Mecklinger 2006 Dywan et al. 2002; Herron & Rugg 2003; Johnson et al. 2003; Tardif et al. 2000 Curran 2004 Rugg et al. 1998, 2000 Curran & Friedman 2004; Wolk et al. 2006 Rosenfeld et al. 2006, 2007; van Hooff 2005; van Hooff & Golden 2002 Farwell & Donchin 1991 ajob 15 The American Journal of Bioethics One might argue that the neuroscientific examination of a criminal suspect is inherently unethical because it violates the suspect’s right-to-privacy. If our own thoughts are open to examination, the argument goes, then nothing is private. Although I appreciate this argument, its application to memory detection is dubious, for the following reason: memory detection is not mind reading. All of the techniques reviewed previously measure neural activity associated with the recognition of old events. Recognition is a thoughtless ability possessed by the most primitive of animals. Engineers build machines that perform recognition tasks, and although these machines are far from simple, their complexity is sensory/perceptual, rather than cognitive, in nature. In some cases (e.g., indirect tests of priming) the brain recognizes an event without the mind being consciously aware. So a true positive result on a memory detection test is achieved without reading the examinee’s mind. All the test is doing is determining whether the brain has been exposed to crime-relevant information. Is this logically different than judging whether a suspect was present at the crime by using physical evidence found on the suspect’s body (e.g., finding a strand of a rape victim’s pubic hair amid the pubic hair of a suspect and using the hair as evidence)? Thoughts aside, it could be argued that one’s memories are private. Consider the analogy of the person as a camera, in which the eyes are the lens and the brain is the storage medium (e.g., memory card). It is disturbing to think that an investigator could access one’s memory card, and the unethical use of such technology is an oft-explored theme in science fiction. However, the camera analogy breaks down in a way that should alleviate most concerns. First of all, imagine that the memory card is stuck in the camera and cannot be removed. Next imagine that there is no way to transfer the image files to another device. Lastly, imagine that there is no LCD (liquid crystal display) screen on the camera to allow one to view the image files. The only access to the files is to confirm their existence by taking the same picture again, in which case the camera can signal that it has taken the picture before. This is reasonably analogous to the access that a memory detection examiner has to an examinee’s memories. It would be difficult to argue that this type of evidence gathering is more invasive to one’s privacy than other accepted types of evidence gathering (e.g., tissue samples for DNA testing). Compare the person-as-camera analogy to a situation in which the perpetrator records the crime on a video or still camera so that he can relive the crime later. Such a recording contains far more information than would be uncovered by a memory detection examination. Who, on ethical grounds, would object to the recording being used as evidence? One who argues that memories are private might also be logically forced to argue that such a recording is private. Slippery-slope arguments are also invalid when applied to memory detection. For example, one might be concerned that methodological advancements in memory detection techniques might allow an examiner to read out the memory that is currently being retrieved by the examinee. But 16 ajob this is purely science fiction. Recall that multiple memories are stored in a single localized network. ERP and fMRI are only equipped to gauge the level of activation in such a network, and the level of activation provides only rudimentary information about one’s memory state. Perhaps someday a completely different technique will be developed that enables memory reading. However, because such a technique would not simply be an improvement of existing techniques, there is no reason to be concerned that the current acceptance of ERP and fMRI techniques as ethical will later be regretted. In other words, ethical issues should be revisited each time a new technique is developed. The compulsory examination of a suspect’s memory for crime-relevant details could be viewed as violating the suspect’s right against self-incrimination. On the other hand, if the examination is voluntary, the suspect should rightly be concerned about how the courts will perceive a refusal to be examined. Similar issues arise with uncooperative witnesses—should they be forced to submit to a memory detection test? There are obvious ethical issues concerning whether memory detection will be used only for its stated purpose. An example of an inappropriate use in a forensic context would be including events that are relevant to a second crime for which there is no probable cause to think that the examinee was involved. Legal systems in free societies have a long history of successfully excluding evidence gathered in such an inappropriate manner. It is important that legal systems remain vigilant about ensuring that memory detection evidence is limited to the crime for which the examinee was knowingly examined. Neurotechnologies carry considerable weight among those (e.g., jurors, judges, suspects, witnesses) who do not understand them (Wolpe et al. 2005). In the Harrington case (reviewed in following text), a key witness whose testimony contributed to a conviction later recanted his testimony when presented with the results of a post-conviction Brain Fingerprinting test. A guilty suspect who is unaware of the false-negative problem might volunteer a confession because he thinks he has no chance of producing a negative result. The courts have to decide whether such consequences amount to coercion. LEGAL ISSUES Legal Admissibility P300 memory detection test results have already been considered by courts in the United States. In Harrington v. State of Iowa (2000), a negative result on a Brain Fingerprinting test (conducted 23 years after the crime) was submitted by the plaintiff as part of a post-conviction petition for a new trial in a murder case. In 2001, an Iowa District Court judge admitted the Brain Fingerprinting evidence based on his judgment that the evidence met the Daubert standard (Daubert v. Merrell Dow Pharmaceuticals, 1993), but denied the petition because he determined that the Brain Fingerprinting evidence (and other new evidence) would probably not have changed January, Volume 8, Number 1, 2008 Neuroimaging Techniques for Memory Detection the outcome of the original trial. Subsequently, a key witness whose testimony contributed to the conviction in the original trial recanted his testimony. According to Brain Fingerprinting Laboratories, the recantation was triggered by the presentation of Harrington’s Brain Fingerprinting test results to the witness. The witness’s new testimony, along with other new information, was included in an appeal to the Iowa Supreme Court, the District Court’s decision was overruled, and a new trial was ordered. When the prosecution decided not to retry the case, Harrington was released. Let us examine the judge’s decision to admit P300 memory detection test evidence based on the Daubert standard. In Daubert v. Merrell Dow Pharmaceuticals (1993), the Supreme Court of the United States recommended that judges consider four factors when deciding whether to admit expert scientific testimony: 1) Has the technique been tested? 2) Has it been subjected to peer-review and been published? 3) What is its error rate? and 4) Is it generally accepted in the relevant scientific community? To aid in making his decision, the judge in the Harrington case heard testimony from three P300 experts: Lawrence Farwell (who administered Harrington’s Brain Fingerprinting test), William Iacono, and Emanuel Donchin. It became clear to the judge that P300 potentials were more likely to meet the standard than the other potentials used by Farwell’s Brain Fingerprinting test, and thus the latter were excluded.5 Although this exclusion was a wise decision, the judge failed to make the important distinction between P300 effects in general, and the specific use of P300 effects for forensic memory detection. P300 effects in general are very well established in the field of psychophysiology, and this was reflected in the testimony of the P300 experts. However, as should be clear from my earlier review, the use of P300 effects for forensic memory detection is far from established. Consider each of the four factors recommended in Daubert v. Merrell Dow Pharmaceuticals (1993). The P300 memory detection technique has not been tested in the field and has not been tested in laboratory or field situations with poor encoding conditions and long retention intervals (factor 1). It has been peer-reviewed and published (factor 2), but not to the point that it is generally accepted by the relevant scientific community (factor 4). Its error rates in relevant situations are unknown, and there is reason to believe that the false negative rate in relevant situations will be high (factor 3). The decision by the Iowa District Court judge to admit P300 memory detection evidence based on the Daubert standard is not binding on any court in Iowa or elsewhere (Moenssens 2002). Nevertheless it sets a precedent that will surely be considered for future cases in which P300 evidence 5. The scientific problems associated with the potentials, other than the P300 potential, used in the Brain Fingerprinting test were reviewed by Rosenfeld (2005). Moenssens (2002), like the Iowa District Court judge, is under the mistaken assumption that the only science yet to be conducted before the Brain Fingerprinting test meets the Daubert standard relates to the these other potentials. I, on the other hand, submit that the use of P300 memory detection does not yet meet the Daubert standard. January, Volume 8, Number 1, 2008 is submitted. Thus, with all due to respect to the judge, who surely made the appropriate decision given the limited evidence before him, I would like to offer the opinion that his decision was wrong. As of the publication date of this article, P300 memory detection tests do not yet meet at least three of the four criteria recommended in Daubert. The use of priming effects and old/new effects for forensic memory detection are even further away from meeting the Daubert standard. Some jurisdictions in the United States use the standard recommended in Frye v. United States (1923), according to which the admission of scientific evidence should be based on whether the technique has “general acceptance” in the relevant scientific field. Although priming effects, old/new effects, and P300 effects have general acceptance as measures of mnemonic processing, their application to criminal investigations will not have general acceptance until the necessary research (reviewed previously) has been conducted. In other words, the memory detection techniques reviewed here do not yet meet the Frye standard. The False-Negative Problem What made the admission of P300 evidence in the Harrington case particularly shocking was that the retention interval was 23 years, and the peer-reviewed publication on which the Brain Fingerprinting test was based (Farwell and Donchin 1991) used a retention interval of one day. A negative result on a memory detection test with a 23-year retention interval is a completely meaningless piece of information for those trying to determine the examinee’s innocence or guilt. Based on the scientific evidence reviewed earlier, it is clear that the forensic application of memory detection is more likely to be limited by false negatives than false positives. Ideally, any forensic technique would have low rates of both false negatives and false positives. Nevertheless, because the criminal justice system is based on the principle that it is worse to convict an innocent person (a false-positive error) than to acquit a guilty person (a false-negative error), and the likelihood of the former might be low, memory detection has forensic potential as a prosecution tool. Assuming that future research using poor encoding conditions and long retention intervals confirms a high false-negative rate, the courts would then have to decide whether to allow evidence from a tool that cannot be used to support the innocence claims of defendants. This hypothetical imbalance would also have interesting implications for the commercialization of memory detection services because such an industry would have only prosecutors (and not defendants) as potential clients. Ethical issues related to rights against self-incrimination have caused some companies developing forensic neurotechnologies to claim that their products will only be used to exonerate the innocent (Pearson 2006). In this context, the false-negative problem creates a real dilemma for companies developing memory detection tools. ajob 17 The American Journal of Bioethics A False-Positive Problem? Advantages of Memory Detection Over Lie Detection Some may think that I have underestimated the likelihood of false positives. For example, even when a memory detection technique has the appropriate level of specificity, crime-relevant events are likely to produce old-like activity in some innocent examinees some of the time. There are at least three methodological constraints designed to address this problem. First, crime-relevant events (e.g., probes) should always be compared with crime-irrelevant events (e.g., irrelevants), and the latter are (in theory) just as likely as the former to produce old-like activity in innocent examinees. Second, there should always be multiple crimerelevant events, and when only a subset of these trigger old-like activity, a negative result should be concluded. The appropriate criterion for concluding a positive result based on the level of brain activity produced by crime-relevant events is yet to be determined. This criterion must take into consideration that the criminal justice system abhors false positives, and that reducing false positives by adjusting the threshold used for declaring a test result positive will increase false negatives. A third methodological constraint requires that the memory detection test be given to a control group of known innocent examinees. A positive result for any of the control examinees would suggest that the test is flawed. The use of control subjects is particularly important because of concerns about the subjectivity of event selection (United States General Accounting Office 2001); in other words, if event selection biases a test to a positive result, then the results of the control subjects should identify the bias. Note that, because a memory detection test cannot be given to a control group of known guilty examinees, it is difficult to know whether the test is biased to produce a negative result, thus compounding the false-negative problem. A second example of a false positive is when an innocent witness to a crime, for whom all crime-relevant events would presumably produce old-like activity, tests positive. Such a witness would not be protected by the aforementioned methodological constraints. It is thus important that memory detection test results are always used in conjunction with other types of evidence that would exonerate the witness. In other words, a positive result should be considered evidence consistent with guilt rather than evidence of guilt (Illes 2004). Successful memory detection requires that details of the crime are only known to the guilty examinee. If details are made public by the media or during legal proceedings, the selection of crime-relevant events becomes extremely difficult, if not impossible. Despite this problem, Brain Fingerprinting Laboratories has put itself in the ridiculous position of selecting probes in cases that have already been publicized in the media and in the courts. If investigators or defense lawyers plan to put suspects through a memory detection test, it is extremely important that details of the crime are not made publicly available. Once details have been made available, the selection of crime-relevant events becomes futile and a memory detection test becomes useless. Some have erroneously implied or suggested that memory detection tests are actually lie detection tests (e.g., Farwell and Donchin 1991; Garland and Glimcher 2006; Rosenfeld 2005). As should be clear from the previous review, priming effects, old/new effects, and P300 effects measure recognition rather than deception. Moreover, they can (and should) be measured without dishonest responding. Lie detection is fraught with issues concerning what defines lying and truthfulness and whether there is a consistent neural state associated with each (Buller 2005; Illes 2004; Wolpe et al. 2005). These issues do not apply to memory detection, which measures simple brain responses consistently evoked by stimulus events depending on their familiarity. Lie detection is also infamously vulnerable to countermeasures (National Research Council 2003). 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Journal of Experimental Psychology: Learning, Memory, and Cognition 2005, Vol. 31, No. 1, 76 – 85 Copyright 2005 by the American Psychological Association 0278-7393/05/$12.00 DOI: 10.1037/0278-7393.31.1.76 This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Individual Differences in Susceptibility to False Memory in the Deese–Roediger–McDermott Paradigm Jason M. Watson Michael F. Bunting Washington University in St. Louis University of Missouri at Columbia Bradley J. Poole Andrew R. A. Conway University of North Carolina at Greensboro University of Illinois–Chicago The authors addressed whether individual differences in the working memory capacity (WMC) of young adults influence susceptibility to false memories for nonpresented critical words in the Deese–Roediger– McDermott associative list paradigm. The results of 2 experiments indicated that individuals with greater WMC recalled fewer critical words than individuals with reduced WMC when participants were forewarned about the tendency of associative lists (e.g., bed, rest, . . .) to elicit illusory memories for critical words (e.g., sleep). In contrast, both high and low WMC participants used repeated study–test trials to reduce recall of critical words. These findings suggest that individual differences in WMC influence cognitive control and the ability to actively maintain task goals in the face of interfering information or habit. possible in any order (i.e., free recall with a warning against guessing). Despite this warning, participants typically recalled the nonpresented critical words with about the same probability as items that appeared in the middle of the study list. These remarkably high levels of false recall (and false recognition) have been widely replicated and extended (see Roediger, McDermott, & Robinson, 1998, for a partial review). There has been considerable recent interest in the nature of falsely remembered information that was never directly presented to an individual. This interest has been nurtured in part by Roediger and McDermott (1995), who adapted an experimental technique originally developed by Deese (1959), hereafter referred to as the Deese–Roediger–McDermott (DRM) paradigm. Roediger and McDermott presented participants with lists of 15 words that were the strongest associates to a missing word in free association norms (Russell & Jenkins, 1954). For example, participants might be presented with the following list of words, all of which are related to the nonpresented critical word sleep: bed, rest, awake, tired, dream, wake, snooze, blanket, doze, slumber, snore, nap, peace, yawn, drowsy. Immediately following the presentation of a study list, participants recalled as many of the list words as Activation-Monitoring Accounts of False Memories Elicited by the DRM Paradigm False memories in the DRM paradigm may result in part from an automatic spread of activation from studied words (e.g., bed, rest, awake) to nonpresented but strongly associated critical words (e.g., sleep). As suggested by Balota et al. (1999), avoiding a false memory for a critical word requires one to differentiate between highly activated but nonpresented critical words and studied words. Hence, false memories in the DRM paradigm may also be due to a breakdown in attentional control or monitoring systems that differentiate the activation of critical words in associative networks from the actual presentation of words at encoding (for additional discussion of activation-monitoring frameworks of the DRM memory illusion, see McDermott & Watson, 2001; Roediger, Balota, & Watson, 2001; Roediger, Watson, McDermott, & Gallo, 2001; Watson, Balota, & Sergent-Marshall, 2001).1 An activation-monitoring framework can be used to explain several findings in the DRM false memory literature. For example, Jason M. Watson, Department of Psychology, Washington University in St. Louis; Michael F. Bunting, Department of Psychology, University of Missouri at Columbia; Bradley J. Poole, Department of Psychology, University of North Carolina at Greensboro; Andrew R. A. Conway, Department of Psychology, University of Illinois–Chicago. Michael F. Bunting was supported by a postdoctoral fellowship at the University of Missouri at Columbia from the Missouri Rehabilitation Research Training Program (Kristofer Hagglund, Principal Investigator), the National Institute of Child Health and Human Development, and the National Institutes of Health Grant 2 T32 HD07460 – 09. We thank April Clift and Jeff Meier for assistance in data management and data collection, respectively. We thank Dave Balota, Dave McCabe, Kathleen McDermott, Keith Hutchison, Jason Chan, and Roddy Roediger for helpful discussion of these results. Correspondence concerning this article should be addressed to Jason M. Watson, Department of Psychology, Campus Box 1125, Washington University in St. Louis, 1 Brookings Drive, St. Louis, MO 63130-4899. E-mail: jason.watson@wustl.edu 1 There are alternative accounts of how false memories are elicited in the DRM paradigm, including fuzzy-trace theory (Brainerd, Reyna, Wright, & Mojardin, 2003; Reyna & Brainerd, 1995) and the discrepancy-attribution hypothesis (Whittlesea & Masson, 2003; Whittlesea & Williams, 2001a, 2001b). 