Perception

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The brain’s interpretation of stimuli informs perception. Two theoretical approaches to perception include bottom-up and top-down perception.

Bottom-up perception describes the perception of stimuli based on concrete characteristics. Top-down perception describes perception of external stimuli based on prior knowledge about their properties. Cognitive psychologists study how and when individuals employ these two types of perception to determine their significance and to shed light on human experiences of the world.

For this Discussion, consider differences between bottom-up and top-down perception.

With these thoughts in mind:

Post a brief explanation of the active nature of perception. Then explain two differences between bottom-up and top-down perception. Finally, provide one example of how everyday experience would be altered if bottom-up perception were impaired, as well as one example of how everyday experience would be altered if top-down perception were impaired.

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

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Thinking With Socio-Mental Filters: Exploring the Social Structuring of Attention and Significance* Thomas DeGloma and Asia Friedman** Department of Sociology, Rutgers University 54 Joyce Kilmer Avenue, Piscataway NJ 08854-8045 Phone: 732.236.9921 Fax 732.445.0974 tdegloma@aol.com DRAFT DO NOT CITE WITHOUT PERSMISSION FROM THE AUTHORS * We would like to thank Eviatar Zerubavel, Deborah Carr, and Ann Mische for their insightful comments and suggestions. ** This work represents the equal contribution of both authors. Name order was determined by coin toss. This paper considers the function of socio-mental filters, cultural mechanisms structuring attention and significance that shape empirical reality into intersubjective experience. As a metaphor, filter brings to mind a perceptual "colander" that the world passes through when it is perceived and given meaning in social context, highlighting the vast amount of technically perceivable data that is normally blocked from our awareness, as well as the socio-mental concentration of the information that passes through to be perceived. Thinking with the metaphor of the filter thus directs our attention to what is normally disattended and therefore rendered insignificant. The acknowledgement of this perceptual residue is one of the strengths of the filter metaphor. A further strength of the metaphor is that, as both noun and verb, filter is evocative of multiple dimensions of socio-mental perception. As a noun, filters suggest cognitive constraint, as the material substance of a filter comprises the blockages, rather than the holes, and as such embodies what is not allowed to pass through. As a verb, filter directs our attention to the dynamic character of the empirical world when understood as always created through a process of filtration. We highlight the ways that both foundational and contextual cultural influences on the structuring of experience, identity, and collective memory can be fruitfully understood as processes of filtration. We further draw attention to the intentional and often strategic use of filters in social life. I. INTRODUCTION: CULTURE, FILTERS, AND COGNITION What are Socio-Mental Filters? How can two strangers consistently make the same split second decision about third person’s sex, or classify most people into the same racial categories upon first glance? How can we immediately determine another’s occupation by observing their uniform? Such snap decisions involve mentally highlighting a small number of sexed or racialized body parts, or particular details of dress, respectively. Likewise, why might those who are otherwise prudish feel completely comfortable viewing the sexual drawings of Egon Schiele or reading the poetry of Ovid? Why do we interpret the same behaviors (consider sexual innuendos) differently when we are at work, at home, or at a bar? And why is habitual behavior understood differently if it involves repeatedly washing one’s hands at work as opposed to rubbing rosary beads in a 1 church? Similar aspects of human behavior are perceived differently in different environments, as different details become highlighted and backgrounded in different contexts. One might assume that all of the distinctions alluded to above are made based on clearcut, objective features of empirical reality; but a close examination of any of these cases would reveal a surprisingly complex empirical reality with multiple potential interpretations, most of which we never even consider in the unproblematic functioning of daily life. Whether the details of a person’s body or of a particular behavior, the meaning we attribute to the phenomena we encounter is largely determined by the particular details we attend while ignoring others. In order to direct our attention to this dynamic structuring of our awareness, this paper considers the function of socio-mental filters, cultural mechanisms that structure attention and significance and shape empirical reality into intersubjective experience. Socio-mental filters refer to the cultural grid that shapes the perception of every experience and interaction we have. They are mechanisms of culture that exist between the natural world and the ways in which we experience it as social beings. Notice the metaphor of the filter. There are filters in cars that allow some things to pass through and filter “impurities” out. There are filters that get added to cameras to allow different amounts of light (or only certain kinds of light) to pass through in order to create a particular visual effect. There are filters to remove toxic elements from water. Filters in general function to let “desirable” parts pass through a certain gateway, while blocking anything defined as “undesirable.” Just as a camera filter is the gateway between the subject and the film, and a water filter between water as it enters a processing plant and that which is suitable for drinking, socio-mental filters form social gates of perception. They mediate the transformation of the world outside of 2 us into the understanding of the world that exists in our minds, as “what we experience through our senses is normally 'filtered' through various interpretive frameworks” (Zerubavel 1997: 24). Although they do mediate individual perception, the filters we are concerned with are the properties of cultural systems. Socio-mental filters work to let culturally approved details enter our awareness, blocking all information that does not fit the normative mold, so that we might share an understanding of day-to-day experience with those around us. Such a view is decidedly sociological, suggesting that we see things not simply as individuals (the position of empiricism) or human beings (the universalist view), but as members of particular social groups with “optical norms” (Zerubavel, 1997: 8-9). Thus filters structure the shared perceptions, beliefs, and meanings upon which social groups, from broad cultures to smaller sub-cultures, are grounded. Filters are shared gateways of cognition that are a fundamental part of the “cultural toolkit” (Swidler 1986) belonging to social groups. Methodology: Because filters are elements of culture functioning on a socio-mental level, and are mostly implicit in their operation, we cannot directly observe them at work or analyze them as we would a text, a cultural artifact, an interview, or other standard forms of data. Methodologically speaking, then, studying the operation of socio-mental filters requires unorthodoxy. Accordingly, in this paper we bring together a variety of eclectic examples of filtration. Although the differences among these quite divergent examples are striking, in the spirit of Eviatar Zerubavel’s “social pattern analysis” (2004) we focus on the similarities among them, the general social patterns we can uncover by comparing seemingly very different entities across 3 different levels of analysis. From specific examples of filtration, through comparative social pattern analysis, we attempt to illustrate some of features of filters in general. Further, Goffman’s notion of the social framing of human experience provided the conceptual foundation from which our analysis springs and, for that reason, we see ourselves as continuing to develop a strand of anti-empiricist theory that is directly traceable to him. The social construction of experience is not a new idea, nor did it entirely originate with Goffman (see also: Mannheim 1936; Shibutani 1955; Bateson 1955 [1972]; Berger and Luckmann 1967 [1966]; Kuhn 1970 [1962]; Schutz and Luckmann 1973; Fleck 1981 [1935]; Davis 1983; Zerubavel 1991, 1992, 1997, 2002; Chayko 2002). But we believe that the concept of filter, briefly but powerfully alluded to by others (Schutz and Luckmann 1973; Davis 1983; Zerubavel 1997; Prager 1998; Eyerman 2004), allows us to improve upon and extend the project Goffman began with his notion of frame. We hope to demonstrate the analytic breadth and depth that is possible when thinking in terms of socio-mental filters. Filters and Filtration: Grammatical Flexibility One of the beautiful things about thinking with the metaphor of filter is that it encompasses both the process of using the attention structure and the structure itself. Used as a noun, the concept of socio-mental filters directs our attention to the perceptual grid that the world passes through when it is perceived and given meaning in social context, the pre-defined system of pathways and blockages through which we view reality. In this sense, filters can be seen as producing a state of cognitive constraint, requiring us to notice some details at the expense of others and requiring certain meanings be adopted while rendering others outside the range of our cognitive options (DeGloma 2003). Thinking with the metaphor of the filter thus directs our 4 attention to what is normally disattended and therefore rendered insignificant. The acknowledgement of this perceptual residue is one of the strengths of the filter metaphor; this important element of socio-mental perception has not been highlighted using other similar concepts, for example the social-psychology concept of schema. Used as a verb, the concept of filter (as in to filter) directs our attention to both the active employment of such a cultural tool as well as to the dynamic character of the empirical world when understood as always created through a process of filtration – the process of pushing