LIFESPAN DEVELOPMENT
A Psychological Perspective Second Edition
By Martha Lally and Suzanne Valentine-French
1
Lifespan Development: A Psychological Perspective
Second Edition
By Martha Lally and Suzanne Valentine-French (Published 2019)
This Open Education Resource (OER) textbook was funded by a grant from the
College of Lake County Foundation and supported by the Business and Social
Sciences Division.
This textbook can be found at:
http://dept.clcillinois.edu/psy/LifespanDevelopment.pdf
Publication is under the following license:
Creative Commons Attribution-Noncommercial-Share Alike 3.0 unported license to view a copy
of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative
Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
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Table of Contents
Chapter 1: Introduction to Lifespan Development
Chapter 2: Heredity, Prenatal Development, and Birth
Chapter 3: Infancy and Toddlerhood
Chapter 4: Early Childhood
Chapter 5: Middle and Late Childhood
Chapter 6: Adolescence
Chapter 7: Emerging and Early Adulthood
Chapter 8: Middle Adulthood
Chapter 9: Late Adulthood
Chapter 10: Death and Dying
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Table of Contents
Chapter 1: Introduction to Lifespan Development ....................................................................................... 9
Lifespan Perspective ............................................................................................................................. 10
Conceptions of Age ............................................................................................................................... 13
Periods of Development......................................................................................................................... 14
Issues in Lifespan Development ............................................................................................................. 16
Historical Theories on Development ....................................................................................................... 17
Contemporary Theories on Development ................................................................................................ 18
Descriptive Research ............................................................................................................................. 24
Correlational Research .......................................................................................................................... 26
Experimental Research .......................................................................................................................... 28
Research Involving Time-Spans ............................................................................................................. 29
Conducting Ethical Research .................................................................................................................. 32
References ............................................................................................................................................ 33
Chapter 2: Heredity, Prenatal Development, and Birth.............................................................................. 35
Heredity ............................................................................................................................................... 35
Genotypes and Phenotypes .................................................................................................................... 36
Genetic Disorders ................................................................................................................................. 37
Chromosomal Abnormalities .................................................................................................................. 39
Behavioral Genetics .............................................................................................................................. 41
Prenatal Development ........................................................................................................................... 43
The Germinal Period ............................................................................................................................. 43
The Embryonic Period ........................................................................................................................... 44
The Fetal Period.................................................................................................................................... 45
Prenatal Brain Development .................................................................................................................. 47
Teratogens ............................................................................................................................................ 47
Maternal Factors ................................................................................................................................... 53
Prenatal Assessment .............................................................................................................................. 57
Complications of Pregnancy .................................................................................................................. 59
Preparation for Childbirth ...................................................................................................................... 60
Stages of Birth for Vaginal Delivery ....................................................................................................... 61
Assessing the Neonate ........................................................................................................................... 63
Problems of the Newborn ...................................................................................................................... 63
Postpartum Maternal Concerns ............................................................................................................... 65
References ............................................................................................................................................ 65
Chapter 3: Infancy and Toddlerhood .......................................................................................................... 71
The Brain in the First Two Years ............................................................................................................ 72
Infant Sleep .......................................................................................................................................... 74
From Reflexes to Voluntary Movements ................................................................................................. 77
Motor Development .............................................................................................................................. 78
Sensory Capacities ................................................................................................................................ 79
Nutrition .............................................................................................................................................. 82
Global Considerations and Malnutrition .................................................................................................. 84
Piaget and the Sensorimotor Stage .......................................................................................................... 85
Language ............................................................................................................................................. 89
Components of Language ...................................................................................................................... 90
Language Developmental Progression .................................................................................................... 91
Theories of Language Development........................................................................................................ 93
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Temperament ........................................................................................................................................ 97
Infant Emotions .................................................................................................................................... 99
Forming Attachments .......................................................................................................................... 101
Erikson: Trust vs. Mistrust ................................................................................................................... 102
Mary Ainsworth and the Strange Situation Technique ............................................................................ 102
Erikson: Autonomy vs. Shame and Doubt ............................................................................................. 106
Measuring Infant Development ............................................................................................................ 106
References .......................................................................................................................................... 106
Chapter 4: Early Childhood ....................................................................................................................... 115
Brain Maturation ................................................................................................................................. 116
Motor Skill Development..................................................................................................................... 117
Toilet Training .................................................................................................................................... 119
Sleep .................................................................................................................................................. 119
Sexual Development in Early Childhood ............................................................................................... 120
Nutritional Concerns ........................................................................................................................... 121
Piaget’s Preoperational Stage ............................................................................................................... 123
Vygotsky’s Sociocultural Theory of Cognitive Development .................................................................. 126
Information Processing ........................................................................................................................ 127
Attention ............................................................................................................................................ 127
Memory ............................................................................................................................................. 128
Neo-Piagetians .................................................................................................................................... 130
Children’s Understanding of the World ................................................................................................. 131
Language Development ....................................................................................................................... 133
Bilingualism ....................................................................................................................................... 134
Preschool ........................................................................................................................................... 135
Autism Spectrum Disorder ................................................................................................................... 136
Erikson: Initiative vs. Guilt .................................................................................................................. 139
Self-Concept and Self-Esteem .............................................................................................................. 139
Self-Control ........................................................................................................................................ 140
Gender ............................................................................................................................................... 140
Theories of Gender Development ......................................................................................................... 141
Transgender Children .......................................................................................................................... 142
Parenting Styles .................................................................................................................................. 143
Spanking ............................................................................................................................................ 145
Sibling Relationships ........................................................................................................................... 146
Play ................................................................................................................................................... 147
Children and the Media ....................................................................................................................... 149
Child Care .......................................................................................................................................... 150
Child Abuse........................................................................................................................................ 151
Adverse Childhood Experiences (ACEs) ............................................................................................... 152
References .......................................................................................................................................... 155
Chapter 5: Middle and Late Childhood .................................................................................................... 164
Physical Development ......................................................................................................................... 164
Sports ................................................................................................................................................ 165
Childhood Obesity .............................................................................................................................. 168
Concrete Operational Thought ............................................................................................................. 170
Information Processing ........................................................................................................................ 172
Language Development ....................................................................................................................... 174
Communication Disorders ................................................................................................................... 174
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Theories of Intelligence ....................................................................................................................... 175
Measuring Intelligence: Standardization and the Intelligence Quotient ...................................................... 179
Extremes of Intelligence: Intellectual Disability and Giftedness ............................................................... 181
Education ........................................................................................................................................... 183
Cultural Differences in the Classroom................................................................................................... 184
Children with Disabilities .................................................................................................................... 187
Children with Disabilities: Legislation .................................................................................................. 191
Erikson: Industry vs. Inferiority ............................................................................................................ 193
Self-Understanding ............................................................................................................................. 193
Kohlberg’s Stages of Moral Development ............................................................................................. 194
Friends and Peers ................................................................................................................................ 196
Bullying ............................................................................................................................................. 199
Family Life......................................................................................................................................... 200
References .......................................................................................................................................... 205
Chapter 6: Adolescence ............................................................................................................................ 215
Growth in Adolescence........................................................................................................................ 215
Sexual Development ........................................................................................................................... 216
Adolescent Brain ................................................................................................................................ 219
Adolescent Sleep ................................................................................................................................ 221
Adolescent Sexual Activity .................................................................................................................. 222
Eating Disorders ................................................................................................................................. 223
Piaget’s Formal Operational Stage ........................................................................................................ 225
Information Processing ........................................................................................................................ 227
Education ........................................................................................................................................... 228