76 This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. INDIVIDUAL DIFFERENCES IN FALSE MEMORIES young adults can take advantage of explicit warning instructions given prior to encoding to reduce but not eliminate false memories (Gallo, Roberts, & Seamon, 1997; Gallo, Roediger, & McDermott, 2001; McDermott & Roediger, 1998; Neuschatz, Benoit, & Payne, 2003). Warnings inform participants that false memories are being elicited in the DRM paradigm through the presentation of associates of a single nonpresented critical word. As suggested by Gallo et al. (1997), warning instructions at encoding may encourage participants to monitor and tag missing critical words as not presented during study, thereby minimizing the likelihood of false memories. Using a multiple study–test trial procedure, McDermott (1996) demonstrated that veridical memory increased across repeated study–test trials, whereas false memory decreased. Within an activation-monitoring framework, young adults may use repeated study–test trials to verify what is presented and to determine what is strongly associated but not presented, gradually improving their veridical memory while concurrently diminishing but not eliminating their false memory with practice. Individual Differences in Susceptibility to False Memory in the DRM Paradigm The DRM paradigm has also been used to provide leverage on understanding the breakdowns in episodic memory that occur with healthy aging (Balota et al., 1999; Budson, Daffner, Desikan, & Schacter, 2000; Kensinger & Schacter, 1999; McCabe & Smith, 2002; Norman & Schacter, 1997; Tun, Wingfield, Rosen, & Blanchard, 1998; Watson et al., 2001; Watson, McDermott, & Balota, 2004). In general, these studies have demonstrated that, compared with young adults, healthy older adults have impaired veridical memory but equivalent or enhanced false memory. The DRM paradigm has also been used to investigate the integrity of episodic memory, lexical processing, and source monitoring in various clinical groups (Baciu et al., 2003; Balota et al., 1999; Moritz, Woodward, Cuttler, Whitman, & Watson, 2004; Schacter, Verfaellie, & Pradere, 1996; Watson et al., 2001). With the exception of amnesic patients (Schacter et al., 1996), false memories elicited by the DRM paradigm appear to be remarkably robust across fairly diverse clinical populations, including individuals with schizophrenia (Moritz et al., 2004) and individuals with dementia of the Alzheimer’s type (Balota et al., 1999; Watson et al., 2001). It is possible that healthy older adults and individuals with Alzheimer’s disease experience breakdowns in the monitoring and/or attentional-inhibitory cognitive control systems that differentiate the overall activation from related words converging on a nonpresented critical word from the item-specific information of studied words (Balota et al., 1999; Hasher & Zacks, 1988; Johnson, Hashtroudi, & Lindsay, 1993; Watson et al., 2001). Given the considerable amount of aging and clinical research that has been conducted with the DRM paradigm, it is surprising how few studies have explored whether individual differences in young adults influence the likelihood of false memories. To this point, the majority of the individual-differences research on young adults has focused on either the reliability of the DRM paradigm (Blair, Lenton, & Hastie, 2002) or whether variability in stimulus materials influences the probability of false memories. For example, some associative lists are more effective than others at eliciting false memories (Gallo & Roediger, 2002; Roediger, Watson, et al., 2001; Stadler, Roediger, & McDermott, 1999). When a warn- 77 ing is given about the DRM illusion prior to encoding, some lists are also more likely than others to have their corresponding critical words identified by participants and subsequently omitted from a recall or recognition memory test (Neuschatz et al., 2003). In another study of individual differences in young adults, Winograd, Peluso, and Glover (1998) found that self-reports of high levels of dissociative experiences and vivid mental imagery correlated with high levels of false memory. Although additional empirical work is necessary, Winograd et al.’s results suggest that some young adults may be more susceptible than others to false memories elicited by the DRM paradigm. Individual Differences in Working Memory Capacity: A Controlled-Attention View Kane and Engle (2002) argued that one of the primary functions of working memory is attentional control. Specifically, working memory or executive attention is used to maintain cognitive representations in an active state in the presence of interfering information. Kane and Engle (2002) suggested that these representations might reflect action plans, goal states, or other task-relevant stimuli in the environment. Hence, from an attentional-control perspective, one might expect individual differences in the working memory capacity (WMC) of young adults to influence behavioral performance in cognitively challenging tasks that require the active maintenance of task goals in the face of potentially interfering information. Consistent with this idea, individuals with low WMC (low spans) perform more poorly than individuals with high WMC (high spans) in situations where successful performance is dependent on minimizing interference, including fan effects, output interference, and proactive and retroactive interference paradigms (Conway & Engle, 1994; Kane & Engle, 2000; Rosen & Engle, 1997, 1998). Additional evidence of individual differences in executive, attentional control in young adults has been obtained through dichotic listening, the antisaccade task, and Stroop color naming (see Conway, Cowan, & Bunting, 2001; Kane, Bleckley, Conway, & Engle, 2001; Kane & Engle, 2003, respectively). Using the Stroop (1935) color naming task, Kane and Engle (2003) demonstrated that low spans produced more naming errors than high spans in the incongruent condition (e.g., participants mistakenly say “red” when the stimulus RED is printed in green ink). However, with respect to motivating the predictions for the present study on WMC and false memories, it is noteworthy that this individual difference in young adult Stroop performance only emerged when 75% of the experimental trials were congruent (e.g., GREEN printed in green ink). That is, high and low spans performed similarly on the Stroop task under experimental conditions where the proportion of congruent trials was low. According to Kane and Engle (2003), it is more challenging to maintain the overarching task goal of color naming across the course of a Stroop experiment when participants are presented with a high proportion of congruent trials in which both the color and the word response match (and, hence, accurate responding is possible whether participants correctly name the ink color or incorrectly name the word that is printed on the computer screen). Therefore, in Stroop experiments in which the proportion of congruent trials is high, accuracy on incongruent trials should be sensitive to individual differences in cognitive control or the ability to successfully maintain the overarching task goal (color naming) and to WATSON, BUNTING, POOLE, AND CONWAY 78 avoid the influence of interfering information or habit (word naming). This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Experiment 1 The primary goal of the present study was to determine whether individual differences in the WMC of young adults influence susceptibility to false memories elicited by the DRM paradigm. As suggested by Kane and Engle’s (2003) study of WMC and Stroop color naming performance, the ability to discriminate the behavioral performance of high and low spans may depend on the use of manipulations that emphasize the active maintenance of overarching task goals. To address this possibility, in Experiment 1 we factorially crossed WMC (high vs. low span) with warning instructions (present vs. absent) administered at encoding. Low span young adults may be less likely than high span young adults to reduce false memories for critical words in the DRM paradigm with warnings at encoding because of underlying group differences in the ability to actively maintain task goals (e.g., identify but do not recall nonpresented critical words) and to avoid the influence of habit (e.g., the relatively automatic activation of critical words in associative networks). In contrast, individual differences in the WMC of young adults may not influence susceptibility to false memories under standard learning conditions without a warning because of the relatively automatic activation of nonpresented critical words for both high and low spans. If this is the case, one might expect a Span ⫻ Warning interaction in the probability of false recall of critical words in Experiment 1. Method Participants. In Experiment 1, undergraduates from the University of Illinois–Chicago were initially screened through the operation span task (La Pointe & Engle, 1990; Turner & Engle, 1989). In this task, participants are required to read aloud a math problem followed by a to-be-remembered word—for example, “Is (8 / 4) ⫹ 3 ⫽ 4? DOG.” After varying numbers of these equation–word pairs, participants are prompted to recall all of the words included in each set in order. Trials were pseudorandomized such that participants could not predict the set size of upcoming equation–word trials. Participants were given points equal to the set size when all of the words in that set were recalled correctly in serial order. Operation span was defined as the sum of the points across all of the individual recall periods. For the purposes of the present study, 50 high and 50 low spans were identified from the upper and lower quartiles of the distribution of span scores from this initial screening session, respectively.2 Materials. Thirty-six 16-word lists of lexical–semantic associates were used in the present study. These 36 lists were originally developed by Watson, Balota, and Roediger (2003) for other purposes and have been shown to elicit false memories for nonpresented critical words (McDermott & Watson, 2001). For these semantic lists, list construction was modeled loosely after procedures used by Roediger and McDermott (1995), whereby the top associates to critical nonpresented words were collected. Although Roediger and McDermott and most other researchers have presented items in the order of strongest to weakest associates, in the present study, the 16 associates were presented in a single random order. Consistent with both McDermott and Watson (2001) and Watson et al. (2003), words in the odd-numbered serial positions were presented in uppercase letters, whereas words in the even-numbered positions were presented in lowercase (see McDermott & Watson, 2001, for additional discussion of why the case was changed across the 16-item list of associates and why a random order of associates was used in development of the Watson et al., 2003, stimuli). Procedure. Each subject studied thirty-six 16-word lists, presented visually on a projection screen at a single duration (i.e., 1 s/word in the center of the screen, with a 32-ms blank screen interstimulus interval). Participants were tested in groups, with a maximum of 10 subjects per session. For each group of participants, the order of lists was randomly determined, but the order of words within each list was held constant across all participants. Participants received a test packet with instructions to study each 16-word list that appeared because they would receive a 45-s free recall memory test at the end of each list. Participants were also told not to guess when trying to remember the words from each list. Prior to the start of the experiment, all of the participants were given a practice list of semantic associates at the same presentation duration as the experimental lists to familiarize them with the testing procedures. As described below, half of the high and low spans were also given additional explicit warning instructions about the DRM false memory paradigm prior to encoding. The remaining half of the high and low spans in Experiment 1 were not given any warning, but they were otherwise treated identically to the warned participants. The between-subjects factorial crossing of WMC (high vs. low span) and warning instruction (present vs. absent) yielded a total of 25 participants per cell (with a grand total of 100 subjects tested in Experiment 1). The warning manipulation in the present study was modeled after the instructions used by Gallo et al. (1997) and McDermott and Roediger (1998). Participants were warned that the forthcoming associative lists were designed to elicit false memories for particular critical words that were never presented. Participants were encouraged to avoid recalling the trick word for each of the 16-word associative lists. To make this instruction more concrete, prior to receiving the practice list, we told warned participants what the practice list would be (e.g., beetle, spider, ant, pest, . . .) and also gave them the identity of the nonpresented critical word (e.g., bug). Hence, if warned participants suspected that a critical word had merely been suggested, it was always correct to identify and to omit this word during free recall (see Gallo, Roediger, et al., 2001; McDermott & Roediger, 1998, for additional discussion of methodological issues regarding the presence of critical words in DRM experiments that use warnings). Results The mean veridical and false recall probabilities are presented in Figure 1 as a function of span and instruction. A series of 2 (span: high or low) ⫻ 2 (warning: present or absent) analyses of variance (ANOVAs) were conducted on veridical recall, false recall of critical words, and other noncritical word intrusions, respectively. On the basis of Kane and Engle’s (2003) study of WMC and goal maintenance, separate planned ANOVAs were also conducted to directly compare the false recall of critical words for the high and low spans in both the no warning (Figure 1A) and warning (Figure 1B) conditions of Experiment 1. Unless otherwise noted, the criterion for significance was set at .05 for all analyses discussed below. Veridical recall. As shown in Figure 1, in general, high spans recalled more studied words (.49) than low spans (.44), and warned participants recalled slightly fewer studied words (.45) than non2 Participants in Experiments 1 and 2 received one of two versions of the operation span task. In one version of this task, the set size varied between two and six math and word combinations per recall period, whereas in the second version, the set size varied between two and five combinations per recall period. In both experiments, when identifying the lower and upper quartiles in the distribution of span scores, low spans scored between 0 and 9 points on the operation span task, whereas high spans scored greater than 20 points, respectively. This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. INDIVIDUAL DIFFERENCES IN FALSE MEMORIES 79 Figure 1. Mean veridical and false recall probabilities as a function of span and instruction. High and low span young adults did not differ in their recall of associated but nonpresented critical words from the Deese– Roediger–McDermott paradigm in the no warning condition (A), whereas high spans recalled fewer critical words than low spans in the warning condition (B). Error bars represent the standard error of the mean. warned participants (.48). Consistent with these observations, a 2 (span) ⫻ 2 (warning) ANOVA on veridical recall yielded a main effect of span, F(1, 96) ⫽ 12.32, MSE ⫽ .006, and a main effect of warning, F(1, 96) ⫽ 5.20, MSE ⫽ .006. The two-way interaction of span and warning did not approach significance (F ⬍ 1.00). False recall of critical words. As shown in Figure 1, high spans recalled fewer critical words (.15) than low spans (.20), and warned participants recalled fewer critical words (.14) than nonwarned participants (.21). Consistent with these observations, a 2 (span) ⫻ 2 (warning) ANOVA on false recall yielded a main effect of span, F(1, 96) ⫽ 4.00, MSE ⫽ .017, and a main effect of warning, F(1, 96) ⫽ 7.21, MSE ⫽ .017. Although the predicted two-way interaction of span and warning in false recall of critical words did not approach significance (F ⬍ 1.00), as shown in Figure 1A, a separate planned ANOVA indicated that when high and low spans were not given an explicit warning to avoid false memories in the DRM paradigm, false recall was roughly comparable across the two groups (.20 vs. .23 for high vs. low spans, respectively), F(1, 48) ⫽ 0.38, MSE ⫽ .024, p ⫽ .54. In contrast, as shown in Figure 1B, when participants were given a warning, high spans (.10) were less likely than low spans (.18) to recall the nonpresented critical words, F(1, 48) ⫽ 7.09, MSE ⫽ .011. Hence, preliminary evidence from the separate planned ANOVAs in the no warning and warning conditions of Experiment 1 suggests that individual differences in the WMC of young adults may influence the probability of false memories in the DRM paradigm. However, as expected, the ability to observe these individual differences may require the use of experimenter-provided warning instructions that are administered at encoding and designed to help participants inhibit or reduce their susceptibility to false memories. Other noncritical word intrusions. A 2 (span) ⫻ 2 (warning) ANOVA on the intrusions per list (not including the recall of critical words) yielded no significant main effects and no interaction (all Fs ⬍ 1.39). Although the null effect of warning on noncritical word intrusions seems reasonable given that the manipulation was specifically designed to reduce false memories for nonpresented critical words in the DRM paradigm, these results should be interpreted with caution, because the average noncritical word intrusion rate collapsed across all four cells of the present study was only .13 intrusions per list. Discussion A controlled-attention view of WMC suggests that individuals with greater WMC (high spans) may be able to exert cognitive control over false memories elicited by the DRM paradigm, thereby reducing the likelihood of these memory errors compared with individuals with reduced WMC (low spans). Consistent with this idea, the results of Experiment 1 indicate that high spans recalled fewer nonpresented critical words than low spans. However, it is noteworthy that individual differences in young adult susceptibility to false memory only emerged when participants were forewarned about the tendency of the associative lists in the DRM paradigm to elicit illusory memories for these critical words. Under standard learning conditions without a warning, high and low span young adults appeared to be equally susceptible to memory errors elicited by the DRM paradigm. In this way, the present study on false memory yields results analogous to those of Kane and Engle (2003), who observed increased Stroop naming errors for low relative to high span young adults, but only when they manipulated task goals by increasing the proportion of congruent trials. Experiment 2 Although the separate planned ANOVAs comparing high and low span false recall of critical words in the no warning and warning conditions of Experiment 1 were justified on the basis of This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. 80 WATSON, BUNTING, POOLE, AND CONWAY Kane and Engle (2003), it is noteworthy that the predicted twoway interaction of span and warning in false recall was not significant. Given this finding, there may be an alternative explanation for the results of Experiment 1. Specifically, as shown in Figure 1, high spans recalled more studied words than low spans in both the no warning and the warning conditions. Consequently, high spans may be better than low spans at monitoring and reducing false recall of critical words in the DRM paradigm simply because of group differences in veridical recall at retrieval as opposed to group differences in goal maintenance of warnings administered at encoding (see Roediger, Watson, et al.’s, 2001, regression analysis for evidence that veridical and false recall are negatively correlated for associative lists and their corresponding critical words, respectively). In this light, the goals of Experiment 2 were twofold. First, we attempted to buttress the conclusion from Experiment 1 that high span young adults can use warnings administered at encoding to reduce false recall of critical words in the DRM paradigm, whereas low span young adults cannot, by demonstrating a statistically significant two-way interaction of span and warning in Experiment 2 (with no group differences predicted in false recall for the standard, no warning condition). Second, to follow up on the alternative explanation of the results of Experiment 1 and gain empirical leverage on what role veridical recall might play in reducing false recall in the DRM paradigm for high and low span young adults, we incorporated a repeated study–test trial procedure in the design of Experiment 2 (McDermott, 1996; Watson et al., 2004). As noted earlier, within an activation-monitoring framework, young adults may use repeated study–test trials to verify what is presented and to determine what is strongly associated but not presented in the DRM paradigm, gradually improving their veridical memory while concurrently diminishing but not eliminating their false memory with practice. From an attentionalcontrol perspective, unlike warning manipulations, which may require the active maintenance of task goals to attenuate false memories, repeated study–test trial manipulations may rely on a somewhat different monitoring mechanism, such as an individual’s ongoing experience or practice with the associative lists (see Watson et al., 2004, for additional discussion of the similarities and differences in warning and repeated study–test trial manipulations in the DRM paradigm). If this is the case, although the low span young adults in Experiment 2 might not use experimenterprovided warnings administered at encoding to reduce false recall, they might use their own memory performance at retrieval to spontaneously reduce false recall of critical words. Method Participants. In Experiment 2, undergraduates from the University of Illinois–Chicago were initially screened through the operation span task (La Pointe & Engle, 1990; Turner & Engle, 1989). As in Experiment 1, 50 high and 50 low spans were identified from the upper and lower quartiles of the distribution of span scores from this initial screening session, respectively. Although subjects were selected from similar points in the distribution of operation span scores, the 100 participants tested in Experiment 2 did not overlap with the 100 participants tested in Experiment 1. Materials. Four 15-word sets of associates were blocked according to their related critical word (i.e., smell, doctor, window, and sleep, where smell was the corresponding critical word from the first set of 15 associates, doctor for the next set of 15 associates, and so forth). Compared with the set of stimuli used in Experiment 1, these four lists and critical words may elicit more robust levels of false recall on the basis of normative data previously collected on young adults (see Stadler et al., 1999). Furthermore, the critical words from these four lists could be considered moderately to highly identifiable. Specifically, Neuschatz et al. (2003) recently found that, on average, when a warning was given, the corresponding nonpresented critical words from these four DRM associative lists were correctly identified by approximately 64% of the participants. Procedure. The 60-word list was digitally recorded in a male voice, and the same recording was used for all study phases. Presentation modality at study was switched from visual in Experiment 1 to auditory in Experiment 2 because auditory presentation has been shown to elicit more false memories than visual presentation in the DRM paradigm (Gallo, McDermott, Percer, & Roediger, 2001; Kellogg, 2001; Smith & Hunt, 1998). Stimuli were presented aurally through headphones worn by participants. For all participants, the 60-word list was presented at an approximate rate of 1 word every 1.25 s. Participants were tested individually. As described below, half of the high and low spans were given explicit warning instructions about the DRM paradigm prior to encoding. The