reality through the pre-defined holes of the noun filter, fitting it into the available forms, shapes and categories. The meaning of nakedness, for instance, undergoes a transformation when filtered through different social contexts, such as an art gallery, a dark park, a nudist retreat, and a bedroom. In each context, certain details of nudity are highlighted (its aesthetic qualities, its threatening qualities, its universal, mundane qualities, and its sexual qualities, respectively)— while other details, those that would lend themselves to the alternate meanings, are ignored. None of these meanings are undeniable or given in a fixed empirical reality; quite the contrary, these meanings are the result of the active structuring of perception through a process of filtering out a large quantity of potentially perceptible details while concentrating our focus on a particular few. Here we may talk of culture in action – the process of eliminating some elements, and thus concentrating others, that results from passing the world through a “cultural colander,” disputing the common notion of a fixed, undeniable, and obvious reality, and instead revealing reality as a socially determined process. II. FILTERS AND FILTRATION IN SOCIAL LIFE 5 Whereas frame analysis (Goffman [1974] 1986) focuses on the distinction between a particular content (a painting, for example) and what it is not (the surrounding wall), sociomental filters direct our attention to a culturally determined structural lattice that allows some information to pass through while blocking the remainder. Keeping this distinction in mind, and highlighting other distinctive features of the filter metaphor as we proceed, we will now briefly discuss the functioning of foundational and contextual filters in social life, emphasizing their impact on the construction of experience, identity, and collective memory in each case. We will further address the intentional manipulation of these filters by individual agents and social movements. Foundational Filters: The concept of socio-mental filters allows for an analysis of what we will call “foundational” levels of perception, emphasizing the structure of perception within Goffman’s radically under-explored “framework of frameworks” ([1974] 1986: 27), directing our analysis to the ways that culture, in a macro-level Durkheimian sense (Durkheim [1912] 1995), impacts the attribution of meaning in social life by blocking some information from our awareness while allowing other information to “pass through.” We are considering the ways in which broad cultural systems and worldviews serve to mediate between the natural world and our experience of it, determining which “raw data” is relevant while filtering out the remainder. The concept of foundational filters allows us to consider the structure of attention associated with such macrolevel phenomenological standpoints. Foundational filters are true to their name, in that they form a foundation for unproblematic everyday functioning within a given culture, spanning times, spaces, and contexts. 6 The concept of frame does not account well for this foundational level of social influence; by definition, foundational influences are those that one cannot put a frame around. They do not have defined beginnings or endings. Given their foundational character, exiting foundational filters is not so common or easy to achieve. Beyond entirely changing one’s cultural habitat, exiting foundational filters requires significant immersion in an alternative cultural system. One of the reasons that paradigm shifts (Kuhn 1970 [1962]) and “culture shocks” are actually so shocking is that they involve switching foundational filters, and thus altering the structure of attention with which one makes sense of the world. For instance, one's experience of sex (as taboo activity or natural phenomenon, for example) largely depends on which “worldview, paradigm, belief system, ideology or ethos” (Davis 1983: 166) one subscribes to, and thus through which one filters otherwise undefined sexual content. While an exposed penis at the beach will be shocking and highly marked from the “Jehovanist” perspective, under which its differences from the rest of the body and its sexualized meaning are emphasized, it is likely to be hardly noticeable from the “Naturalist” point of view, under which such differences are "irrelevant." Each sexual belief system filters the human body through a different “cognitive-normative grid” (ibid: 165-172). Further, the foundational “cognitive framework” through which we filter our experiences largely determines our experience of safety and danger, as the “Cautious,” the “Confident,” and the “Neutral” worldviews determine what is marked as dangerous and what is not (Simpson 1996). Like the sexual filters mentioned above, these foundational filters mediate human experience by determining some information to be relevant, and thus meaningful, and other information to be relatively mundane. 7 We likewise filter our experience of organic material through broad cultural filters in order to determine what is (and what is not) edible. As Zerubavel points out, for instance, it has nothing to do with intrinsic empirical differences why we eat chicken but not parrot and cow but not horse. We only experience cow and chicken as more edible than horse and parrot because we filter our perceptions of these animals through the foundational categories "pet" and "food," which lead us to highlight the differences between them and ignore the similarities (Zerubavel 1997: 54). Similarly, our culture often determines what we do, and do not, experience as laughable (Davis 1993). Such foundational filters can be particular to certain cultures and can also span cultures, being associated with larger worldviews, most notably religion; the exposed parts of the female body, for example, take on radically different meanings for Islamic fundamentalists and Unitarians. Foundational filters are further used both to ascribe identity and are shared properties of collective identities. In the first case, we attribute identity to others, such as a sexed identity, based on the foundational filters through which we perceive them (Friedman 2004). When viewing the human body, for instance, a very small number of parts are highly marked determinants of another person’s sex. The much larger number of body parts which are "unsexed" in our culture are ignored or otherwise unnoticed, essentially filtered out of our perception. Whether we are dealing with sex, race, beauty, or cleanliness, a focus on the filtration process highlights the way that socially shared structures of attention and disattention contribute to the ascription of identity, and thus to our culturally founded understanding and classification of others. In the second case, which focuses on the subjects as opposed to the object of identity construction, identity is constructed around shared foundational filters. Catholics, for example, 8 share particular worldviews through which experiences (such as pregnancy) are filtered. In perceiving a fetus, traditional Catholics highlight its human biological characteristics in order to ascribe a particular meaning to the fetus (life). Such a foundational filter has become fundamental to the Catholic identity. Pro-choice atheists, on the other hand, highlight the nonliving characteristics of the fetus (lack of development and lack of sentience, for example). An understanding of the construction of identity as taking place around shared socio-mental filters highlights the ways that “thought collectives” (Fleck 1981 [1935]) share particular ways of filtering experience, jointly recognizing specific details as relevant, and thus sharing common meanings. With this framework in mind, cultures, as well as religions and schools of thought, can be defined as large collectives that share a set of foundational filters. Finally, foundational filters are as relevant to the interpretation of the past as they are to experience and identity in the present. Cultural groups attend to specific events (Baumeister and Hastings 1997) and personas (Schwartz 1987, 1990; Frisch 1989) despite others, and this structure of mnemonic attention comes to define the present day collective and contribute to its solidarity. Shared filters are thus fundamental features of macro-level “remembrance environments” (Zerubavel 1997: 81), as the structure of what is attended and what is disattended determines the meaning we attribute to past experiences and events. American slavery takes on a different meaning, for example, when filtered through the progressive/modernist narratives of the Harlem Renaissance as contrasted with the tragic/redemptive narrative associated with the teachings of Marcus Garvey (Eyerman 2004: 92). A different meaning is also attributed to slavery (as well as the Holocaust, the Vietnam War, or child sex abuse) depending on whether one filters this historic experience through a culture of survivorhood (DeGloma 2004) or a traditionalist perspective. Survivor movements, for example, highlight events that signify 9 perpetration and atrocity, emphasizing negative affect as opposed to any aspect of the past that might present it in a more favorable light. In each case above, different aspects, details, and ramifications of the past become prominent depending on which filter is employed. In short, the concept of foundational filters allows us to explore the important relationships between the broad cultural structuring of our awareness and the meaning we attribute to our experiences in the world. Furthermore, in structuring knowledge and meaning, foundational filters further provide for the socio-mental classification of people, things, and experiences into categories and orders of hierarchy. Foundational filters are thus fundamental to the discursive or productive power (Foucault 1978) inherent in the production of knowledge and categories, in that they structure our attention to facilitate the creation of degrees of significance as well as similarities and differences. Contextual Filters: While the concept of frame focuses our attention on the organization of the boundaries around any given context, such as a bedroom, an art museum, or a television show, the concept of contextual filters shifts our focus to the organization of attention and relevance within particular contexts. Even within a particular frame, certain details are noticed at the expense of others, rendering, for example, a child’s toy sword more relevant than his hair color within a play-fighting frame (see Bateson [1955] 1972), or violent and disturbing details of details of one’s past more relevant than countless other details in the context of a psychotherapy session (see Prager 1998: 1-16). Stated another way, filter analysis heightens our focus on how context determines what we see and what we ignore within any given frame of reference. As Davis has put it, the concept of socio-mental filters “directs attention to the modifications experience undergoes as it passes through a contextual scheme” (Davis 1983: 285 n. 17, emphasis added). 