School Based Preparatory Experiences ................................................................................................. 230
Teenagers and Working ....................................................................................................................... 230
Teenage Drivers .................................................................................................................................. 231
Self-concept and Self-esteem in Adolescence ........................................................................................ 233
Erikson: Identity vs. Role Confusion..................................................................................................... 233
Parents and Teens: Autonomy and Attachment ...................................................................................... 237
Peers .................................................................................................................................................. 238
Romantic Relationships ....................................................................................................................... 239
References .......................................................................................................................................... 240
Chapter 7: Emerging and Early Adulthood ............................................................................................... 246
Emerging Adulthood Defined .............................................................................................................. 246
Cultural Variations .............................................................................................................................. 248
When Does Adulthood Begin? ............................................................................................................. 249
Young Adults Living Arrangements ..................................................................................................... 250
The Physiological Peak........................................................................................................................ 251
Obesity .............................................................................................................................................. 252
A Healthy, But Risky Time .................................................................................................................. 254
Gender ............................................................................................................................................... 257
Sexuality ............................................................................................................................................ 258
Beyond Formal Operational Thought: Postformal Thought ..................................................................... 265
Education ........................................................................................................................................... 266
Career Development and Employment .................................................................................................. 268
Sexism ............................................................................................................................................... 270
Temperament and Personality in Adulthood .......................................................................................... 274
Attachment in Young Adulthood .......................................................................................................... 276
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Relationships with Parents and Siblings ................................................................................................ 279
Erikson: Intimacy vs. Isolation ............................................................................................................. 280
Factors influencing Attraction .............................................................................................................. 280
Friendships ......................................................................................................................................... 281
Love .................................................................................................................................................. 281
Adult Lifestyles .................................................................................................................................. 283
Intimate Partner Abuse ........................................................................................................................ 291
Parenthood ......................................................................................................................................... 293
References .......................................................................................................................................... 295
Chapter 8: Middle Adulthood ................................................................................................................... 307
Physical Changes ................................................................................................................................ 308
Sensory Changes ................................................................................................................................. 309
Health Concerns ................................................................................................................................. 311
Digestive Issues .................................................................................................................................. 319
Sleep .................................................................................................................................................. 319
Exercise, Nutrition, and Weight............................................................................................................ 321
Climacteric ......................................................................................................................................... 324
The Climacteric and Sexuality .............................................................................................................. 327
Brain Functioning ............................................................................................................................... 328
Crystalized versus Fluid Intelligence..................................................................................................... 329
Middle Adults Returning to Education .................................................................................................. 331
Gaining Expertise: The Novice and the Expert....................................................................................... 332
Work at Midlife .................................................................................................................................. 333
Leisure ............................................................................................................................................... 336
Midlife Crisis? .................................................................................................................................... 338
Stress ................................................................................................................................................. 339
Erikson: Generativity vs Stagnation ...................................................................................................... 344
Midlife Relationships .......................................................................................................................... 345
Middle Adult Lifestyles ....................................................................................................................... 348
Grandparents ...................................................................................................................................... 352
Friendships ......................................................................................................................................... 354
Women in Midlife ............................................................................................................................... 356
Religion and Spirituality ...................................................................................................................... 356
References .......................................................................................................................................... 358
Chapter 9: Late Adulthood ........................................................................................................................ 371
Late Adulthood in America .................................................................................................................. 371
The "Graying" of the World ................................................................................................................. 372
Life Expectancy vs Lifespan ................................................................................................................ 373
Gender Differences in Life Expectancy ................................................................................................. 375
Age Categories in Late Adulthood ........................................................................................................ 377
Theories of Aging ............................................................................................................................... 380
Physical Changes of Aging .................................................................................................................. 383
Sensory Changes in Late Adulthood ..................................................................................................... 385
Nutrition ............................................................................................................................................ 390
Chronic Conditions ............................................................................................................................. 390
Brain Functioning ............................................................................................................................... 394
Sleep .................................................................................................................................................. 396
Sexuality ............................................................................................................................................ 397
How Does Aging Affect Information Processing? .................................................................................. 399
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Memory ............................................................................................................................................. 399
Attention and Problem Solving............................................................................................................. 401
Intelligence and Wisdom ..................................................................................................................... 403
Neurocognitive Disorders .................................................................................................................... 404
Work, Retirement, and Leisure ............................................................................................................. 407
Ageism .............................................................................................................................................. 411
Living Arrangements ........................................................................................................................... 412
Erikson: Integrity vs. Despair ............................................................................................................... 414
Generativity in Late Adulthood ............................................................................................................ 414
Social Networks in Late Adulthood ...................................................................................................... 416
Late Adult Lifestyles ........................................................................................................................... 418
Gay and Lesbian Elders ....................................................................................................................... 421
Elder Abuse ........................................................................................................................................ 422
Substance Abuse and the Elderly .......................................................................................................... 423
Successful Aging ................................................................................................................................ 424
References .......................................................................................................................................... 425
Chapter 10: Death and Dying .................................................................................................................... 438
Death Defined..................................................................................................................................... 439
Most Common Causes of Death ........................................................................................................... 440
Suicide ............................................................................................................................................... 443
Fatal Drug Overdoses .......................................................................................................................... 446
Where do People Die? ......................................................................................................................... 447
Developmental Perceptions of Death and Death Anxiety ........................................................................ 448
Curative, Palliative, and Hospice Care .................................................................................................. 449
Family Caregivers ............................................................................................................................... 451
Advanced Directives ........................................................................................................................... 452
Cultural Differences in End-of-Life Decisions ....................................................................................... 452
Euthanasia .......................................................................................................................................... 454
Religious Practices after Death ............................................................................................................. 455
Green Burial ....................................................................................................................................... 456
Grief, Bereavement, and Mourning ....................................................................................................... 457
Models of Grief .................................................................................................................................. 458
Grief: Loss of Children and Parents ..................................................................................................... 460
Mourning ........................................................................................................................................... 462
References .......................................................................................................................................... 463
OER Attribution Information..................................................................................................................... 467
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Chapter 1: Introduction to Lifespan Development
Developmental Psychology, also known as Human Development or Lifespan Development, is
the scientific study of ways in which people change, as well as stay the same, from conception to
death. You will no doubt discover in the course of studying that the field examines change across
a broad range of topics. These include physical and other psychophysiological processes,
cognition, language, and psychosocial development, including the impact of family and peers.
Originally concerned with infants and
Figure 1.1
children, the field has expanded to include
adolescence and more recently, aging and the
entire life span. Previously, the message was
once you are 25, your development is
essentially completed. Our academic
knowledge of the lifespan has changed, and
although there is still less research on
adulthood than on childhood, adulthood is
gaining increasing attention. This is
particularly true now that the large cohort
known as the “baby boomers” are beginning
to enter late adulthood. The assumption that
early childhood experiences dictate our future
is also being called into question. Rather, we
Source
have come to appreciate that growth and
change continues throughout life and experience continues to have an impact on who we are and
how we relate to others. We now recognize that adulthood is a dynamic period of life marked by
continued cognitive, social, and psychological development.
You will also discover that developmental psychologists investigate key questions, such as
whether children are qualitatively different from adults or simply lack the experience that adults
draw upon. Other issues that they deal with is the question of whether development occurs
through the gradual accumulation of knowledge or through shifts from one stage of thinking to
another, or if children are born with innate knowledge or figure things out through experience,
and whether development is driven by the social context or something inside each child. From
the above explanation, you may be thinking already that developmental psychology is related to
other applied fields. You are very right. The field informs several applied fields in psychology,
including, educational psychology, psychopathology, and forensic developmental psychology. It
also complements several other basic research fields in psychology including social psychology,
cognitive psychology, and comparative psychology. Lastly, it draws from the theories and
research of several scientific fields including biology, sociology, health care, nutrition, and
anthropology.