remaining half of the high and low spans were not given any warning, but they were otherwise treated identically to the warned participants. The between-subjects factorial crossing of WMC and warning yielded a total of 25 participants per cell (with a grand total of 100 subjects tested in Experiment 2). Study–test trial was manipulated within subjects. As in Experiment 1, the warning manipulation was modeled after the instructions used by Gallo et al. (1997) and McDermott and Roediger (1998). Participants were warned that the forthcoming associative lists were designed to elicit false memories for particular critical words that were never presented. Participants were encouraged to avoid recalling the trick word for each of the four sets of 15 words that had been combined to form the 60-word list. To make this warning more concrete, we gave participants a sample list (i.e., chair; see Stadler et al., 1999) at the same presentation rate as the forthcoming study list. Hence, if participants suspected that a critical word had merely been suggested, it was always correct to omit this word during free recall. Nonwarned participants were also informed that they would receive sets of associate lists and also received the sample list (but chair was not identified as a nonpresented trick word, as it was for warned participants). Participants were given a test packet that contained five different response sheets with 60 numbered blanks per sheet. Participants were given instructions to study each 60-word list because they would receive a 5-min free recall memory test at the end of each list. Participants were told to try to improve their memory performance with each successive study episode of the 60-word list and were told not to guess when trying to remember the words from each list. Before each of the five study episodes, warned participants were also instructed about the tendency for DRM lists to elicit recall of nonpresented trick words. Results The mean veridical and false recall probabilities are presented in Figure 2 as a function of span, study–test trial, and instruction. A series of 2 (span: high or low) ⫻ 2 (warning: present or absent) ⫻ 5 (study–test trial: one through five) mixed-factor ANOVAs were conducted on veridical recall, false recall of critical words, and other noncritical word intrusions, respectively. On the basis of Kane and Engle’s (2003) study of WMC and goal maintenance, separate planned 2 (span) ⫻ 5 (study–test trial) mixed-factor ANOVAs were also conducted to directly compare the false recall of critical words for the high and low spans in both the no warning (Figure 2A) and warning (Figure 2B) conditions of Experiment 2. Unless otherwise noted, the criterion for significance was set at .05 for all analyses discussed below. This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. INDIVIDUAL DIFFERENCES IN FALSE MEMORIES 81 Figure 2. Mean veridical and false recall probabilities as a function of span, study–test trial, and instruction. Consistent with the results of Experiment 1, high and low span young adults did not differ in their recall of associated but nonpresented critical words from the Deese–Roediger–McDermott paradigm in the no warning condition (A), whereas high spans recalled fewer critical words than low spans in the warning condition (B). In contrast to the warning results, both high and low spans used repeated study–test trials or practice to reduce recall of critical words. Error bars represent the standard error of the mean. Veridical recall. As shown in Figure 2, consistent with the results of Experiment 1, high spans recalled more studied words (.61) than low spans (.57), and, in general, participants recalled more studied words from the first (.28) to the fifth study–test trial (.79). Consistent with these observations, a 2 (span) ⫻ 2 (warning) ⫻ 5 (study–test trial) ANOVA yielded a main effect of span, F(1, 96) ⫽ 7.26, MSE ⫽ .036, and a main effect of study–test trial, F(4, 384) ⫽ 1,483.74, MSE ⫽ .003. However, these two main effects were qualified by the three-way interaction of span, warning, and study–test trial, which indicated that high spans increased their veridical recall by a greater amount across trials than the low spans, but only in the warning condition, F(4, 384) ⫽ 2.63, MSE ⫽ .003. The main effect of warning and the remaining interactions in this ANOVA did not approach significance (all ps ⬎ .11). To further investigate the nature of the observed three-way interaction of span, warning, and study–test trial in Experiment 2, we conducted additional 2 (span) ⫻ 5 (study–test trial) mixedfactor ANOVAs on veridical recall in the no warning and warning conditions, and these ANOVAs revealed four important points. First, as shown in Figure 2A, collapsed across study–test trial, high spans (.60) and low spans (.57) did not differ in their recall of studied words in the standard, no warning condition, F(1, 48) ⫽ 1.11, MSE ⫽ .035, p ⫽ .30. Second, in contrast, as shown in Figure 2B, collapsed across study–test trial, high spans recalled more studied words (.62) than low spans (.56) in the warning condition, F(1, 48) ⫽ 7.54, MSE ⫽ .036. Third, as shown in Figure 2, in both the no warning and the warning conditions, collapsed across working memory span, veridical recall increased across repeated study–test trials, F(4, 192) ⫽ 743.51, MSE ⫽ .003, and F(4, 192) ⫽ 740.59, MSE ⫽ .003, respectively. Fourth, as shown in Figure 2A, high and low span veridical recall was roughly equivalent across repeated study–test trials in the no warning condition, F(4, 192) ⫽ 2.01, MSE ⫽ .003, p ⫽ .10; however, as shown in Figure 2B, the high span advantage in veridical recall appeared to increase slightly with repeated study– test trials in the warning condition, F(4, 192) ⫽ 2.53, MSE ⫽ .003. False recall of critical words. As shown in Figure 2, warned participants recalled fewer critical words (.26) than nonwarned participants (.36), and, in general, participants recalled fewer critical words from the first (.38) to the fifth study–test trial (.27). Consistent with these observations, a 2 (span) ⫻ 2 (warning) ⫻ 5 (study–test trial) ANOVA yielded a main effect of warning, F(1, 96) ⫽ 6.27, MSE ⫽ .219, and a main effect of study–test trial, F(4, 384) ⫽ 6.46, MSE ⫽ .029. More important, as predicted, the statistically significant two-way interaction of span and warning indicated that high spans decreased their recall of critical words in the warning (.18) relative to the no warning condition (.39), whereas low span false recall was not influenced by the warning manipulation (⬵ .33), F(1, 96) ⫽ 5.58, MSE ⫽ .219. The main effect of span and the remaining interactions in this ANOVA did not approach significance (all ps ⬎ .29). Additional planned 2 (span) ⫻ 5 (study–test trial) mixed-factor ANOVAs on false recall of critical words in the no warning and warning conditions revealed five important points. First, as shown in Figure 2A, when high and low span young adults were not given an explicit warning to avoid false memories in the DRM paradigm, false recall was roughly comparable across the two groups (⬵ .36 collapsed across study–test trial and span), F(1, 48) ⫽ 0.70, MSE ⫽ .262, p ⫽ .41. Second, in contrast, as shown in Figure 2B, when participants were given a warning prior to encoding the DRM lists, high spans (.18) were less likely than low spans (.33) to recall the nonpresented critical words, F(1, 48) ⫽ 7.28, This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. 82 WATSON, BUNTING, POOLE, AND CONWAY MSE ⫽ .178. Hence, as predicted and consistent with the preliminary results of Experiment 1, individual differences in the WMC of young adults influenced the probability of false recall in the DRM paradigm. Furthermore, additional ANOVAs on the warning factor confirmed that high spans used the warning to reduce their recall of nonpresented critical words, F(1, 48) ⫽ 11.07, MSE ⫽ .235, whereas low spans did not, F(1, 48) ⫽ .01, MSE ⫽ .205, p ⫽ .92. Third, as shown in Figure 2, in both the no warning and the warning conditions, in contrast to the pattern observed in veridical recall, false recall decreased across repeated study–test trials, F(4, 192) ⫽ 2.22, MSE ⫽ .031, p ⬍ .07, and F(4, 192) ⫽ 4.94, MSE ⫽ .029, respectively. Moreover, additional ANOVAs indicated that both high and low spans used repeated study–test trials to decrease the probability of false recall, F(4, 192) ⫽ 4.66, MSE ⫽ .022, and F(4, 192) ⫽ 2.60, MSE ⫽ .037, respectively. Specifically, collapsed across the no warning and warning conditions in Figure 2, high span false recall decreased from .37 to .25 for the first to the fifth study–test trial, respectively, whereas low span false recall decreased from .40 to .28. In this way, the results of Experiment 2 yielded a dissociation in which low span young adults benefited from practice but not warnings designed to reduce false memories in the DRM paradigm, whereas high span young adults benefited from both manipulations. Fourth, in both the no warning and the warning conditions, for both high and low spans, false recall decreased across repeated study–test trials (i.e., both Fs ⬍ 1.00 for the Study–Test Trial ⫻ Span interaction). Fifth, separate ANOVAs on false recall for the high and low spans indicated that warnings and repeated study–test trials did not interact for either group (i.e., both Fs ⬍ 1.00 for the Study–Test Trial ⫻ Warning interaction). Other noncritical word intrusions. A 2 (span) ⫻ 2 (warning) ⫻ 5 (study–test trial) ANOVA was conducted on the raw number of intrusions per test (not including the recall of critical words). However, caution is warranted in interpreting these intrusion data because the mean raw number of intrusions collapsed across all of the independent variables in the present study was quite low (⬵ .49 items/test) considering that participants studied a 60-item word list at encoding. Nevertheless, as one might expect with repeated study episodes, intrusions decreased from the first (.94) to the fifth study–test trial (.23), F(4, 384) ⫽ 20.62, MSE ⫽ .412. The two-way interaction of span and study–test trial also approached significance, F(4, 384) ⫽ 2.12, MSE ⫽ .412, p ⫽ .08, indicating that intrusions may have decreased slightly more for low spans (1.18 to 0.28) than for high spans (0.70 to 0.18) from the first to the fifth study–test trial, respectively. The remaining main effects and interactions in this ANOVA did not approach significance (all ps ⬎ .13). Consistent with Experiment 1, the null effect of warning on noncritical word intrusions in Experiment 2 seems reasonable given that the manipulation was specifically designed to reduce false memories for nonpresented critical words in the DRM paradigm. Discussion There were two main findings in Experiment 2. First, consistent with a controlled-attention view of individual differences in WMC (Kane & Engle, 2002), the statistically significant two-way interaction of span and warning indicated that high span young adults used warnings administered at encoding to reduce false recall of critical words in the DRM paradigm, whereas low span young adults did not. Second, in contrast to these warning results, both high and low span young adults used repeated study–test trials to reduce but not eliminate the recall of nonpresented critical words in the DRM paradigm. Hence, in addition to replicating the individual differences in susceptibility to false memories that we observed in Experiment 1, as predicted, Experiment 2 yielded a dissociation in which low span young adults benefited from practice but not warnings designed to reduce false memories in the DRM paradigm (whereas high span young adults clearly benefited from both manipulations). Taken together, these results suggest that despite breakdowns in the ability to actively maintain task goals (e.g., using experimenter-provided warnings administered at encoding to reduce susceptibility to false memories), low spans have a preserved ability to engage in spontaneous, self-initiated source monitoring (e.g., using practice with the associative lists and their own memory performance at retrieval to reduce false memories elicited by the DRM paradigm). General Discussion The primary goal of the present study was to determine whether individual differences in the WMC of young adults influence susceptibility to false memories. To achieve this goal, we tested 200 high and low span young adults using the DRM false memory paradigm, in which lists of associates (e.g., bed, rest, awake, . . . ) converge on and activate a nonpresented critical word (e.g., sleep). To influence the likelihood of false memories, we included warning instructions at encoding (Experiments 1 and 2) and repeated study–test trials (Experiment 2), both of which are thought to influence the source monitoring or attentional–inhibitory control component of an activation-monitoring framework of false memories in the DRM paradigm (Balota et al., 1999; Watson et al., 2004). Individual Differences, Warnings, and False Memories in the DRM Paradigm Winograd et al. (1998) found that self-reports of high levels of dissociative experiences and vivid mental imagery correlated with high levels of false recognition for nonpresented critical words in the DRM paradigm. Although these results suggest that some young adults may be more susceptible than others to false memories elicited by the DRM paradigm, it is noteworthy that individual differences in 10 different cognitive (e.g., vocabulary, memory, and aptitude tests) or personality measures (e.g., the Dissociative Experiences Scale; Bernstein & Putnam, 1986) did not correlate with participants’ false recall of critical words. More important for the purposes of the present study, Winograd et al. did not include a measure of WMC in the design of their experiment (e.g., operation span; Turner & Engle, 1989). Hence, on the basis of Winograd et al.’s findings, it is unclear whether individual differences in the WMC of young adults influence susceptibility to false memories in the DRM paradigm. To determine whether individual differences in the WMC of young adults influence susceptibility to false memories in the DRM paradigm, in the present study we factorially crossed WMC This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. INDIVIDUAL DIFFERENCES IN FALSE MEMORIES (high vs. low span) with warning instructions (present vs. absent) administered at encoding. From a controlled-attention perspective, one might expect individual differences in the WMC of young adults to influence behavioral performance in cognitively challenging tasks that require the active maintenance of task goals in the face of potentially interfering information (Kane & Engle, 2002). Consistent with this hypothesis, the results of Experiments 1 and 2 indicate that high spans recalled fewer nonpresented critical words than low spans. However, individual differences in susceptibility to false memory only emerged when participants were forewarned about the tendency of the associative lists to elicit illusory memories for nonpresented critical words (with no difference observed between high and low span false recall in the standard, no warning condition of the DRM paradigm; see Figures 1 and 2). Furthermore, the statistically significant two-way interaction of span and warning demonstrated in Experiment 2 ruled out the alternative explanation of the results of Experiment 1, in which one might have argued that the individual differences we observed in false recall were due to group differences in veridical recall at retrieval for the high and low span young adults. Moreover, the pattern of results observed in the present study cannot simply be attributed to the selection of extreme groups of young adults from our distribution of operation span scores or simple scaling effects, independent of the presence of a warning at encoding. Rather, the idea is that WMC is a proxy for cognitive control (Kane & Engle, 2002). Following this logic, high and low spans differ in their ability to actively maintain task goals (e.g., identify but do not recall the nonpresented critical words) and, hence, are more susceptible to the influence of habit (e.g., the relatively automatic activation of critical words in associative networks in the DRM paradigm). The findings of the present study also appear to constrain the potential effectiveness of warning instructions intended to reduce false memories elicited by the DRM paradigm. Although young adults have been shown to reduce but not eliminate false memories in the DRM paradigm when given detailed warning instructions at encoding (Gallo et al., 1997; McDermott & Roediger, 1998), the results of the present study suggest that low span young adults are unlikely to reduce false memories with these detailed warning instructions. This finding is particularly striking because if warned participants suspected that a critical word had merely been suggested, it would have always been correct to identify and to omit this word during free recall (i.e., critical words were never used as studied items in the present study). In this light, the present results extend recent work by Neuschatz et al. (2003) demonstrating that some DRM associative lists are more likely than others to have their corresponding critical words (a) identified by forewarned participants and (b) subsequently omitted from a recall or recognition memory test. Similarly, the results of the present study suggest that some young adults (high spans) are more likely than others (low spans) to benefit from experimenter-provided warnings prior to encoding, thereby reducing their susceptibility to false memories in the DRM paradigm. Indeed, low spans did not use warnings administered at encoding to reduce false recall in Experiment 2, in which the critical words were never presented but considered moderate to highly identifiable on the basis of normative data on these DRM materials published by Neuschatz et al. 83 Individual Differences, Repeated Study–Test Trials, and False Memories in the DRM Paradigm Using a multiple study–test trial procedure in conjunction with the DRM paradigm, McDermott (1996) was the first to demonstrate that veridical memory increased across repeated study–test trials, whereas false memory decreased (see Budson et al., 2000; Kensinger & Schacter, 1999; Watson et al., 2004, for replications and extensions). Within an activation-monitoring framework (Balota et al., 1999), young adults may use repeated study–test trials to verify what is presented and to determine what is strongly associated but not presented, gradually improving their veridical memory while concurrently diminishing (but not eliminating) their false memory with practice. More important for the purposes of the present article, as shown in Figure 2, both high and low span young adults used repeated study–test trials to reduce but not eliminate their recall of nonpresented critical words in the DRM paradigm. Therefore, the present study yielded a dissociation in which low span young adults benefited from practice but not warnings designed to reduce false memories in the DRM paradigm. In contrast, high span young adults benefited from both manipulations and greatly reduced their recall of nonpresented critical words when these two types of monitoring manipulations were combined (see Watson et al., 2004, for a similar study comparing the differential effectiveness of warnings and repeated study–test trials in young and older adults). Furthermore, with respect to using the results of Experiment 2 to rule out a retrieval-monitoring account of the results of Experiment 1, as shown in Figure 2, although the high spans recalled slightly more studied words than the low spans in the warning condition across study–test trials, the high spans evidently did not use their increasing veridical memory advantage across trials to modulate the influence of the warning manipulation and further reduce their probability of false recall. That is, in contrast to the findings in veridical recall, there was no three-way interaction of span, warning, and study–test trial for the recall of nonpresented critical words in Experiment 2. From an attentional-control perspective, repeated study–test trials may rely on a different underlying mechanism than warnings to successfully reduce susceptibility to associative false memories in the DRM paradigm (Watson et al., 2004). Briefly, the idea is that practice provides multiple chances to learn the associative lists, giving participants the opportunity to discount the perceptual support for critical words provided by their own output at test in favor of the perceptual information that can be gleaned from additional study episodes. In this light, the results of the present study suggest that individual differences in WMC do not influence young adults’ ability to spontaneously use repeated study–test trials to monitor their own memory performance at retrieval to reduce false recall in the DRM paradigm. However, consistent with the individual differences and WMC literature (see Kane & Engle, 2002, for a review), as expected, the results of the present study clearly demonstrated (a) breakdowns for low span young adults in the active maintenance of task goals, as evidenced by (b) the inability of low spans to use experimenter-provided warning instructions administered at encoding to reduce false memories for nonpresented critical words elicited by the DRM paradigm. WATSON, BUNTING, POOLE, AND CONWAY 84 This document is copyrighted by the American Psychological Association or one of its allied publishers. 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Vol 463 | 7 January 2010 | doi:10.1038/nature08637 ARTICLES Preventing the return of fear in humans using reconsolidation update mechanisms Daniela Schiller1,2, Marie-H. Monfils1,3, Candace M. Raio2, David C. Johnson2, Joseph E. LeDoux1 & Elizabeth A. Phelps1,2 Recent research on changing fears has examined targeting reconsolidation. During reconsolidation, stored information is rendered labile after being retrieved. Pharmacological manipulations at this stage result in an inability to retrieve the memories at later times, suggesting that they are erased or persistently inhibited. Unfortunately, the use of these pharmacological manipulations in humans can be problematic. Here we introduce a non-invasive technique to target the reconsolidation of fear memories in humans. We provide evidence that old fear memories can be updated with non-fearful information provided during the reconsolidation window. As a consequence, fear responses are no longer expressed, an effect that lasted at least a year and was selective only to reactivated memories without affecting others. These findings demonstrate the adaptive role of reconsolidation as a window of opportunity to rewrite emotional memories, and suggest a non-invasive technique that can be used safely in humans to prevent the return of fear. Learning about potential dangers in the environment is critical for adaptive function, but at times fear learning can be maladaptive, resulting in excessive fear and anxiety. Research on changing fears has highlighted several techniques, most of which rely on the inhibition of the learned fear response. An inherent problem with these inhibition techniques is that the fear may return, for example with stress1. Recent research on changing fears targeting the reconsolidation process overcomes this challenge to some extent. During reconsolidation, stored information is rendered labile after being retrieved, and pharmacological manipulations at this stage result in an inability to retrieve the memories at later times, suggesting that they are either erased or persistently inhibited2–6. Although these pharmacological manipulations are potentially useful for changing learned fears, their use in humans can be problematic. Here we show that invasive techniques are not necessary to alter fear by targeting reconsolidation. This is based on the premise that reconsolidation is an adaptive update mechanism by which new information is incorporated into old memories3,7,8. By introducing new information during the reconsolidation period, it may be possible to permanently change the fear memory. In the present study, we provide evidence in humans that old fear memories can be updated with non-fearful information provided during the reconsolidation window. As a consequence, fear responses are no longer expressed. Furthermore, this effect is specific to the targeted fear memory, and not others, and persists for at least a year. These findings demonstrate the adaptive role of reconsolidation as a window of opportunity to rewrite emotional memories, and suggest a non-invasive technique that can be used safely and flexibly in humans to prevent the return of fear. Pharmacological blockade of reconsolidation In contrast to the traditional view of memory formation as a one-time process of consolidation9,10, the reconsolidation hypothesis suggests that memories are consolidated each time they are retrieved2–6. Evidence for reconsolidation of emotional memories comes from studies using pharmacological perturbation after retrieval11–13. The retrieval-induced plasticity allows the transition from a labile to a stable state after which memories are no longer prone to interference14. 