10 If the concept of foundational filters has Durkheimian roots, then the concept of contextual filters is rooted in Weber’s theory of value spheres (Weber 1946 [1915]), as our analysis of contextual filters emphasizes the logics associated with multiple realms of activity in society, focusing on their respective attention structures. Such an analysis thus runs counter to the logic of Goffman’s concept of “primary frameworks,” defined as a base perspective without any “prior or ‘original’ interpretation” ([1974] 1986: 21), focusing instead on an ever-present and multifarious variety of possible interpretations without any “base” or “original” interpretation. We mean context broadly to include places, environments, times, institutions, or situations that establish a clear field of relevance within which our awareness is structured and meaning is attributed. Whereas exiting foundational filters is difficult (if not impossible), we exit contextual filters all the time as we enter and leave different “contexts.” Contextual filters get layered on top of foundational filters, temporarily altering the shape and pattern of the lattice that experience passes through. The concept of contextual filters allows us to conceptualize the ways that different contexts provide socio-mental filters through which our experiences become meaningful. Thus we experience food and money differently depending on whether we are at home or at work (Nippert-Eng 1995: 60-67) and genital touch differently depending on whether we are in the context of the bedroom or the gynecologist’s office (Emerson 1970), in each case emphasizing different characteristics of otherwise empirically quite similar sensory experiences. Likewise, any time we enter an institutional building we adopt a contextual filter. Thus, yelling is unnoticed on floor of the stock exchange (though not in the bathroom of the building) or at a sporting event because it is “irrelevant”—unmarked—whereas yelling in a library or doctor’s office is impossible not to notice. The empirically identical act of yelling takes on entirely 11 different meanings in the different contexts. Our interpretation of any given experience, then, is the result of the context, specifically the contextual filter, which instructs us in what to highlight and what to ignore. The notion of filter once again specifically directs our attention to questions about relevance and irrelevance, or what elements are “filtered out” and what elements are allowed to pass through a filter and thus become significant to meaning. We must disattend the similarities between libraries and the Stock Exchange and accentuate their differences in order to “properly” ascribe meaning to yelling in the different contexts. Similarly, we are mentally primed to seize on cues that signify the differences between running away from danger and running just for the sake of running. We must apply a contextual filter to the act, filtering out the similarities and highlighting the smaller number of differences, in order to ascribe a different meaning to each case. Just as different environments (churches, bedrooms, and dark alleyways, for example) provide for contextual filters, so do different times. Consider the way in which traditional western families experience meals at 7:00 a.m. and meals at 7:00 p.m. differently, which requires ignoring all of the similarities between the meals, including the purpose of the experience (eating), the use of the same plates and utensils, and possibly even the consumption of the same exact food (bread and potatoes, for example, are staples of both breakfast and dinner). Note also the differences associated with “night-time” and “day-time” in terms of both the compensation adults receive for work (Zerubavel 1985 [1981]) and the way children experience visits by magical beings (Clark 1995). Further, consider the differences in the experience of 11:59 p.m. on December 31st and 11:59 p.m. on August 14th. In each case, the different experiences are created through a process of filtration: we mentally focus on the differences between the two time 12 periods and disattend all of the potential similarities. Different time periods thus provide sociomental filters through which otherwise similar experiences take on different meanings. Further, specific contexts can provide socio-mental filters that render certain aspects of identity (whether of self or other) relevant and, by necessity, others irrelevant. For example, we ascribe different identities to people depending on where we meet them. This socio-mental process involves constructing others' identities by highlighting certain details while ignoring others. Female-to-male transsexuals, for example, are often read as “male” in small towns. But in metropolitan areas, where the context provides the category "butch," they can also be read as "butch-females.” The difference lies not with the individual’s gender performance, but rather the shape, structure, and quantity of the holes in the contextual filter. Similarly, we are likely to have a different interpretation of someone if we met them at a party as opposed to if we had met them at a business meeting, since each context demands that we recognize (and ignore) different details of a person's appearance and personality. In addition to their role in the ascription of others' identities, contextual filters are also used in order to formulate our own identities at times through emphasizing certain contextually shared characteristics at the expense of differences. Individuals often come to identify as survivors in the context of group therapy sessions and consciousness raising meetings by emphasizing the traumatic details of their past (DeGloma 2004). Similarly, problem-drinkers come to identify as alcoholics in the context of A.A. meetings (Howard 2000), emphasizing common problems, turning points, and recovery trajectories. Finally, the concept of contextual filters allows us to consider the structuring of attention involved when the past is viewed through different social contexts. Like foundational filters, contextual filters provide for “remembrance environments” (Zerubavel 1997: 81), but at a 13 different level of permanence (more transitory and fleeting in experiential terms) than those associated with broad cultures and macro-level thought communities. Thus different facets of the Civil War and Reconstruction periods are portrayed in African-American history texts as compared to more general history text books,1 and different details of American slavery are highlighted in African-American owned versus white-owned plantation museums, giving the past different meanings (Eichstedt and Small 2002). Further, one’s autobiographical past often takes on different meaning in the context of psychotherapy as compared with other contexts, such as when constructing a resumé. Upon engaging these various contexts, different aspects, details, and ramifications of the past are promoted at the expense of other possibilities. Environments, times, fields (consider science, art, or religion), and institutionalized interactions (consider the context of being pulled over by a police officer, no matter where the geographic location!) all provide us with contextual filters that structure our attention, and thus our understanding of significance, in socially shared ways. Given the temporary and fleeting nature of contextual filters, we can come to understand our daily lives as involving a relatively constant transformation of meaning. As we move from context to context, we interpret our experiences according to the respective filters that each provides. What is highly marked in one context becomes unremarkable in the next, and so on. Intentional Filtration: The concept of intentional filtration allows us to consider the ways in which actors and groups knowingly reference and employ foundational and contextual filters in order to attribute meaning to particular experiences. Such an intentional use of these cultural tools involves the 1 Based on a preliminary review of several history texts. Inspired by W. E. B. Du Bois’ “The Propaganda of History.” Pages 711-729 in Black Reconstruction in America: 1860-1880. 14 conscious attempt to produce an intersubjective reality for specific purposes. When two lovers, for example, “play doctor” they are mutually adopting a medical-professional filter to temporarily transform the character of their interaction for sexual purposes. Such an active employment of context to transform experience also provides for the appeal of baseball fantasy camps, Mormon handcart treks, and Civil War reenactments. In each, the contextual filter through which the activity is perceived involves playing-up certain details of experience and identity (those that support the fantasy) and playing-down other features and details (particularly those that would signify a continuity with quotidian life) in order to transform the experience itself. Frame analysis falls short in accounting for how and why some individuals or social groups strategically highlight particular details of identity, experience, or history at the expense of others. When a political organization like Vietnam Veterans Against War attributes meaning to the Vietnam War, highlighting previously unattended details, such as the massacre of Vietnamese civilians or the psychological symptoms of American veterans, or when transgendered people perform identity by playing up certain sexed details of their bodies and downplaying others, particular socio-mental filters are strategically employed toward desired ends. Unlike Goffman’s discussion of “fabrications” (Goffman [1974] 1986): 83-123, 156-200), the filtration metaphor does not require that we think in terms of the “truth” or “falsehood” of contradictory perceptions. Stated differently, in Goffman’s formulation there is a Reality, and the fabricator is aware of it. What "fabrication" precludes, however, is the analysis of multiple equally "legitimate" competing perceptions. Social