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The Time Machine of Human Development
ave you ever fantasized about traveling in a time machine to the distant past to see live dinosaurs or into a future
featuring ying cars and moving sidewalks? These are fantastic ideas, but in a way every human being’s development
is like a trip in a time machine. From the moment life begins, we are on a developmental journey into the future.
Generally speaking, that personal journey through time is lengthening as the human life span increases.
Consider the long life of U.S. pediatrician Leila Denmark. Dr. Denmark (1898–2012) lived to age 114. In her life-
time, the United States changed from a nation in which women could not vote or own property to one where women
are CEOs, mayors, governors, senators, and candidates for the highest offi ce in the land. She had the mind-boggling
experiences of seeing the rst cars ever manufactured and the rst moon walk, both World Wars, and the wars in
Vietnam, Iraq, and Afghanistan, plus the Great Depression of the 1930s and the global recession at the start of the
twenty-fi rst century. The only woman in her medical school graduating class in 1928, Dr. Denmark dedicated herself to
serving the needs of impoverished children until she retired—at age 103 .
An astonishing variety of events and experiences can be part of one human life span. Someone born in the early
1990s has on average over 50 years to ll with experiences. Imagine if such an individual rode this time machine of
life well into the twenty-fi rst century. What would be the path of that person’s development as a human being—a
path in some ways unique but in many ways in common with the development of all people? In this chapter, you
step into the time machine of human development, looking back on your own development and seeing yourself as an
infant, a child, and an adolescent—and getting new perspective on your present plus a glimpse into your future.
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Exploring Human Development // 279
Developmental psychologists are interested in all the ways a person grows and changes
throughout the time travel that is life, from its beginning to its inevitable end. We start by
defi ning human development and examining central issues in developmental psychology.
In the heart of the chapter, we look at the processes and outcomes of development in
three broad domains of life: physical, cognitive, and socioemotional. We then explore the
links among these developmental areas by probing gender development, followed by a
survey of moral development and death, dying, and grieving. The chapter closes with a
look at the positive ways individuals can shape their development in adulthood. Throughout,
we consider how the active developer—the time traveler himself or herself—can infl uence
the journey of life and its meaning.
Development refers to the pattern of continuity and change in human capabilities that
occurs throughout the course of life. Most development involves growth, although it also
includes decline (for example, physical abilities may decline with age). Let’s begin our
consideration of human development by addressing several key questions and issues that
are especially relevant to understanding how human beings grow and change through the
life span.
Research Methods in
Developmental Psychology
Human development is about the changes that occur with age. To know what age-related
differences mean, however, we must consider the kind of research presented.
In studies with a cross-sectional design , a number of people are assessed at one point
in time. Age differences can then be noted. By examining how the ages of these indi-
viduals relate to the characteristics measured, researchers can nd out whether younger
individuals differ from older ones. Age differences, however, are not the same as devel-
opmental change.
One problem in cross-sectional studies is cohort effects. Cohort effects are differences
between individuals that stem not necessarily from their ages but from the historical and
social time period in which they were born and developed (Schaie, 2009). For instance,
individuals who were born in the 1940s might be less likely to have attended college
than those born in the 1990s. Differences observed between these groups might be due
not to their age but rather to these differing experiences. Consider your own cohort. How
might experiences that are unique to your age group lead you and your peers to be
different from other generations?
In contrast to a cross-sectional study, a longitudinal study, as described in Chapter 1,
assesses the same participants multiple times over a lengthy period. A longitudinal study
can nd out not only whether age groups differ but also whether the same individuals
change with respect to a particular characteristic as they age. Strong statements about
developmental changes in psychological characteristics require longitudinal designs.
Using these and other methods, human development researchers have grappled with big
questions that are relevant to all of psychology, as we consider next.
The pattern of continuity
and change in human capa-
bilities that occurs through-
out life, involving both
growth and decline.
cross-sectional design
A research design in which
agroup of people are as-
sessed on a psychological
variable at one point in
Exploring Human Development
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280 // CHAPTER 8 // Human Development
How Do Nature and Nurture
Influence Development?
D e v e l o p m e n t a l p s y c h o l o g i s t s a r e i n t e r e s t e d i n u n d e r s t a n d i n g h o w n a t u r e a n d n u r t u r e
contribute to development. Nature refers to a person’s biological inheritance, especially
his or her genes. Nurture refers to the individual’s environmental and social experiences.
Understanding development requires that we take into account the contributions of both
genes (nature) and the environment (nurture).
I n C h a p t e r 2 , w e c o n s i d e r e d t h e c o n c e p t o f a genotype ( t h e i n d i v i d u a l s g e n e t i c h e r i t a g e
the actual genetic material). We also examined the idea of a phenotype (the persons
observable characteristics). The phenotype shows the contributions of both nature
(genetic heritage) and nurture (environment). Whether and how the genotype is
expressed in the phenotype may depend on the environment. For example, a person
might be born with the genes to be the next Michael Phelps; but in the absence of
environmental factors such as good nutrition, sound medical care, access to a swim-
ming pool, and superb coaching, that potential might never be reached.
One example of the role of environmental in uences on genetic expression is a genetic
condition called phenylketonuria (PKU). Caused by two recessive genes, PKU results in
an inability to metabolize the amino acid phenylalanine. Decades ago, it was thought
that the genotype for PKU led to a speci c phenotype, namely, irreversible brain damage,
intellectual disability, and seizures. However, experts now know that as long as indi-
viduals with the genotype for PKU stick to a diet that is very low in phenylalanine, these
characteristics in the phenotype can be avoided (Cotugno & others, 2011). These envi-
ronmental precautions can change the phenotype associated with this genotype.
The PKU example tells us that a person’s observable characteristics (phenotype) might
not re ect his or her genetic heritage (genotype) very precisely because of the particular
experiences the person has had. Instead, for each genotype, a range of phenotypes may
be expressed, depending on environmental experiences. The person whom we see
before us emerges out of an interplay of genetic and environmental experiences.
Development is the product of nature, nurture, and the complex interaction of the
two (Beaver & Belsky, 2012; Cicchetti & Rogosch, 2012; Dick, 2011).
One crucial source of nurture is our parents, and recently some parents have
been taking a very active role in their children’s lives. To read about how parenting
ts into the nature-versus-nurture question, check out Challenge Your Thinking.
Although it might be easy to think of genes as the blueprint for a person, devel-
opment is not a process that follows a genetic master plan (Turkheimer, 2011). In fact,
it is dif cult to tell a simple story about how development occurs. One way that scientists
and philosophers think about complex processes such as development is through the
concept of emergent properties. An emergent property is a big entity (like a person)
that is a consequence of the interaction of multiple lower-level factors (Gottlieb,
2007). Development is about the complex interactions of genes and experience that
build the whole person.
Do Early Experiences
Rule Us for Life?
T h e P K U e x a m p l e a b o v e s u g g e s t s t h e p o w e r o f e a r l y e x p e r i e n c e ( n u r t u r e ) i n
human development. A key question in developmental psychology is the extent
to which childhood experiences determine aspects of later life. Some research
shows that unless infants experience warm, nurturing caregiving in the rst year or
so of life, they will not develop to their full potential (Phillips & Lowenstein, 2011;
Sroufe, Cof no, & Carlson, 2010). Other studies demonstrate the power of later expe-
rience in in uencing development in adulthood (Stanley & Isaacowitz, 2011). Life-span
An individual’s biological
inheritance, especially his
orher genes.
An individual’s
and social
Wh a t f a c t o r s
in your childhood environment
influenced your expr es s i on
of your gi f t s and abi l i t i es?
A f lock of birds
flying in formation illustrates
an emer gent pr oper t y. The
bi r ds may a ppe a r t o be f ol l owi ng
a l eader , but t hey ar en t .
Instead, each individual bird
is following it s own local rules.
Wh a t y o u s e e a s a f l o c k o f b i r d s i s
in fact a collect ion of individual
bi r ds, each one doi ng i t s
own t hi ng” but cr eat i ng t he
formation (the emergent
pr oper t y) you r ecogni ze
as a f l ock.
Phenyl al ani ne i s a maj or
compon ent of t he ar t i f i ci al
sweet ener aspar t ame (check
the side of a diet soda can . . .).
In most developed nat i ons,
infant s are t est ed for PKU
shor t l y af t er bi r t h.
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Exploring Human Development // 281
Challen ge
ompared to past generations,
today’s parents are more
likely to be preoccupied with
their children’s lives and behaviors.
Whereas decades ago parents might
have worried about getting their chil-
dren into the right college, today
some parents obsess over enrolling
their little ones in the right preschool
and kindergarten. Is this obsession
necessary to ensure healthy develop-
ment? Some experts would give that
question a de nite no.
Judith Harris (1998), author of
the book The Nurture Assumption,
argues that what parents do makes
no difference in children’s behavior. Spank them. Hug them.
Read to them. Ignore them. It will not in uence how they turn
out, because genes and peers are far more important than par-
ents in children’s development, Harris maintains. Similarly, de-
velopmental researcher Sandra Scarr (1992, 2000) suggests
that “superparenting” is unnecessary. She asserts that the geno-
type is so strong that it makes most environmental experiences
irrelevant. Scarr suggests that the only parenting that has a neg-
ative effect on a child is parenting that is far outside the normal
range—for example, chronic physical abuse. Apart from such
extremes, Scarr asserts, genes are the primary determinant of
developmental outcomes. So, can parents take a breather? Not
Claims such as those of Harris and Scarr have met with a re-
storm of criticism. Diana Baumrind (1993) countered that “good
enough” parenting is not good enough, and she cited evidence
that highly demanding and highly
responsive parents are more
likely to have high-achieving and
socially well-adjusted children. A
longitudinal study by W. Andrew
Collins and his colleagues
(2000) supported Baumrind’s
claims; it showed that even with
genetic in uences taken into ac-
count, parenting practices made
a difference in children’s lives.
Baumrind also expressed con-
cern that Scarr’s opinion might
lead parents to give up the
important responsibility of
childrearing or to conclude that
their efforts on behalf of their children are not worthwhile.
So, in the view of those in the Baumrind and Collins camp, al-
though a person’s genetic heritage certainly has a role to play in de-
velopment, we cannot cuddle our genes, be scolded by them, laugh
with them, or look to them for ad-
vice. For those important aspects
of experience we need parents—
super or otherwise (Sandler,
Wolchik, & Schoenfelder, 2011).