1 Why would such a recurrent window of vulnerability exist for old memories? From an evolutionary perspective, reconsolidation may serve as an adaptive update mechanism allowing for new information, available at the time of retrieval, to be integrated into the initial memory representation3,7,8. This view captures the fluidity of memory and suggests a dynamic process through which memories are formed, updated and maintained. Using Pavlovian fear conditioning as a model paradigm, research in non-human animals has detailed the molecular processes involved in emotional memory reconsolidation by pharmacologically blocking various stages of this process, after which the memory was no longer expressed. Most of these studies use protein synthesis inhibitors, or other pharmacological agents, that are not safe for use in humans3,4,6,11–14. Because the ability to impair emotional memories has important implications for the treatment for anxiety disorders linked to traumatic memories, such as post-traumatic stress disorder (PTSD), identifying techniques to target reconsolidation that can be used flexibly and safely in humans is critical. One possibility is to capitalize on reconsolidation as an update mechanism. If an old fear memory could be restored while incorporating neutral or more positive information provided at the time of retrieval, it may be possible to permanently modify the fearful properties of this memory. Although this approach captures the very essence of reconsolidation, it has been surprisingly neglected in emotion research in humans and other animals. Until now, there is only one demonstration of this approach in non-human animals using fear conditioning8, and efforts to alter fear memories by introducing non-fearful information during initial consolidation have had mixed results15–17. In humans, studies of motor and declarative memory suggest new information presented during the reconsolidation window may interfere with the older memories by either impairing the memory18 or modifying it to incorporate the new information7,19. However, there is robust evidence that motor, declarative and emotional memories rely on distinct memory systems in the brain20, and the reconsolidation process and effect of new information presented during the reconsolidation window may differ depending on the type of memory being updated. Center for Neural Science, 2Psychology Department, New York University, New York, New York 10003, USA. 3Psychology Department, University of Texas, Austin, Texas 78712, USA. 49 ©2010 Macmillan Publishers Limited. All rights reserved ARTICLES NATURE | Vol 463 | 7 January 2010 Interference of reconsolidation using extinction In the present study, we sought to capitalize on reconsolidation as an update mechanism and attempted to alter emotional memories with new information. We propose that updating a fear memory with non-fearful information, provided through extinction training, would rewrite the original fear response and prevent the return of fear. A recent study in rats8 provides strong evidence in support of this hypothesis. In brief, 24 h after fear conditioning, rats were reminded of the conditioned stimulus using a single retrieval trial, and subsequently underwent extinction training. The extinction phase was conducted either within or outside the reconsolidation window, which lasts about 6 h11,18. It was found that fear responses returned only in rats that underwent extinction after reconsolidation was completed. In contrast, rats that had extinction training during the reconsolidation window did not show recovery of fear. To test this hypothesis in humans, we designed two experiments examining whether extinction training conducted during the reconsolidation window would block the return of extinguished fear. In the first study, three groups of subjects underwent fear conditioning using a discrimination paradigm with partial reinforcement (Fig. 1a). Two coloured squares were used. One square (conditioned stimulus1, hereafter termed CS1) was paired with a mild shock to the wrist (unconditioned stimulus) on 38% of the trials, whereas the other square was never paired with shock (CS2). A day later, all three groups underwent extinction training in which the two conditioned stimuli were repeatedly presented without the unconditioned stimulus. In two groups the fear memory was reactivated before extinction using a single presentation of the CS1. One group (n 5 20) received the reminder trial 10 min before extinction (within the reconsolidation a Day 1 Day 2 Group 1: Acquisition Reminder Group 2: Acquisition Reminder Group 2: Acquisition No reminder 10 min 6h Day 3 Extinction Re-extinction Extinction Re-extinction Extinction Re-extinction Spontaneous recovery: (1st trial of re-extinction) – (last trial of extinction) b 0.35 10 min 6h No reminder Mean differential SCR * * * * * 0.25 0.15 0.05 –0.05 Acquisition Extinction Re-extinction Figure 1 | Extinction during reconsolidation prevents spontaneous recovery of extinguished fear. a, Experimental design and timeline. b, Mean differential SCRs (CS1 minus CS2) during acquisition (late phase), extinction (last trial) and re-extinction (first trial) for each experimental group (10-min reminder, 6-h reminder and no reminder). The three groups showed equivalent fear acquisition and extinction. Spontaneous recovery (first trial of re-extinction versus the last trial of extinction) was found in the group that had not been reminded or that was reminded 6 h before extinction. In contrast, there was no spontaneous recovery in the group reminded 10 min before extinction. *P , 0.05 (between acquisition and extinction, or between extinction and re-extinction within group). Error bars represent standard errors. window), whereas the second group (n 5 23) was reminded 6 h before extinction (outside the reconsolidation window11,18). The third group (n 5 22) was not reminded of the fear memory before extinction training. Twenty-four hours later, all three groups were presented again with the conditioned stimuli without the unconditioned stimulus (re-extinction) to assess spontaneous fear recovery. The measure of fear was the skin conductance response (SCR). At each stage, the differential fear response was calculated by subtracting responses to the CS2 from responses to the CS1. The results of the spontaneous recovery experiment are presented in Fig. 1b (see also Supplementary Fig. 1). Subjects that showed successful levels of fear acquisition and extinction were included in the analysis. We verified that these levels were equivalent between the groups using two-way analysis of variance (ANOVA) with main effects of group (10 min, 6 h and no reminder) and time (early and late phase). For both acquisition and extinction there was a significant main effect of time (F1,62 5 9.92, P , 0.05; F1,62 5 19.59, P , 0.01, respectively) but no effect of group or interaction. Follow-up t-tests confirmed that subjects had significantly stronger responses to CS1 than to CS2 during acquisition (late phase; 10-min group: t 5 2.68, P , 0.05; 6-h group: t 5 3.72, P , 0.05; no-reminder group: t 5 3.72, P , 0.05), but by the last trial of extinction there was no difference (10-min group: t 5 20.94; 6-h group: t 5 20.23; no-reminder group: t 5 20.79; all not significant). The decrease in fear responses from acquisition (late phase) to extinction (last trial) for each group was assessed using a two-way ANOVA with main effects of group (10 min, 6 h and no reminder) and time (acquisition, extinction). This showed a significant main effect of time (F1,62 5 29.9, P , 0.01), but no effect of group or interaction. Follow-up t-tests confirmed the reduction of fear in all three groups (10-min group: t 5 2.70, P , 0.05; 6-h group: t 5 4.06, P , 0.05; no-reminder group: t 5 4.07, P , 0.05), and there was no difference in the level of fear reduction between the groups (P . 0.5 for all three comparisons). Spontaneous recovery was assessed using a two-way ANOVA with main effects of group (10 min, 6 h and no reminder) and time (early and late phase of re-extinction, defined by the mean first four responses versus the subsequent four, respectively) showing a significant main effect of time (F1,62 5 6.26, P , 0.05), and a group 3 time interaction (F2,62 5 4.63, P , 0.05). Follow-up t-tests compared the differential responses between the last trial of extinction and the first trial of re-extinction. Spontaneous recovery was found in subjects who did not receive a reactivation trial before extinction (t 5 2.69, P , 0.05), or who underwent extinction 6 h after fear reactivation (t 5 2.66, P , 0.05). In contrast, subjects that had extinction 10 min after reactivation showed no spontaneous recovery (t 5 0.28, not significant). These results indicate that the spontaneous recovery of fear after extinction can be prevented if extinction training is conducted during the time window in which the fear memory is proposed to be undergoing reconsolidation. Persistence of reconsolidation blockade In this initial study, we used a 24 h interval to test for long-term memory, which, for practical reasons, is the standard in human fear recovery experiments16,17,21–23. However, if the fear memory is persistently altered, as would be predicted if we are affecting reconsolidation of the fear memory, we would expect this effect to last for much longer time intervals. In an attempt to examine whether the observed blockade of fear memory persists, we invited the participants for a follow-up test after approximately 1 year (10–14 months). Nineteen of the 65 original participants were located and included in the follow-up study (10-min group, n 5 8; 6-h group, n 5 4; no-reminder group, n 5 7). We collapsed subjects from the two groups previously showing spontaneous recovery (that is, 6 h and no reminder) into one group. As mentioned earlier, after the spontaneous recovery test, subjects were re-extinguished using ten non-reinforced presentations of the stimuli ensuring that all subjects showed no evidence of conditioned fear at 50 ©2010 Macmillan Publishers Limited. All rights reserved ARTICLES NATURE | Vol 463 | 7 January 2010 the conclusion of the initial experiment. This re-extinction allowed us to conduct a second test of fear recovery a year later. For this second recovery test, we used a more potent recovery assay, namely reinstatement, in which subjects were exposed to four unsignalled shocks, followed by non-reinforced presentations of the conditioned stimuli. The index of fear recovery (Fig. 2 and Supplementary Fig. 2) was the difference in the conditioned fear response at the end of re-extinction after the initial spontaneous recovery test and the conditioned fear response immediately after reinstatement 1 year later. The conditioned fear response at the end of re-extinction and post-reinstatement was calculated using a differential SCR score (CS1 minus CS2). A twoway ANOVA with main factors of group (10 min, 6 h/no-reminder) and stage (re-extinction, post-reinstatement) showed a significant main effect of group (F1,17 5 5.89, P , 0.05). The group 3 stage interaction was marginally significant (F1,17 5 2.78, P , 0.07, one-tail). Follow-up one-tail t-test comparisons showed that reinstatement was significant in the 6-h/no-reminder group (t 5 2.12, P , 0.03), but not the 10-min group (t 5 0.22, not significant). Moreover, the reinstatement index was significantly larger in the 6-h/no-reminder group than the 10-min group (t 5 1.75, P , 0.05). Lastly, a comparison of post-reinstatement conditioned fear between the groups showed a significant difference (t 5 2.18, P , 0.03). These results indicate that reactivation of a fear memory renders it labile and extinction training during this lability period leads to a long lasting blockade of recovery of fear. In contrast, recovery of fear a year later was observed after regular extinction training. Fear recovery was also observed when extinction training was conducted with a sufficient temporal gap after reactivation, presumably allowing for reconsolidation to be complete. Specificity of reconsolidation blockade If interfering with reconsolidation using extinction is to be clinically useful, it is also important to determine whether it is specific. In reallife situations, a traumatic event can be associated with several cues, and each could potentially trigger the recollection of the event and elicit fear reactions. To assess the specificity of this fear blockade technique, we examined whether interfering with the reconsolidation of one fear predictive cue would affect the fate of another, associated cue. 0.2 In a second experiment, more than one stimulus was associated with the same aversive outcome (Fig. 3a). Specifically, using a withinsubject design, subjects underwent fear conditioning using three coloured squares. Two squares (CSa1 and CSb1) were paired with the shock on 38% of the trials. The third square (CS2) was never paired with the shock. A day later, subjects received a single presentation of CSa1 and the CS2, but not CSb1. Ten minutes after the reminder trial, extinction training was conducted (within the reconsolidation window) using repeated presentations of all conditioned stimuli without the aversive outcome. Reinstatement of the fear memory was conducted 24 h later, when subjects returned to the experiment room and received four unsignalled presentations of the shock. Ten minutes later, the conditioned stimuli were presented without the aversive outcome (re-extinction). The results of the experiment are presented in Fig. 3b (see also Supplementary Fig. 3). Subjects (n 5 18) that showed successful fear acquisition and extinction were included. We verified that these levels were equivalent between the two conditioned stimuli (CSa1 and CSb1) using two-way ANOVAs with main effects of stimulus (CSa1, CSb1 and CS2) and time (early and late phase, defined by the mean response during the first and second half of each phase, respectively). In acquisition, there was a significant main effect of stimulus (F2,51 5 3.51, P , 0.05) and a stimulus 3 time interaction (F2,51 5 3.27, P , 0.05). In extinction, there was a significant main effect of time (F1,51 5 48.74, P , 0.01). Follow-up t-tests were used to further assess acquisition and extinction of fear. We compared the mean SCR to CSa1 or CSb1 with the CS2 during the second half of the acquisition session. Subjects showed significantly stronger responses to CSa1 than to CS2 (t 5 6.01, P , 0.05), as well as to CSb1 compared to CS2 (t 5 6.68, P , 0.05). Moreover, the level of acquisition to CSa1 and CSb1 was equivalent (t 5 0.76, not significant). To a CSa+ CSb+ CS– 0.8 0.6 Mean SCR Reinstatement index Day 3 Reinstatement 4 × US 10 min Extinction Re-extinction CSa+ CSb+ CS– CSa+ CSb+ CS– Reinstatement: (1st trial of re-extinction) – (last trial of extinction) 0.7 0.1 CSa+ CS– 10 min b * Day 2 Reminder Day 1 Acquisition CSa+ (reminded) CSb+ (not reminded) CS– * * * 0.5 0.4 0.3 0.2 0 0.1 0 –0.1 10 min 6 h/ no reminder Figure 2 | Blockade of the return of fear persists one year later. The reinstatement index is the difference in the conditioned fear response (CS1 minus CS2) at the end of re-extinction after the initial spontaneous recovery test and the conditioned fear response immediately after reinstatement a year later. The magnitude of the reinstatement was significantly higher in the 6-h/no-reminder group than in the 10-min group, which showed no reinstatement. *P , 0.05; error bars represent standard errors. Acquisition Extinction Re-extinction Figure 3 | Blockade of the return of fear is specific to reactivated memories. a, Experimental design and timeline. US, unconditioned stimulus. b, Mean SCRs (CSa1, CSb1 and CS2) during acquisition (late phase), extinction (last trial) and re-extinction (first trial). Subjects had equivalent levels of acquisition and extinction of conditioned fear to the two conditioned stimuli. The index of fear recovery was the first trial of re-extinction (after reinstatement) minus the last trial of extinction (before reinstatement). Fear reinstatement was found only to CSb1 (not reminded before extinction training), but not to CSa1 (reminded 10 min before extinction training). *P , 0.05 (between acquisition and extinction, or extinction and reextinction for each stimulus). Error bars represent standard errors. 51 ©2010 Macmillan Publishers Limited. All rights reserved ARTICLES NATURE | Vol 463 | 7 January 2010 assess fear extinction, we compared the mean SCR to CSa1 or CSb1 with the CS2 during the last trial of extinction. There were no significant differences in responses to CSa1 compared to CS2 (t 5 20.26, not significant), or to CSb1 compared to CS2 (t 5 20.56, not significant), and responses to CSa1 and CSb1 were equally extinguished (t 5 0.23, not significant). Moreover, subjects had successful reduction of fear, as assessed by comparing the SCR during the second half of acquisition with the last trial of extinction, to both CSa1 (t 5 2.62, P , 0.05) and CSb1 (t 5 4.08, P , 0.05) but not to the CS2 (t 5 20.09, not significant), which was low to begin with. To assess the recovery of fear, we used a two-way ANOVA with main effects of stimulus (CSa1, CSb1 and CS2) and time (early and late phase of re-extinction, defined by the mean first four responses versus the last four, respectively), which revealed a stimulus 3 time interaction (F2,51 5 5.14, P , 0.01). Using follow-up t-tests, we compared the SCR during the last trial of extinction (before reinstatement) with the first trial of re-extinction (after reinstatement). Subjects showed reinstated fear responses only to CSb1, which is the stimulus that was not reminded before extinction (t 5 2.16, P , 0.05). In contrast, fear responses to CSa1, which was reminded 10 min before extinction training, did not recover (t 5 0.22, not significant). As expected, there were also no fear responses to the CS2 (t 5 0.16, not significant). Thus, extinction during reconsolidation affected only the reactivated memory and no other trace associated with the original event. Discussion The present findings suggest a new technique to target specific fear memories and prevent the return of fear after extinction training. Using two recovery assays, we demonstrated that extinction conducted during the reconsolidation window of an old fear memory prevented the spontaneous recovery or the reinstatement of fear responses, an effect that was maintained a year later. Moreover, this manipulation selectively affected only the reactivated conditioned stimulus while leaving fear memory to the other non-reactivated conditioned stimulus intact. It has been suggested that the adaptive function of reconsolidation is to allow old memories to be updated each time they are retrieved3,7,8. In other words, our memory reflects our last retrieval of it rather than an exact account of the original event. This notion has received support from interference paradigms targeting motor and declarative memories7,18,19. These studies demonstrate that new information provided during reconsolidation could affect old memories by modifying or interfering with them, but in contrast to the present study, they do not provide evidence for memory blockade. This difference in the effect of new information presented during reconsolidation on the subsequent qualities of different types of memory may be due to the diverse nature of the underlying memory systems. For instance, unlike the distributed cortical representation of declarative memories20, conditioned fear has a more discrete neural representation localized in the amygdala24. Indeed, in the lateral amygdala, pharmacological blockade of the molecular cascade engaged by retrieval prevents the reconsolidation of fear memories in rats4. This raises the possibility that our behavioural manipulation, namely, extinction training during reconsolidation, targeted the same molecular mechanism. Although the current behavioural study does not provide direct evidence that a process of reconsolidation mediates the effects of extinction training, support for this hypothesis comes from recent findings in rats8. After fear consolidation, a single isolated retrieval trial before extinction prevented the recovery of fear in rats. Interestingly, plasticity in the lateral amygdala induced by the conditioned stimulus retrieval was impaired by the presentation of a conditioned stimulus 1 h later, indicating possible interference with the reconsolidation process, similar to the interference caused to reconsolidation by pharmacological blockade in rats4. Together, these findings reveal cross-species similarities, which may reflect an evolutionarily preserved adaptive mechanism whereby the neural representation of fear memory can be significantly altered through time-dependent molecular mechanisms triggered by exposure to fear-eliciting stimuli. The current results also suggest that timing may have a more important role in the control of fear than previously appreciated. Standard extinction training, without previous memory reactivation, also triggers the fear memory. Given this, one might expect mere extinction training to have similar effects. That is, the first trial of extinction might serve as the reminder cue triggering the reconsolidation cascade, which is immediately followed by extinction. However, there is abundant evidence that during standard extinction training the non-reinforced presentations of the fear-eliciting cue induce new inhibitory learning, which competes for expression with the initial fear learning, resulting in the recovery of fear responses in some