9
Learning Objectives: Lifespan Perspective
•
•
•
•
Explain the lifespan perspective and its assumptions about development.
Differentiate periods of human development.
Explain the issues underlying lifespan development
Identify the historical and contemporary theories impacting lifespan development
Lifespan Perspective
Paul Baltes identified several underlying principles of the lifespan perspective (Baltes, 1987;
Baltes, Lindenberger, & Staudinger, 2006).
Development is lifelong. Lifespan theorists believe that development is life-long, and change is
apparent across the lifespan. No single age period is more crucial, characterizes, or dominates
human development. Consequently, the term lifespan development will be used throughout the
textbook.
Development is multidirectional. Humans change in many directions. We may show gains in
some areas of development, while showing losses in other areas. Every change, whether it is
finishing high school, getting married, or becoming a parent, entails both growth and loss.
Development is multidimensional. We change across three general domains/dimensions;
physical, cognitive, and psychosocial. The physical domain includes changes in height and
weight, sensory capabilities, the nervous system, as well as the propensity for disease and illness.
The cognitive domain encompasses the changes in intelligence, wisdom, perception, problemsolving, memory, and language. The psychosocial domain focuses on changes in emotion, selfperception and interpersonal relationships with families, peers, and friends. All three domains
influence each other. It is also important to note that a change in one domain may cascade and
prompt changes in the other domains. For instance, an infant who has started to crawl or walk
will encounter more objects and people, thus fostering developmental change in the child’s
understanding of the physical and social world.
Development is multidisciplinary. As mentioned at the start of the chapter, human
development is such a vast topic of study that it requires the theories, research methods, and
knowledge base of many academic disciplines.
Development is characterized by plasticity. Plasticity is all about our ability to change and
that many of our characteristics are malleable. For instance, plasticity is illustrated in the
brain’s ability to learn from experience and how it can recover from injury.
Development is multicontextual. Development occurs in many contexts. Baltes (1987)
identified three specific contextual influences.
10
•
Normative age-graded influences: An age-grade is a specific age group, such as
toddler, adolescent, or senior. Humans in a specific age-grade share particular
experiences and developmental changes.
•
Normative history-graded
influences: The time period in
which you are born (see Table 1.1)
shapes your experiences. A cohort
is a group of people who are born
at roughly the same period in a
particular society. These people
travel through life often
experiencing similar circumstances.
•
Table 1.1 Which generation (cohort) are you?
Generation
Silent Generation
Baby Boomers
Generation X
Millennials
Generation Z
Born between …
1928 and 1945
1946 and 1964
1965 and 1980
1981-1996
1997-Present
Source
Non-normative life influences: Despite sharing an age and history with our peers,
each of us also has unique experiences that may shape our development. A child who
loses his/her parent at a young age has experienced a life event that is not typical of
the age group.
Another context that influences our lives is our social standing, socioeconomic status, or social
class. Socioeconomic status (SES) is a way to identify families and households based on their
shared levels of education, income, and occupation. While there is certainly individual variation,
members of a social class tend to share similar lifestyles, patterns of consumption, parenting
styles, stressors, religious preferences, and other aspects of daily life. All of us born into a class
system are socially located, and we may move up or down depending on a combination of both
socially and individually created limits and opportunities.
Families with higher socioeconomic status usually are in occupations (e.g., attorneys, physicians,
executives) that not only pay better, but also grant them a certain degree of freedom and control
over their job. Having a sense of autonomy or control is a key factor in experiencing job
satisfaction, personal happiness, and ultimately health and well-being (Weitz, 2007). Those
families with lower socioeconomic status are typically in occupations that are more routine, more
heavily supervised, and require less formal education. These occupations are also more subject
to job disruptions, including lay-offs and lower wages.
Poverty level is an income amount established by the federal government that is based on a set
of income thresholds that vary by family size (United States Census Bureau, 2016). If a family’s
income is less than the government threshold, that family is considered in poverty. Those living
at or near poverty level may find it extremely difficult to sustain a household with this amount of
income. Poverty is associated with poorer health and a lower life expectancy due to poorer diet,
less healthcare, greater stress, working in more dangerous occupations, higher infant mortality
rates, poorer prenatal care, greater iron deficiencies, greater difficulty in school, and many other
problems. Members of higher income status may fear losing that status, but the poor may have
greater concerns over losing housing.
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Today we are more aware of the
variations in development and the impact Figure 1.2
that culture and the environment have on
shaping our lives. Culture is the totality
of our shared language, knowledge,
material objects, and behavior. It
includes ideas about what is right and
wrong, what to strive for, what to eat,
how to speak, what is valued, as well as
what kinds of emotions are called for in
certain situations. Culture teaches us
how to live in a society and allows us to
advance because each new generation
can benefit from the solutions found and
Source
passed down from previous
Think of other ways culture may have affected your
generations. Culture is learned from
development. How might cultural differences influence
parents, schools, houses of worship,
interactions between teachers and students, nurses and patients,
media, friends and others throughout a
or other relationships?
lifetime. The kinds of traditions and
values that evolve in a particular culture serve to help members function and value their own
society. We tend to believe that our own culture’s practices and expectations are the right
ones. This belief that our own culture is superior is called ethnocentrism and is a normal byproduct of growing up in a culture. It becomes a roadblock, however, when it inhibits
understanding of cultural practices from other societies. Cultural relativity is an appreciation
for cultural differences and the understanding that cultural practices are best understood from
the standpoint of that particular culture.
Culture is an extremely important context for human development and understanding
development requires being able to identify which features of development are culturally
based. This understanding is somewhat new and still being explored. Much of what
developmental theorists have described in the past has been culturally bound and difficult to
apply to various cultural contexts. The reader should keep this in mind and realize that there is
still much that is unknown when comparing development across cultures.
Lifespan vs. Life expectancy: At this point you must be wondering what the difference between
lifespan and life expectancy is, according to developmentalists. Lifespan, or longevity, refers to
the length of time a species can exist under the most optimal conditions. For instance, the grey
wolf can live up to 20 years in captivity, the bald eagle up to 50 years, and the Galapagos tortoise
over 150 years (Smithsonian National Zoo, 2016). The longest recorded lifespan for a human
was Jean Calment who died in 1994 at the age of 122 years, 5 months, and 14 days (Guinness
World Records, 2016). Life expectancy is the predicted number of years a person born in a
particular time period can reasonably expect to live (Vogt & Johnson, 2016).
12
Conceptions of Age
How old are you? Chances are you would answer that question based on the number of years
since your birth, or what is called your chronological age. Ever felt older than your
chronological age? Some days we might “feel” like we are older, especially if we are not feeling
well, are tired, or are stressed out. We might notice that a peer seems more emotionally mature
than we are, or that they are physically more capable. So years since birth is not the only way we
can conceptualize age.
Biological age: Another way developmental researchers can think about the concept of age is to
examine how quickly the body is aging, this is your biological age. Several factors determine the
rate at which our body ages. Our nutrition, level of physical activity, sleeping habits, smoking,
alcohol consumption, how we mentally handle stress, and the genetic history of our ancestors, to
name but a few.
Psychological age: Our psychologically
adaptive capacity compared to others of our
chronological age is our psychological age.
This includes our cognitive capacity along
with our emotional beliefs about how old we
are. An individual who has cognitive
impairments might be 20 years of age, yet
has the mental capacity of an 8-year-old. A
70- year-old might be travelling to new
countries, taking courses at college, or
starting a new business. Compared to others
of our age group, we may be more or less
adaptive and excited to meet new challenges.