movements, for instance, often strategically employ filters in order to attribute alternate meanings to political activity. One form such a strategic filtration can take is historical 15 analogy (Zerubavel 2003: 48-52). When a contemporary peasant-based socialist movement in Mexico calls itself the “Zapatistas,” or when, in the year 2000, out-of-town college students working on an independent political campaign for City Council in New Brunswick, New Jersey call themselves “freedom-riders,”2 they are not only bridging the past and present, but are strategically employing a socio-mental filter through which contemporary movement experience takes on meaning, deliberately highlighting continuities with particular historical precedents while downplaying potentially important differences. Further, the form that a social movement organization takes, such as a labor “union” (Clemens 1996),3 a “survivor” movement (DeGloma 2004), an anarchist “collective,” or an underground “cell structure,” itself provides a distinct contextual filter through which movement activities become meaningful. Intentional filtration can also provide a means for the rationalization of deviant behavior. Thus a Catholic Priest pedophile can explain his interactions with his children victims as being “like playing patty-cake with the boys in the sandbox” (Scheper-Hughes 1998: 303), filtering what is otherwise seen as sex abuse through a context that emphasizes the benign game-like attributes of the interaction (see also DeGloma 2003). Similarly, the Nazis strategically drew on a hygienic filter to engineer the meaning of mass killings in the death camps (“showers”) as well as the elimination of the international Jewry in general (“social hygiene”). Such an intentional filtration, along with their use of other filters, such as a bureaucratic filter (Bauman 1989), helps to explain how such a system of genocide can be maintained, as well as how Nazis themselves were able to “split” their military selves from aspects of their lives grounded in different contexts, such as family (see Lifton 1896). 2 New Brunswick People’s Campaign for City Council. April – November 2000. In “Organizational Form as Frame: Collective Identity and Political Strategy in the American Labor Movement, 1820-1920,” Clemens makes a similar argument using Goffman’s language of frame analysis. 3 16 The concept of intentional filtration further allows us to consider the ways that actors consciously reference and manipulate contextual and foundational filters in both the performance and ascription of identity. When, for example, adults interact in teen chat rooms on the internet, they are intentionally drawing on a contextual filter in order to “pass” as younger. Other forms of “passing” can also be understood as examples of intentional filtration, as when a transsexual or transgendered person strategically highlights and disguises certain aspects of his or her body, or when someone deliberately emphasizes certain visual or linguistic cues, and de-emphasizes others, to pass as a different race or nationality. Likewise, other types of disguises call on contextual and foundational filters. When thieves and F.B.I. agents, for example, pose as garbage collectors, they deliberately highlight certain culturally recognizable cues to signal the application of the contextual filter “sanitation worker,” thereby rendering unseen and irrelevant any perceptual information that would expose them. Even more common is the invocation and manipulation of filters related to style. In certain geographic areas, wearing “gang colors” intentionally communicates that one is to be understood through a pre-defined set of categories and meanings, thus calling attention to certain aspects of identity and downplaying or backgrounding others. Wearing a certain style of jeans can also communicate identity, invoking foundational filters of race, class, and nationality through which one’s appearance is then filtered. Similarly, when punks wear safety pins as jewelry, for example, they signify that the “punk” identity filter should be applied, but they also further invoke and refuse the hegemonic meaning of safety pins, which is that they are supposed to be hidden, not highlighted (see Hebdige 1979: 26, 90, 117). Finally, the concept of intentional filtration allows us to consider the ways that individuals and groups manipulate contextual and foundational filters in order to attribute 17 meaning to history and construct collective memory. By highlighting different details of the past, John Kerry's presidential campaign and the Swift Boat Veterans for Truth were able to engineer radically different personas for Kerry depending on whether they highlighted his heroic war activity (Purple Heart), for instance, or his anti-war activity (throwing back of the medals). Likewise, the Republican National Convention and Michael Moore's film “Fahrenheit 9/11” highlighted different historical details of September 11, 2001 in order impute radically different meanings to President Bush in his capacity as a leader. In addition to the conscious emphasis of some historical details and ignorance of others, strategic mnemonic filtration also involves emphasizing a specific “causal nexus” (Baumeister & Hastings 1997: 290) through which a past event can take on meaning. Thus the American Civil War (ibid.) is conceptualized differently depending on whether the past is filtered through a southern or northern account of history, each side attributing blame to the other for starting the war. Similarly, the early history of Northern Ireland takes on a different meaning when filtered through the Republican accounts of the Sinn Fein and the Royalist accounts of the Ulster Unionists, each group emphasizing different national origins and historical turning points. Further, depending on the filter employed, certain “events” take on different beginnings and endings. The discovery of America, for example, takes place at a different time as perceived through the standard western foundational filter, which highlights the "discovery" and downplays the prior existence of other groups in America, as opposed to an Afro-centric filter or a Native American cultural filter (see Zerubavel 2003). The potential application of different socio-mental filters to the “same” event can result in tension between alternative structures of attention, since such an act often takes on clear moral and/or political implications. Many situations where filters are intentionally applied, notably as a 18 social movement strategy, are thus marked by the potential for dispute or conflict concerning which meaning or identity ought to be appropriately associated with a given event, experience, or individual. Just as switching contextual filters leads us to perceive difference in otherwise empirically similar data, minor intentional variations in attention – playing up a specific detail or playing down another – can lead to radically different meanings associated with the same experience.4 Thus two social movements with conflicting accounts of the past, for example, can agree upon more than they dispute and still be considered to be “in opposition” to one another. Individuals also intentionally employ filters to ascribe a particular meaning to their biographical past. Such filters often take structured narratological forms (Hankiss 1981) and involve presenting a past that “fits” with one’s contemporary presentation of self and present objectives. Whether a social movement or biographical strategy, intentional mnemonic filtration highlights important ways that individuals and groups employ socio-mental filters in order to consciously attribute meaning to past experience and “produce” the past for the objectives of the present. Whether in service of the creation of experience, identity or history, intentional filtration involves perceptual agency; a deliberate deployment of foundational and contextual filters and a “working knowledge” of culturally available determinants of attention. As such, intentional filtration focuses our analysis on the manipulation of the acts of attending and ignoring the variety of details that are technically available to all who perceive a given subject matter. Conclusion: Frame analysis and social filter analysis each highlight different processes involved with the social organization of perception, and, as such, the metaphor of filter captures dimensions of 4 Ann Mische. Personal Communication. Wednesday 9/22, 2004. 19 perception that the metaphor of frame does not. By directing our analytical focus to the structuring of our awareness, the concept of filter highlights the vast amount of potentially perceivable data that is normally blocked from our awareness, as well as the socio-mental concentration of the information that passes through to be perceived. As socio-mental "colanders" operating on a variety of levels of social organization, filters work to structure the perception of empirical realities and create intersubjective meaning. Thinking with socio-mental filters, we suggest, offers a number of theoretical advantages for our understanding of the sociocultural structuring of cognition, and thus ought to be included in our theoretical toolkit. Works Cited: Bateson, Gregory. 1972 [1955]. “A Theory of Play and Fantasy.” pp. 177-193 in Steps to an Ecology of Mind. New York: Ballantine Press. Bauman, Zygmunt. 1989. Modernity and the Holocaust. Ithaca, New York: Cornell University Press. Baumeister, Roy and Stephen Hastings. 1997. “Distortions in Collective Memory: How Groups Flatter & Deceive Themselves.” Pp. 277-92 in Collective Memory of Public Events: Social Psychological Perspectives. James W. Pennebaker, et. al., Eds. Mahwah, New Jersey: Lawrence Erlbaum. Berger, Peter L. and Thomas Luckmann. 1967 [1966]. The Social Construction of Reality: A Treatise in the Sociology of Knowledge. Garden City: Doubleday Anchor. Chayko, Mary. 2002. Connecting: How We Form Social Bonds and Communities in the Internet Age. Albany: State University of New York. Clark, Cindy Del. 1995. Flights of Fancy, Leaps of Faith: Children’s Myths in Contemporary America. Chicago, IL: University of Chicago Press. Clemens, Elizabeth S. 1996. “Organizational Form as Frame: Collective Identity and Political Strategy in the American Labor Movement.” Pp. 205-226 in Comparative Perspectives on Social Movements: Political Opportunities, Mobilizing Structures, and Cultural Framings. Doug McAdam, John D. McCarthy, Mayer N. Zald, Eds. Cambridge, Massachusetts, Cambridge University Press. 