circumstances16,17,21–23,25,26. Our findings indicate that the timing of extinction relative to the reactivation of the memory can capitalize on reconsolidation mechanisms. Two factors may be important determinants in this process: the timing of extinction training relative to retrieval, and/or the chunking of the conditioned stimulus presentations during extinction relative to reactivation (that is, the fact that they are massed relative to the single retrieval trial during the reconsolidation phase). Further studies are required to disentangle these possibilities. In conclusion, the present study showed that updating fear memories with non-fearful information provided through extinction training led to the blockade of previously learned fear responses and a lasting change in the original fear memory. These results have significant implications for the treatment of anxiety disorders. Current forms of therapy rely heavily on extinction27,28, but the fact that extinguished fear could recover under certain conditions dampens the resilience of anxiety patients after treatment. The discovery that certain pharmacological manipulation can potentially erase memories through effects on reconsolidation has been encouraging; however, most compounds showing such effects in various species are toxic to humans. Recently, there has been promising evidence using compounds that are testable on humans, namely b-adrenergic receptor blockers29, which also show effects in trauma patients30, but these effects are not observed in every case31. The present study proposes that such invasive techniques are not necessary. Using a more natural intervention that captures the adaptive purpose of reconsolidation allows a safe and easily implemented way to prevent the return of fear. METHODS SUMMARY Two experiments were designed to examine whether extinction training conducted during the reconsolidation window would block the return of extinguished fear. The measure of fear was the SCR. In the first study, three groups of subjects underwent a discrimination fear conditioning paradigm with partial reinforcement. Two coloured squares (CS1 and CS2) were used. The CS1 was paired with a mild shock to the wrist (unconditioned stimulus) on about onethird of the trials, and the CS2 was never paired with the shock. A day later, all three groups underwent extinction training (repeated conditioned stimulus presentations without the unconditioned stimulus). In two groups the fear memory was reactivated before extinction using a single presentation of the CS1. One group received the reminder trial 10 min before extinction (within the reconsolidation window), whereas the second group was reminded 6 h before extinction (outside the reconsolidation window). The third group was not reminded of the fear memory before extinction training. To assess spontaneous fear recovery, a day later all three groups were presented with the conditioned stimuli without the unconditioned stimulus (re-extinction). About a year later, the return of fear was assessed again using a different recovery assay (reinstatement). The second experiment used a within-subject design where subjects underwent fear conditioning using three coloured squares. Two squares (CSa1 and CSb1) were paired with the shock on about one-third of the trials. The third square (CS2) was never paired with the shock. A day later, subjects received a single presentation of CSa1 and the CS2, but not CSb1. Ten minutes after the reminder trial, extinction training was conducted (within the reconsolidation window) using repeated presentations of all conditioned stimuli without the unconditioned stimulus. Reinstatement of the fear memory was conducted 52 ©2010 Macmillan Publishers Limited. All rights reserved ARTICLES NATURE | Vol 463 | 7 January 2010 24 h later, when subjects returned to the experiment room and received four unsignalled presentations of the shock. Ten minutes later the conditioned stimuli were presented without the aversive outcome (re-extinction). Full Methods and any associated references are available in the online version of the paper at www.nature.com/nature. Received 24 August; accepted 5 November 2009. Published online 9 December 2009. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. Miracle, A. D., Brace, M. F., Huyck, K. D., Singler, S. A. & Wellman, C. L. 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Neurocircuitry models of posttraumatic stress disorder and extinction: human neuroimaging research—past, present and future. Biol. Psychiatry 60, 376–382 (2006). 29. Kindt, M., Soeter, M. & Vervliet, B. Beyond extinction: erasing human fear responses and preventing the return of fear. Nature Neurosci. 12, 256–258 (2009). 30. Brunet, A. et al. Effect of post-retrieval propranolol on psychophysiologic responding during subsequent script-driven traumatic imagery in post-traumatic stress disorder. J. Psychiatr. Res. 42, 503–506 (2008). 31. Tollenaar, M. S., Elzinga, B. M., Spinhoven, P. & Everaerd, W. Psychophysiological responding to emotional memories in healthy young men after cortisol and propranolol administration. Psychopharmacology (Berl.) 203, 793–803 (2009). Supplementary Information is linked to the online version of the paper at www.nature.com/nature. Acknowledgement We thank K. Doelling for assistance with data collection and discussions on the revised version of the manuscript. We also thank Y. Niv and M. Milad for advice on the experimental protocols. This study was funded by the James S. McDonnell Foundation and National Institutes of Health (NIH) grant R21 MH072279 (E.A.P.), NIH grants R37 MH038774, P50 MH058911, RO1 MH046516 and K05 MH067048 (J.E.L.), Postdoctoral fellowships NSERC, CIHR and AHFMR (M.-H.M.), and a Fulbright award (D.S.). Author Contributions D.S. designed the experiments, collected and analysed data, interpreted the data and wrote the first draft of the manuscript; C.M.R. and D.C.J. collected the data and contributed to experimental design, analysis, interpretation and the final version of the manuscript; M.-H.M., J.E.L. and E.A.P. contributed to experimental design, data interpretation, and the final version of the manuscript. Author Information Reprints and permissions information is available at www.nature.com/reprints. Correspondence and requests for materials should be addressed to E.A.P. (liz.phelps@nyu.edu). 53 ©2010 Macmillan Publishers Limited. All rights reserved doi:10.1038/nature08637 METHODS Experiment 1. The study consisted of three consecutive stages conducted 24 h apart: day 1, acquisition; day 2, reactivation and extinction; and day 3, re-extinction (Fig. 1a). During acquisition, three randomly assigned groups of subjects underwent a Pavlovian discrimination fear-conditioning paradigm with partial reinforcement. The conditioned stimuli (CS1, CS2) were yellow and blue squares (4 s) and the unconditioned stimulus was a mild shock to the wrist (200 ms) coterminating with the CS1. The inter-trial-interval (ITI) was 10–12 s. The CS1 was paired with the shock on a 38% partial reinforcement schedule and the CS2 was never paired with shock (10 CS1, 10 CS2, 6 CS1 with shock). Subjects were instructed to pay attention to the computer screen and to try to figure out the relationship between the stimuli appearing on the screen and the shocks. A day later, all three groups underwent extinction training in which the CS1 and CS2 were repeatedly presented without the unconditioned stimulus. In two groups, the fear memory was reactivated before extinction. During reactivation, the CS1 was presented once (unreinforced), followed by a 10-min break. One group (n 5 20) underwent extinction after the 10-min break (10 CS1, 11 CS2; within the reconsolidation window). The second group (n 5 23) underwent extinction 6 h after the reactivation (10 CS1, 11 CS2; outside of the reconsolidation window). In the third group (n 5 22), the fear memory was not reactivated. After the break, extinction immediately followed for half of the subjects in this group, or was conducted 6 h later for the other half (11 CS1, 11 CS2). During the break, all participants watched a pre-selected television show episode. Day 3 consisted of re-extinction in which participants were presented with non-reinforced presentations of the stimuli (10 CS1, 11 CS2). During all sessions (acquisition, reminder, extinction and reextinction), with the exception of the breaks, the participants were attached to the SCR and shock electrodes, and the shock stimulator was set to the ‘on’ position. To examine how long the blockade of memory persists, we invited the participants of the experiment to come back to the laboratory after about a year (10–14 months). Twenty-three participants were located (10-min group, n 5 10; 6-h group, n 5 5; no-reminder group, n 5 8). As mentioned earlier, after the spontaneous recovery test, subjects were re-extinguished using ten nonreinforced presentations of the stimuli, which allowed us to reassess their recovery of fear. We used a more potent recovery assay, namely, reinstatement, in which subjects were exposed to four unsignalled shocks, followed by non-reinforced presentations of the same conditioned stimuli that were used in the spontaneous recovery experiment (10 CS1, 10 CS2, using two randomized orders counterbalanced across subjects). The index of fear recovery was the difference in the conditioned fear response at the end of re-extinction after the initial spontaneous recovery test and the conditioned fear response immediately after reinstatement a year later. Specifically, a differential SCR score (CS1 minus CS2) was calculated for the end of re-extinction (mean of last two trials) and post-reinstatement (mean of first four trials). We collapsed subjects from the two groups previously showing spontaneous recovery (that is, 6 h and no reminder) into one group. Subjects that failed to re-extinguish after the spontaneous recovery test (differential SCR score . 0.2) or showed no measurable responses to the shocks during reinstatement were not included in the analysis (four subjects). The final analysis included 19 subjects (10-min group, n 5 8; 6-h/no-reminder group, n 5 11). Throughout the session, the participants were attached to the SCR and shock electrodes, and the shock stimulator was set to the ‘on’ position. Experiment 2. The study consisted of three consecutive stages conducted 24 h apart: day 1, acquisition; day 2, reactivation and extinction; and day 3, reinstatement and re-extinction, using a within-subject design (Fig. 2a). During acquisition, subjects underwent fear conditioning using three coloured squares. Two squares (CSa1 and CSb1) were paired with the shock on a 38% partial reinforcement schedule. The third square (CS2) was never paired with the shock (eight nonreinforced presentations of CSa1, CSb1 and CS2 each, intermixed with an extra 5 CSa1 and 5 CSb1 presentations that co-terminated with the shock). The stimuli were presented for 4 s each with a 10–12 s variable ITI. Subjects were instructed to pay attention to the computer screen and to try to figure out the relationship between the stimuli appearing on the screen and the shocks. Day 2 consisted of reactivation and extinction. During reactivation, the CSa1 and the CS2 were each presented once (unreinforced), in a counterbalanced fashion. Participants were then given a 10-min break in which they watched a pre-selected television show episode. Extinction immediately followed and consisted of non-reinforced presentations of the three stimuli (10 CSa1, 11 CSb1 and 11 CS2). Day 3 consisted of reinstatement and re-extinction. During reinstatement, subjects were administered four unsignalled shocks. After a 10-min break, a re-extinction session began in which participants were presented with non-reinforced presentations of the three stimuli (10 CSa1, 10 CSb1 and 11 CS2). During all sessions (acquisition, reminder, extinction, reinstatement and re-extinction), with the exception of the breaks, the participants were attached to the SCR and shock electrodes, and the shock stimulator was set to the ‘on’ position. Psychophysiological stimulation and assessment. Mild shocks were delivered through a stimulating bar electrode attached with a Velcro strap to the right inner wrist. A Grass Medical Instruments stimulator charged by a stabilized current was used. Subjects determined the level of the shock themselves, beginning at a very mild level of shock (10 V) and gradually increasing the level until the shock reached the maximum level that they determined was uncomfortable, but not painful (the maximum level was 60 V). All shocks were given for 200 ms, with a current of 50 pulses per second. SCR was assessed using two Ag–AgCl electrodes, which were connected to a BioPac Systems skin conductance module. The electrodes were attached to the first and second fingers of the left hand, between the first and second phalanges. SCR waveforms were analysed offline, using AcqKnowledge 3.9 software (BIOPAC Systems Inc.). SCR amplitudes to the conditioned and unconditioned stimuli were the dependent measures of conditioned and unconditioned responses, respectively. The level of SCR response was determined by taking the base-to-peak difference for the first waveform (in microsiemens, ms) in the 0.5–4.5 s window after stimulus onset. The minimal response criterion was 0.02 ms. The raw SCR scores were square-root transformed to normalize distributions. These normalized scores were scaled according to each subject’s unconditioned response by dividing each response by the mean square-roottransformed unconditioned stimulus response. ©2010 Macmillan Publishers Limited. All rights reserved Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
17 Feb 2006 9:54 AR XMLPublishSM (2004/02/24) P1: OKZ 10.1146/annurev.clinpsy.2.022305.095315 ANRV271-CP02-18.tex Annu. Rev. Clin. Psychol. 2006. 2:469–98 doi: 10.1146/annurev.clinpsy.2.022305.095315 c 2006 by Annual Reviews. All rights reserved Copyright  First published online as a Review in Advance on January 16, 2006 RECOVERED MEMORIES Elizabeth F. Loftus Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. Department of Psychology and Social Behavior, University of California, Irvine, California 92697-7085; email: eloftus@uci.edu Deborah Davis Department of Psychology, University of Nevada, Reno, Nevada 89557; email: debdavis@unr.nevada.edu Key Words repression, influence, false memory, therapy, childhood sexual abuse ■ Abstract The issues surrounding repressed, recovered, or false memories have sparked one of the greatest controversies in the mental health profession in the twentieth century. We review evidence concerning the existence of the repression and recovery of autobiographical memories of traumatic events and research on the development of false autobiographical memories, how specific therapeutic procedures can lead to false memories, and individual vulnerability to resisting false memories. These findings have implications for therapeutic practice, for forensic practice, for research and training in psychology, and for public policy. CONTENTS INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EVIDENCE FOR REPRESSION AND RECOVERY OF MEMORIES OF TRAUMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Retrospective Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prospective Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Case Histories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EVIDENCE FOR THE EXISTENCE OF FALSE MEMORIES OF ABUSE . . . . . . False Memories of Real-Life Trauma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Experiences of the “Retractors” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laboratory Research on the Malleability of Autobiographical Memory . . . . . . . . . Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . THERAPEUTIC PROCESS AND FALSE MEMORIES OF ABUSE . . . . . . . . . . . . A Priori Assumptions Regarding Abuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Confirmation Biases and the Dangers of Specific Hypothesis Testing . . . . . . . . . . Plausibility-Enhancing “Evidence” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adopting and Confirming the Belief in Abuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . THERAPY AND SOCIAL INFLUENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Individual Vulnerability to False Memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1548-5943/06/0427-0469$20.00 470 471 471 473 473 476 476 477 478 480 480 480 481 482 483 489 489 469 17 Feb 2006 9:54 470 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS Ability to Resist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 Motivation to Resist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 RECOVERED MEMORIES AND PUBLIC POLICY . . . . . . . . . . . . . . . . . . . . . . . . 492 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. INTRODUCTION On November 28, 1989, George Franklin was arrested for the murder of his daughter’s childhood playmate—a murder that had allegedly occurred almost 20 years earlier (see MacLean 1993). The evidence against him? Nothing but the recently “recovered” memory of his now 29-year-old daughter, who claimed to have repressed her memory of having witnessed the murder two decades ago. The Franklin case was far from unique. Parents were being accused and convicted of other terrible crimes, primarily childhood sexual abuse, sometimes involving years of horrific abuse that was allegedly repressed in memory. Typically, these accusations arose on the basis of memories that adult children had “recovered” during psychotherapy. Some mental health professionals were even promoting the notion that numerous victims had experienced horrific satanic ritual abuse about which they were harboring repressed memories (Rogers 1992, Wright 1994). But scholarly analyses (e.g., Holmes 1990) were revealing that there was little in the way of support for widespread assumptions among therapists and in popular folklore that traumatic memories are particularly likely, relative to nontraumatic memories, to be “repressed” and later recovered intact through techniques such as hypnosis, guided imagery, and other suggestive therapeutic procedures. Analyses of how false memories could develop in the therapeutic setting soon followed (e.g., Lindsay & Read 1994, Loftus 1993, Loftus & Ketcham 1994, Ofshe & Watters 1994, Tavris 1993) and sparked a heated response from the therapeutic community (e.g., Alpert 1995, Terr 1994, Whitfield 1995) and alleged survivors of sexual abuse and their supporters that marked the beginning of a controversy that has been among the most vitriolic and emotionally charged in the history of psychology. This debate, known as the memory wars, has been referred to as “psychology’s most fiercely contested ground” (Crews 2004). But underlying a very practical side of the debate—centered on real-life concerns for victims of either true abuse or of false allegations—is another debate surrounding the very nature of memory and how it works: whether memory might work differently for traumatic versus more ordinary events, and whether it might be distorted or confabulated as a result of therapeutic procedures commonly employed by some therapists. On the one side were primarily practicing therapists who argued that there was and still is overwhelming support for the psychoanalytic notion of repressed memories (sometimes referred to by other terms, such as dissociated memory or traumatic amnesia; e.g., Brown et al. 1998). Traumatic memories such as those of sexual abuse were viewed as fundamentally different from more ordinary memories because they tend to be encoded in ways that render them inaccessible in everyday life. Moreover, suggestive memory recovery procedures and therapeutic 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 471 interactions were viewed as necessary to break through the barrier of repression and bring memories into conscious awareness, which was in turn viewed as necessary for the patient to improve. Therapists who supported such a position tended to view the incidence of “repressed” memories of abuse as relatively high, and therefore the frequency with which such memories were “recovered” in therapy as unsurprising. Many such therapists also viewed even extremely bizarre claims such as satanic ritual abuse among children and adults as credible. And finally, they argued that false memories for such events were particularly unlikely. On the other side were the clinical, social, and cognitive researchers who had long studied the fallibility and suggestibility of memory. Beginning with the assumption that, if anything, memories for trauma are stronger than are those for ordinary events, these researchers viewed traumatic experiences as unlikely to be repressed and as subject to the same sources of distortion and confabulation as memories of other kinds of experiences. These scholars and scientists found no compelling evidence that people massively repress sexual abuse and then reliably recover the memories later (see Piper at al. 2000, Pope et al. 1998). In one survey, 79% said that there was no support for the statement, “Traumatic experiences can be repressed for many years and then recovered,” or that the data were inconclusive (Kassin et al. 2001). Moreover, the repression skeptics worried that suggestive procedures used by some psychotherapists to try to extract allegedly buried trauma memories (such as direct suggestion that the patient was probably abused, guided imagery, hypnosis, age regression, or dream analysis) could lead to false memories—even such seemingly improbable false memories as those of satanic abuse. In the following sections, we review evidence concerning the existence of recovered memories. We focus upon the controversial sense of this term, which involves memories of abuse that are “recovered” during suggestive psychotherapy. We also review evidence for the existence and mechanisms of creation of false memories and discuss how these processes apply in therapy. EVIDENCE FOR REPRESSION AND RECOVERY OF MEMORIES OF TRAUMA Most fundamentally, to demonstrate that memories can be repressed and later recovered, at least three things must be verified: (a) that the abuse did take place, (b) that it was forgotten and inaccessible for some period of time, and (c) that it was later remembered (see, e.g., Pope & Hudson 1995). Studies used to support repression generally do not meet these criteria. Retrospective Studies In a retrospective memory study, individuals are interviewed today and asked whether they were abused in the past as well as other questions assessing the 17 Feb 2006 9:54 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. 