Despite the strong criticism of
her views, Harris (2009) pub-
lished a revised and updated
edition of her earlier book,
restating her claim that parents
matter far less than most
people think.
Genes or Superparents: Which Matters More to Kids?
What Do You Think?
What is your position in this
debate? Why?
Why might today’s parents
be more likely than parents
in the past to try to be
developmentalists stress that experiences throughout life contribute to development
(Lüdtke & others, 2011; Specht, Egloff, & Schmukle, 2011). Both early and later expe-
rience make signi cant contributions to development, so no one is doomed to be a total
prisoner of his or her childhood.
A key concept in understanding the role of negative early experiences in later devel-
opment is resilience. Resilience refers to a person’s ability to recover from or adapt to
dif cult times. Resilience means that despite encountering adversity, a person shows
signs of positive functioning (DiCorcia & Tronick, 2011). Resilience can involve factors
that compensate for dif culties, buffering the individual from the effects of these hard-
ships. Moderate dif culties early in life can be strengthening experiences that lay the
groundwork for future coping (Seery, Holman, & Silver, 2010). Although often studied
as an aspect of childhood (Masten, 2009) and adolescence (Montgomery, 2010), resilience
can also characterize development in adulthood (Gooding & others, 2012; McFadden &
Basting, 2010).
A person’s ability to recover
from or adapt to dif cult
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282 // CHAPTER 8 // Human Development
Nature, Nurture, and You
B e c a u s e y o u c a n n o t p i c k y o u r g e n e s o r y o u r p a r e n t s , i t w o u l d s e e m a s i f y o u a r e s t u c k
with the genes and environment you got at birth. However, the truth is that you have a
vital role to play throughout development. As an active developer, you take the raw ingre-
dients of nature and nurture and make them into the person you are (Turkheimer, 2011).
Indeed, some psychologists believe that people can develop beyond what their genetic
inheritance and environment give them. They argue that a key aspect of development
involves seeking optimal experiences in life (Armor, Massey, & Sackett, 2008). History
is lled with examples of people who go beyond what life has given them to achieve
extraordinary things. Such individuals author a unique developmental path, sometimes
transforming apparent weaknesses into real strengths.
In individuals’ efforts to experience life in optimal ways, they develop life themes that
involve activities, social relationships, and life goals (Frensch, Pratt, & Norris, 2007;
Rathunde, 2010). Some people are more successful at constructing optimal life
experiences than others. Among the public gures who have succeeded are Martin
Luther King, Jr., Mother Teresa, Nelson Mandela, Bill and Melinda Gates, and
Oprah Winfrey. These individuals looked for and found meaningful life themes
as they developed. Their lives were not restricted to biological survival or to settling
for their particular life situations.
Three Domains of Development
The pattern of development is complex because it is the product of several processes in
three domains of life—physical, cognitive, and socioemotional:
Physical processes involve changes in an individual’s biological nature. Genes inher-
ited from parents, the hormonal changes of puberty and menopause, and changes
throughout life in the brain, height and weight, and motor skills all re ect the devel-
opmental role of biological processes.
Human development is complex because it is the product of several processes. The hormonal changes of puberty, a baby’s observation of a mobile, and
an older couple’s embrace refl ect physical, cognitive, and socioemotional processes, respectively.
A person does not
have t o be f amous t o t ake an
act i ve r ol e i n s hapi ng hi s or
her d evel opmen t .
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Exploring Human Development // 283
Cognitive processes i n v o l v e c h a n g e s i n a n i n d i v i d u a l s t h o u g h t , i n t e l l i -
gence, and language. Observing a colorful mobile as it swings above a
crib, constructing a sentence about the future, imagining oneself as a con-
testant on The X Factor or as president of the United States, memorizing
a new telephone number—these activities re ect the role of cognitive pro-
cesses in development.
Socioemotional processes involve changes in an individual’s relationships
with other people, changes in emotions, and changes in personality. An
infant’s smile in response to her mother’s touch, a girl’s development of
assertiveness, an adolescent’s joy at the senior prom, a young man’s
aggressiveness in sport, and an older couple’s affection for each other all
re ect the role of socioemotional processes.
Throughout this chapter we will trace these developmental processes along
the broad periods of the life span, namely:
Childhood , the period from infancy (birth to 24 months) through child-
hood (up to about age 10).
Adolescence , the period beginning around ages 10 to 12 and spanning the transition
from childhood to adulthood.
Adulthood, the period that is generally separated into early (the 20s and 30s), middle
(the 40s and 50s), and late (age 60 and beyond).
A f t e r t r a c i n g changes in physical, cognitive, and socioemotional development
across the life span, we will turn to topics that demonstrate how strongly intertwined
these processes are, including gender and moral development as well as death and
dying. Think of Hannah, an infant whose parents place a teddy bear in her crib. As
an infant she might simply look at the teddy bear when her parents jiggle it in front
of her. Over time, she not only can see the teddy bear but also can reach for it. She
might even remember that the teddy bear exists and might cry for it when it is not
with her. As a toddler, when she carries it around, she is demonstrating her physical
abilities to do so, as well as her capacity to use the teddy bear as a source of comfort.
As an adolescent, Hannah might no longer sleep with her teddy, but she might give
him a place of honor on a shelf. As you read this chapter’s separate sections on
physical, cognitive, and socioemotional development, remember that you are studying
the development of an integrated human being in whom body, mind, emotion, and
social relationships are interdependent.
1. The late Diana, Princess of Wales, de-
voted a considerable effort to eliminat-
ing land mines. Her work illustrates
A. a life theme.
B. a genotype.
C. a socioemotional process.
D. a phenotype.
2. Development can be best described as
A. due entirely to nature.
B. due entirely to nurture.
C. the product of the interaction of
nature and nurture.
D. none of the above
3. An example of an optimal experience is
A. cooking food to eat.
B. getting a great buy on those boots
you wanted.
C. volunteering time to teach adults
D. competing with others.
APPLY IT! 4. Sonja and Pete are engi-
neers who met during college. They share a
love of mathematics and science and have
successful engineering careers. When their
daughter Gabriella is born, they decorate
her room with numbers and spend a great
deal of time counting objects and talking
about math with her. In her school years,
Gabriella is particularly gifted in mathemat-
ics. Gabriella does not become an engineer,
but she does have a career as a terrific
math teacher. Which statement is most
accurate in describing Gabriella?
A. Her math ability is a direct result of her
genetic heritage.
B. Her math ability is a direct result of her
environmental experiences.
C. The fact that she became a teacher in-
stead of an engineer shows that neither
genetics nor environment matters that
much to development.
D. Gabriella’s development shows the
influence of genetics, environment, their
interaction, and Gabriella’s capacity to
forge a life theme that is meaningful
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284 // CHAPTER 8 // Human Development
(a) (b) (c)
FIGURE 8.1 From Embryo to Fetus (a) At about 4 weeks, an embryo is about 0.2 inch (less than 1 centimeter) long. The head, eyes, and ears begin
to show; the head and neck are half the length of the body; the shoulders will be located where the whitish arm buds are attached. (b) At 8 weeks, the developing
individual is about 1.6 inches (4 centimeters) long and has reached the end of its embryonic phase. It has become a fetus. Everything that will be found in the
fully developed human being has now begun to form. The fetal stage is a period of growth and perfection of detail. The heart has been beating for a month, and the
muscles have just begun their rst exercises. (c) At 4½ months, the fetus is just over 7 inches (about 18 centimeters) long. When the thumb comes close to the
mouth, the head may turn, and the lips and tongue begin their sucking motions—a re ex for survival.
In exploring human development in this section, we rst trace the ways that individuals
grow and change physically , starting with prenatal ( b e f o r e b i r t h ) p h y s i c a l d e v e l o p m e n t .
Then we consider the physical changes associated with childhood, adolescence, and the
phases of adulthood. Throughout, we consider the ways the brain changes in each devel-
opmental period.
Prenatal Physical Development
Prenatal development is a time of astonishing change, beginning with conception. Con-
ception occurs when a single sperm cell from the male merges with the female’s ovum
(egg) to produce a zygote, a single cell with 23 chromosomes from the mother and 23
from the father.
T H E C O U R S E O F P R E N A T A L D E V E L O P M E N T Development from zygote
to fetus is divided into three periods:
Germinal period—weeks 1 and 2: The germinal period begins with conception. After
1 week and many cell divisions, the zygote is made up of 100 to 150 cells. By the
end of 2 weeks, the mass of cells has attached to the uterine wall.
Embryonic period—weeks 3 through 8: T h e r a t e o f c e l l d i f f e r e n t i a t i o n i n t e n s i es,
support systems for the cells develop, and the beginnings of organs appear (Figure8.1a).
In the third week, the neural tube, which eventually becomes the spinal cord, starts
to take shape. Within the rst 28 days after conception, the neural tube is formed and
closes, encased inside the embryo. Problems in neural tube development can lead to
Physical Development
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Physical Development // 285
birth defects such as spina bi da, in which the spinal cord is not completely
enclosed by the spinal column, or severe underdevelopment of the brain.
Folic acid, a B vitamin found in orange juice and leafy green vegetables,
greatly reduces the chances of neural tube defects. By the end of the
embryonic period, the heart begins to beat, the arms and legs become
more differentiated, the face starts to form, and the intestinal tract appears
(Figure 8.1b).
Fetal period—months 2 through 9: At 2 months, the fetus is the size of a
kidney bean and has already started to move around. At 4 months, the fetus
is 5 inches long and weighs about 5 ounces (Figure 8.1c). At 6 months, the fetus
has grown to a pound and a half. The last three months of pregnancy are the time
when organ functioning increases, and the fetus puts on considerable weight and size,
adding baby fat. The average newborn is about 19 inches long and weighs about
Until about 60 years ago, mothers and their doctors were unaware of the role that
maternal diet and behavior might play for the developing fetus. Although it oats in a
comfortable, well-protected womb, the fetus is not immune to the larger environment
surrounding the mother (Dunkel Schetter, 2011). Indeed, sometimes prenatal develop-
ment is disrupted by environmental insults.
T H R E A T S T O T H E F E T U S A teratogen is any agent that causes a birth defect.