Remember you are as young or old as you
feel.
Figure 1.3 You are as young as you feel!
Source
Social age: Our social age is based on the social norms of our culture and the expectations our
culture has for people of our age group. Our culture often reminds us whether we are “on target”
or “off target” for reaching certain social milestones, such as completing our education, moving
away from home, having children, or retiring from work. However, there have been arguments
that social age is becoming less relevant in the 21st century (Neugarten, 1979; 1996). If you look
around at your fellow students in your courses at college you might notice more people who are
older than the more traditional aged college students, those 18 to 25. Similarly, the age at which
people are moving away from the home of their parents, starting their careers, getting married or
having children, or even whether they get married or have children at all, is changing.
Those who study lifespan development recognize that chronological age does not completely
capture a person’s age. Our age profile is much more complex than this. A person may be
physically more competent than others in their age group, while being psychologically immature.
So, how old are you?
13
Periods of Development
Table 1.2 Age Periods of Development
Age Period
Description
Prenatal
Starts at conception, continues through implantation in the uterine
wall by the embryo, and ends at birth.
Infancy and
Toddlerhood
Starts at birth and continues to two years of age
Early Childhood
Starts at two years of age until six years of age
Middle and Late
Childhood
Starts at six years of age and continues until the onset of puberty
Adolescence
Starts at the onset of puberty until 18
Emerging
Adulthood
Starts at 18 until 25
Early Adulthood
Starts at 25 until 40-45
Middle Adulthood
Starts at 40-45 until 65
Late Adulthood
Starts at 65 onward
Table 1.2 reflects unique aspects of the various stages of childhood and adulthood that will be
explored in this book. So, while both an 8-month old and an 8-year-old are considered children,
they have very different motor abilities, social relationships, and cognitive skills. Their
nutritional needs are different and their primary psychological concerns are also distinctive. The
same is true of an 18-year-old and an 80-year-old, as both are considered adults.
Prenatal Development: Conception occurs and development begins. All of the major structures
of the body are forming, and the health of the mother is of primary concern. Understanding
nutrition, teratogens, or environmental factors that can lead to birth defects, and labor and
delivery are primary concerns.
Figure 1.4
Infancy and Toddlerhood: The first two years of life are ones of
dramatic growth and change. A newborn, with a keen sense of
hearing but very poor vision, is transformed into a walking, talking
toddler within a relatively short period of time. Caregivers are also
transformed from someone who manages feeding and sleep
schedules to a constantly moving guide and safety inspector for a
mobile, energetic child.
Source
Early Childhood: This period is also referred to as the preschool years and consists of the years
which follow toddlerhood and precede formal schooling. As a two to six-year-old, the child is
14
busy learning language, is gaining a sense of self and greater independence, and is beginning to
learn the workings of the physical world.
Middle and Late Childhood: The ages of six to the onset of puberty comprise middle and late
childhood, and much of what children experience at this age is connected to their involvement in
the early grades of school. Now the world becomes one of learning and testing new academic
skills and by assessing one’s abilities and accomplishments by making comparisons between self
and others.
Adolescence: Adolescence is a period of dramatic physical change marked by an overall growth
spurt and sexual maturation, known as puberty. It is also a time of cognitive change as the
adolescent begins to think of new possibilities and to consider abstract concepts such as love,
fear, and freedom. Ironically, adolescents have a sense of invincibility that puts them at greater
risk of dying from accidents or contracting sexually transmitted infections that can have lifelong
consequences.
Emerging Adulthood: The period of emerging adulthood is a transitional time between the end
of adolescence and before individuals acquire all the benchmarks of adulthood. Continued
identity exploration and preparation for full independence from parents are demonstrated.
Although at one’s physiological peak, emerging adults are most at risk for involvement in violent
crimes and substance abuse.
Early Adulthood: The twenties and thirties are identified
as early adulthood. Intimate relationships, establishing
families, and work are primary concerns at this stage of
life.
Figure 1.5
Middle Adulthood: The forties through the mid-sixties is
referred to as middle adulthood. This is a period in which
aging becomes more noticeable and when many people
are at their peak of productivity in love and work.
Late Adulthood: Late adulthood is sometimes
subdivided into two categories: The young-old who are
from 65-84 years and the oldest-old who are 85 years and
older. One of the primary differences between these
groups is that the young-old are still relatively healthy,
productive, active, and the majority continue to live
independently. With both age groups the risks of diseases
such as, arteriosclerosis, cancer, and cerebral vascular
disease increases substantially.
15
Source
Issues in Lifespan Development
Nature and Nurture: Why are you the way you are? As you consider some of your features
(height, weight, personality, being diabetic, etc.), ask yourself whether these features are a result
of heredity or environmental factors, or both. Chances are, you can see the ways in which both
heredity and environmental factors (such as lifestyle, diet, and so on) have contributed to these
features. For decades, scholars have carried on the "nature/nurture" debate. For any particular
feature, those on the side of nature would argue that heredity plays the most important role in
bringing about that feature. Those on the side of nurture would argue that one's environment is
most significant in shaping the way we are. This debate continues in all aspects of human
development, and most scholars agree that there is a constant interplay between the two forces. It
is difficult to isolate the root of any single behavior as a result solely of nature or nurture.
Continuity versus
Discontinuity: Is human
development best characterized
The tree represents continuous development, while the ladybug
represents discontinuous/stage development.
as a slow, gradual process, or is
it best viewed as one of more
abrupt change? The answer to
that question often depends on
which developmental theorist
you ask and what topic is being
studied. The theories of Freud,
Erikson, Piaget, and Kohlberg
are called stage theories. Stage
theories or discontinuous
development assume that
Source
developmental change often
occurs in distinct stages that
are qualitatively different from each other, and in a set, universal sequence. At each stage of
development, children and adults have different qualities and characteristics. Thus, stage
theorists assume development is more discontinuous. Others, such as the behaviorists,
Vygotsky, and information processing theorists, assume development is a more slow and gradual
process known as continuous development. For instance, they would see the adult as not
possessing new skills, but more advanced skills that were already present in some form in the
child. Brain development and environmental experiences contribute to the acquisition of more
developed skills.
Figure 1.6
Active versus Passive: How much do you play a role in your own developmental path? Are you
at the whim of your genetic inheritance or the environment that surrounds you? Some theorists
see humans as playing a much more active role in their own development. Piaget, for instance
believed that children actively explore their world and construct new ways of thinking to explain
the things they experience. In contrast, many behaviorists view humans as being more passive in
the developmental process.
16
Stability versus Change: How similar are you to how you were as a child? Were you always as
out-going or reserved as you are now? Some theorists argue that the personality traits of adults
are rooted in the behavioral and emotional tendencies of the infant and young child. Others
disagree, and believe that these initial tendencies are modified by social and cultural forces over
time.
Historical Theories on Development
Preformationist View: Well into the 18th century, children
were merely thought of as little adults. Preformationism, or
the belief that a tiny, fully formed human is implanted in the
sperm or egg at conception and then grows in size until birth,
was the predominant early theory. Children were believed to
possess all their sensory capabilities, emotions, and mental
aptitude at birth, and as they developed these abilities unfolded
on a predetermined schedule (Thomas, 1979). The environment
was thought to play no role in determining development.