20 Davis, Murray S. 1983. Smut: Erotic Reality/Obscene Ideology. Chicago, IL: University of Chicago Press. -----. 1993. What's so Funny?: The Comic Conception of Culture and Society. Chicago, IL: University of Chicago Press. DeGloma, Thomas E., Jr. 2003. “Memory and the Cognitive Masking of Child Sex Abuse: Framing and Cognitive Asymmetries of Power in the Family.” Presented at the Annual Meeting of the American Sociological Association, Atlanta, GA. 2003. -----. 2004. “Safe Space and Contested Memories: Survivor Movements and the Foundation of Alternative Mnemonic Traditions." Conference paper presented at History Matters: Spaces of Violence, Spaces of Memory. April 23-24, 2004. New School University, New York. Durkheim, Emile. 1995 [1912]. The Elementary Forms of Religious Life. New York: The Free Press. Eichstedt, Jennifer L. and Small, Stephen. 2002. Representations of Slavery: Race and Ideology in Southern Plantation Museums. Washington D. C.: Smithsonian Institution Press. Emerson, Joan P. 1970. “Behavior in Private Places: Sustaining Definitions of Reality in Gynecological Examinations” pp. 74-93 in Recent Sociology No. 2: Patterns of Communicative Behavior, edited by Hans-Peter Dreitzel. London, England: Macmillan. Eyerman, Ron. 2004. “Cultural Trauma: Slavery and the Formation of African American Identity.” Pp. 60-111 in Cultural Trauma and Collective Identity. Jeffrey C. Alexander, Ron Eyerman, Bernhard Giesen, Neil J. Smelser, Piotr Sztompka. Berkeley, California: University of California Press. Fleck, Ludwik. 1981 [1935]. Genesis and Development of a Scientific Fact. Chicago, IL: University of Chicago Press. Foucault, Michel. 1990 [1978]. The History of Sexuality, Volume I: An Introduction, translated by Robert Hurley. New York: Vintage Books. Friedman, Asia. 2004. "Sex Seen: The Socio-Optical Construction of Sexed Bodies." Presented at the Annual Meeting of the American Sociological Association, San Francisco, CA. Frisch, Michael. 1989. “American History and the Structures of Collective Memory: A Modest Exercise in Empirical Iconography.” Journal of American History. 75: 1130-55. Goffman, Erving. [1974] 1986. Frame Analysis: An Essay on the Organization of Experience. Boston, Mass: Northeastern University Press. Hankiss, Agnes. 1981. “Ontologies of the Self: On the Mythological Rearranging of One’s Life History.” Pp. 203-209 in Biography and Society: The Life History Approach in the Social Sciences. Beverly Hills, CA: Sage. 21 Hebdige, Dick. 1979. Subculture: The Meaning of Style. London and New York: Routledge. Howard, Jenna. 2000. “Memory Reconstruction in Autobiographical Narrative Construction: Analysis of the Alcoholics Anonymous Recovery Narrative.” Qualifying Paper, Department of Sociology, Rutgers University. Kuhn, Thomas S. 1970 [1962]. The Structure of Scientific Revolutions. Chicago: University of Chicago Press. Lifton, Robert Jay. 1986. The Nazi Doctors: Medical Killing and the Psychology of Genocide. New York: Basic Books, Inc. Mannheim, Karl. 1936. Ideology and Utopia: An Introduction to the Sociology of Knowledge. New York: Harvest. Nippert-Eng, Christena. 1995. Home and Work: Negotiating Boundaries through Everyday Life. Chicago, Illinois. University of Chicago Press. Prager, Jeffrey. 1998. Presenting the Past: Psychoanalysis and the Sociology of Misremembering. Cambridge, Massachusetts: Harvard University Press. Scheper-Hughes, Nancy. 1998. “Institutionalized Sex Abuse and the Catholic Church.” Pp. 295317 in Small Wars: The Cultural Politics of Childhood. Nancy Scheper-Hughes and Carolyn Sargent, Eds. Berkeley, California: University of California Press. Schutz, Alfred and Thomas Luckmann. 1973. The Structures of the Life World. Evanston: Northwestern University Press. Schwartz, Barry. 1987. George Washington: The Making of an American Symbol. New York: The Free Press. -----. 1990. “The Reconstruction of Abraham Lincoln.” In Collective Remembering. David Middleton and Derek Edwards, Eds. London, England: Sage Publications. Shibutani, Tamotsu. 1955. “Reference Groups as Perspectives.” American Journal of Sociology 60: 562-69. Simpson, Ruth. 1996. "Neither Clear Nor Present: The Social Construction of Safety and Danger," Sociological Forum 11: 549-61. Swidler, Ann. 1986. “Culture in Action: Symbols and Strategies.” American Sociological Review 51: 273-286. Weber, Max. 1946 [1915]. From Max Weber: Essays in Sociology, Tr. and ed. H. Gerth and C. Wright Mills. New York: Oxford University Press. 22 Zerubavel, Eviatar. 1985 [1981]. Hidden Rhythms: Schedules and Calendars in Social Life. Berkeley, California: University of California Press. ------. 1991. The Fine Line: Making Distinctions in Everyday Life. Chicago: University of Chicago Press. ------. 1992. Terra Cognita: The Mental Discovery of America. New Brunswick: Rutgers University Press. -----. 1997. Social Mindscapes: An Invitation to Cognitive Sociology. Cambridge, Mass.: Harvard University Press. -----. 2002. “The Elephant in the Room: Notes on the Social Organization of Denial.” Chapter 2 in Culture in Mind: Toward a Sociology of Culture and Cognition, Karen A. Cerelo, ed. New York: Routledge. -----. 2003. Time Maps: Collective Memory and the Social Shape of the Past. Chicago, IL: University of Chicago Press. -----. 2004. “Generally Speaking: The Logic and Mechanics of Social Pattern Analysis.” Presented at the Annual Meeting of the American Sociological Association, San Francisco, CA. 23 PERSPECTIVES OPINION What attributes guide the deployment of visual attention and how do they do it? Jeremy M. Wolfe and Todd S. Horowitz As you drive into the centre of town, cars and trucks approach from several directions, and pedestrians swarm into the intersection. The wind blows a newspaper into the gutter and a pigeon does something unexpected on your windshield. This would be a demanding and stressful situation, but you would probably make it to the other side of town without mishap. Why is this situation taxing, and how do you cope? The world presents the visual system with an embarrassment of riches. Given a brain of any reasonable size, it is impossible to process everything everywhere at one time1. The human visual system copes with this problem in a number of ways. Rather than having high-resolution processing at all locations, the best resolution is confined to the fovea, with massive losses in acuity occurring only a few degrees into the periphery. There are restrictions in the wavelengths of light that are processed, the spatial and temporal frequencies that can be detected, and so forth. All of these ‘front-end’ reductions in the amount of information fail to solve the problem. To deal with the still-overwhelming excess of input, the visual system has attentional mechanisms for selecting a small subset of possible stimuli for more extensive processing while relegating the rest to only limited analysis. Even though William James famously declared that “Everyone knows what attention is”2, there is no single, satisfying definition of attention. The term covers a diverse set of selective processes in the nervous system. We can attend to a specific task, attend to tactile stimuli in preference to auditory, attend to a specific visible stimulus that is 2° to the left of fixation, and so on. This article is restricted to consideration of visual attention. Even within vision, there is good evidence that attention has its effects in diverse ways. Attention to a stimulus might enhance the signal produced by that stimulus3,4. It might more precisely tune the visual system to a stimulus attribute, excluding other input as noise3. Attention might restrict processing to one part of the visual field5 or to an object6, or it might restrict processing to a window in time7. Faced with this welter of possibilities, we will use an operational definition of one aspect of attention in this paper. We are concerned with the deployment of attention in visual search tasks. It is possible to discuss the role of attention in these tasks while remaining agnostic about distinctions between noise reduction, stimulus enhancement and so forth. In a typical visual search task, an observer looks for a target item among distracting items. In the laboratory, this might be a search for a big red vertical line in a display containing lines of other colours, sizes and orientations. However, visual search is no mere laboratory curiosity. From the search for socks in the laundry to the search for weapons in carry-on luggage, our environment abounds with search tasks. Indeed, these processes of attentional selection, revealed by visual search experiments, are presumably the processes that NATURE REVIEWS | NEUROSCIENCE are used whenever anything in the world becomes the current object of visual attention. The starting point for any understanding of the deployment of attention in visual search is the observation that some search tasks are easy and efficient while others are not. Consider FIG. 1a. If you are asked to find the red target or the tilted target or the big target, it is intuitively clear that the number of distracting items does not make much difference. The colour, orientation or size attributes that define the targets can efficiently guide attention to the target. On the other hand, among these ‘5’s there is a ‘2’ target. Once it has been found, there is no difficulty in discriminating a 2 from a 5. However, attention cannot be guided by the spatial position information that differentiates those characters. The more 5s that are present, the more difficult the search task will be8. The purpose of this article is to review the status of these guiding attributes. What properties can guide attention and what cannot? For about 25 years, the answer to that question has been framed in terms of Treisman’s highly influential feature integration theory9. Treisman followed Neisser10 in proposing a two-stage architecture for human vision (FIG. 2a) in which a set of basic features was generated in an initial, parallel,‘preattentive’ stage. Other processes, like those that bound features to objects and permitted object recognition, were restricted to one or at most a few objects at a time. Consequently, attention was required to select a subset of the input for this more advanced processing. Later models, such as guided search11,12, kept the two-stage architecture but noted that the preattentive stage could guide the deployment of attention to select appropriate objects for the second stage. Therefore, a preattentive stage that could process colour and orientation could efficiently guide