Teratogens include chemical substances ingested by the mother (such as nicotine, if the
mother smokes) and certain illnesses (such as rubella, or German measles). Sub-
stances that are ingested by the mother can lead to serious birth defects (Holmes
& Westgate, 2011). Heroin is an example of a teratogen. Babies born to heroin
users are at risk for many problems, including premature birth, low birth weight,
physical defects, breathing problems, and death.
Fetal alcohol spectrum disorders (FASD) a r e a c l u s t e r o f a b n o r m a l i t i e s a n d
problems that appear in the offspring of mothers who drink alcohol heavily dur-
ing pregnancy (Yang & others, 2012). These abnormalities include a small head;
facial characteristics such as wide-spaced eyes, a attened nose, and an underdeveloped
upper lip; defects in the limbs and heart; and below-average intelligence. Heavy drinking
is linked to FASD, but even moderate drinking can lead to serious problems (Cannon &
others, 2012). The best advice for a woman who is pregnant or thinking of becoming
pregnant is to avoid alcohol.
The effects of chemical teratogens depend on the timing of exposure (May & Gossage,
2011). The body part or organ system that is developing when the fetus encounters the
teratogen is most vulnerable. Genetic characteristics may buffer or worsen the effects of
a teratogen. Perhaps most importantly, the environment the child encounters after birth
can in uence the ultimate effects of prenatal insults.
S e x u a l l y t r a n s m i t t e d i n f e c t i o n s ( S T I s ) a l s o t h r e a t e n t h e f e t u s . S o m e S T I s , s u c h a s
gonorrhea, can be transferred to the baby during delivery. Others, including syphilis and
AIDS, can also infect the fetus while it is in the womb. Because the human immunode-
ciency virus (HIV) that causes AIDS leads to an incurable infection, antiviral medica-
tions are given to HIV-positive mothers to reduce the chances that they will pass the
virus to their fetus. Besides transmission of infections to the fetus and newborns, STI
exposure enhances the risk of stillbirth, as well as a number of other problems, such as
eye infections and blindness (in the case of gonorrhea). Many STIs also increase the risk
of preterm birth.
A preterm infant, one who is born prior to 37 weeks after conception, may be at risk
for developmental dif culties. Whether a preterm infant will have developmental prob-
lems is a complex issue, however. Postnatal experience plays a crucial role in determin-
ing the ultimate effects of preterm birth. For example, research has shown that massage
can improve developmental outcomes for premature infants (Field, Diego, & Hernandez-
Rief, 2010, 2011).
A realit y check for
pr egnant women who cont i nue
to smoke to alleviate stress:
Imagine a baby puffing on a lit
ci gar et t e. A pr egnan t woman
who smokes i s smoki ng f or t wo.
Not e t hat 2 8 days
is before most women even
know t hey ar e pr egnant . That s
why doct or s r ecommend t hat al l
women who mi gh t bec ome pr eg na nt
take folic acid supplements (about
400 micrograms a day) to
pr event neu r al t ube def ect s.
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286 // CHAPTER 8 // Human Development
Physical Development
in Infancy and Childhood
Human infants are among the world’s most helpless neonates. One reason for that help-
lessness is that we are born not quite nished. From an evolutionary perspective, what
sets humans apart from other animals is our enormous brain. Getting that big brain out
of the relatively small birth canal is a challenge that nature has met by sending human
babies out of the womb before the brain has fully developed. The rst months and years
of life allow the developing human (and his or her environment) to put the nishing
touches on that important organ.
R E F L E X E S Newborns come into the world equipped with several genetically wired
re exes that are crucial for survival. Babies are born with the ability to suck and swal-
low. If they are dropped in water, they will naturally hold their breath, contract their
throats to keep water out, and move their arms and legs to stay a oat at least brie y.
Some re exes persist throughout life—coughing, blinking, and yawning, for example.
Others, such as automatically grasping something that touches the ngers, disappear in
the months following birth as higher brain functions mature and infants develop voluntary
control over many behaviors. Figure 8.2 shows some examples of infant re exes.
M O T O R A N D P E R C E P T U A L S K I L L S Relative to the rest of the body, a new-
born’s head is gigantic, and it ops around uncontrollably. Within 12 months, the infant
becomes capable of sitting upright, standing, stooping, climbing, and often walking.
During the second year, growth decelerates, but rapid gains occur in such activities as
running and climbing.
Motor skills and perceptual skills are coupled and depend on each other. To reach for
something, the infant must be able to see it. Babies are continually coordinating their
movements with information they perceive through their senses to learn how to maintain
their balance, reach for objects in space, and move across various surfaces and terrains
(Adolph & others, 2008; Clear eld, 2011). Consider what happens when a baby sees a
fun toy across the room. Because she can see it, she is motivated to get it. She must
What provokes the response?
Stroking of the infant’s
lower back, next to the
spinal cord
What the infant does
infant curves toward the
side that was stroked
and looks like a fencer
when doing so.
What provokes the response?
Sudden noise or
What the infant does
infant throws his or her
head back and arms and
legs out (and then cries).
What provokes the response?
Stroking of the inner or
outer sole of the infant’s
What the infant does
If the
inner sole is stroked, the
infant curls his or her toes.
If the outer sole is stroked,
the toes spread out.
What provokes the response?
Something that is placed
in the infant’s hand
What the infant does
infant grasps the item and
can hold on very well—
almost enough to support
his or her own weight.
What provokes the response?
Stroking of the infant’s
What the infant does
turns in the direction of
the touch, and the infant
opens his or her mouth for
Gripping Toe Curling
or Startle Galant
FIGURE 8.2 Some Infant Reflexes Infants are born with a number of re exes to get them through life, and they are incredibly cute when they perform
them. These re exes disappear as infants mature.
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Physical Development // 287
FIGURE 8.3 Infants’ Use of “Sticky Mittens” to
Explore Objects Amy Needham and her colleagues (2002) found that
“sticky mittens” enhance young infants’ object exploration skills.
perceive the current state of her body and learn
how to use her limbs to get to the goal. Action in
turn educates perception. For example, watching
an object while holding and touching it helps
infants to learn about its texture, size, and hard-
ness. Moving from place to place in the environ-
ment teaches babies how objects and people look
from different perspectives and whether surfaces
will support their weight.
Infants are energetic developers. When infants
are motivated to do something, they may create a
new motor behavior, such as reaching out to grab
a new toy or mommy’s earrings. That new behav-
ior is the result of many converging factors: the
developing nervous system, the body’s physical
properties and its movement possibilities, the goal
the infant is motivated to reach, and environmental
support for the skill (van Hof, van der Kamp, &
Savelsbergh, 2008).
Researchers used to think that motor milestones (such as sitting up, crawling,
and walking) unfolded as part of a genetic plan. Psychologists now recognize
that motor development is not the consequence of nature or nurture alone
(Keen, 2011).
Environmental experiences play a role in motor development. In one
study, 3-month-old infants participated in play sessions wearing “sticky
mittens”— mittens with palms that stick to the edges of toys and allow the
infants to pick up the toys (Needham, Barrett, & Peterman, 2002, p. 279)
(Figure 8.3). Infants who participated in sessions with the mittens grasped
and manipulated objects earlier in their development than a control group
of infants who did not receive the “mitten” experience. The experienced infants
looked at the objects longer, swatted at them, and were more likely to put the
objects in their mouths.
Psychologists face a daunting challenge in studying infant perception. Infants cannot
talk, so how can scientists learn whether they can see or hear certain things? Psycholo-
gists who study infants rely on what infants can do to understand what they know
(Hollich, 2006). One thing infants can do is look. The preferential looking technique
involves giving an infant a choice of what object to look at. If an infant shows a reliable
preference for one stimulus (say, a picture of a face) over another (a scrambled picture
of a face) when these are repeatedly presented in differing locations, we can infer that
the infant can tell the two images apart.
Using this technique, researchers have found that as early as 7 days old, infants
are already engaged in organized perception of faces and are able to put together
sights and sounds. If presented with two faces with mouths moving, infants will
watch the face whose mouth matches the sounds they are hearing (Lewkowicz,
2010; Lewkowicz & Hansen-Tift, 2012; Pascalls & Kelly, 2008). At 3 months,
infants prefer real faces to scrambled faces, and their mother’s face to a strang-
er’s (Barrera & Maurer, 1981). Research using brain imaging suggests that
infants may know more than even this clever strategy can tell us.
T H E B R A I N A s a n i n f a n t p l a y s , c r a w l s , s h a k e s a r a t t l e , s m i l e s , a n d
frowns, his or her brain is changing dramatically. At birth and in early
infancy, the brain’s 100 billion neurons have only minimal connections. The
infant brain literally is ready and waiting for the experiences that will create
these connections. During the rst 2 years of life, the dendrites of the neurons
branch out, and the neurons become far more interconnected (Figure 8.4).
Myelination, the process of encasing axons with fat cells (the myelin sheath
A research tech-
nique that in-
volves giving an
infant a choice
ofwhat object
tolook at.
The br ai n’ s pl ast i ci t y mak es
it different from any ot her
bodi l y or gan. I t comes i nt o t he
wor l d r eady f or wh at ever wor l d
it might encount er, and t he
features of that world influence
it s very st ruct ure. Ot her organs
physi cal l y gr ow as we do. But t he
br ai n s ver y esse nce i s a t t a ched t o
the world in which it lives.
Infants motor skills
ar e l i mi t ed by gr avi t y. I nf ant s
can somet i mes d o a l ot mor e when
wei ght l ess. Hol di n g a baby up i n a
kiddi e pool , we can see how t he
infant can st and and even t ake
some st eps qui t e def t ly, wi t hout
body wei g ht get t i ng i n t he wa y.
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288 // CHAPTER 8 // Human Development
described in Chapter 2), begins prenatally and continues after birth well into adolescence
and adulthood (Abrahám & others, 2011).
During childhood, synaptic connections increase dramatically. Recall from Chapter 2
that a synapse is a gap between neurons that is bridged by chemical neurotransmitters.
Nearly twice as many synapses are available as will ever be used (Huttenlocher, 1999).
The connections that are made become stronger and will survive; the unused ones will
be replaced by other neural pathways or disappear. In the language of neuroscience, these
unused connections will be “pruned. Figure 8.5 illustrates the steep growth and later
pruning of synapses during infancy in speci c areas of the brain.