Figure 1.7
John Locke (1632-1704): Locke, a British philosopher, refuted
the idea of innate knowledge and instead proposed that children
Source: A tiny person inside a sperm.
are largely shaped by their social environments, especially their
education as adults teach them important knowledge. He
believed that through education a child learns socialization, or what is needed to be an
appropriate member of society. Locke advocated thinking of a child’s mind as a tabula rasa or
blank slate, and whatever comes into the child’s mind comes from the environment. Locke
emphasized that the environment is especially powerful in the child’s early life because he
considered the mind the most pliable then. Locke indicated that the environment exerts its
effects through associations between thoughts and feelings, behavioral repetition, imitation, and
rewards and punishments (Crain, 2005). Locke’s ideas laid the groundwork for the behavioral
perspective and subsequent learning theories of Pavlov, Skinner and Bandura.
Jean-Jacques Rousseau (1712-1778): Like Locke, Rousseau also believed that children were
not just little adults. However, he did not believe they were blank slates, but instead developed
according to a natural plan which unfolded in different stages (Crain, 2005). He did not believe
in teaching them the correct way to think, but believed children should be allowed to think by
themselves according to their own ways and an inner, biological timetable. This focus on
biological maturation resulted in Rousseau being considered the father of developmental
psychology. Followers of Rousseau’s developmental perspective include Gesell, Montessori,
and Piaget.
Arnold Gesell (1880-1961): Gesell spent 50 years at the Yale Clinic of Child Development, and
with his colleagues he studied the neuromotor development of children. Gesell believed that the
child’s development was activated by genes and he called this process maturation (Crain, 2005).
Further, he believed that development unfolded in fixed sequences, and he opposed efforts to
teach children ahead of schedule as he believed they will engage in behaviors when their nervous
systems had sufficiently matured.
17
Figure 1.8
Sigmund Freud from Wikimedia
Sigmund Freud (1856-1939): Freud was a very influential
figure in the area of development. Freud emphasized the
importance of early childhood experiences in shaping our
personality and behavior. In our natural state, we are biological
beings and are driven primarily by instincts. During childhood,
however, we begin to become social beings as we learn how to
manage our instincts and transform them into socially
acceptable behaviors. His assumptions were that personality
formed during the first few years of life. The ways in which
parents or other caregivers interacted with children were
assumed to have a long-lasting impact on children’s emotional
states. His beliefs formed the psychodynamic perspective and
his theories of psychosexual development and psychopathology
dominated the field of psychiatry until the growth of
behaviorism in the 1950s.
However, Freud’s theory has been heavily criticized for several reasons. One is that it is very
difficult to test scientifically (Crews, 1998). Freud suggested that much of what determines our
actions were unknown to us, and as scientists we cannot measure these unconscious concepts. A
second criticism is that Freud’s case studies were not validated and cannot be used as evidence
for his theories. Many later theories, particularly behaviorism and humanism, came about as
challenges to Freud’s views.
Contemporary Theories on Development
Figure 1.9
Erikson (1902-1994) and Psychosocial Theory: Now, let's turn to a
less controversial psychodynamic theorist, Erik Erikson. Erikson
presents eight developmental stages that encompass the entire
lifespan. For that reason, Erikson’s psychosocial theory forms the
foundation for much of our discussion of psychosocial development.
Erikson (1950) proposed a model of lifespan development that
provides a useful guideline for thinking about the changes we
experience throughout life. Erikson broke with Freud’s emphasis on
sexuality as the cornerstone of social-emotional development and
instead suggested that social relationships fostered development.
Erikson proposed that each period of life has a unique challenge or
crisis that the person who reaches it must face, referred to as
psychosocial crises. According to Erikson, successful development
Erik Erikson
involves dealing with and resolving the goals and demands of each of
these psychosocial crises in a positive way. These crises are usually
called stages, although that is not the term Erikson used. If a person does not resolve a stage
successfully, it may hinder their ability to deal with later stages. For example, the person who
does not develop a sense of trust (Erikson’s first stage) may find it challenging as an adult to
form a positive intimate relationship (Erikson’s sixth stage). Or an individual who does not
develop a clear sense of purpose and identity (Erikson’s fifth stage) may become self-absorbed
and stagnate rather than work toward the betterment of others (Erikson’s seventh stage).
18
However, most individuals are able to successfully complete the eight stages of his theory (See
Table 1.3).
Table 1.3 Erikson’s Psychosocial Stages
Age range
Birth to 12 to
18 months
Psychosocial crisis
Trust versus Mistrust
Positive resolution of crisis
The child develops a feeling of trust in caregivers.
18 months to
3 years
Autonomy versus
Shame/Doubt
The child learns what can and cannot b e controlled and
develops a sense of free will.
3 to 6 years
Initiative versus Guilt
The child learns to become independent by exploring,
manipulating, and taking action.
6 to 12 years
Industry versus Inferiority
12 to 18 years
Identity versus Role
Confusion
The child learns to do things well or correctly according to
standards set by others, particularly in school.
The adolescent develops a well-defined and positive sense of
self in relationship to others.
19 to 40 years
Intimacy versus Isolation
40 to 65 years
Generativity versus
Stagnation
65 to death
Ego Integrity versus
Despair
The person develops the ability to give and receive love and to
make long-term commitments.
The person develops an interest in guiding the development
of the next generation, often by becoming a parent.
The person develops acceptance of how one has lived.
Erikson’s theory has been criticized for focusing so heavily on crises and assuming that the
completion of one crisis is a prerequisite for the next crisis of development. His theory also
focused on the social expectations that are found in certain cultures, but not in all. For instance,
the idea that adolescence is a time of searching for identity might translate well in the middleclass culture of the United States, but not as well in cultures where the transition into adulthood
coincides with puberty through rites of passage and where adult roles offer fewer choices.
Learning Theory: Also known as Behaviorism, is based on the premise that it is not possible to
objectively study the mind, and therefore psychologists should limit their attention to the study of
behavior itself. The most famous behaviorist was Burrhus Frederick (B. F.) Skinner (1904–
1990), who expanded the principles of behaviorism and also brought them to the attention of the
public at large. Skinner used the ideas of stimulus and response, along with the application of
rewards or reinforcements, to train pigeons and other animals. In addition, he used the general
principles of behaviorism to develop theories about how best to teach children and how to create
societies that were peaceful and productive (Skinner, 1957, 1968, 1972).
The behaviorists made substantial contributions to psychology by identifying the principles of
learning. Although the behaviorists were incorrect in their beliefs that it was not possible to
measure thoughts and feelings, their ideas provided new insights that helped further our
understanding regarding the nature-nurture debate as well as the question of free will. The ideas
of behaviorism are fundamental to psychology and have been developed to help us better
understand the role of prior experiences in a variety of areas of psychology.
19
Social Learning Theory, or learning by watching others, was developed by Albert Bandura
(1977). His theory calls our attention to the ways in which many of our actions are not learned
through conditioning, as suggested by Skinner. Young children frequently learn behaviors
through imitation. Especially when children do not know what else to do, they learn by modeling
or copying the behavior of others.
Bandura (1986) suggests that there is interplay between the environment and the individual. We
are not just the product of our surroundings, rather we influence our surroundings. There is
interplay between our personality and the way we interpret events and how they influence us.
This concept is called reciprocal determinism. An example of this might be the interplay
between parents and children. Parents not only influence their child's environment, perhaps
intentionally through the use of reinforcement, etc., but children influence parents as
well. Parents may respond differently with their first child than with their fourth. Perhaps they
try to be the perfect parents with their firstborn, but by the time their last child comes along they
have very different expectations, both of themselves and their child. Our environment creates us
and we create our environment.