attention to a target that was defined by the combination of colour and orientation (for example, a red vertical item) even if preattentive stages could not bind colour to orientation in parallel at all locations. VOLUME 5 | JUNE 2004 | 1 ©2004 Nature Publishing Group PERSPECTIVES a b c d Figure 1 | Easy and difficult examples of visual search. a | It is easy to find the red, tilted or big ‘5’. It is not easy to find the ‘2’ among the ‘5’s. b,c | It is difficult to find the horizontal pairs of triangles in b, but in c it is easy because the early visual system can use intersection information to infer that the blue items occlude pink rectangles. d | In this panel, search for the ‘plus’ is inefficient because the intersection information here does not guide attention. The original account was appealing. Simple features such as size and motion were extracted preattentively. More complex properties required attention. However, the accumulation of information about guiding attributes over the past 20 years makes it clear that this twostage, linear approach will not work. Several lines of objection have been raised13,14, but the core problem for us is that there are multiple examples of ‘features’ that are available early in visual processing and also in attentive vision, but that are not available to guide the deployment of attention. At the same time, there are properties of guiding attributes that are not reflected in attentive vision. This makes it difficult to envision the guiding representation as a stage in a linear sequence of visual processes, like a filter — even a tunable filter — between early vision and the attentional bottleneck. As an example, consider intersections. In FIG. 1b, it is not easy to find the two horizontal pairs of triangles. In FIG. 1c, it is quite easy because early visual processes can handle occlusion information15. Interpreting occlusion requires that the early visual system successfully interprets intersections. Clearly, later object recognition processes can use intersection information. However, as shown in FIG. 1d, intersection does not serve as a source of guidance8. The linear model would have to explain how intersection information could be present, then absent, then present again. It might be better to think of a ‘guiding representation’ as a control device, sitting to one side of the main pathway from early vision to object recognition (FIG. 2b). Its contents are abstracted from the main pathway and it, in turn, controls access to the attentional bottleneck. However, it would not, itself, be part of the pathway. Departure from the linear model has been a feature of several recent theoretical approaches to the guidance of attention. Hochstein and Ahissar16 offer a ‘reverse hierarchy’ model 2 in which properties that are abstracted late in visual processing feed back onto early stages. In an approach that more closely resembles the architecture of FIG. 2b, DiLollo and colleagues13 propose that “Initial processing is performed by a set of input filters whose functional characteristics are programmable under the control of prefrontal cortex.” For our purposes, there are two important points to be made about a guidance control module — wherever it is located in the brain. First, as the intersection example illustrates, it does not have access to all of the information that is available in the visual pathway that runs from early vision through the bottleneck to object recognition. Second, as DiLollo et al. note, when the control module exerts its control over access to the bottleneck, it is not acting as a filter in the simple physical sense of that term. The problem with filters is that they remove information. Consider the following: as we discuss below, guidance by attributes such as colour and orientation seems to be coarse and categorical. Attention is guided to ‘red’ and ‘steep’, not to 640 nm or 23° left of vertical. Suppose that a target is known to be categorically ‘red’. Filtering for ‘red’ would pass what was red and reject what was not. However, imagine a task in which observers must determine whether a red object has a green spot on it, and not a black or a blue one. Introspection will tell you that this is a straightforward task, but a filter that eliminated the ‘not-red’ would make it impossible. Rather than altering the stimulus, as a filter might, the hypothetical control module guides selection like a security screener at an airport. Based on a rather abstract representation of the notion of ‘threat’, the screener selects some individuals for more attention than others. Although attending to an object or location might have perceptual consequences17, guidance itself should not. | JUNE 2004 | VOLUME 5 Conceiving of guidance as a control module also avoids a potential pitfall in models of the reverse hierarchy16 variety. It is reasonable to assume that attention can be guided by some ‘late’ information (see, for example, Torralba’s theoretical work on guidance by scene properties18). If that information fed back onto early visual processes and acted as a filter, one could imagine odd recursive problems where feedback about a scene reduced the ability to see the scene. Torralba’s model, for example, generates images where only the ground plane is visible during a search for people, but we are not meant to suppose that this is what is seen. As with the search for ‘red’, it seems more plausible that late information could inform the guidance of attention by altering the representation in a guiding module placed outside the main pathway to object recognition. In the remainder of this article, we discuss the attributes that are abstracted from early vision that can guide attention. In keeping with the hypothesis that guidance is separate from the the main pathway to object recognition, we avoid the use of the term ‘preattentive’ and its associated theoretical implications. Attributes will be discussed in terms of their ability to guide the deployment of attention. Identifying ‘guiding’ attributes One of the most productive ways to study the differences between visual search tasks is to measure reaction time (RT) — the time that is required to say that a target is present or absent — as a function of the set size (the number of items in the display). The slope of the RT × set size function indexes the cost of adding an item to the search display. So, varying the set size in the colour search task in FIG. 1 will produce little or no change in RT. The slope will be near zero and we can label such a search as efficient. By contrast, in the search for a 2 among 5s, the slope will increase at a rate of about 20–40 ms per item for trials www.nature.com/reviews/neuro ©2004 Nature Publishing Group PERSPECTIVES when a target is present. The slope will be a bit more than twice that steep when the target is absent. We can label such tasks as inefficient. Note that this assumes that the stimuli are large enough and sparse enough that it is not necessary to fixate each one. If search is limited by the rate of eye movements, slopes are in the range of 150–300 ms per item. If the world were simple, search tasks would fall into two dichotomous groups, as originally proposed by Treisman9. There would be parallel tasks, where a guiding feature defined the target, and serial tasks, where no adequate guiding feature was present. We could then use some objective slope criterion (such as 10 ms per item, which has often been proposed in the search literature) as the marker for the presence of a guiding feature. However, when we pool data from many different subjects in many different tasks (as in FIG. 3), the resulting histogram makes it clear that there is no obvious division that splits search tasks into different categories based on slope19. Note that this does not mean that the distribution in FIG. 3 could not be the sum of two or more distinct, underlying distributions20. But it does mean that no simple slope criterion defines the presence of a guiding feature. If a simple slope value is not definitive, what can define a guiding attribute? There are several measures, none of which is completely definitive by itself. An accumulation of converging evidence makes the most convincing case. Note, for the remainder of this paper, that a ‘feature’ will generally refer to a specific value (such as red) on a specific ‘dimension’ (such as colour). Simple feature searches are generally very efficient. Although features cannot be defined by applying a simple criterion slope value, the closer the slope is to 0 ms per item, the more likely it is that the target is defined by a guiding feature. A shallow slope is not perfectly definitive because combinations of features can produce shallow slopes. For example, as shown in FIG. 4a, it is easy to find a black ‘X’ defined by a conjunction of shape and luminance polarity21. In this case, luminance or colour processes can guide attention to the black items and some shape process can guide attention to the item with line terminators22. These guiding signals are strong enough that attention can be swiftly guided to the intersection of the two sets of items11,12. Other criteria. Efficient search is, therefore, a necessary but not sufficient property for showing the presence of a guiding feature. There are at least four other indicators that can provide converging evidence. a Preattentive vision Attentive vision Colour Orientation Size Motion Binding, object recognition Depth etc b Early vision Attentive vision Binding, object recognition Colour Orientation Size Motion Depth etc Guiding representation Figure 2 | Models of visual processing. a | A standard two-stage model with a parallel front end followed by an attentional bottleneck leading to processes such as object recognition. b | We suggest that it is useful to think of a ‘guiding representation’ that is derived from the main visual pathway and that guides access to the attentional bottleneck in the pathway but that is not, itself, part of the pathway. First, in many cases, a texture region that possesses a unique basic feature segments ‘effortlessly’ from a background texture that does not23,24. This is illustrated in FIG. 4b for colour and orientation. This is not a perfect diagnostic because there are instances of segmentation without efficient search, and efficient search without segmentation25. Still, a property that produces both efficient search and effortless texture segmentation is a good candidate for guiding attribute status. Second, for many attributes, the presence of a property is more readily detected