Brain-imaging studies show that children’s brains also undergo amazing anatomical
changes. Repeated brain scans of the same children for up to four years show that the
amount of brain material in some areas can nearly double within as little as a year, fol-
lowed by a drastic loss of tissue as unneeded cells are purged and the brain continues
to reorganize itself. The overall size of the brain does not change very much, but local
patterns within the brain change tremendously. From 3 to 6 years of age, the most rapid
Synaptic density
100 1,000 10,0008,0006,0004,0003,0002,0001,500600500400300200 800
Birth 1 Year
Age in days (from conception)
3 Years 11 Years
Newborn Adolescence
Visual cortex (vision)
Auditory cortex (hearing)
Prefrontal cortex (reasoning,
Synaptic Density in
the Human Brain from
Infancy to Adulthood
The graph shows the dramatic
increase and then pruning
in synaptic density in three
regions of the brain: visual
cortex, auditory cortex, and
prefrontal cortex. Synaptic
density is believed to be an
important indication of the
extent of connectivity between
At birth 1 month 3 months 15 months 24 months
Dendritic Spreading
Note the increase in
connections among neurons
over the course of the rst
2years of life.
Reprinted by permission of the
publisher from The Postnatal
Development of the Human Cerebral
Cortex, Vols. I–VIII by Jesse Leroy
Conel, Cambridge, Mass.: Harvard
University Press, Copyright © 1939,
1975 by the President and Fellows
of Harvard College.
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growth takes place in the frontal lobe areas, which are involved in
planning and organizing new actions and in maintaining attention to
tasks. These brain changes are not simply the result of nature; new
experiences in the world also promote brain development (Levine &
others, 2012; Sullivan & others, 2006; Trainor, Lee, & Bosnyak,
2011). Thus, as in other areas of development, nature and nurture
operate together.
Physical Development
in Adolescence
Adolescence refers to the developmental period spanning the transition
from childhood to adulthood, beginning around 10 to 12 years of age
and ending at 18 to 21 years of age. Dramatic physical changes charac-
terize adolescence, especially early adolescence. Among the major phys-
ical changes of adolescence are those involving puberty and the brain.
P U B E R T Y T h e s i g n a t u r e p h y s i c a l c h a n g e i n a d o l e s c e n c e i s puberty ,
a period of rapid skeletal and sexual maturation that occurs mainly in
early adolescence. In general, we know when an individual is going
through puberty, but we have a hard time pinpointing its beginning and
its end. Except for menarche (girls’ rst menstrual cycle), no single marker de nes it.
For boys the rst whisker or rst nocturnal ejaculation (or wet dream) could mark its
appearance, but both may go unnoticed.
The jump in height and weight that characterizes pubertal change occurs about two
years earlier for girls than for boys (Figure 8.6). In the United States today, the average
beginning of the growth spurt is 9 years of age for girls and 11 years for boys. The peak
of pubertal change occurs at an average age of 11½ for girls and 13½ for boys.
Hormonal changes lie at the core of pubertal development. The concentrations of
certain hormones increase dramatically during puberty (Dorn & Biro, 2011). Testo s-
terone, an androgen, is associated in boys with the development of genitals, an increase
in height, and voice change. Estradiol, an estrogen, is associated in girls with breast,
uterine, and skeletal development. Developmental psychologists believe that hormonal
changes account for at least some of the emotional ups and downs of adolescence,
but hormones are not alone responsible for adolescent behavior (Negriff, Susman, &
Trickett, 2011).
F r o m o u r d i s c u s s i o n e a r l i e r i n t h i s c h a p t e r , r e c a l l t h a t p h y s i c a l a n d s o c i o e m o t i o n a l
development are intertwined. This link is demonstrated in the implications of timing
of puberty for socioemotional outcomes. Boys who mature earlier than their peers
tend to show more positive socioemotional outcomes, such as being popular
with their peers and having higher self-esteem (Graber, Brooks-Gunn, & Warren,
2006). In one study, boys who matured early in adolescence were more suc-
cessful and less likely to drink alcohol or smoke cigarettes than late-maturing
boys some 39 years later (Taga, Markey, & Friedman, 2006). In contrast, girls
who are early bloomers tend to be less outgoing and less popular, and they are
more likely to smoke, use drugs, become sexually active, and engage less in academic
pursuits (Dorn & Biro, 2011).
T H E A D O L E S C E N T B R A I N Brain-imaging studies show important changes in
the brain during adolescence (Raznahan & others, 2011). These changes focus on the
earlier development of the amygdala, which involves emotion, and the later development
of the prefrontal cortex, which is concerned with reasoning and decision making (Figure
8.7). These changes in the brain may help to explain why adolescents often display very
strong emotions but may not successfully control these passions. Because of the relatively
A period of rapid
skeletal and sex-
ual maturation
that occurs
mainly in early
Physical Development // 289
Height gain (in./year)
2 4 6 8 1210 14 16 18
Age (years)
FIGURE 8.6 Pubertal Growth Spurt
On average, the pubertal growth spurt begins and
peaks about two years earlier for girls (starts at 9,
peaks at 11½) than for boys (starts at 11½, peaks
at 13½).
From J. M. Tanner et al., in Archives of Diseases in Childhood 41, 1966.
Reproduced with permission from the BMJ Publishing Group.
Recent l y, exper t s ha ve
not ed t hat chi l dr en seem t o be
ent er i ng puber t y ear l i er t han i n
pr evi ous t i mes. What f ac t or s
mi g h t e x p l a i n t h i s c h a n g e ?
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290 // CHAPTER 8 // Human Development
slow development of the prefrontal cortex, which continues to mature into early adult-
hood, adolescents may lack the cognitive skills to control their impulses effectively. This
developmental disjunction may account for increased risk taking and other problems in
adolescence (Casey, Jones, & Somerville, 2011).
A major question is which comes rst—biological changes in the brain or experiences
that stimulate these changes? Consider a study in which the prefrontal cortex thickened
and more brain connections formed when adolescents resisted peer pressure (Paus &
others, 2008). Were the results due to biology or to experience? This correlational study
cannot answer that question, and once again we encounter the fascinating truth about the
brain: It shapes and is shaped by experience.
Physical Development
in Adulthood
As in other developmental periods, our bodies change during adult-
hood. Most of the changes that occur after adolescence involve
declines in physical and perceptual abilities, as we now consider.
P H Y S I C A L C H A N G E S I N E A R L Y A D U L T H O O D Most
adults reach their peak physical development during their 20s and
are the healthiest then. Early adulthood, however, is also the time
when many physical skills begin to decline. The downward trend
in strength and speed often is noticeable in the 30s. Another realm
in which physical changes occur with age is in the ability to per-
ceive the world. Hearing loss is very common with age. In fact,
starting at about age 18, hearing begins a gradual decline.
P H Y S I C A L C H A N G E S I N M I D D L E A N D L A T E A D U L T -
HOOD M a n y p h y s i c a l c h a n g e s i n t h e 4 0 s o r 5 0 s i n v o l v e c h a n g e s
in appearance. The skin has begun to wrinkle and sag because of
the loss of fat and collagen in underlying tissues. Small, localized
areas of skin pigmentation produce age spots, especially in areas
exposed to sunlight such as the hands and face. Hair becomes
After all these years, I’m finally comfortable in
my own skin. Maybe it’s because my skin is a lot
bigger than it used to be!”
Reprinted by permission of Randy Glasbergen.
Involved in processing
information about em otion
Prefrontal Cortex
Involved in higher-order cognitive
functioning, such as decision making
FIGURE 8.7 Developmental
Changes in the Adolescent’s
Brain The amygdala, which is responsible
for processing information about emotion,
matures earlier than the prefrontal cortex,
which is responsible for making decisions
and other higher-order cognitive functions.
Teenage Brains and
Risk Taking
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Physical Development // 291
Have you ever thought about how
long you are likely to live? Might
you be able to live to be 100 years
old? Type in the following on your
Internet browser: The Living to Be
100 Life Expectancy Calculator. That
will give you access to Dr. Thomas
Perl’s website (www.livingtobe100.
com), where in only about 10
minutes you can answer questions
about different aspects of your life
that will provide a number indicating
how long you are likely to live. A
special benefi t is that you also will
get feedback about how to improve
your number. Dr. Perl is currently
conducting one of the largest studies
of centenarians (those who live to
be100), and his life expectancy
calculator is based on research that
has been conducted on the factors
that predict longevity.
How i s y our c ur r en t
behavi or bui l di ng a f oundat i on
for a healthy late adulthood? I f
your f ut ur e s el f coul d t i me- t r avel
to visit you, would he or she say
“Thanks!”—or inst ead “What
wer e you t hi n ki n g?
thinner and grayer due to a lower replacement rate and a decline in melanin production.
Individuals lose height in middle age as a result of bone loss in the vertebrae, and many
gain weight (Onwudiwe & others, 2011). Once individuals reach their 40s, age-related
changes to their vision usually become apparent, especially dif culty in seeing things up
close. The sense of taste can also be affected by age, as taste buds (described in Chapter
3) are less likely to be replaced.
For women, entering middle age means that menopause will soon occur. Usually
in the late 40s or early 50s, a woman’s menstrual periods cease. With menopause comes
a dramatic drop in the ovaries’ production of estrogen. Estrogen decline produces
uncomfortable symptoms in some menopausal women, such as hot ashes (sudden,
brief ushing of the skin and a feeling of elevated body temperature), nausea, fatigue,
and rapid heartbeat. However, menopause overall is not the negative experience for
most women it was once thought to be (Henderson, 2011; Judd, Hickey, & Bryant,
With age, for both men and women, a variety of bodily systems are likely to
show the effects of wear and tear as the body becomes less and less able to repair
damage and regenerate itself (Lamoureux & others, 2010). Physical strength
declines and motor speed slows; bones may become more brittle (especially
for women). Nearly every bodily system changes with age. Signi cantly, how-
ever, even as age is associated with some inevitable decline, important aspects
of successful aging are within the person’s control. For instance, a healthy diet
and regular exercise can help to prevent or slow these effects. Regular physical
activity can have wide-reaching bene ts not only for physical health but for cogni-
tive functioning as well (Kraft, 2012; Snowden & others, 2011). A recent study of older
adults, for example, revealed that exercise increased the size of the hippocampus and
improved memory (Erickson & others, 2011).
O n e w a y o l d e r a d u l t s n a v i g a t e t h e p h y s i c a l c h a n g e s a s s o c i a t e d w i t h a g e i s t h r o u g h a
process of changing their goals and developing new ways to engage in desired activities.