Other social influences: TV or not TV? Bandura, Ross and Ross (1963)
began a series of studies to look at the impact of television on the behavior
of children. Bandura began by conducting an experiment in which he
showed children a film of a woman hitting an inflatable clown or “bobo”
doll. Then the children were allowed in the room, where they found the doll
and during their play they began to hit it. The children also demonstrated
novel ways of being aggressive toward the doll that were not demonstrated
by those children who did not see the aggressive model. Bandura’s
research raised concerns about the impact of violence on young children.
Since then, considerable research has been conducted on the impact of
violent media on children’s aggression including playing video games.
Figure 1.10
The Bobo Doll
Source
Cognitive Theory: The cognitive theories focus on how our mental
processes or cognitions change over time. Three important theories are Jean Piaget’s, Lev
Vygotsky’s, and Information-processing.
Jean Piaget (1896-1980) was one of the most influential cognitive theorists in development. He
was inspired to explore children’s ability to think and reason by watching his own children’s
development. He was one of the first to recognize and map out the ways in which children's
intelligence differs from that of adults (Piaget, 1929). He became interested in this area when he
was asked to test the IQ of children and began to notice that there was a pattern in their wrong
answers. He believed that children's intellectual skills change over time and that maturation,
rather than training, brings about that change. Children of differing ages interpret the world
differently. Piaget theorized that children progressed through four stages of cognitive
development (see Table 1.4).
20
Table 1.4 Piaget’s Stages of Cognitive Development
Stage
Approximate
age range
Characteristics
Stage attainments
Sensorimotor
Birth to about
2 years
Children experience the world through their
fundamental senses of seeing, hearing,
touching, and tasting.
Object permanence
Preoperational
2 to 7 years
Children acquire the ability to internally
represent the world through language and
mental imagery. They also start to see the
world from other people’s perspectives.
Theory of mind;
rapid increase in
language ability
Concrete
operational
7 to 11 years
Children become able to think logically. They
can increasingly perform operations on objects
that are real.
Conservation
Formal
operational
11 years to
adulthood
Adolescents can think systematically, can
reason about abstract concepts, and can
understand ethics and scientific reasoning.
Abstract logic
Piaget has been criticized for overemphasizing the role that physical maturation plays in
cognitive development and in underestimating the role that culture and experience plays.
Looking across cultures reveals considerable variation in what children are able to do at various
ages. Research has shown considerable overlap among the four stages and that development is
more continuous.
Lev Vygotsky (1896-1934) was a Russian psychologist who wrote in the early 1900s, but whose
work was not discovered by researchers in the United States until the 1960s and became more
widely known in the 1980s (Crain, 2005). His sociocultural theory emphasizes the importance
of culture and interaction in the development of cognitive abilities. Vygotsky differed with
Piaget in that he believed that a person not only has a set of abilities, but also a set of potential
abilities that can be realized if given the proper guidance from others. Vygotsky developed
theories on teaching that have been adopted by educators today.
Information Processing is not the work of a single theorist, but based on the ideas and research
of several cognitive scientists studying how individuals perceive, analyze, manipulate, use, and
remember information. This approach assumes that humans gradually improve in their
processing skills; that is, cognitive development is continuous rather than stage-like. The more
complex mental skills of adults are built from the primitive abilities of children. We are born
with the ability to notice stimuli, store, and retrieve information. Brain maturation enables
advancements in our information processing system. At the same time, interactions with the
environment also aid in our development of more effective strategies for processing information.
Urie Bronfenbrenner (1917-2005) developed the Ecological Systems Theory, which provides
a framework for understanding and studying the many influences on human development
(Bronfenbrenner, 1979). Bronfenbrenner recognized that human interaction is influenced by
21
larger social forces and that an understanding of these forces is essential for understanding an
individual. The individual is impacted by several systems including:
o Microsystem includes the individual’s setting and those who have direct, significant
contact with the person, such as parents or siblings. The input of those is modified by the
cognitive and biological state of the individual as well. These influence the person’s
actions, which in turn influence systems operating on him or her.
o Mesosystem includes the larger organizational structures, such as school, the family, or
religion. These institutions impact the microsystems just described. The philosophy of
the school system, daily routine, assessment methods, and other characteristics can affect
the child’s self-image, growth, sense of accomplishment, and schedule thereby impacting
the child, physically, cognitively, and emotionally.
o Exosystem includes the larger contexts of community. A community’s values, history,
and economy can impact the organizational structures it houses. Mesosystems both
influence and are influenced by the exosystem.
o Macrosystem includes the cultural elements, such as global economic conditions, war,
technological trends, values, philosophies, and a society’s responses to the global
community.
o Chronosystem is the historical context in which these experiences occur. This relates to
the different generational time periods previously discussed, such as the baby boomers
and millennials.
In sum, a child’s experiences are shaped by larger forces, such as the family, schools, religion,
culture, and time period. Bronfenbrenner’s model helps us understand all of the different
environments that impact each one of us simultaneously. Despite its comprehensiveness,
Bronfenbrenner’s ecological system’s theory is not easy to use. Taking into consideration all the
different influences makes it difficult to research and determine the impact of all the different
variables (Dixon, 2003). Consequently, psychologists have not fully adopted this approach,
although they recognize the importance of the ecology of the individual. Figure 1.11 is a model
of Bronfenbrenner’s Ecological Systems Theory.
22
Figure 1.11
Source
23
Learning Objectives: Research Methods
•
•
•
•
Define the scientific method
Compare research methods noting the advantages and disadvantages of each.
Explain research involving time spans
Explain ways to conduct ethical research
An important part of learning any science, including psychology, is having a basic knowledge of
the techniques used in gathering information. The hallmark of scientific investigation is that of
following a set of procedures designed to keep questioning or skepticism alive while describing,
explaining, or testing any phenomenon. Science involves continuously renewing our
understanding of the subjects in question and an ongoing investigation of how and why events
occur. The scientific method is the set of assumptions, rules, and procedures scientists use to
conduct research.
A research design is the specific method a researcher uses to collect, analyze, and interpret
data. Psychologists use three major types of research designs in their research, and each provides
an essential avenue for scientific investigation. Descriptive research is research that describes
what is occurring at a particular point in time. Correlational research is research designed to
discover relationships among variables and to allow the prediction of future events from present
knowledge. Experimental research is research in which a researcher manipulates one or more
variables to see their effects. Each of the three research designs varies according to its strengths
and limitations.
Descriptive Research
Case Study: Sometimes the data in a descriptive research project are based on only a small set
of individuals, often only one person or a single small group. These research designs are known
as case studies which are descriptive records of one or a small group of individuals’
experiences and behavior. Sometimes case studies involve ordinary individuals. Developmental
psychologist Jean Piaget observed his own children. More frequently, case studies are
conducted on individuals who have unusual or abnormal experiences. The assumption is that by
carefully studying these individuals, we can learn something about human nature. Case studies
have a distinct disadvantage in that, although it allows us to get an idea of what is currently
happening, it is usually limited to static pictures. Although descriptions of particular
experiences may be interesting, they are not always transferable to other individuals in similar
situations. They are also time consuming and expensive as many professionals are involved in
gathering the information.
Observations: Another type of descriptive research is known as observation. When using
naturalistic observation, psychologists observe and record behavior that occurs in everyday
settings. For instance, a developmental psychologist might watch children on a playground and
24
describe what they say to each other. However, naturalistic observations do not allow the
researcher to have any control over the environment.
Laboratory observation, unlike the naturalistic observation, is conducted in a setting created by
the researcher. This permits the researcher to control more aspects of the situation. One example
of laboratory observation involves a systematic procedure known as the strange situation test,
which you will learn about in chapter three. Concerns regarding laboratory observations are that
the participants are aware that they are being watched, and there is no guarantee that the behavior
demonstrated in the laboratory will generalize to the real world.