472 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS continuity of memory over time, such as whether they ever forgot the abuse. In scores of such studies, some individuals will claim that they were abused and that there was a time when they forgot the abuse (see, e.g., Briere & Conte 1993, Melchert 1996), but the inherent common flaws of these studies render them virtually uninterpretable (see, e.g., Brenneis 2000; Kihlstrom 1998, 2005; McNally 2003b, 2004). Perhaps the most fundamental flaws are lack of validation of the abuse and lack of assessment of the conditions under which the “memory” was retrieved. Though some studies have attempted to validate reported abuse, criteria for validation are often suspect, relying, for example, on participant reports that they had verified the abuse (see, e.g., Herman & Schatzow 1987) or the outcome of legal proceedings (see, e.g., Burgess et al. 1995). Often, researchers fail to report rates of verification separately for those who always remembered the abuse versus those who report periods of amnesia or repression, leaving open the question of the rate of verified “recovered” memories (see, e.g., van der Kolk & Fisler 1995). Still others mix selfreports of verification from patients with apparently more objective verification by police or therapists, but without clear delineation of the frequency of each (see, e.g., Kluft 1997). Nonetheless, although few instances of abuse have been conclusively verified, a number of studies have reported instances of apparent verification of once unrecalled abuse (see McNally 2003b). Other studies have not attempted to validate the abuse at all, and have used persons whose memories were recovered in suspect circumstances without comparison to those whose memories were recovered more naturally. Incredibly, one of the most influential studies of this type recruited subjects through a national network of therapists specializing in treatment of abuse survivors (Briere & Conte 1993). Of those claiming past abuse, 59% reported experiencing a time when they could not remember the abuse. Given a variety of methodological issues (see McNally 2003a), the claim of past nonmemory is uninterpretable. In other studies, patients claiming recovered memory of abuse appear to have undergone questionable procedures such as hypnosis or guided imagination. Indeed, fully two thirds of those reporting periods of amnesia in Roe & Schwartz’s (1996) study reported first recovery of the memory during hypnosis. In another study, participants who never remembered abuse but who had joined incest survivor groups to help them remember were classified as having repressed abuse (Herman & Schatzow 1987). A second general set of concerns surrounds the interpretation of forgetting and recovery. Episodes of abuse may not be experienced as traumatic or even labeled as abuse at the time, and hence forgetting cannot be regarded as traumatic repression. Indeed, one study found that women who reported having forgotten their abuse rated it as having been less upsetting when it occurred than those who had never forgotten (Loftus et al. 1994). In other studies, participants’ own interpretations of failures to remember abuse have included failure to understand the experience as abusive until later and deliberate attempts not to think about it. Many reported that they could have remembered if they tried or if they had been reminded or 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 473 asked about it. However, since all such reports are either guesses about whether the person could remember or subjective assessments of reasons for failure to remember rather than responses to actual attempts to remember, they are difficult to interpret. Further, it is well documented that one can fail to remember that one previously remembered the abuse. For some apparently verified instances of recovered memories, it has been shown that the person actually did remember during the alleged amnestic period, but later forgot previously remembering and talking about the abuse to others (see Brenneis 2000). In one study, women who claimed that they had undergone periods of forgetting their abuse said later in the same interview that they had never forgotten (Fivush & Edwards 2004). Finally, studies of memory for real-life traumata of all sorts suffer from additional problems such as misinterpreting general difficulty with everyday memory as reflecting repression of a specific traumatic event or failure to rule out injury and organic causes of amnesia. Prospective Studies In a prospective memory study, individuals with a record of abuse or other trauma in the past are later interviewed to see what they remember. One well-known study (Williams 1994) involved women who had reported sexual abuse that had occurred when they were aged 10 months to 12 years old. In interviews some l7 years later, 38% did not mention the abuse incident. These results are frequently used to support the notion that a significant percentage of women repress their memories of sexual abuse. But numerous critics have questioned this interpretation (Kihlstrom 2005, Loftus et al. 1994, McNally 2003b), noting the myriad reasons other than repression that could cause participants to fail to mention the abuse. Some had experiences as children when they were so young (under age 2) that childhood amnesia would lead us to expect no memory for the abuse. Even if they did remember it, some may have simply not wanted to report the abuse to an interviewer for reasons such as embarrassment or lack of rapport (Della Femina et al. 1990). Moreover, by design, participants were not asked directly about the abuse, and had they been asked, may well have been able to report it. Finally, normal forgetting occurs for all sorts of events, even ones that would have been rather upsetting or traumatic. Nearly a decade later, Goodman et al. (2003) published a conceptual “replication” of the Williams study. Participants had been involved in a study of the effects of criminal prosecutions on sex abuse victims when they were ages 3–l7 and were interviewed by the authors three times 10–16 years later. By the final interview, only 8% did not report the abuse. Although their study has been criticized for using a “prosecution” sample, its results do cast doubt on the claim that large percentages of women have repressed their memories and have no awareness of real past abuse. Case Histories A third source of evidence offered to support the claim of massive repression is anecdotal cases (sometimes called “anecdata”), where a therapist writes an account 17 Feb 2006 9:54 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. 474 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS of a case history along with an interpretation that the patient has repressed and later reliably recovered the memory. Other reports involve a set of case histories analyzed and possibly “verified” by the researcher. But one problem with case histories is that the therapist/author is typically the only person who has access to the “data,” which are often subjective and not convincingly subjected to objective external verification. Few instances exist where the selectivity has been scrutinized, but one clear example can be found in the 1997 case history of “Jane Doe” (Corwin & Olafson 1997), who was videotaped in 1984 recounting specifics of sexual abuse allegedly committed by her mother. Eleven years later, when Jane was l7, she was videotaped again. This time, she at first did not remember the abuse, and then she did. The therapists published an account of Jane Doe’s life, her allegedly repressed/recovered memory, and the case was cited as verified (e.g., Gleaves et al. 2004). Loftus & Guyer (2002a,b) used public records and newspaper clippings and eventually located Doe’s family. From court documents and other information, they learned that the case was not even remotely a proven case of repressed memory. In fact, much newly discovered evidence cast doubt on whether abuse had occurred at all and pointed to the very real possibility that the abuse narrative had been planted in Jane’s mind by individuals who wished to remove her from her mother. This scrutinized case is a cautionary tale that raises questions about the role of case histories in medicine, science, and mental health. Case histories can be compelling, but they are bounded by the motivations and interpretations of the storyteller. Problems with motivational biases characterize many case histories involving litigated events. Claims of repression are sometimes necessary in order to file suit after delays that would normally exceed statutes of limitations. Nor can outof-court settlements be taken as proof of claims of abuse. Innocents sometimes settle to avoid legal and emotional costs and risks of litigation. Such issues limit the weight of evidence provided by allegedly “corroborated” cases of recovered memories of trauma involved in legal proceedings. Notwithstanding these problems, there are a large number of case reports, some with better verification than others. Schooler et al. (1997) give the impression that they discovered several case histories for which the necessary three-pronged evidence specified by Pope & Hudson (1995) was obtained: The abuse did occur, it was forgotten for some period of time, and it was later remembered. Unfortunately, even in some of these the “documentation” was merely the subject’s word. Moreover, these cases provided no evidence for repression per se. In fact, most memory recoveries reportedly occurred outside of therapy, and some subjects reported that they had forgotten the event even though it was later discovered that they had discussed it with others during the period of “amnesia.” Brenneis (2000) analyzed “verified” case histories provided by Schooler et al. (1997) and others, noting that the most adequately verified accounts tend to share several features: (a) the memories were typically not (with one exception) recovered in the context of therapy, and in all cases the moment of recovery was 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 475 unrelated to any therapeutic activity, (b) the memories were triggered by external events that “reminded” the person of the original abuse, (c) once prompted, the memories “completely unwound instantly” (Schooler et al. 1997, p. 271) and required no interpretation or deciphering, (d) the memories were mostly for single, not repeated, events, (e) assailants were primarily nonfamily members, and ( f ) the events dated from age 9 and older. Finally, information from friends and relatives often revealed that despite the person’s claim of amnesia, the event had been discussed with others during the period of claimed amnesia. These features stand in contrast to the typical pattern for memory recovery in therapy, which involves very effortful and gradual recovery through extremely suggestive therapeutic processes and memory recovery procedures. When memories emerge in this context, they tend to begin as vague and lacking detail but to unfold and become more vivid and elaborate over time. Further, Brenneis (2000) noted that “this constellation of features—multiple events over long periods of time, beginning in early childhood, involving bodily penetration, and enacted by male family members—is seldom if ever found among verified recovered memory cases” (p. 75). Wagenaar & Crombag (2005) provide a devastating analysis of the case of JR— a man Schooler interviewed some nine years after he allegedly recovered memories of abuse by a priest—in which they note that the JR narrative contains innumerable unproven and often suspicious assumptions. Schooler says that JR recovered his memory without a therapist, but JR was in therapy at the time. Schooler implies that JR had no motive, but JR actually did start a lawsuit. Schooler was impressed by a second individual who apparently also implied wrongdoing by the priest, but that second individual was not independent, as he came forth after learning about JR. As Wagenaar & Crombag (2005) note, case histories like that of JR do not meet two of the most important criteria for empirical research: public control and replicability. It is virtually impossible for readers to check most of the details of JR’s story because of the anonymity. We cannot critically question those who provided information nor can we have access to case information. The story is simply hearsay. (See Wagenaar & Crombag 2005, Chapter 5, for an excellent discussion of when case histories can be used successfully to illustrate something important.) In sum, there is little support for the notion that trauma is commonly banished out of awareness and later reliably recovered by processes beyond ordinary forgetting and remembering. Although there have been some apparent instances of verified lost and recovered memories (see, e.g., Brenneis 2000, Gleaves et al. 2004), it is not clear how much scrutiny has been applied, and crucial questions of the base rate at which such verified instances occur and how it depends upon the circumstances of retrieval (through specific procedures during therapy versus as the result of a retrieval cue that occurred in everyday life) remain essentially unanswered. Yet over the past couple of decades, many persons have reported having experienced massive abuse that was repressed and recovered, which raises the question of whether some or all such “memories” might be false. 17 Feb 2006 9:54 476 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. EVIDENCE FOR THE EXISTENCE OF FALSE MEMORIES OF ABUSE Recovered memory therapy advocates note that no controlled experimental evidence confirms that false memories of traumatic events can be implanted. Indeed, ethics restrict experimentation on the impact of memory recovery procedures on recovery of true traumatic memories or implantation of false ones, making laboratory evidence specific to trauma and abuse for both camps rare. Given such limitations, critics of “recovered memories” offer several kinds of evidence demonstrating that false memories for mundane and relatively traumatic autobiographical events can be implanted. False Memories of Real-Life Trauma For most claims of massive repression and recovery, there is little confirming or disconfirming evidence. But some “memories” can be shown to be factually, psychologically, geographically, or biologically impossible. As with case histories of alleged lost and recovered memories, those of false memory for trauma must also meet stringent criteria of proof: both that the person did have memories for the trauma in question and that the event actually did not happen. Indeed, many such case histories are available for abuse- and nonabuse-related trauma (see reviews in McNally 2003b; Schacter 1996, 2001), such as being kidnapped and held hostage (something that happened to classmates instead of oneself), being gang-raped by Satanists (although one’s hymen remains intact), enduring the surgical removal of one’s clitoris (contradicted by the patient’s gynecologist), witnessing the sacrificial killing of persons later found alive, and even for having committed heinous crimes such as murders or sexual abuse (Henkel & Coffman 2004, Kassin 2006, Wright 1994). While some claims have been proven factually inaccurate, others are simply impossible, such as detailed narrative memories of events occurring in the first days to six months of life (Arnold 1994, Usher & Neisser 1993). Although children do encode and remember such events during early life, these memories tend to be eventually lost, as adult reports of childhood memories rarely address events that occurred earlier than age 3 (see Bauer 2006). Among the most frequently reported impossible false memories of trauma are those of abduction by space aliens. Although approximately 17% of Americans believe that aliens have abducted humans (and presumably returned them alive), we assume that memories of such events are clearly false. Nevertheless, large numbers of patients have reported memories of alien abductions that have largely developed in therapy and under hypnosis or while the patient was subject to other methods used in recovered memory therapy (see Mack 1994, McNally 2003b). A large category of false memories concerns various forms of satanic ritual abuse reported by patients in recovered memory therapy. Alleged acts included gang rape; sacrifice of babies and other ritual murders; consumption of blood and 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 477 human waste; forced pregnancies or abortions; dancing, chanting, and other Satan worship activities; and brutal torture designed to cause victims to forget all they endured (see Loftus & Ketcham 1994, Noblitt & Perskin 2000, Ofshe & Watters 1994, Scott 2001). Such cases had so permeated our culture that as of 1991, the American Bar Association reported that 25% of prosecuting attorneys had handled cases involving satanic abuse (Qin et al. 1998). In a 1996 survey of clinicians from the American Psychological Association (Bottoms et al. 1996), 13% had cases involving children and 11% had cases involving adults with claims of satanic ritual abuse (with some therapists reporting more than 100 cases). None had obtained convincing verification of the abuse, nor have subsequent attempts to examine the validity of such claims found reliable evidence (see, e.g., La Fontaine 1998, Lanning 1991, Weir & Wheatscroft 1995). One recent survey found that satanic ritual abuse was reported in 19% of more than 1700 cases involving families who reported false allegations of abuse against a family member (McHugh et al. 2004). Across studies, 95% to 100% of patients had no recollection of abuse prior to therapy (McNally 2003b). Despite vigorous protests from recovered memory therapists (Terr 1994, Whitfield 1995), there are cogent reasons to believe that almost all such claims are false (see McNally 2003a,b). In summary, although there is disagreement regarding the plausibility of some of the above instances of memory for trauma, there can be no doubt that “memories” for factually false as well as impossible or at least highly improbable horrific traumatic events were developed, particularly among persons subjected to suggestive memory recovery procedures. Some have viewed the prevalence of memories for satanic ritual abuse as the strongest evidence of real-life false memories of trauma (e.g., Ofshe & Watters 1994, Ross 1995). Experiences of the “Retractors” In the l990s, hundreds of individuals who had been persuaded that they had repressed and recovered memories of abuse began to realize their memories were false, and many sued their former therapists for planting false memories. Scores were studied by psychologists trying to gain insight into the processes by which the patients developed and later retracted their beliefs (see, e.g., De Rivera 1997; Lief & Fetkewicz 1995; Nelson & Simpson 1994; Ost et al. 2001, 2002). These studies revealed that the modal retractor first sought therapy for depression and then recovered “memories” of abuse during therapy, but later came to believe the “memories” were actually products of therapeutic suggestion. More than 90% recovered their memories in therapy; in one study (Lief & Fetkewicz 1995), 48% recovered memories of satanic ritual abuse and 38% recovered memories of witnessing murder. The vast majority had undergone suggestive procedures such as hypnosis. Retractors reported substantial pressure to recover memories, and noted that when they expressed doubts in their new memories, they were told that such doubt is common but not a sign of inaccuracy. Most reported that outside pressure played little to no role in their retractions (see, e.g., Ost et al. 2002). Instead, the retractions appeared to be based primarily on the experiential qualities of the 17 Feb 2006 9:54 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. 478 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS “memories” themselves. In essence, the memories did not seem truly “real,” being either too clear and vivid (and increasing in vividness over time, rather than declining, as do most memories) or too vague and dreamlike. Although many retractors have provided some insights into the processes they went through, these are case histories and are therefore subject to many of the limitations of case histories identified earlier (see entire Psychological Inquiry, 1997, Vol. 8, #4 for commentaries on the meaning of retractor reports). Not surprisingly, therapists have found these accounts unconvincing, arguing—ironically—that retractors are easily swayed by social pressure or that they are motivated by the potential of lawsuits against their therapists (see, e.g., Blume 1995, Brown et al. 1998). Notwithstanding such criticisms, there is little doubt that at least some people have developed clearly false memories that they later recognize as such. Laboratory Research on the Malleability of Autobiographical Memory Research in the past several decades has shown that it is relatively easy to change details of memories for previously experienced events (see reviews in Davis & Loftus 2006; Loftus 2005; entire Handbook of Eyewitness Psychology, Vols. I and II), but it is also possible to implant entirely false autobiographical memories, even of highly implausible or even impossible events. Using strong forms of suggestion in a paradigm known as the “familial informant false narrative procedure” or simply the “lost-in-the-mall” technique (Lindsay et al. 2004, Loftus 1993, Loftus & Pickrell 1995), people have been led to believe that, as children, they were lost in a shopping mall for an extended time, had an accident at a family wedding, were the victim of a vicious animal attack, nearly drowned and had to be rescued by a lifeguard, etc. These false memories can be planted by telling individuals that their relatives have provided the information and then suggestively interviewing the individuals to try to elicit memory reports. Across many studies utilizing the lost-in-the-mall procedure, an average of approximately 30% of subjects have developed partial or complete false beliefs or memories (Lindsay et al. 2004), although these rates can vary from 0% with relatively implausible events (receiving a rectal enema; Pezdek et al. 1997) to more than 50% for more mundane events (a ride in a hot air balloon; Wade et al. 2002). Techniques such as those involving guided imagination (e.g., Libby 2003), suggestive dream interpretation, or exposure to doctored photographs have also led subjects to believe falsely that they experienced events in their distant and even in their recent past (Loftus 2003). Some develop false memories right away, whereas others begin with little memory but after several suggestive interviews begin to recall false events in great detail (Ost et al. 2005). Implanted memories might be viewed as fleeting and unimportant. But even false beliefs implanted in laboratory studies have repercussions affecting later thoughts, behaviors, and intentions. In several studies, false memories of having EVIDENCE THAT FALSE AUTOBIOGRAPHICAL MEMORIES CAN BE CREATED 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 479 gotten sick after eating particular foods as children led to avoidance of the foods as adults (Bernstein et al. 2005). Several criticisms have been lodged regarding the autobiographical memory implantation research. Most prominent are (a) that we often cannot know for sure (despite familial reports otherwise) that those who develop “false” memories did not experience the target event, and (b) that target events in such experiments are less traumatic and more plausible than those commonly “recovered” in therapy. In response to such criticisms, researchers have endeavored to implant both impossible and highly traumatic or “implausible” autobiographical memories. To address the criticism of verification, for example, Braun et al. (2002) led subjects to believe the impossible event that they had met Bugs Bunny (a Warner Brothers character) at a Disney resort (after exposure to fake Disney ads featuring Bugs Bunny). These authors found that a single fake ad led 16% of subjects to claim they had met Bugs. Even higher rates of false belief were obtained by Braun-LaTour et al. (2004), and ads containing pictures of Bugs produced more false memories than those with only verbal mention of him. The criticism involving the degree of trauma has been more widely addressed. Although researchers have not attempted to plant memories of abuse, they have attempted to plant memories for relatively unpleasant, and in some cases fairly traumatic, events such as hospitalizations, medical procedures, near drowning, or vicious animal attacks. Finally, researchers have planted highly implausible memories for both mundane (e.g., rubbing chalk on one’s head or kissing a plastic frog) and strange and dramatic (witnessing demonic possession as a child) events (Loftus 2003). Whereas it may be more difficult (or even sometimes impossible) to plant implausible memories in many circumstances, this difficulty can be overcome by changing the degree of implausibility first (Hyman & Loftus 2002). Just such a strategy was demonstrated by Mazzoni et al. (2001), who first exposed some participants to material designed to enhance the plausibility of demon possession and later attempted to plant memories of having personally witnessed such an event. Those exposed to the plausibility-enhancing manipulation later reported greater likelihood that they had personally witnessed demon possession. A final criticism of the memory implantation studies is that although false beliefs that one has experienced the event may be planted in many subjects, detailed false memories, particularly for more implausible or more traumatic events, have been planted in relatively few individuals. However, one might argue that given the ease with which false memories can be planted in a short period of time, the rate of false memory development in long-term therapy might be substantially more. RECONSTRUCTIVE INFLUENCES OF BELIEFS, GOALS, AND SELF-VIEWS ON AUTOBIOGRAPHICAL MEMORY Studies concerned with the retrospective bias have shown that reports of our own past attitudes or behaviors are biased by current self-views, goals, and beliefs (and vice versa; Dawes 1991, Wilson & Ross 2003). Similarly, recollections of one’s own behavior tend to change to conform to newly acquired information about how one should behave, so that we believe we behaved in a 17 Feb 2006 9:54 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. 