than its absence. This leads to so-called ‘search asymmetries’26–28. So, for example, it is easier to find a moving item among stationary distractors than vice versa29. This is useful only if the easy search is efficient. For example, it is easier to find a mirror-reversed letter among regular letters than vice versa, but both searches are inefficient and the mirrored target is easier to NATURE REVIEWS | NEUROSCIENCE find only because the regular letter distractors can be rejected more rapidly. Rosenholtz30 describes other important cautions about the interpretation of search asymmetries. Third, Treisman31 suggests that the ability to participate in ‘illusory conjunctions’ is evidence for feature status. For example, if red vertical and green horizontal items are briefly presented, then observers will often report seeing the occasional red horizontal or green vertical item. The interpretation of this information is complicated by existence of higherorder illusory conjunctions, for example in word formation32. Finally, detection of a target that is defined by a candidate feature should be able to tolerate some distractor heterogeneity (FIG. 4c,d). On the basis of FIG. 4c, one might be tempted to conclude that junction type (T versus L) or perhaps even letter identity has featural status. However, what should be irrelevant variation VOLUME 5 | JUNE 2004 | 3 ©2004 Nature Publishing Group PERSPECTIVES 600 Target-present slopes No. of instances Target-absent slopes 400 200 0 0 20 40 60 Slope (ms per item) Figure 3 | Distribution of slopes from individual sessions in a wide range of search tasks. Sessions are generally 300–400 trials. The distribution is clearly not biomodal. Modified, with permission, from REF. 19  (1998) American Psychological Society. in orientation destroys the efficiency of that search (FIG. 4d). On the other hand, efficient colour search for the red L survives orientation variation with ease. Disruption by distractor heterogeneity can indicate that the wrong feature has been identified as the source of guidance. In FIG. 4c, the T might be found by the orientation of the triangle that would enclose it (its convex hull). This would be disrupted by orientation variation, whereas the identity of a T-junction would not be. This test is most important for ‘higher order’ features, where it is often possible that other simpler, more basic features are driving the efficient search. To summarize, no single diagnostic assures the presence of a guiding feature. Converging evidence from several of the tests described here makes it possible to identify guiding attributes with some assurance. Signal and noise in feature search. When a unique feature defines a target in visual search, efficient visual search is not guaranteed. The difference between the target and the distractors can be considered to be a signal that must be found amidst the noise of the a b surrounding distractors. The qualitative nature of this signal detection problem is neatly captured by Duncan and Humphreys’33 formulation of their ‘attentional engagement theory’. Search efficiency increases as a function of target–distractor (TD) difference (signal) and decreases as a function of distractor– distractor (DD) difference (noise). More formal signal detection approaches (generally involving relatively simple stimuli) can be found elsewhere34–36. Research on visual search for colour illustrates these ideas and reveals certain limitations. FIGURE 5a–d shows a set of stimuli with varying TD differences. FIGURE 5e shows, schematically, the data that might be expected from such an experiment37. For a range of relatively large TD differences (as in FIG. 5c,d), RTs will be fast, slopes of the RT × set size function will be near zero, and error rates, even for briefly presented displays, will be low. Once the TD difference drops below some critical value, RTs, slopes and/or errors will begin to increase. The first important point is that any type of search for a target defined by a unique basic feature can be made arbitrarily difficult if the TD difference can be made c arbitrarily small, whereas search for targets not defined by a unique basic feature cannot be made arbitrarily easy by increasing the TD difference. The second important point is that the bend in the function in FIG. 5e is not located at the resolution limit for that feature. Staying with the example of colour, for a given point in colour space, one can define an elliptical set of other points that represent ‘just noticeable differences’ in colour known as a MacAdam ellipse38. To have an efficient search for one colour among homogeneous distractors, the difference needs to be much greater than the just noticeable difference. Moreover, the shape of the efficient search contour around a specific location in colour space does not look like a scaled version of a MacAdam ellipse37. The metrics of colour difference for foveal colour discrimination are quite unlike those that govern deployment of attention in visual search. FIGURE 5f–h illustrates the effects of DD differences. It is easy to find the orange target among red or yellow homogeneous distractors (FIG. 5f or h). However, when the distractors are heterogeneous, the task becomes more difficult. The nature of the heterogeneity is important. Specifically, search is inefficient if distractors flank the target in the feature space. If a line can be drawn in a two-dimensional colour space, with the target colour on one side and the distractors on another, then search will be easy. Assuming that the TD differences are large enough, these targets and distractors are ‘linearly separable’39,40. If such a line cannot be drawn, search will be inefficient. These are general principles — not curiosities of colour processing. In the search for oriented targets, large TD differences in orientation will support efficient search9. Smaller differences will not41. Foster’s data show that the critical TD difference for efficient orientation search is much larger (~15°) than the minimum difference needed d X O X O O O X X X X X O X O O X O X O X O X O O OX XO X O O X Figure 4 | Clues to guidance. a | Some conjunctions are very easy to find. In this case, the target is the black X — a shape–luminance polarity conjunction 21. b | Segmentation of texture regions on the basis of the colour or orientation of their local elements. c | Both the ‘T’ and the red ‘L’ appear to ‘pop out’, but pop-out of the T does not survive irrelevant variation in orientation (d). This indicates that the distinction between T- and L-junctions is not a guiding feature. 4 | JUNE 2004 | VOLUME 5 www.nature.com/reviews/neuro ©2004 Nature Publishing Group PERSPECTIVES a b c d RT, slope or errors e a f b g c d h Figure 5 | Target–distractor and distractor–distractor differences. a–d | Search is easier when the target–distractor (TD) difference is larger. A simple feature search can produce steep slopes and/or long reaction times (RTs) if the TD difference is small (e). f–h | Distractor heterogeneity makes search harder (compare g with f or h). Part e modified, with permission, from REF. 37  (1990) Optical Society of America. to discriminate oriented lines (~1–2°). His data also show that variation in these critical values is not the same as the variation in discriminability with orientation. Search is inefficient when distractor orientations flank target orientations. So, it is easy to find a vertical target among homogeneous distractors tilted 20° to the left or 20° to the right. It is quite difficult to find the same vertical target among heterogeneous distractors tilted 20° left and right42. The effects of distractor heterogeneity again reinforce the differences between determinants of search performance and determinants of discriminability. In search, the categorical status of the target is important. So, search is more efficient if the target is uniquely steep, shallow, or tilted left or right42. What attributes guide visual search? One goal of this review is to provide the best current list of the attributes that guide the deployment of attention. Most of the candidates for this list have not been put through all the tests described above. Nevertheless, TABLE 1 is an effort to make such a list. Note that the references are representative, not exhaustive. They are intended to provide the interested reader with pointers to the main evidence for and, in some cases, against the featural status of various attributes. Further discussion can be found in various review chapters43–45. The list is organized into five groups of candidate sources of guidance. The first category of ‘undoubted’ attributes are those for which there is so much evidence that it is almost beyond question that these are dimensions whose features can guide search. This certainty fades as we go along the categories until we reach the final category of proposed attributes where the best evidence indicates that these are not guiding attributes. In the remainder of this paper, we briefly consider some of the issues raised by this list. The undoubted guiding attributes. Colour, motion, orientation and size are all supported as guiding attributes by large amounts of convincing data. However, in the case of size, it is possible that properties such as size and spatial frequency might be disentangled into two or more separate dimensions46. Probable guiding attributes. These are attributes where more data would help to clear up ambiguities. For example, in the case of luminance onset, under some circumstances, NATURE REVIEWS | NEUROSCIENCE luminance offsets might also work47. The only reason to question luminance polarity as a guiding attribute is that it might be a subset of colour (that is, it might be the black–white or luminance axis of a three-dimensional colour space). Motion might be a single dimension, or speed and direction might be separate dimensions48. Vernier offset — a small lateral break in a line — is a less than assured guiding property, because it might be reducible to a form of an orientation cue49. In the case of stereopsis, there might be a broader dimension of something like three-dimensional layout that would capture various depth cues including stereopsis, the various pictorial depth cues, and shading. The cues would merely serve to create three-dimensional surfaces in the way that wavelength (not a guiding dimension) creates colour. Shape is, perhaps, the most vexed of the guiding attributes, and several other attributes on this list have the same problems. It is clear that some aspects of shape are available