Survey: In other cases, the data from
descriptive research projects come in the
form of a survey, which is a measure
administered through either a verbal or
written questionnaire to get a picture of the
beliefs or behaviors of a sample of people of
interest. The people chosen to participate in
the research, known as the sample, are
selected to be representative of all the people
that the researcher wishes to know about
called the population. A representative
sample would include the same percentages
of males, females, age groups, ethnic groups,
and socio-economic groups as the larger
population.
Figure 1.12
How many surveys have you taken?
Source
Surveys gather information from many individuals in a short period of time, which is the greatest
benefit for surveys. Additionally, surveys are inexpensive to administer. However, surveys
typically yield surface information on a wide variety of factors but may not allow for in-depth
understanding of human behavior. Another problem is that respondents may lie because they
want to present themselves in the most favorable light, known as social desirability. They also
may be embarrassed to answer truthfully or are worried that their results will not be kept
confidential. Additionally, questions can be perceived differently than intended.
Interviews: Rather than surveying participants, they can be interviewed which means they are
directly questioned by a researcher. Interviewing participants on their behaviors or beliefs can
solve the problem of misinterpreting the questions posed on surveys. The examiner can explain
the questions and further probe responses for greater clarity and understanding. Although this
can yield more accurate results, interviews take longer and are more expensive to administer than
surveys. Participants can also demonstrate social desirability, which will affect the accuracy of
the responses.
Psychophysiological Assessment: Researchers may also record psychophysiological data, such
as measures of heart rate, hormone levels, or brain activity to help explain development. These
measures may be recorded by themselves or in combination with behavioral data to better
understand the bidirectional relations between biology and behavior. Special equipment has been
developed to allow researchers to record the brain activity of very young and very small research
25
subjects. One manner of understanding associations between brain development and behavioral
advances is through the recording of event-related potentials (ERPs). ERPs are recorded by
fitting a research participant with a stretchy cap that contains many small sensors or electrodes.
These electrodes record tiny electrical currents on the scalp of the participant in response to the
presentation of stimuli, such as a picture or a sound.
Figure 1.13
Source
The use of ERPs has provided important insight as to how
infants and children understand the world around them.
Webb, Dawson, Bernier, and Panagiotides (2006) examined
face and object processing in children with autism spectrum
disorders, those with developmental delays, and those who
were typically developing. The children wore electrode caps
and had their brain activity recorded as they watched still
photographs of faces of their mother or of a stranger, and
objects, including those that were familiar or unfamiliar to
them. The researchers examined differences in face and
object processing by group by observing a component of the
brainwaves. Findings suggest that children with autism are
in some way processing faces differently than typically
developing children and those with more general
developmental delays.
Secondary/Content Analysis involves analyzing information that has already been collected or
examining documents or media to uncover attitudes, practices or preferences. There are a
number of data sets available to those who wish to conduct this type of research. For example,
the U. S. Census Data is available and widely used to look at trends and changes taking place in
the United States. The researcher conducting secondary analysis does not have to recruit
subjects, but does need to know the quality of the information collected in the original study.
Correlational Research
In contrast to descriptive research, which is designed primarily to provide static pictures,
correlational research involves the measurement of two or more relevant variables and an
assessment of the relationship between or among those variables. For instance, the variables of
height and weight are systematically related (correlated) because taller people generally weigh
more than shorter people.
The Pearson Correlation Coefficient, symbolized by the letter r, is the most common statistical
measure of the strength of linear relationships among variables. The value of the correlation
coefficient ranges from r= –1.00 to r = +1.00. The strength of the linear relationship is indexed
by the distance of the correlation coefficient from zero (its absolute value). For instance, r = –.54
is a stronger relationship than r= .30, and r = .72 is a stronger relationship than r = –.57. The
direction of the linear relationship is indicated by the sign of the correlation coefficient. Positive
values of r (such as r = .54 or r = .67) indicate that the relationship is positive (i.e., the pattern of
the dots on the scatter plot runs from the lower left to the upper right), whereas negative values
26
of r (such as r = –.30 or r = –.72) indicate negative relationships (i.e., the dots run from the upper
left to the lower right).
When the straight line indicates that
individuals who have high values for one
Figure 1.14
variable also tend to have high values for
the other variable, as in part (a), the
relationship is said to be a positive
correlation. Examples of positive
correlations include those between
education and income, and between age
and mathematical abilities in children. In
each case people who score higher on one
of the variables also tend to score higher
on the other variable. Negative
correlations, in contrast, as shown in
part (b), occur when high values for one
variable tend to be associated with low
Some examples of relationships between two variables as shown in
scatter plots. Source:
values for the other variable. Examples
of negative correlations include those
between the age of a child and the number of diapers the child uses, and between practice and
errors made on a learning task. In these cases, people who score higher on one of the variables
tend to score lower on the other variable.
An important limitation of correlational research designs is that they cannot be used to draw
conclusions about the causal relationships among the measured variables. Consider, for instance,
a researcher who has hypothesized that viewing violent behavior will cause increased aggressive
play in children. He has collected, from a sample of fourth-grade children, a measure of how
much violent television each child views during the week, as well as a measure of how
aggressively each child plays. The researcher discovers a positive correlation between the two
measured variables. Although this positive correlation appears to support the hypothesis, it
cannot be taken to indicate that viewing violent television causes aggressive behavior as there are
other possible explanations. One alternative is that children who behaved aggressively at school
want to watch violent television shows. Still another possible explanation for the observed
correlation is that it has been produced by the presence of a third variable.
A third variable is a variable that is not part
of the research hypothesis but produces the
observed correlation between them. In our
example a potential third variable is the
discipline style of the children’s parents.
Parents who use a harsh and punitive
discipline style may produce children who
both like to watch violent television and who
behave aggressively in comparison to
children whose parents use less harsh
discipline.
Figure 1.15
27
For this reason, we are left with the basic limitation of correlational research: Correlation does
not demonstrate causation! It is important that when you read about correlational research
projects, you keep in mind the possibility of third variables.
Strengths and limitations: Correlational research can be used when experimental research is
not possible because the variables cannot be manipulated or it would be unethical to use an
experiment. Correlational designs also have the advantage of allowing the researcher to study
behavior as it occurs in everyday life. We can also use correlational designs to make predictions.
For instance, we can predict from the scores on a battery of tests the success of job trainees
during a training session. However, we cannot use such correlational information to determine
whether one variable caused another variable. For that, researchers rely on an experiment.
Experimental Research
The goal of the experimental method is to provide more definitive conclusions about the causal
relationships among the variables in a research hypothesis than what is available from
correlational research. Experiments are designed to test hypotheses, or specific statements about
the relationship between variables. Experiments are conducted in a controlled setting in an effort
to explain how certain factors or events produce outcomes. A variable is anything that changes
in value. In the experimental research design, the variables of interest are called the independent
variable and the dependent variable. The independent variable in an experiment is the causing
variable that is created or manipulated by the experimenter. The dependent variable in an
experiment is a measured variable that is expected to be influenced by the experimental
manipulation.
A good experiment randomly assigns participants to at least two groups that are compared. The
experimental group receives the treatment under investigation, while the control group does not
receive the treatment the experimenter is studying as a comparison. For instance, to assess
whether violent TV affects aggressive behavior the experimental group might view a violent
television show, while the control group watches a non-violent show. Additionally, experimental
designs control for extraneous variables, or variables that are not part of the experiment that
could inadvertently affect either the experimental or control group, thus distorting the results.
Despite the advantage of determining causation, experiments do have limitations. One is that
they are often conducted in laboratory situations rather than in the everyday lives of people.