Psychologists refer to this process as selective optimization with compensation, which
means that older adults match their goals with their current abilities and compensate for
declines by nding other ways to do the things they enjoy (Riediger & Freund, 2006).
A 75-year-old who can no longer drive because of cataracts might become an
expert on her city’s train and bus system, for example.
O n t h e i s l a n d o f O k i n a w a ( p a r t o f J a p a n ) , i n d i v i d u a l s l i v e l o n g e r t h a n
anywhere else in the world, and Okinawa has the world’s highest prevalence
of centenarians p e o p l e w h o l i v e t o 1 0 0 y e a r s o r b e y o n d . E x a m i n a t i o n o f
Okinawans’ lives provides insights into their longevity. Speci c factors are
diet (they eat nutritious foods such as grains, sh, and vegetables); lifestyle
(they are easygoing and experience low stress); community (Okinawans
look out for one another and do not isolate or ignore older adults); activity
(they lead active lifestyles, and many older adults continue to work); and
spirituality (they nd a sense of purpose in spiritual matters) (Willcox &
others, 2008). Just as physical changes are interwoven with socioemotional
processes in childhood and adolescence, so they are as human beings enter
the later stages of life.
Biological Theories of Aging Of the many proposed biological the-
ories of aging, three especially merit attention: cellular-clock theory, free-
radical theory, and hormonal stress theory.
T h e cellular-clock theory i s L e o n a r d H a y ick’s (1977) view that cells
can divide a maximum of about 100 times and that, as we age, our cells
become less capable of dividing. Hay ick found that cells extracted from
adults in their 50s to 70s had divided fewer than 100 times. The total
number of cell divisions was roughly related to the individuals age. Based
on the way cells divide, Hay ick places the upper limit of the human life
span at about 120 years.
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292 // CHAPTER 8 // Human Development
Recently, scientists have been examining why cells lose their ability to
divide. The answer may lie at the tips of chromosomes (Mather & others,
2011). Each time a cell divides, the telomeres p r o t e c t i n g t h e e n d s o f c h r o -
mosomes shorten (Figure 8.8). After about 100 replications, the telomeres
are dramatically reduced, and the cell no longer can reproduce (Prescott &
others, 2011). There is considerable interest in discovering ways to maintain
high levels of the telomere-extending enzyme—telomerase—through genetic
manipulation of chemical telomerase activators. Meditation, described in Chapter 4,
might also help to enhance telomerase activity. A recent study found that indi-
viduals who participated in a three-month meditation retreat (which included
meditating for 6 hours a day) showed greater telomerase activity relative to a
control group (Jacobs & others, 2011).
T h e free-radical theory of aging states that people age because unstable
oxygen molecules known as free radicals are produced inside their cells. These
molecules damage DNA and other cellular structures (Harman, 1956; Kregel & Zhang,
2006). The damage done by free radicals may lead to a range of disorders, including
cancer and arthritis (Eckert, Schmitt, & Gotz, 2011).
Hormonal stress theory argues that aging in the body’s hormonal system can lower
resistance to stress and increase the likelihood of disease. As individuals age, the
hormones stimulated by stress stay in the bloodstream longer than is the case for
younger people. Prolonged, elevated levels of stress hormones are linked to increased
risks for many diseases, including cardiovascular disease, cancer, and diabetes (Hefner,
2011). Recently, the hormonal stress theory of aging has focused on the role of
chronic stress in diminishing the functioning of the immune system (Mahbub,
Brubaker, & Kovacs, 2011).
Aging and the Brain Just as the aging body has a greater capacity for renewal
than previously thought, so does the aging brain. For decades, scientists believed that no
new brain cells are generated past early childhood. However, researchers have recently
discovered that adults can grow new brain cells throughout life (Curtis, Kam, & Faull,
Chromosome tips, called telomeres,
protect DNA during cell division.
Normal cell after
new cell division
Dividing cell
Cell death
Telomeres shorten as cell undergoes many cell divisions.
Ultimately, telomeres become too short, exposing DNA, which
becomes damaged, and the cell dies. This is the normal life and
death cycle of a cell.
DNA within the chromosome
FIGURE 8.8 Telomeres and Aging The photograph shows telomeres lighting up
the tips of chromosomes. The gure illustrates how the telomeres shorten every time a cell
divides. Eventually, after about 100 divisions, the telomeres are greatly reduced in length. As
a result, the cell can no longer reproduce and it dies.
Pe opl e of t en say l i f e s
too short. But imagine living
to be 120 years old. At age
70 you would st ill have
50 years to fill with life.
Par t i ci pant s pai d
over $3,000 t o take part
in t his unusual st udy!
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Physical Development // 293
2011), although evidence is limited to two areas of the brain: the hip-
pocampus and the olfactory bulb (Ming & Song, 2011).
Even in late adulthood, the brain has remarkable repair capability
(Couillard-Despres, Iglsseder, & Aigner, 2011; Gil-Mohapel & others,
2011; Zeng & others, 2011). Stanley Rapaport (1994) compared the
brains of younger and older adults when they were engaged in the
same tasks. The older adults brains literally rewired themselves to
compensate for losses. If one neuron was not up to the job, neighbor-
ing neurons helped to pick up the slack. Rapaport concluded that as
brains age, they can shift responsibilities for a given task from one
region to another.
Changes in lateralization may provide one type of adaptation in
aging adults. Lateralization i s t h e s p e c i a l i z a t i o n o f f u n c t i o n i n o n e
hemisphere of the brain or the other. Using neuroimaging techniques,
researchers have found that brain activity in the prefrontal cortex is
lateralized less in older adults than in younger adults when they are
engaging in cognitive tasks (Cabeza, 2002; Raw & others, 2012). For
example, when younger adults are given the task of recognizing words
they have previously seen, they process the information primarily in the
right hemisphere, whereas older adults are more likely to use both
hemispheres (Madden & others, 1999). The decrease in lateralization
in older adults might play a compensatory role in the aging brain (Angel
& others, 2011). That is, using both hemispheres may improve the cog-
nitive functioning of older adults.
Research from the Nun Study (described in Chapter 1) supports the
role of experience in maintaining brain function. Recall that this study
involves nearly 700 nuns in a convent in Mankato, Minnesota (Snowdon,
2003, 2007) (Figure 8.9). By examining the nuns’ donated brains as
well as others, neuroscientists have documented the aging brain’s ability
to grow and change. Even the oldest Mankato nuns lead intellectually
challenging lives, and neuroscientists believe that stimulating mental
activities increase dendritic branching. Keeping the brain actively
engaged in challenging activities can help to slow the effects of age, as
we noted in Chapter 6.
In sum, in the physical domain across the life span, we see a dramatic pattern of
growth and change in infancy, childhood, and adolescence followed by leveling off
and decline in adulthood. How might this progression in uence (and be in uenced
by) the way the developing person thinks about himself or herself and the world? To
examine this question, we turn to the cognitive domain of human development.
FIGURE 8.9 The Brains of the
Mankato Nuns At 95 years old, Nun Study
participant Sister Nicolette Welter remains an
active contributing member of her community
of sisters. (Inset) A neuroscientist holds a brain
donated by one of the Mankato Nun Study
1. The first two weeks after conception are
referred to as the
A. fetal period.
B. germinal period.
C. embryonic period.
D. zygotic period.
2. Puberty is generally characterized by all
of the following except
A. a decrease in concentrations of cer-
tain hormones.
B. a dramatic increase in height and
C. an increase in idealistic and abstract
D. the development of thought.
3. The hormone associated with girls’
breast, uterine, and skeletal develop-
ment during puberty is
A. testosterone.
B. estradiol.
C. androgen.
D. norepinephrine.
APPLY IT! 4. Gabriel’s grandfather
has always been a fitness nut. Even at
age83, he continues to work out, lifting
weights, swimming, and taking pride in
his physique. After his grandfather beats
him in a swimming race, Gabriel rolls his
eyes and comments that all this work
makes no sense at this point in his grand-
father’s life. Aside from calling him on his
sour grapes, what would you say about
Gabriel’s viewpoint?
A. Gabriel is right. All that working out
isprobably inappropriate and even
unhealthy for someone in his 80s.
B. Gabriel is wrong, because if his grandfa-
ther stays active, he can completely
avoid all of the physical changes associ-
ated with age.
C. Gabriel is wrong. His grandfather’s hard
work might be paying off in a variety of
ways, including his physical health and
his cognitive and emotional functioning
D. Gabriel is right, and his grandfather
seems to be in denial about the effects
of age on physical development.
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294 // CHAPTER 8 // Human Development
Jean Piaget (1896–1980)
Piaget, the famous Swiss psychologist,
changed the way we think about the
development of children’s minds.
So, w e assi mi l at e
ex per i ences i nt o s chemas
and accommodat e s chemas
to experience.
Cognitive development refers to how thought, intelligence, and language processes
change as people mature. Cognition refers to the operation of thinking and also to our
cognitive skills and abilities. In this section, you will encounter one of the
biggest names in all of psychology, Jean Piaget, who presented a theory of
cognitive development that has had lasting impact on the eld. We examine
Piaget’s contributions and also consider more recent research on the relation-
ship between cognitive abilities and age.
Cognitive Development from
Childhood into Adulthood
The Swiss developmental psychologist Jean Piaget (1896–1980) traced cog-
nitive development through childhood into adulthood. Let’s begin by review-
ing Piaget’s approach.
P I A G E T S T H E O R Y O F C O G N I T I V E D E V E L O P M E N T I n P i a g e t s
view, human beings use schemas to make sense of their experience. As we
considered in Chapter 6, a schema is a mental concept or framework that
organizes information and provides a structure for interpreting it. Schemas
are expressed as various behaviors and skills that the child can exercise
inrelation to objects or situations. For example, sucking is an early, simple schema.
Later and more complex schemas include licking, blowing, crawling, and hiding.
In adulthood, schemas may represent more complex expectations and beliefs about
the world.
Piaget (1952) described two processes responsible for how people use and adapt their
Assimilation o c c u r s w h e n i n d i v i d u a l s i n c o r p o r a t e n e w i n f o r m a t i o n i n t o e x i s t i n g
knowledge. As a result of assimilation, the person, when faced with a new experience,
applies old ways of doing things. For infants, this might involve applying the schema
of sucking to whatever new object they encounter. For an adolescent, it might mean
using the skills learned while playing video games to drive a car. For an adult, it
might mean solving a con ict with a spouse using ways that worked in the past with
friends or previous romantic partners.