480 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS more consistent, sensible, or desirable way than we actually did. Given this reconstructive bias in autobiographical memory, what direct and indirect reconstructive effects might the sheer belief that one has been abused exert? Even simply considering the possibility that one has been abused might exert such effects, but some patients may come to adopt a highly elaborate personal identity as an abuse survivor. Kihlstrom (1998) coined the term “false memory syndrome,” which he described as “a condition in which a person’s identity and interpersonal relationships are centered around a memory of traumatic experience which is objectively false but in which the person strongly believes . . . the syndrome may be diagnosed when the memory is so deeply ingrained that it orients the person’s entire personality and lifestyle” (p. 16). Though some have objected to the use of the term “syndrome” (Pope 1996), clearly many patients do experience their status as abuse victims as the central or even the primary aspect of their identity. Self-definition as an abuse survivor is likely to exert reconstructive influence on autobiographical memory, which in turn is presumed to serve essentially as the basis of one’s identity. Pressures exist to conform memories to current identity as well as to conform current identity to memories [see entire issue 11, no. 2, of Memory (2003) on autobiographical memory; Tafarodi et al. 2003 on self-esteem and memory]. Summary There is little doubt that abuse can be forgotten and later remembered, although ordinary forgetting and remembering seem more than adequate to account for this. Nor can there be doubt that false memories of abuse or other trauma can be confabulated. Doubt remains, however, regarding the base rates at which each occurs and the circumstances and persons for which each is most likely. Why do some people, and not others, develop false memories? How does this depend upon the social context in which memories are triggered? And fundamentally, how—if at all—are encoding, storage, and retrieval for traumatic or highly emotional content different? When traumatic material is inaccessible for a period of time, what are the processes responsible? Although progress has been made with respect to each question, much remains to be learned. THERAPEUTIC PROCESS AND FALSE MEMORIES OF ABUSE Bearing in mind that false memories can be created, we consider below how this occurs and what might be done to minimize the likelihood. A Priori Assumptions Regarding Abuse As most accounts of the “recovered memory” controversy have documented, a dramatic increase in awareness of sexual abuse began in the 1980s, accompanied by widespread media coverage of abuse and recovered memories as well as a number 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 481 of popular books on the topic. This situation has essentially “primed” the notion of abuse, including repressed memories of abuse, in the general population, and elevated awareness among therapists already acquainted with concepts of trauma and repression. Among the effects of priming particular “schemas” are selective attention to relevant information, biased interpretation of relevant information, and constructive and reconstructive memory processes that generally consist of confabulation of schema-consistent (but false) memories and distortion of memories of past events toward consistency with currently activated schemas (Davis & Follette 2001, Davis & Loftus 2006, Kunda 1999). A patient that has been exposed to accounts of repressed abuse, and with abuse fully primed in her mind, may present with a pre-existing idea that she may have been abused. Likewise, the therapist may expect a high rate of repressed abuse among patients, or particular types of patients, thereby setting in motion a biased assessment process—often followed with vigorous suggestive efforts to test and verify the abuse hypothesis. Confirmation Biases and the Dangers of Specific Hypothesis Testing Confirmatory biases are likely to manifest in initial interview and assessment processes, possibly in both patient and therapist. A patient already considering or convinced of abuse may offer information she perceives as relevant to abuse, perhaps even arguing its significance in terms of abuse. A therapist who perceives abuse as prevalent or likely may inquire about symptoms and facts seen as diagnostic, and if the patient has already brought up the possibility of abuse, rather than engage in a systematic differential diagnosis to examine and rule out alternatives, the therapist may jump directly to the conclusion that the patient in fact was abused. Such “premature cognitive commitment” (Pope & Brown 1996) is among common errors of clinical judgment that some clinicians warn of. Rather than conducting objective hypothesis testing, the therapist may embark upon a quest to discover abuse-consistent evidence (including reports of consistent information and memories from the patient), discounting any inconsistent evidence and doggedly pursuing the presumption of abuse notwithstanding protests and inconsistent evidence from the patient. In recognition of these processes, critics of recovered memory therapy point to scientific literature documenting the dangers of the confirmation bias (the tendency to affirm the diagnosis one is considering) in clinical diagnosis and judgment (see, e.g., Garb 1998). Indeed, even clinicians largely in the recovered memory camp of the debate have warned of the dangers of the confirmation bias in diagnosis (e.g., Pope & Brown 1996). This bias has been documented even under circumstances in which clinicians are asked to review an unknown patient’s file to evaluate whether the patient suffers a particular disorder without any contact with the patient, without any reason to favor the designated diagnosis, and in an effort to provide an unbiased assessment (e.g., Copeland & Snyder 1995; see Kassin & Gudjonsson 2004 and Meissner & Kassin 2004 for discussion of confirmation biases among interrogators). 17 Feb 2006 9:54 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. 482 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS The tendency to confirm clinical hypotheses results in part from biases in interpretation. However, consistent with the vast literature documenting expectancy confirmation processes in social interaction (e.g., Kirsch 1999), biased interviewing procedures also contribute in that questions are typically asked in a manner that tends to elicit apparently confirming information from the patient or interviewee (see, e.g., Fazio et al. 1981, Snyder 1984, Snyder & Thomsen 1988). The therapist may also suggest activities to the patient that would likewise tend to elicit (apparently) confirmatory information, such as reading survivor literature, completing various “homework” activities focused on abuse, or participating in survivor groups. These activities may serve to elicit more apparently abuse-consistent information from the patient. Furthermore, some therapists instruct patients to avoid exposure to contradictory information and those who might provide it rather than objectively testing the abuse hypothesis by seeking, and encouraging patients to seek, informative abuse-inconsistent information as well. Many, if not most, patients enter therapy in search of an explanation for their problems. This very need for explanation may render patients vulnerable to accepting seemingly plausible potential causes. Believing a patient was abused, a therapist might directly suggest this hypothesis, as well as provide apparently confirmatory “evidence,” such as the extent to which the patient’s symptoms conform to those thought to be associated with abuse. Particularly when combined with other “evidence” gleaned from survivor literature, survivor groups, media, and other sources, the abuse hypothesis may seem a compelling explanation to patients who fail to realize their symptoms may be better explained in other ways. The very existence of a potential explanation may motivate some patients to prematurely seize and freeze on the abuse hypothesis, thereby causing them to engage in a strongly biased search for and interpretation of information and to defend against doubt. Some therapists may also be driven by motives—ranging from fierce victim advocacy to potential financial rewards of prolonged therapy—that tend to encourage confirmatory strategies. THE ROLE OF MOTIVATED COGNITION Plausibility-Enhancing “Evidence” Biased hypothesis-testing strategies are likely to elicit apparently confirmatory evidence. The therapist faced with any set of evidence (even were it not selective and biased) can succumb to a number of heuristic and other fallacies of reasoning that result in a tendency to confirm the abuse hypothesis (see Garb 1998), as can patients. Schematic processing can result in selective attention to abuse-relevant information, disregard for abuse-irrelevant information, and interpretative biases toward consistency with the abuse hypothesis, including explaining away apparently inconsistent information. This includes retrospective biases of interpretation such as the “hindsight” bias (Fischhoff 1975), whereby the past is interpreted as consistent with current knowledge. 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 483 Therapists may also fall prey to the “representativeness” heuristic (Kahneman & Tversky 1972), assuming that if a patient’s symptoms fit those viewed as consistent with abuse, the patient must have been abused. This, of course, is the message of much of the survivor literature (e.g., Bass & Davis 1988). Such logic is fallacious, in that “If Abuse, then Symptom” does not logically imply “If Symptom, then Abuse.” Abuse-related symptoms can result from abuse as well as from many other causes. The problem is further complicated by a questionable assumption regarding the true association of various symptoms with abuse. “The phenomenon of recovered memories has been greatly confounded by the assumption made by some clinicians that repetitive behavioral patterns, special sensory reactivities, and unbidden ideation in the form of flashbacks or nightmares necessarily reflect implicit memory for unremembered events. . .. In short, without a corresponding explicit memory, the existence of past trauma cannot be conclusively inferred from any repetitive behaviors or intrusive ideation” (Brenneis 2000, p. 67). Notwithstanding these and other misunderstandings of what constitutes (or does not constitute) valid indicators of abuse, therapist and patient may each offer “evidence” to the other, in support of their own hypotheses. If the patient has not yet adopted the abuse hypothesis, the therapist may proceed with a number of leading and even coercive procedures designed to elicit confirmation, including persistent persuasion and efforts to elicit consistent information and failure to believe inconsistent information at all or to interpret it as actually inconsistent with repressed abuse. Just as the memory implantation research reveals, information that serves to render previously implausible information subjectively more plausible can smooth the way for the development of false memories. Suggestive influences inside and outside of therapy are likely to enhance the plausibility of abuse, notwithstanding the absence of memories. Persuasive information can come from the media, survivor literature, survivor groups, therapist suggestions, and other sources. When apparently authoritative sources state unequivocally that particular symptoms are pathognomic of abuse, the plausibility that a person suffering from such symptoms could have been abused is enhanced. PLAUSIBILITY, BELIEF, AND MEMORY Adopting and Confirming the Belief in Abuse If a patient comes to believe that she may have been abused, efforts by both therapist and patient may ensue to confirm and defend the new survivor identity. These may include memory recovery procedures in and outside of therapy, participation in survivor groups, solicitation of consistent information from family, witnesses, and others—all with significant potential both to bias construction of historical narratives and to lead to confabulation of false memories. Whether the patient has yet adopted the survivor identity or not, the therapist may suggest a variety of memory recovery procedures, both in and outside of therapy, such as hypnosis, age regression, dream MEMORY RECOVERY PROCEDURES 17 Feb 2006 9:54 484 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS interpretation, guided abuse-related imagery, use of photographs to trigger memories, instructions to work at remembering (including through journaling or other homework), and interpreting physical symptoms as implicit memories (see, e.g., Poole et al. 1995). These and other procedures, and their potential to cause false memories, have been extensively discussed (e.g., Brainerd & Reyna 2005, Loftus & Ketcham 1994, McNally 2003a,b). Prominent in the memory recovery arsenal is hypnosis. Interestingly, however, as reviewed by Mazzoni et al. (2006), both memory-enhancing and memory-distorting functions of hypnosis have been recognized and employed by therapists beginning with Freud, Janet, and other early psychotherapists. Therapists have used hypnotic memory retrieval in two opposite ways, without any apparent awareness of the implications that one use had for the other. That is, while they viewed hypnosis as an excellent memory recovery tool to recover accurate memories, they also deliberately used hypnosis as a suggestive memory confabulation tool to create “healing” positive pseudomemories to replace “true” traumatic memories previously “recovered” through hypnosis. Indeed, modern research has verified both functions. Hypnosis can lead to retrieval of greater numbers of or increased detail for accurate memories as well as to greater production of false memories. Persons under hypnosis have developed a number of bizarre or impossible memories, such as memories of satanic ritual abuse (described above), impossible memories from infancy (Spanos et al. 1999), memories from previous lives, sexual abuse during past lives (Stevenson 1994, Spanos et al. 1991), and even memories from one’s own future (see reviews by Kihlstrom 1997, Mazzoni et al. 2006, McNally 2003b). Hypnotic age-regression, a procedure commonly employed by recovered memory therapists (see Poole et al. 1995), is subject to the same distortions as hypnotic memories of recent events (see Nash 1987). As Mazzoni et al. (2006) point out, if hypnosis is not a reliable means of recovering memories of recent events, there is no reason to expect it to be more effective for memories of the distant past or childhood. Nor is there any reason to expect that it can facilitate retrieval of memories beyond the veil of infantile amnesia. Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. HYPNOSIS Therapists commonly employ various imaging activities in their sessions and in homework assignments for clients. Guided imagery, whereby a client is asked to actively try to imagine and create images of past events, is viewed by researchers as dangerous in that these vivid and elaborate images may later become confused with memories. Indeed, memory researchers have shown that imagining events tends to inflate perceptions of the likelihood they had actually occurred—an effect generally referred to as “imagination inflation” (Garry et al. 1996), and a host of studies have shown that active imagination/visualization of events, objects, or persons can lead to false memories of having actually seen, performed, or experienced them. Imagination has produced false memories for simple perceptions, such as having seen or heard objects or sounds, as well as for more complex recent personal actions (such as having said or done something, GUIDED IMAGERY 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 485 both mundane and bizarre) and distant autobiographical memories for a range of events (see reviews by Davis & Loftus 2006; Johnson et al. 1993; Mazzoni & Memon 2003; Schacter 1996, 2001; Thomas & Loftus 2002). Even paraphrasing event descriptions or explaining how an event might have happened can produce inflation (see, e.g., Sharman et al. 2004, 2005). Techniques emphasizing imagination not only can generate false memories, but also can inflate confidence in those memories (see Arbuthnott et al. 2001 on imagery, Mazzoni et al. 2006 on hypnosis, Spanos et al. 1999 on age regression). Presumably, like other implantation techniques, imagination works in a threestage process whereby people first come to believe an event is plausible, next come to believe the event did actually occur, and finally reinterpret their narratives and images of the event as actual memories (Mazzoni et al. 2001). Imagery and imagination may contribute to all levels of this process. Imagery is crucial to plausibility and hence persuasion [see Green & Brock (2002) for evidence that narratives are persuasive to the extent they evoke imagery of their contents]. Research from the source-monitoring tradition has shown that images can be confused with real memories, particularly when they have many of the subjective characteristics of real memories. Johnson et al. (1988) reasoned that when real memories are vague and lacking in vivid detail, as when memories are from the distant past or were never encoded richly in the first place, it is easier to confuse imagined and real events. Another common tool of psychotherapy, dream interpretation, can lead some to develop false memories. Mazzoni and her colleagues (see, e.g., Mazzoni et al. 1999) studied direct suggestion in the form of a psychologist’s bogus interpretation of dreams. For some participants, these bogus interpretations (i.e., the same interpretation given to all subjects, regardless of the dream reported, and with no reason to believe the interpretation applied to each subject) led to false memories for mildly traumatic suggested events. Dreams themselves may also be confused with actual experiences in some cases (Kemp et al. 2003). DREAM INTERPRETATION As an apparently sensible “context reinstatement” procedure, therapists may recommend that patients use family photos to trigger lost memories. But autobiographical memory can be distorted through exposure to photographs (Lindsay et al. 2004). Brainerd & Reyna (2005) suggest that this apparently sensible procedure may backfire because the photos are employed in the context of delayed repeated attempts to recall after previous attempts have failed. FAMILY PHOTOS When “memories” are difficult to retrieve, a variety of memory recovery techniques may be used repeatedly over a long period. Even in the absence of other suggestive procedures and influences, evidence exists to show that (a) as time passes, both spontaneous false memories and false reports in response to suggestion increase (even for short delays involving hours, days, or weeks), (b) repeated attempts to recall increase the yield of false as well as true information, REPEATED RECALL 17 Feb 2006 9:54 486 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS (c) information recalled in later attempts is proportionately more likely to be false, (d) the previous two findings are particularly likely when there are long delays between repeated-recall tests and the index experience, and (e) these patterns obtain for autobiographical memory as well as for laboratory tasks (see review by Brainerd & Reyna 2005). As images appear through various efforts to retrieve memories they may combine with related inferences to develop into full narratives of abusive events. The person may then misunderstand the source of these images and narratives [an error of source monitoring (Johnson et al. 1993)], misattributing them to true memories of the abusive events. But how does this process of misattribution occur? Figure 1 depicts a model of this process. Modern theories of the development of false memories (Brainerd & Reyna 2005) assume that remembering consists of subjectively experienced internal representations of an event combined with judgment criteria for determining whether these representations correspond to a previously experienced index event. Internal representations can be either verbatim traces (i.e., of the exact surface form and other specific information, much like seeing with the mind’s eye) or gist traces (i.e., of the essential semantic meaning or generalized physical form of objects and events, for example, “going to the movie” versus specific visual images of the people, objects, and actions involved). Judgment criterion can also vary in specificity. At one extreme, the person may require vivid, elaborate verbatim memory traces (i.e., the ability to fully picture the event in the mind’s eye or ear) in order to label the internal representations as a memory. At the other, the person may label even fuzzy, unelaborated fragmented gist traces as memories. Generally, the stronger the person’s verbatim and gist traces, and the weaker (or more gist-based) the judgment criterion, the more likely a particular representation is to be judged as a memory. Therefore, therapeutic and nontherapeutic factors that influence the strength of either form of trace or of the nature of the judgment criterion can contribute to source-monitoring errors. To understand how this would occur, we must first address what contributes to the strength of both verbatim and gist traces. Verbatim traces consist of vivid internal images of the index event. A number of factors influence the strength of such images, including the depth of original encoding, personal memorial abilities, and the passage of time. Unfortunately, vivid images may also be created independent of actual experience, such as through the various guided imagery procedures commonly practiced in recovered memory therapy. These highly elaborated internally generated images would possess the apparent verbatim trace representations of actual events and therefore pass even the stringent verbatim-match judgment criterion for assessing validity. Gist traces, on the other hand, may be created through both overlapping and dissimilar processes. Like verbatim representations, gist traces may be strengthened by depth of encoding or personal memorial abilities. However, whereas verbatim memory becomes relatively weaker over time, gist traces become relatively more dominant. Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. ABUSE-RELATED IMAGES AND THEIR MISATTRIBUTION AS MEMORIES ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) Causes of source monitoring failures/memory misattributions AR Figure 1 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. 17 Feb 2006 9:54 P1: OKZ RECOVERED MEMORIES 487 17 Feb 2006 9:54 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. 488 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS Also, whereas verbatim memory, by definition, can be contributed to only by the target event, gist memory may come to include overall meanings that represent the combined semantic understanding of the nature of the event. Hence, gist traces may be affected by one’s overall event-relevant knowledge structure, such as when memory is affected by schematic processing. Thus, like verbatim traces, gist traces can be artificially created or strengthened through various imaging procedures, but can also be strengthened through other activities serving to develop abuse-related schemas, beliefs, and personal narratives. When confronted with the need to judge a particular internal trace, the more existing memory support that can be retrieved to “verify” an experience (and the less contradictory information), the more likely the person will label the trace as a true memory. Such support can include the quality of verbatim and gist traces as well as related images, narratives within which the target event resides, semantic knowledge, beliefs, and other relevant traces. In other words, the more information of any kind that is available to increase the subjective likelihood that an internal trace represents an actual event, the more likely it will be judged as a memory. As depicted in Figure 1, repeated cueing of relevant information (such as through priming abuse, developing abuse narratives, discussing abuse) tends to create rich abuse-related memory support. One may also use familiarity as the judgment criteria, whereby things that simply feel sufficiently familiar are judged as memories. The feeling of familiarity may be increased through the same forms of memory “support” discussed above. Familiarity, or gist-based criteria generally, are more lax judgment criteria and are empirically associated with more reported false memories. Given this background, we can now summarize how therapeutic and associated processes directly and indirectly promote source-monitoring errors. As shown in Figure 1, the social influences that keep abuse primed, promote schematic processing, and support belief in abuse exert persuasive influence on both verbatim and gist memory traces as well as on the judgment criteria applied to those traces. Above, we discussed the way in which verbatim and gist traces can be developed and/or elaborated through therapeutic procedures. Essentially, various imaging activities in and outside of therapy can produce vivid artificial images that resemble verbatim memories (particularly among those with substantial imaginative ability) and also contribute to gist traces. This abuse-related memory support is added to by the various suggestive procedures that develop rich abuse-related narratives, personal abuse-related identities, and abuse-supportive beliefs. These apparent verbatim and gist traces and semantic memory support enhance the plausibility of, and confer a sense of familiarity upon, abuse “memories.” As depicted in Figure 1, therapeutic and nontherapeutic processes also directly and indirectly affect the judgment criteria applied to target internal representations. Generally, the impaired cognitive processes that tend to be characteristic of recovered memory patients (see below) are known to be associated with source-monitoring errors, tendencies toward automatic (e.g., schematic) rather than controlled processing, susceptibility to social influence, and use of gist-based 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 489 judgment criteria (see Brainerd & Reyna 2005, Davis & Loftus 2005, Davis & O’Donohue 2004 for reviews). People who are already susceptible are then subject to other influences that affect judgment criteria. Therapists often directly argue for lax criteria, suggesting that no “memory” should be doubted, and that even bodily sensations and other nonmental reactions should be interpreted as memories. Essentially, familiarity, gist-based, and other unique criteria are promoted. Further, all abuse-supportive beliefs (particularly those supporting specific episodic memories) can directly lower the criteria applied to internal representations. That is, the more the person simply believes an event occurred, the less episode-specific verbatim or gist trace is needed to support a conclusion of verity. The patient’s own faith in the effectiveness of memoryrecovery procedures can similarly directly lower the criteria. Once interpreted as real, of course, such “memories” serve to reinforce the belief in abuse and solidify the survivor identity, perhaps thereby encouraging development of additional false memories. THERAPY AND SOCIAL INFLUENCE Social influence is, in a sense, the point of therapy. The patient hopes to find solutions to problems with the help of a presumably knowledgeable authority. If the relationship develops as desired, the therapist will possess the primary attributes known to promote social influence: likeability, credibility, and power (control over desired resources) (see Pratkanis & Aronson 2001). The patient is likely to feel strong emotional attachment to, great respect for, and even dependence on, the therapist, feelings which would render her more susceptible to believing information and adopting behavioral suggestions such as joining survivor groups, reading survivor literature, or engaging in memory-recovery activities at home. These same feelings would render the person more susceptible to biasing therapist suggestions in and outside of specific activities such as hypnosis or guided imagery. But influence in therapy is actually bidirectional. The abuse hypothesis neither is always first suggested nor is most strongly promoted by the therapist. Patients’ own biases and preconceptions developed outside of therapy can exert a strong influence upon their own hypothesis-testing activities as well as those of their therapists. Individual Vulnerability to False Memories Given that therapeutic procedures possess considerable potential to create false beliefs and memories in some, it is important to consider which patients might be especially susceptible to social influence or memory distortion. Here, we focus upon the issue of social influence. (See Brainerd & Reyna 2005 for a discussion of individual differences in memory distortions.) One might expect patients to be generally more susceptible to influence, and particularly from therapists from 17 Feb 2006 9:54 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. 490 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS whom they are seeking answers. As Brainerd & Reyna (2005) note, “Confused and uncertain people are looking for information that will shed light in dark corners, and they may believe that it can be found in therapy. To find answers, however, they must adopt attitudes of openness, exploration, and discovery with respect to the events of their lives, and they must trust in the wisdom and experience of their therapists. Obviously, these latter characteristics are not commensurate with a narrow, realitybased perspective on memory. Rather, the perspective is a much broader one that searches for answers and solutions in the events of one’s life, which is not precisely the same thing as searching for autobiographical facts” (pp. 386–387). Notwithstanding elevated vulnerability within the general patient population, there will be notable individual differences. To understand who might be most vulnerable to social influence, it is first necessary to understand what is needed to resist social influence. Davis & O’Donohue (2004) provide an extensive analysis of the processes and abilities that promote or undermine resistance to influence with regard to resisting powerful influence in police interrogations (see Knowles & Linn 2004 on resistance to influence in other contexts). Sources of resistance that are most relevant here reduce to two general factors: (a) the ability to resist (consisting of the ability to understand and evaluate relevant information and the ability to exert one’s will to refuse to comply) and (b) the motivation to resist. Ability to Resist The immediate antecedents of the ability to resist are the abilities to (a) analyze relevant information and (b) exert one’s will in a particular direction. These two abilities are in turn affected by both chronic and acute individual differences. To understand and evaluate relevant information adequately, one must possess adequate relevant knowledge and have adequate chronic intellectual abilities. To see flaws in abuse-relevant suggestions, for example, one would be aided both by clear existing autobiographical knowledge and memories and by domain-specific knowledge regarding abuse, therapy, memory, and other relevant facts. Given this knowledge, one would also need to possess the intellectual abilities to analyze incoming suggestions in light of this knowledge and to have the acute capacity to bring relevant knowledge and abilities to bear. The latter requires the intact self-regulatory resources needed to control cognitive processes, including attention (to attend to relevant incoming information, to access relevant information from long-term memory, and to exclude distracting information) and working memory (to hold relevant information in mind while assessing its implications). Self-regulation is central to these abilities. Although many may think of selfregulation as relevant to control of overt behaviors, substantial research has demonstrated that depletion of self-regulatory resources impairs intellectual performance of all sorts, including resistance to persuasion. Furthermore, self-regulatory capacity varies between individuals and can be easily depleted through such means as CHRONIC AND ACUTE INTELLECTUAL ABILITIES 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 491 previous exertions of effort or will, physical depletion, emotional stress, difficult social interactions, and resisting temptation (Baumeister & Vohs 2004; see Davis & O’Donohue 2004 for self-regulation and interrogation). Recovered-memory therapy patients are likely to suffer depleted self-regulatory resources due to psychopathology, emotional distress, poor physical condition secondary to distress (and such factors as sleep difficulties), difficult interactions with family, problems at work, and other factors. This depletion would impair intellectual functioning and ability to analyze relevant information as well as the ability to exert one’s will. Substantial evidence supports the importance of intellectual and self-regulatory capacities for suggestibility. Such factors as IQ, age-related intellectual abilities, physical and emotional status, and acute and chronic self-regulatory capacities have been shown to influence suggestibility and persuasion, including development of false memories and other memory distortions (see reviews by Bruck & Melnyk 2004, Davis & Loftus 2005, Davis & O’Donohue 2004, Gudjonsson 2003, Kassin & Gudjonsson 2004). The inclination to use these capacities is also relevant. Some are more inclined to carefully analyze incoming information (referred to as systematic or central route processing) whereas others rely on heuristic cues such as source attractiveness or credibility to assess likely accuracy (referred to as heuristic or peripheral route processing; see Cacioppo et al. 1996). The latter are particularly prone to rely on those seen as credible authorities without careful consideration of the basis of their opinions. The ability to exert one’s will in the direction of resistance to suggestion is also crucial. The most coercive form of recovered memory therapy will greatly resemble a coercive interrogation. That is, the suggestion will be relentless. Just as interrogators relentlessly pursue a particular preconceived version of the target crime and the suspect’s guilt, the therapist will make many varied and repeated suggestions regarding abuse, will not recognize arguments or evidence provided by the patient against the abuse hypothesis as valid, and will reinterpret apparently inconsistent evidence as actually irrelevant or supportive and all consistent evidence as confirming evidence. In other words, in the strongest form of recovered memory therapy, the patient will be faced with consistent powerful external forces toward acceptance and compliance, thereby requiring strong and intact self-regulatory capacity to resist. THE ABILITY TO EXERT ONE’S WILL RESISTANCE IN THE CONTEXT OF STRONG PRIMING AND DIRECTED ATTENTION Even if a person suffers no impairments of self-regulation, knowledge, or cognitive resources, access to relevant information may be impaired by factors that selectively direct attention to confirming information. If the patient is in a situation where abuse has been suggested, where therapeutic interactions and procedures focus on abuse-related content, where suggestions to read survivor literature or to join survivor discussion groups have been adopted, and there has been a focus on efforts to remember abuse, the full situation will surely selectively direct attention to abuseconsistent content. The therapist is likely to ask questions that will tend to elicit 17 Feb 2006 9:54 492 AR ANRV271-CP02-18.tex LOFTUS  XMLPublishSM (2004/02/24) P1: OKZ DAVIS abuse-consistent content. Hence, even if the patient possesses knowledge (personal historical knowledge or other) that would contradict the abuse hypothesis, abuse and relevant consistent information may be so strongly primed and cognitively available that the contradictory information is effectively kept out of awareness. The same therapeutic activities that selectively direct attention to abuse-related content will also tend to control the interpretation of information that is considered. As noted by researchers studying influence in the interrogation room, interrogators essentially persuade suspects to confess (including to confess falsely) by controlling both the information that is attended to and considered and the interpretation given to that information (e.g., Davis & O’Donohue 2004, Ofshe & Leo 1997). Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. THE ROLE OF DIRECTED INTERPRETATION Motivation to Resist One may see flaws in a suggestion and be able to resist but nevertheless have no desire to do so. Motivation can also affect the inclination to carefully scrutinize suggestions and therefore the initial detection of any flaws. Motivation to resist may be directly diffused by attraction and emotional attachment to the source, by his assumed expertise and authority, and by perceived helplessness in the face of his or her power or excessive dependence on the source (see Pratkanis & Aronson 2001 for reviews regarding source characteristics and influence). Individual differences in tendencies to trust authorities, to view them as credible or powerful, or to depend upon them are associated with greater deference and compliance (see Gudjonnson 2003, Kassin & Gudjonnson 2004). Further, as thoroughly documented in the persuasion literature, resistance is fueled by motivated commitment to current beliefs and by pre-existing inconsistent attitudes and beliefs. In the context of therapy, motivation to resist may be undermined by the need to understand the source of one’s problems (as discussed above) and by abuse-consistent beliefs developed prior to or in the process of therapy. Finally, external influences such as friends, other accusers, and family may directly encourage or discourage abuse-related assumptions. Generally, however, the therapeutic context is likely to undermine resistance in many patients, often progressively so as more abuse-consistent beliefs develop throughout the process. This is perhaps most likely to occur in dispositionally suggestible people who are also most confused, most motivated to find an explanation for their problems, and who possess pre-existing beliefs concerning themselves, repression, and the accused that would support developing abuse narratives. RECOVERED MEMORIES AND PUBLIC POLICY The controversies surrounding allegedly repressed memories have created unfortunate tensions among professionals. But out of this process have come useful discussions by clinicians and nonclinicians writing together about changes in practices that would minimize the problems that false accusations can bring to all 17 Feb 2006 9:54 AR ANRV271-CP02-18.tex XMLPublishSM (2004/02/24) P1: OKZ Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES 493 involved. We found many instances where clinicians and scientists have provided useful advice that stemmed from the research we have reviewed. But we give one of the last words to a clinician, Sarnoff (2001), who has worried that a focus on “believing the victim” (p. 169) has essentially eliminated healthy skepticism as a quality to be encouraged in all who encounter questionable claims. We particularly resonate to her concerns, having learned this truth about memory: Just because a “memory” report is detailed, just because a person expresses it with confidence and emotion, does not mean that the event actually happened. Keeping that truth in mind may help to minimize harm to the many victims of the “memory wars”: the patients who were misdiagnosed, the innocents who were falsely accused, the good therapists who suffered damaged reputations, and the genuine victims of abuse whose experiences were trivialized by the dubious claims of others. Many clinicians will be aware that prominent professional organizations such as the American Medical Association, the American Psychological Association, the Australian Psychological Society, and the British Royal College of Psychiatrists have issued strong warnings against practices associated with recovered memory therapy (see the collected statements in Brainerd & Reyna 2005). It is our hope that this review will provide greater understanding of the basis of these recommendations and of the processes that contribute to the development of false memories of all kinds. In light of the biasing potential inherent to clinical diagnosis and therapy, it is essential for clinicians of the future to be well trained in the dangers of subjectivity and suggestive procedures such as those covered here. ACKNOWLEDGMENTS Gratitude is expressed to the Grawemeyer Prize in Psychology for funding used to carry out this research. DD has testified as an expert witness on memory but has not done so specifically with respect to recovered memories. EL occasionally testifies as an expert witness in trials where recovered memories are an issue. The Annual Review of Clinical Psychology is online at http://clinpsy.annualreviews.org LITERATURE CITED Alpert JL. 1995. Sexual Abuse Recalled. Northvale, NJ: Jason Aronson Arbuthnott KD, Arbuthnott DW, Rossiter L. 2001. 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Child Abuse Negl. 19:491–505 Whitfield CL. 1995. Memory and Abuse. Deerfield Beach, FL: Health Commun. Williams LM. 1994. Recall of childhood trauma: a prospective study of women’s memories of child sexual abuse. J. Consult. Clin. Psychol. 62:1167–76 Wilson AE, Ross M. 2003. The identity function of autobiographical memory: Time is on our side. Memory 11:137–49 Wright L. 1994. Remembering Satan. New York: Knopf P1: JRX February 24, 2006 16:34 Annual Reviews AR271-FM Annual Review of Clinical Psychology Volume 2, 2006 Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. CONTENTS THE HISTORY AND EMPIRICAL STATUS OF KEY PSYCHOANALYTIC CONCEPTS, Lester Luborsky and Marna S. Barrett DOCTORAL TRAINING IN CLINICAL PSYCHOLOGY, Richard M. McFall METHODOLOGICAL AND CONCEPTUAL ISSUES IN FUNCTIONAL MAGNETIC RESONANCE IMAGING: APPLICATIONS TO SCHIZOPHRENIA RESEARCH, Gregory G. Brown and Lisa T. Eyler THE USE OF STRUCTURAL ANALYSIS OF SOCIAL BEHAVIOR (SASB) AS AN ASSESSMENT TOOL, Lorna Smith Benjamin, Jeffrey Conrad Rothweiler, and Kenneth L. Critchfield 1 21 51 83 REINTERPRETING COMORBIDITY: A MODEL-BASED APPROACH TO UNDERSTANDING AND CLASSIFYING PSYCHOPATHOLOGY, Robert F. Krueger and Kristian E. Markon WOMEN’S MENTAL HEALTH RESEARCH: THE EMERGENCE OF A BIOMEDICAL FIELD, Mary C. Blehar POSTTRAUMATIC STRESS DISORDER: ETIOLOGY, EPIDEMIOLOGY, AND TREATMENT OUTCOME, Terence M. Keane, Amy D. Marshall, and Casey T. Taft 111 135 161 THE PSYCHOPATHOLOGY AND TREATMENT OF BIPOLAR DISORDER, David J. Miklowitz and Sheri L. Johnson 199 ATTEMPTED AND COMPLETED SUICIDE IN ADOLESCENCE, Anthony Spirito and Christianne Esposito-Smythers ENDOPHENOTYPES IN THE GENETIC ANALYSES OF MENTAL DISORDERS, Tyrone D. Cannon and Matthew C. Keller SCHIZOTYPAL PERSONALITY: NEURODEVELOPMENTAL AND PSYCHOSOCIAL TRAJECTORIES, Adrian Raine AUTISM FROM DEVELOPMENTAL AND NEUROPSYCHOLOGICAL PERSPECTIVES, Marian Sigman, Sarah J. Spence, and A. Ting Wang OBESITY, Anthony N. Fabricatore and Thomas A. Wadden MILD COGNITIVE IMPAIRMENT AND DEMENTIA, Marilyn S. Albert and Deborah Blacker 237 267 291 327 357 379 vii P1: JRX February 24, 2006 viii 16:34 Annual Reviews AR271-FM CONTENTS COGNITION AND AGING IN PSYCHOPATHOLOGY: FOCUS ON SCHIZOPHRENIA AND DEPRESSION, Philip D. Harvey, Abraham Reichenberg, and Christopher R. Bowie CONTINGENCY MANAGEMENT FOR TREATMENT OF SUBSTANCE ABUSE, Maxine Stitzer and Nancy Petry PERSONALITY AND RISK OF PHYSICAL ILLNESS, Timothy W. Smith and Justin MacKenzie Annu. Rev. Clin. Psychol. 2006.2:469-498. Downloaded from arjournals.annualreviews.org by MEDICAL CENTER LIBRARY on 04/03/06. For personal use only. RECOVERED MEMORIES, Elizabeth F. Loftus and Deborah Davis 389 411 435 469 INDEX Subject Index ERRATA An online log of corrections to Annual Review of Clinical Psychology chapters (if any) may be found at http://www.AnnualReviews.org 499

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