to guide attention. It is not clear exactly what those aspects are. Evidence can be mustered for closure (for example, O versus C) or the topological property of having a ‘hole’, but closure could also be the state of not having clear line terminators. The various claims for the featural status of letters (see below) are endlessly complicated by our inability to settle on a set of shape features. For the present, it is clear that a feature such as line termination can distinguish between ‘O’ and ‘Q’, but it is not clear that such features can account for all of the search effects that are seen with letter stimuli. Observers are sensitive to the direction of curvature (for example, left versus right)27. If the curves are part of the bounding contour of an object, this becomes concavity and convexity, with a possible preference for concavities50. So, concavity and convexity could be features of a curvature dimension. Taken into three dimensions, the concavity and convexity of surfaces might be the ‘real’ features in studies that argue for shading as a feature. Possible guiding attributes. Shading or lighting direction is also an interesting case for other reasons. Early evidence such as Ramachandran’s ‘eggs’ study51 looked persuasive, but recent work (Ostrovsky, Y., Cavanagh, P. & Sinha, P., unpublished observations) suggests that we are not very sensitive to the actual properties of shadows. It might be that shading information is available in early vision. Like other depth cues, it might merely create other guiding attributes (such as surface orientation, convexity and concavity) while not guiding attention itself. VOLUME 5 | JUNE 2004 | 5 ©2004 Nature Publishing Group PERSPECTIVES Table1 | Attributes that might guide the deployment of attention Undoubted attributes* 26,27,37,39,40 -Colour -Motion30,56,57 -Orientation41,42,58–61 -Size (including length and spatial frequency)27,62,63 Probable attributes‡ -Luminance onset (flicker) -Luminance polarity21,66 -Vernier offset67 -Stereoscopic depth and tilt68–70 -Pictorial depth cues71–73 -Shape27,58,74–80 -Line termination22,81,82 -Closure26,77,83–85 -Topological status77,86,87 -Curvature27,67,88 Possible attributes§ 64,65 Doubtful cases|| 51,89 -Lighting direction (shading) -Glossiness (luster)52 -Expansion90,91 -Number27,81 -Aspect ratio27 28,53,92 -Novelty -Letter identity (over-learned sets, in general)93–95 -Alphanumeric category96–99 Probable non-attributes¶ -Intersection8,58 -Optic flow29,91 -Colour change64 -Three-dimensional volumes (such as geons)100,101 -Faces (familiar, upright, angry and so on)102–108 -Your name109 -Semantic category (for example, ‘animal’,‘scary’)10 Attributes are grouped by the likelihood that they are, in fact, sources of guidance of attention. References are representative but not exhaustive. *‘Undoubted’ meaning that they are supported by many studies with converging methods. ‡Less confidence owing to limited data, dissenting opinions or the possiblity of alternative explanations. §Still less confidence. ||Unconvincing, but still possible. ¶Suggested guiding features where the balance of evidence argues against inclusion on the list. The evidence for shininess or gloss as a guiding attribute comes from a single experiment on binocular luster52. Current work in our laboratory casts doubt on the generality of the finding. Expansion is problematic because of limited data and because it could be a version of a depth cue, a size cue, a motion cue or some combination of these. Its independent status has not been verified. Candidate dimensions such as number (is this clump made of one item or two?) and aspect ratio (for example, ovals among circles) could be on the list, but the evidence is scant and these should be revisited. Doubtful cases. The central issue in the case of novelty is whether a novelty feature can survive any degree of distractor heterogeneity. For example, a mirror-reversed ‘N’ will pop-out among Ns and a mirror-reversed ‘Z’ will pop-out among Zs53, but it is unclear whether novel mirror Ns and Zs will pop-out from a mixture of boring Ns and Zs. They should, if ‘novel letter’ had the status of a guiding feature. Nobody believes that nature has equipped us with parallel processors for the Roman alphabet. The crucial question in letter search (and some related tasks) is whether overlearned sets acquire the ability to guide attention54,55. In the case of alphanumeric stimuli, it is exceedingly difficult to sort out possible visual confounds. It is worth noting that letter search tasks (like novelty tasks, above) seem to be vulnerable to distractor heterogeneity. The alphanumeric category refers to the specific claim that a letter might pop-out among numbers and vice versa. These effects (such as the ‘zero–oh’ effect) have been difficult to replicate. Probably not guiding attributes. Intersection, once a plausible guiding attribute, has fallen off the list of guiding attributes8. Earlier 6 experiments used stimuli that confounded intersection with other features such as line termination. Optic flow, colour change and three-dimensional volume are reasonable candidates that might have guided the deployment of attention. However, the data indicate that they do not. Faces are also natural candidates for guiding features. However, the preponderance of evidence indicates that, although faces are ‘special’ stimuli, they are processed one at a time. Evidence for guidance by faces tends to be followed by a study that shows that another visual feature is at work. This point is debatable and, certainly, there are others who would place faces higher on this list. The substantial and growing literature on search for semantically or affectively meaningful stimuli has a similar feel to it. An ability to find threatening snakes and spiders efficiently seems to have more to do with their visual status as distinctive shapes than their affective status as scary objects. Conclusion Some properties of visual stimuli can be used to control the deployment of attention. These are not simply the properties of early stages of visual processing. Instead, they seem to be a specific abstraction from the visual input. We can call this abstraction the guiding representation. On the basis of several decades of research, a list of guiding attributes can be proposed. Some dimensions, such as colour, size and orientation, are assured places on that list. Others, such as line termination, are probably guiding attributes, whereas others, such as threat, are probably not. 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Online links FURTHER INFORMATION Visual attention lab: http://search.bwh.harvard.edu Access to this interactive links box is free online. VOLUME 5 | JUNE 2004 | 7 ©2004 Nature Publishing Group Copyright of Nature Reviews Neuroscience is the property of Nature Publishing Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. Journal of Experimental Psychology: Human Perception and Performance 2007, Vol. 33, No. 1, 48 –56 Copyright 2007 by the American Psychological Association 0096-1523/07/$12.00 DOI: 10.1037/0096-1523.33.1.48 Bottom-Up Guidance in Visual Search for Conjunctions Michael J. Proulx 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. Johns Hopkins University Understanding the relative role of top-down and bottom-up guidance is crucial for models of visual search. Previous studies have addressed the role of top-down and bottom-up processes in search for a conjunction of features but with inconsistent results. Here, the author used an attentional capture method to address the role of top-down and bottom-up processes in conjunction search. The role of bottom-up processing was assayed by inclusion of an irrelevant-size singleton in a search for a conjunction of color and orientation. One object was uniquely larger on each trial, with chance probability of coinciding with the target; thus, the irrelevant feature of size was not predictive of the target’s location. Participants searched more efficiently for the target when it was also the size singleton, and they searched less efficiently for the target when a nontarget was the size singleton. Although a conjunction target cannot be detected on the basis of bottom-up processing alone, participants used search strategies that relied significantly on bottom-up guidance in finding the target, resulting in interference from the irrelevant-size singleton. Keywords: attention, visual search, bottom-up, top-down, conjunction search for a unique feature singleton (such as a vertical line among horizontal lines) by strategically relying on bottom-up processing to search for the unique object in the display or by strategically relying on top-down processing to search for the target-defining feature of “vertical” in the display (cf. singleton-detection mode versus featuresearch mode, respectively; Bacon & Egeth, 1994). Note that the use of bottom-up processing versus top-down processing can be contingent on the strategy used by the participant, consistent with the contingent-capture hypothesis (Folk, Remington, & Johnston, 1992). Of course, the use of bottom-up processing might be involuntary (cf. Theeuwes, 2004); however, the main concern here is not whether bottom-up processing is automatic or contingent but, rather, whether bottom-up processing plays a key role in conjunction search. Egeth, Virzi, & Garbart (1984) were the first to provide evidence for the top-down guidance of attention in conjunction search. A conjunction search task generally has two distractor types, with each type sharing one feature with the target. Egeth et al. kept the number of one distractor type constant and varied only the number of the other distractor items. They found that participants could restrict attention to one target featur...
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Running head: PERCEPTION

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Perception
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PERCEPTION

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Our senses are constantly being bombarded by numerous stimuli through our five senses;
seeing, smelling, hearing, tasting and feeling. This process of sensing is called sensation, and it
triggers other crucial processes that assist in our awareness of our environment. Once the senses
are picked up, they are interpreted by our brain and develop a perception of our surrounding
(Denworth, 2014). Imagine the number of sensations that are actually taking place in a particular
mome...


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