Therefore, we do not know whether results that we find in a laboratory setting will necessarily
hold up in everyday life. Second, and more important, is that some of the most interesting and
key social variables cannot be experimentally manipulated because of ethical concerns. If we
want to study the influence of abuse on children’s development of depression, these relationships
must be assessed using correlational designs because it is simply not ethical to experimentally
manipulate these variables. Characteristics of descriptive, correlational, and experimental
research designs can be found in Table 1.5.
28
Table 1.5 Characteristics of the Three Research Designs
Research
Design
Goal
Advantages
Disadvantages
Descriptive
To create a snapshot of
the current state of
affairs
Provides a relatively
complete picture of what is
occurring at a given time.
Allows the development of
questions for further study.
Does not assess
relationships among
variables. May be unethical
if participants do not know
they are being observed.
Correlational
To assess the
relationships between
and among two or
more variables
Allows testing of expected
relationships between and
among variables and the
making of predictions. Can
assess these relationships in
everyday life events.
Cannot be used to draw
inferences about the
causal relationships
between and among the
variables.
Experimental
To assess the causal
impact of one or
more experimental
manipulations on a
dependent variable
Allows drawing of
conclusions about the
causal relationships among
variables.
Cannot experimentally
manipulate many
important variables. May
be expensive and time
consuming.
Source: Stangor, C. (2011). Research methods for the behavioral sciences (4th ed.). Mountain View, CA: Cengage.
Research Involving Time-Spans
Cross-sectional research compares samples that
represent a cross-section of the population who vary
in age. Participants might be asked to complete a
survey or take a test of some physical or cognitive
skill. The attitudes or skill levels based on age are
compared. In cross-sectional research, respondents
are measured only once, and consequently this
method is not expensive or time consuming. In
addition, because participants are only tested at one
point in time, practice effects are not an issue as
children do not have the opportunity to become better
at the task over time. There is also no need to keep in
contact with, or follow-up with, participants over time.
Figure 1.16 Cross-Sectional
Source
However, cross-sectional research does not allow the researcher to look at the impact of having
been born in a certain time-period, which is known as the cohort effect. For example, those born
during the depression have very different views about and experiences with the internet than
29
those born in the last twenty years. Different attitudes about the Internet, for example, might not
be due to a person’s biological age as much as their life experiences as members of a cohort.
Longitudinal research involves studying a group of people who are the same age, and
measuring them repeatedly over a period-of-time. This type of design allows researchers to study
individual differences in development. Longitudinal studies may be conducted over the short
term, such as a span of months, or over much longer durations including years or decades. For
these reasons, longitudinal research designs are optimal for studying stability and change over
time.
Figure 1.17 Longitudinal Research
Source
Problems with longitudinal research include being very time consuming and expensive.
Researchers must maintain continued contact with participants over time, and these studies
necessitate that scientists have funding to conduct their work over extended durations. An
additional risk is attrition. Attrition occurs when participants fail to complete all portions of a
study. Participants may move, change their phone numbers, or simply become disinterested in
participating over time. Researchers should account for the possibility of attrition by enrolling a
larger sample into their study initially, as some participants will likely drop out over time. Even
with a large sample size, the experimenter never knows if there was something different about
the individuals who dropped out versus those that remained in the study.
The results from longitudinal studies may also be impacted by repeated assessments. Consider
how well you would do on a math test if you were given the exact same exam every day for a
week. Your performance would likely improve over time not necessarily because you developed
better math abilities, but because you were continuously practicing the same math problems.
This phenomenon is known as a practice effect. Practice effects occur when participants
become better at a task over time because they have done it again and again; not due to natural
psychological development.
Sequential research includes elements of both longitudinal and cross-sectional research
designs. Similar to longitudinal designs, sequential research features participants who are
followed over time; similar to cross-sectional designs, sequential work includes participants of
different ages. This research design is also distinct from those that have been discussed
previously in that individuals of different ages are enrolled into a study at various points in time
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to examine age-related changes, development within the same individuals as they age, and
account for the possibility of cohort effects.
Figure 1.18 Sequential Research
Source
For example, in a study with a sequential design, a researcher might enroll three separate groups
of children (Groups A, B, and C). Children in Group A would be enrolled when they are 2 years
old and would be tested again when they are 4 and 6 years old. This is similar in design to the
longitudinal study described previously. Children in Group B would also be enrolled when they
are 2 years old, but this would occur two years later when Group A is now 4 years old. Finally,
children in Group C would be enrolled when they are 2 years old and Group A is now 6 and
Group B is now 4. At this time, the children would represent a cross-sectional design (2, 4, and
6 years of age). Further, along the diagonal children of the same age can be compared to
determine if cohort effects are evident. Sequential designs are appealing because they allow
researchers to learn a lot about development in a relatively short amount of time.
Because they include elements of longitudinal and cross-sectional designs, sequential research
has many of the same strengths and limitations as these other approaches. For example,
sequential work may require less time and effort than longitudinal research, but more time and
effort than cross-sectional research. Although practice effects may be an issue if participants are
asked to complete the same tasks or assessments over time, attrition may be less problematic
than what is commonly experienced in longitudinal research since participants may not have to
remain involved in the study for such a long period-of-time. Table 1.6 identifies advantages and
disadvantages for each of the described time span research design.
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Table 1.6 Time Span Research Designs Advantages and Disadvantages
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Conducting Ethical Research
One of the issues that all scientists must address concerns the ethics of their research. Research in
psychology may cause some stress, harm, or inconvenience for the people who participate in that
research. Psychologists may induce stress, anxiety, or negative moods in their participants,
expose them to weak electrical shocks, or convince them to behave in ways that violate their
moral standards. Additionally, researchers may sometimes use animals, potentially harming
them in the process.
Decisions about whether research is ethical are made using established ethical codes developed
by scientific organizations, such as the American Psychological Association, and federal
governments. In the United States, the Department of Health and Human Services provides the
guidelines for ethical standards in research. The following are the American Psychological
Association code of ethics when using humans in research (APA, 2016).
•
No Harm: The most direct ethical concern of the scientist is to prevent harm to the
research participants.
•
Informed Consent: Researchers must obtain informed consent, which explains as much
as possible about the true nature of the study, particularly everything that might be
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expected to influence willingness to participate. Participants can withdraw their consent
to participate at any point.
Infants and young children cannot verbally indicate their willingness to participate, much
less understand the balance of potential risks and benefits. As such, researchers are
oftentimes required to obtain written informed consent from the parent or legal guardian
of the child participant. Further, this adult is almost always present as the study is
conducted. Children are not asked to indicate whether they would like to be involved in a
study until they are approximately seven years old. Because infants and young children
also cannot easily indicate if they would like to discontinue their participation in a study,
researchers must be sensitive to changes in the state of the participant, such as
determining whether a child is too tired or upset to continue, as well as to what the parent
desires. In some cases, parents might want to discontinue their involvement in the
research. As in adult studies, researchers must always strive to protect the rights and wellbeing of the minor participants and their parents when conducting developmental
research.
•
Confidentiality: Researchers must also protect the privacy of the research participants’
responses by not using names or other information that could identify the participants.
•
Deception: Deception occurs whenever research participants are not completely and
fully informed about the nature of the research project before participating in it.
Deception may occur when the researcher tells the participants that a study is about one
thing when in fact it is about something else, or when participants are not told about the
hypothesis.
•
Debriefing: At the end of a study debriefing, which is a procedure designed to fully
explain the purposes and procedures of the research and remove any harmful aftereffects
of participation, must occur.
References
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Crain, W. (2005). Theories of development concepts and applications (5th ed.). New Jersey: Pearson.
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