Accommodation occurs when individuals adjust their schemas to new information.
Accommodation means that rather than using one’s old ways of doing things, a new
experience promotes new ways of dealing with experience. Existing schemas can be
changed and new schemas can be developed in response to new experiences. For
example, after several months of experience, the infant who has been sticking every-
thing in her mouth might begin to accommodate the sucking schema by being more
selective with it. The adolescent who has typically gone with the ow of social pres-
sure might develop a new way of dealing with peer pressure by standing up for his
or her beliefs. For an adult, accommodation may mean rethinking old strategies for
problem solving when a new challenge, such as the loss of a job or the onset of
illness, presents itself.
P I A G E T S S T A G E S O F C O G N I T I V E D E V E L O P M E N T According to Piaget,
we go through four stages in understanding the world (Figure 8.10). Each stage involves
a qualitatively different way of making sense of the world than the one before it.
An individual’s incorporation
of new information into ex-
isting knowledge.
An individual’s adjustment
of his or her schemas to new
Cognitive Development
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Cognitive Development // 295
The infant constructs an
understanding of the world
by coordinating sensory
experiences with physical
actions. An infant progresses
from reflexive, instinctual
action at birth to the begin-
ning of symbolic thought
toward the end of the stage.
The child begins to represent
the world with words and
images. These words and
images reflect increased
symbolic thinking and go
beyond the connection of
sensory information and
physical action.
The child can now reason
logically about concrete
events and classify objects
into different sets.
The adolescent reasons
in more abstract, idealistic,
and logical ways.
Formal Operational
Concrete Operational
11 Years of Age
Through Adulthood
7 to 11 Years of Age2 to 7 Years of AgeBirth to 2 Years of Age
FIGURE 8.10 Piaget’s Four Stages of Cognitive Development Jean Piaget described how human beings, through development, become ever
more sophisticated thinkers about the world.
S e n s o r i m o t o r S t a g e P i a g e t s rst stage, the sensorimotor stage , l a s t s f r o m b i r t h
to about 2 years of age. In this stage, infants construct an understanding of the world
by coordinating sensory experiences (such as seeing and hearing) with motor (physical)
actions—hence the term sensor i motor . A s n e w b o r n s t h e y h a v e l i t t l e m o r e t h a n r e exive
patterns with which to work. By the end of this stage, 2-year-olds show complex sen-
sorimotor patterns and are beginning to use symbols or words in their thinking.
Object permanence is Piaget’s term for the crucial accomplishment of understanding
that objects continue to exist even when they cannot directly be seen, heard, or touched.
Piaget believed that “out of sight” literally was “out of mind” for very young infants.
Piaget studied object permanence by showing an infant an interesting toy and then cov-
ering the toy with a blanket. Piaget reasoned that if infants understood that the toy still
existed, they would try to uncover it (Figure 8.11). Piaget thought the development of
object permanence continues throughout the sensorimotor period.
P r e o p e r a t i o n a l S t a g e P i a g e t s s e c o n d s t a g e o f c o g n i t i v e d e v e l o p m e n t , t h e
preoperational stage , lasts from approximately 2 to 7 years of age. Preoperational
thought is more symbolic than sensorimotor thought. In preschool years, children
begin to represent their world with words, images, and drawings. Thus, their
thoughts begin to exceed simple connections of sensorimotor information and
physical action.
The type of symbolic thinking that children are able to accomplish during
this stage is limited. They still cannot perform what Piaget called operations,
by which he meant mental representations that are “reversible. Preoperational
children have dif culty understanding that reversing an action may restore the
original conditions from which the action began.
A well-known test of whether a child can think “operationally” is to present a
child with two identical beakers, A and B, lled with liquid to the same height
sensorimotor stage
Piaget’s fi rst stage of cogni-
tive development, lasting
from birth to about 2 years
of age, during which infants
construct an understanding
of the world by coordinating
sensory experiences with
motor (physical) actions.
Piaget’s term
forthe crucial
of understanding
that objects and
events continue
to exist even
when they can-
not directly be
seen, heard, or
Piaget’s second
stage of cogni-
tive develop-
ment, lasting
from about 2 to
7years of age,
during which
thought is more
symbolic than
Wi t h o b j e c t p e r ma n e n c e ,
the infant starts thinking
ab out f ut ur e event s, as i n
“When will I see Mommy again?
The chi l d can t ak e comf or t i n t he
knowl edge t hat Mommy wi ll be
ba ck. Obj ect per ma ne nce al so mea ns
get t i ng a f i r st t as t e of t he
human capaci t y f or l ongi ngf or
mi s s i n g s o me o n e w h o i s
not t her e.
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296 // CHAPTER 8 // Human Development
(Figure 8.12). Next to them is a third beaker (C). Beaker C is tall and thin, whereas
beakers A and B are short and wide. The liquid is poured from B into C, and the child
is asked whether the amounts in A and C are the same. The 4-year-old child invariably
says that the amount of liquid in the tall, thin beaker (C) is greater than that in the short,
wide beaker (A). The 8-year-old child consistently says the amounts are the same. The
4-year-old child, a preoperational thinker, cannot mentally reverse the pouring action;
that is, she cannot imagine the liquid going back from container C to container B. Piaget
said that such a child has not grasped the concept of conservation , a belief in the
permanence of certain attributes of objects despite super cial changes.
The child’s thought in the preoperational stage is egocentric. This does not mean
that the child is self-centered or arrogant but that preoperational children cannot put
FIGURE 8.11 Object Permanence Piaget regarded object permanence as one of infancy’s landmark cognitive accomplishments. For this
5-month-old boy, out of sight is literally out of mind. The infant looks at the toy dog (left), but when his view of the toy is blocked (right), he does not search
for it. > If this boy fails to try to nd the toy dog, Piaget assumed that meant he does not know it still exists. What other factors might explain his
lack of looking for the toy? > What motor skills are necessary for the little boy to perform this behavior? > What kinds of goals are required for him
to seek out the toy?
FIGURE 8.12 Piaget’s Conservation
Task The beaker test determines whether a child
can think operationally—that is, can mentally reverse
action and understand conservation of the substance.
(a) Two identical beakers are presented to the child,
each containing the same amount of liquid. As the
child watches, the experimenter pours the liquid from B
into C, which is taller and thinner than A and B. (b) The
experimenter then asks the child whether beakers A and
C have the same amount of liquid. The preoperational
child says no. When asked to point to the beaker that
has more liquid, the child points to the tall, thin one.
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Cognitive Development // 297
themselves in someone else’s shoes. They cannot take another person’s mental states
into account.
Preoperational thinking is also intuitive. This means that preoperational chil-
dren make judgments based on gut feelings rather than logic. In reaching a basic
level of operational understanding, the child progresses to the third of Piaget’s
cognitive stages.
C o n c r e t e O p e r a t i o n a l S t a g e P i a g e t s concrete operational stage (7 to 11 years
of age) involves using operations and replacing intuitive reasoning with logical reasoning
in concrete situations. Children in the concrete operational stage can successfully com-
plete the beaker task described above. They are able to mentally imagine the operation
of reversing the pouring of the liquid back into the wide beaker. Many of the concrete
operations identi ed by Piaget are related to the properties of objects. For instance, when
playing with Play-doh, the child in the concrete operational stage realizes that the amount
of Play-doh is not changed by changing its shape. One important skill at this stage of
reasoning is the ability to classify or divide things into different sets or subsets and to
consider their interrelations. (You might remember learning the childhood song that goes,
“One of these things is not like the others, which effectively aimed to coax you into
concrete operations.)
Concrete operational thought involves operational thinking, classi cation skills, and
logical reasoning in concrete but not hypothetical contexts. According to Piaget, this kind
of abstract, logical reasoning occurs in the fourth, and nal, cognitive stage.
F o r m a l O p e r a t i o n a l S t a g e I n d i v i d u a l s e n t e r t h e formal operational stage o f
cognitive development at 11 to 15 years of age. This stage continues through the adult
years. Formal operational thought is more abstract and logical than concrete operational
thought. Most importantly, formal operational thinking includes thinking about things
that are not concrete, making predictions, and using logic to come up with hypotheses
about the future.
Unlike elementary schoolchildren, adolescents can conceive of hypothetical, purely
abstract possibilities. This type of thinking is called idealistic because it involves compar-
ing how things are to how they might be. Adolescents also think more logically. They
begin to think more as a scientist thinks, devising plans to solve problems and system-
atically testing solutions. Piaget called this type of problem solving hypothetical-deductive
reasoning . T h e p h r a s e d e n o t e s a d o l e s c e n t s a b i l i t y t o d e v e l o p h y p o t h e s e s , o r b e s t h u n c h e s ,
about ways to solve a problem such as an algebraic equation. It also denotes their ability
to systematically deduce, or come to a conclusion about, the best path for solving the
problem. In contrast, before adolescence, children are more likely to solve problems by
trial and error.
I n s u m m a r y , o v e r t h e c o u r s e o f P i a g e t s f o u r d e v e l o p m e n t a l s t a g e s , a p e r s o n p r o -
gresses from sensorimotor cognition to abstract, idealistic, and logical thought. Piaget
based his stages on careful observation of children’s behavior, but there is always room
to evaluate theory and research. Let’s consider the current thinking about Piaget’s theory
of cognitive development.
E V A L U A T I N G A N D E X P A N D I N G O N P I A G E T S T H E O R Y Piaget opened
up a new way of looking at how children’s minds develop. We owe him for a long list
of masterful concepts that have enduring power and fascination. These include the con-
cepts of schemas, assimilation, accommodation, cognitive stages, object permanence,
egocentrism, and conservation. We owe Piaget, for example, for the currently accepted
vision of children as active, constructive thinkers who play a role in their own develop-
ment. Nevertheless, just as other psychological theories have been criticized and amended,
so have Piaget’s.
Baillargeon: An Alternative View of Object Permanence As methods have
improved for testing infants and children, researchers have found that many cognitive
operational stage
Piaget’s third
stage of cogni-
tive develop-
ment, lasting
from about 7 to
11 years of age,
during which the
individual uses
operations and
replaces intuitive
reasoning with
logical reasoning
in concrete
formal operational stage
Piaget’s fourth stage of cog-
nitive development, which
begins at age 11 to 15 and
continues through adult-
hood; it features thinking
about things that are not
concrete, making predic-
tions, and using logic to
come up with hypotheses
about the future.
Pr e s c h o o l e r s a r e n t
trying to make their parents
cr azy . They may say r emar k abl y
cr uel t hi ngs, bu t t hey ar e not
abl e t o gauge how t hei r wor ds
mi g h t ma k e s o me o n e e l s e f e e l .
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298 // CHAPTER 8 // Human Development
abilities emerge earlier in children than Piaget thought (Sloane, Baillargeon, & Premack,
2012). Piaget’s object permanence task, for example, has been criticized for not giving
infants a chance to show their stuff. Rather than indicating that small children do not
have a sense of object permanence, such a task might be demonstrating that these chil-
dren simply are not able to enact the plan of getting the toy back.
Indeed, Renee Baillargeon has documented that infants as young as 3 months of age
know that objects continue to exist even when hidden, and that even these very young
infants have expectations about objects in the world that seem quite a bit more sophis-
ticated than Piaget imagined (Baillargeon, Scott, & He, 2010; Baillargeon & others, 2012;
Luo, Kaufman, & Baillargeon, 2009).
In one study, researchers showed 3-month-old infants a puppet show of Minnie Mouse
(Luo & Baillargeon, 2005). In the center of the stage was a at cardboard cutout of a
castle, with an open door in the middle. Minnie entered stage right and proceeded toward
the castle, disappearing behind. When Minnie went behind the castle walls from one
side, the infants looked for her to come out on the other side. Furthermore, if, as she
made her way behind the castle walls, Minnie did not appear in the open doorway,
infants as young as 3 months were surprised. Not only did they realize that Minnie still
The Joy of the Toy
hen kids are playing, they are often playing with toys. Toys have been around for a very
long time. Archaeologists have dated the rst toy, an ancient Egyptian doll made of
paper, cloth, and string, to 2000 B.C.E. Today, toys are a huge U.S. industry. From 2004 to 2010,
Americans spent nearly $22 billion on toys every year (NPD Group, 2011), and nearly half of Amer-
icans have toys on their holiday shopping lists (Harris Interactive, 2011).
Toy manufacturers are well aware of the importance of understanding developmental psychology
when designing toys. As noted by toy designer Barry Kudrowitz (quoted in Benson, 2006),
“Before brainstorming, the designer should know what types of behaviors are typical for
that age group; . . . the social, mental, and physical abilities of the age group, and
what types of play are most common.” Developmental psychology courses are required
in the toy design degree program at the Fashion Institute of Technology in New York
City, where the rst U.S. toy design program was founded in the 1980s.
Toy manufacturers conduct a great deal of research examining toys and chil-
dren’s cognitive and perceptual abilities. Outside the toy industry, psychologists
have investigated such topics as the effects of advertising on toy preferences
and the infl uence of toys on children’s body images. They have found, for
example, that boys are more susceptible than girls to gender in ads (Pike &
Jennings, 2005) and that exposure to Barbie can predict lowered body image
among girls (Dittmar, Halliwell, & Ive, 2006).
The value of a toy lies in its capacity to capture a child’s imagination. How many parents have
stood by in shock as their child tossed aside an expensive new toy and played for hours with the
box it came in? In that box, the child may have discovered a house, a cave, a car, or a spaceship.
In 2011, the blanket was inducted into the Toy Hall of Fame. Every kid knows that if you have a
blanket, you’ve got a tent, a superhero cape, and a magic carpet—not to mention a great cover
for reading by ashlight when you are supposed to be sleeping.
These r esear cher s
al so moni t or ed i nf ant f aci al
expr es s i ons . Thr ee- mont h-
ol d j aws dr oppi ng i n s hock?
To o c u t e .
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Cognitive Development // 299
existed, but they also had expectations about where she was
heading, and they believed that she certainly should appear
in the door as she passed behind the castle. Also, memory
and other forms of symbolic activity occur much earlier than
Piaget thought possible (Sloane, Baillargeon, & Premack,
Vygotsky: Cognitive Development in Cultural
Context Piaget did not think that culture and education
play important roles in children’s cognitive development.
For Piaget, the child’s active interaction with the physical
world was all that was needed to go through these stages.
The Russian psychologist Lev Vygotsky (1962) took a dif-
ferent approach, recognizing that cognitive development is
an interpersonal process that happens in a cultural context.
Vygotsky thought of children as apprentice thinkers who develop as they interact in
dialogue with more knowledgeable others, such as parents and teachers. Vygotsky
believed that these expert thinkers spur cognitive development by interacting with a child
in a way that is just above the level of sophistication the child has mastered. In effect,
these interactions provide scaffolding that allows the child’s cognitive abilities to be
built higher and higher.
Teachers and parents, in other words, provide a framework for thinking that is
always just at a level the child can strive to attain. Furthermore, in Vygotsky’s
view, the goal of cognitive development is to learn the skills that will allow the
individual to be competent in his or her particular culture. These expert thinkers
are not simply guiding a child into a level of cognitive sophistication, but also,
along the way, sharing with the child important aspects of culture, such as lan-
guage and customs. For Vygotsky, a child is not simply learning to think about the
world—he or she is learning to think about his or her own world .
Revisionist Views of Adolescent and Adult Cognition Researchers have
also expanded on Piaget’s view of adolescent cognition. In addition to advancing
into Piaget’s stage of formal operational thinking, another characteristic of adoles-
cent thinking, especially in early adolescence, is egocentrism. Although egocen-
trism has been noted as an aspect of children’s cognition, adolescent egocentrism
involves the belief that others are as preoccupied with the adolescent as he or she
is, that one is unique, and that one is invincible (meaning unable to be harmed)
(Albert & Steinberg, 2011). Egocentrism at this developmental stage is revealed, for
example, when an adolescent perceives others to be noticing and watching her or him
more than is the case. Think of the teenage girl who says, “My mother has no idea
about how much pain I’m going through. She has never been hurt like me! Why did
he break up with me?”
The sense of invincibility is the most dangerous aspect of adolescent egocentrism.
This belief may lead to behaviors such as drag racing, drug use, and unsafe sex. In
one study of sixth- through twelfth-graders, feeling invincible was linked to risky
behaviors such as smoking cigarettes, drinking alcohol, and delinquency (Aalsma,
Lapsley, & Flannery, 2006).
Just as Piaget may have underestimated infant cognition, he may have overestimated
some of adolescents’ and adults’ cognitive achievements. Formal operational thought
does not emerge as consistently and universally in early adolescence as Piaget envisioned
(Kuhn, 2008), and many adolescents and adults do not reason as logically as Piaget
proposed. It may be that even in adulthood, we do not use logical reasoning to make
decisions but rather to justify decisions that are the product of the intuitive hunches that
characterize cognition in childhood (Mercier & Sperber, 2011).
Finally, developmental psychologists interested in cognition have noted that cognitive
changes can occur a f ter Piaget’s formal operations stage. For Piaget, formal operational
Scaf f ol di ng i s a way of
learning t hat we use t hroughout
life. Whenever we int eract wit h
someone who has mor e exper t i se,
we have a new scaf f ol d t o cl i mb.
At ever y age we put
our own s pe ci a l st amp on
egocent r i sm. Have you ever
not i ced t hat each of your
inst ruct ors seems t o t hink
that his or her class is the
onl y one you r e t aki n g?
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300 // CHAPTER 8 // Human Development
thought is the highest level of thinking, and he argued that no new qualitative changes
in cognition take place in adulthood. Developmental psychologists, however, in expand-
ing their focus to the entire life span, have tracked the ways that cognitive skills might
change throughout adulthood.
Cognitive Processes in Adulthood
Although Piaget did not recognize changes in cognitive processes in adulthood, research-
ers have examined how these processes might change throughout adult life. When, dur-
ing your life journey, do you think your cognitive skills are likely to peak?
C O G N I T I O N I N E A R L Y A D U L T H O O D Between the ages of 20 and 30, per-
ceptual speed is at its peak. Individuals in early adulthood have quick re exes and are
better able to respond to sensory input than at any other time in adulthood (Schaie, 2009).
Some cognitive abilities increase between the ages of 20 and 30, as adults accrue greater
capacities for reasoning and verbal memory (Schaie, 2009). Cognitive abilities in early
adulthood may serve as a kind of reserve that promotes positive development throughout
adulthood (Bielak & others, 2012). Longitudinal research shows that cognitive abilities
in early adulthood predict better physical (Phillips & others, 2011) and psychological
(Gale & others, 2008) outcomes in later life. How can people in early adulthood maxi-
mize their cognitive resources? Recall from Chapter 7 that by engaging in challenging
tasks, by thinking outside the box, and by exposure to different cultures we can optimize
our cognitive skills.
C O G N I T I O N I N M I D D L E A D U L T H O O D What happens to cognitive skills
in middle adulthood? The answer depends on the methods researchers use to address
this question. We have seen that in cross-sectional studies, a number of people of
different ages are assessed at one point in time. By examining how the ages of these
individuals relate to the cognitive abilities measured, researchers can nd out whether
younger people differ from older people. Research using cross-sectional designs has
compared individuals in early and middle adulthood on two forms of cognitive abili-
ties: crystallized intelligence , an individuals accumulated information and verbal
skills, and u i d i n telligence , the ability to reason abstractly. The results show that
crystallized intelligence is higher in middle adulthood compared to early adulthood,
but uid intelligence is higher in early adulthood compared to middle adulthood (Horn
& Cattell, 1967).
Recall that in contrast to cross-sectional research, a longitudinal study assesses the
same participants repeatedly over a lengthy period. A longitudinal study of intelligence
in middle adulthood might consist of giving the same intelligence test to the same
individuals over a 20-year time span, when they are 40, 50, and 60 years of age.
Whether data on intelligence are collected cross-sectionally or longitudinally can make
a difference in the conclusions we draw about cognitive ability in middle adulthood
(Schaie, 2009).
K. Warner Schaie is conducting an extensive longitudinal study of intellectual abilities
in adulthood. Five hundred individuals were tested initially in 1956 and have been tested
repeatedly over the years (Schaie, 1994, 2007). New waves of participants are added
periodically. Schaie (2006) has measured a host of different cognitive abilities, and the
results of his studies are shown in Figure 8.13. Schaie found middle adulthood to be a
time of peak performance for aspects of both crystallized intelligence (vocabulary) and
uid intelligence (spatial orientation and inductive reasoning). Based on the longitudinal
data he has collected so far, Schaie (2006, 2007) concludes that middle adulthood, not
early adulthood, is the developmental time frame when many people reach their peak for
a range of intellectual skills.
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Cognitive Development // 301
C O G N I T I O N I N L A T E A D U L T H O O D Many contemporary psychologists
conclude that a number of dimensions of intelligence decline in late adulthood but
that some are maintained or may even increase (see Figure 8.13). A consistent nding
is that when the speed of processing information is involved, older adults do not
perform as well as their younger counterparts. Decline in the speed of processing
is apparent in middle-aged adults and becomes more pronounced in older adults
(Salthouse, 2012).
Older adults also tend to not do as well as younger adults in most aspects of memory
(Salthouse, 2012). In the area of memory involving knowledge of the world (for instance,
the capital of Peru or the chemical formula for water), older adults usually take longer
than younger adults to remember the information, but they often are able to retrieve it
(Singh-Manoux & others, 2012). Further, in the important area of memory in which
individuals manipulate and assemble information to solve problems and make deci-
sions, decline occurs in older adults.
Some aspects of cognition might improve with age. One such area is wisdom ,
expert knowledge about the practical aspects of life (Taylor, Bates, & Webster,
2011). Wisdom may increase with age because of the buildup of life experiences,
but individual variations characterize people throughout their lives (Staudinger &
Gluck, 2011). Thus, not every older person has wisdom, and some young people are
wise beyond their years.
Even for those aspects of cognitive aging that decline, older adults can improve
their cognitive skills with training (Schaie, 2006; Willis & Schaie, 2005). Physical
activity can help to ward off cognitive declines. One study showed that residents of a
retirement community who rode a stationary bike as part of a video game and virtual
reality tour showed less cognitive decline than those who engaged in traditional exer-
cise or none at all (Anderson-Hanley & others, 2012). Still, many experts conclude
that older adults are less able to adapt than younger adults and thus are limited with
respect to how much they can improve their cognitive skills (Salthouse, 2012; Stanford
Center for Longevity, 2012).
Expert knowl-
edge about the
practical aspects
of life.
Mean scores
25 32 39 46 6053 67 74 81 88
Age (years)
Inductive reasoning
Spatial orientation
Perceptual speed
Numeric ability
Verbal ability
Verbal memory
FIGURE 8.13 Longitudinal
Changes in Six Intellectual
Abilities from Age 25 to Age 88
This graph shows the levels of functioning for
six different intellectual abilities for men and
women across adulthood (Schaie, 2006).
> When does the highest level of functioning
occur for each skill? > Which two skills
decline in middle age? > How do the
patterns of verbal ability change for men
and women across the life span? > Which
cognitive ability shows the earliest signs
In younger individuals
wi sdom may c ome at a cost .
They mi ght gai n wi sd om f r om
living t hrough difficult life
exper i ences .
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302 // CHAPTER 8 // Human Development
1. Of the following activities, the one that
uses crystallized intelligence is
A. reciting facts about the Civil War.
B. solving a jigsaw puzzle.
C. using a mathematical formula to
solve a problem.
D. visualizing the way an object would
look if rotated.
2. Most cognitive skills reach their peak
during ______, and most show decline
during _____
A. early adulthood; middle adulthood.
B. middle adulthood; late adulthood.
C. adolescence; early adulthood.
D. adolescence; middle adulthood.
3. Vygotsky stressed that cognitive devel-
opment is an interpersonal process that
happens in a ________ context.
A. historical
B. physical
C. cultural
D. positive
APPLY IT! 4. Tyrone is babysitting his
younger cousins, who are ages 3, 4, and 9.
For lunch, each child will be drinking apple
juice, which they all love. Tyrone has only
three serving cups—one that is short and
wide, and two that are tall and thin.
Although Tyrone pours the same amount of
juice into all the cups, the younger kids
fuss and fight over who gets stuck with the
short, wide cup. The 9-year-old shrugs and
takes the wide cup. Tyrone later proclaims,
“Those other two kids are really spoiled
brats! Thank goodness the oldest is not so
selfish.” Which of the following best applies
to Tyrone’s conclusion?
A. Tyrone is right—young kids are more
likely to be spoiled and whiny.
B. Tyrone does not understand that the
younger kids do not recognize that the
amount of juice in the cups is the same.
The 9-year-old is not being unselfish; he
or she knows the amounts are the same.
C. The 9-year-old probably does not under-
stand that the wider cup contains the
same amount of juice as the other two.
D. Tyrone probably got an A in Develop-
mental Psychology.
So far we have examined the developmental course of physical and cognitive changes.
How do our social and emotional lives change through childhood and adulthood? Recall
that s ocioem o tional processes i n v o l v e c h a n g e s i n a n i n d i v i d u a l s s o c i a l r e l a t i o n s h i p s ,
emotional life, and personal qualities.
Socioemotional Development in Infancy
Emotionally speaking, an infant does not enter the world as a blank slate. When we
observe the newborns behind the window of a hospital nursery, one thing is clear:
Humans differ from one another in terms of their emotional demeanor from the very
beginnings of life. Some are easygoing, and some are prone to distress. Furthermore, in
the earliest days of life, infants encounter a social network that will play an important
role as they develop their sense of self and the world. To begin exploring the socioemo-
tional aspects of development, we focus rst on these ingredients of emotional and social
processes that are present very early in life—infant temperament and attachment.
T E M P E R A M E N T Temperament refers to an individual’s behavioral style and
characteristic ways of responding. For infants, temperament centers on their emotionality
and ways of reacting to stimuli in the environment. Does the infant look with interest at
a new toy, or shy away? Is he or she easily soothed after an upset? Answers to these
questions provide information about infant temperament.
There are a number of ways to think about infant temperament. For example, psy-
chiatrists Alexander Chess and Stella Thomas (1977) identi ed three basic types of tem-
perament in children:
The easy child generally is in a positive mood, quickly establishes regular routines
in infancy, and easily adapts to new experiences.
The dif cult child t e n d s t o b e f u s s y a n d t o c r y f r e q u e n t l y a n d e n g a g e s i n i r r e g u -
lar daily routines.
The slow-to-warm-up child has a low activity level, tends to withdraw from new
situations, and is very cautious in the face of new experiences.
Other researchers have suggested that we should think about infants as being high
or low on different dimensions, such as effortful control or self-regulation (controlling
arousal and not being easily agitated), inhibition ( b e i n g s h y a n d s h o w i n g d i s t r e s s i n a n
An individual’s behavioral
style and characteristic ways
of responding.
Socioemotional Development
Cul t ur e can
influence the meaning
of a di f f i cul t chi l d. I n
cul t ur es wher e women
ar e exp ect ed t o spend al l
of t h ei r t i me and ener gy
cat er i n g t o t hei r chi l d r en,
a di f f i cul t chi l d mi ght
be j ust t he t i cket .
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Socioemotional Development // 303
unfamiliar situation), and negative affectivity ( t e n d i n g t o b e f r u s t r a t e d o r s a d ) ( K a g a n ,
2008). Thus, psychologists have not reached agreement about the core dimensions of
temperament (Evans & Rothbart, 2009). The emotional characteristics that a child brings
into the world serve as a foundation for later personality (Casalin & others, 2012; Komsi
& others, 2006), and the child’s earliest social bonds might set the stage for later social
A T T A C H M E N T Just as infants require nutrition and shelter, they need warm social
interaction to survive and develop. A classic study by Harry Harlow (1958) demon-
strates the essential importance of warm contact. Harlow separated infant monkeys
from their mothers at birth and placed them in cages in which they had access to
two arti cial “mothers.” One of the mothers was a physically cold wire mother; the
other was a warm, fuzzy cloth mother (the “contact comfort” mother). Each mother
could be out tted with a feeding mechanism. Half of the infant monkeys were fed
by the wire mother, half by the cloth mother. The infant monkeys nestled close to
the cloth mother and spent little time on the wire one, even if it was the wire mother
that gave them milk (Figure 8.14). When afraid, the infant monkeys ran to the comfy
mom. This study clearly demonstrates that what the researchers described as “contact
comfort,not feeding, is crucial to the attachment of an infant to its caregiver.
Infant attachment i s t h e c l o s e e m o t i o n a l b o n d b e t w e e n a n i n f a n t a n d h i s o r h e r
caregiver. British psychiatrist John Bowlby (1969, 1989) theorized that the infant and the
mother instinctively form an attachment. In Bowlby’s view, the newborn comes into the
world equipped to stimulate the caregiver to respond; it cries, clings, smiles, and coos.
Bowlby thought that our early relationships with our caregiver are internalized so that
they serve as our schemas for our sense of self and the social world. Many developmen-
tal psychologists concur that attachment during the rst year provides an important foun-
dation for later development (Sroufe, Cof no, & Carlson, 2010).
Mary Ainsworth devised a way to study differences in childrens attachment, called the
strange situation test ( A i n s w o r t h , 1 9 7 9 ; A i n s w o r t h & o t h e r s , 1 9 7 8 ) . I n t h i s p r o c e d u r e , c a r e -
givers leave infants alone with a stranger and then return. Reponses of children to this situ-
ation are used to classify their attachment style. Ainsworth used the term secure attachment
infant attachment
The close emotional bond
between an infant and its
secure attachment
The ways that infants use
their caregiver, usually their
mother, as a secure base
from which to explore the
As s kept i cal s ci ent i s t s ,
psychol ogi st s needed Har l ow
to demonstrate that even
if t he warm, snuggly mot her
di dn’ t pr ovi de f ood, she was
st i l l a sour ce of comf or t .
Fed on cloth mother
Fed on wire mother
Mean hours per day
15 610 11–15 16–20 21–25
Days of age
Hours per day spent
with cloth mother
Hours per day spent
with wire mother
Contact Time with Wire
and Cloth Surrogate
Mothers Regardless of
whether the infant monkeys
were fed by a wire or a cloth
mother, they overwhelmingly
preferred to spend contact
time with the cloth mother.
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304 // CHAPTER 8 // Human Development
to describe how infants use the caregiver, usually the mother, as a secure base from which
to explore the environment. In the strange situation, the secure infant is upset when the
mother leaves, but calms down and appears happy to see her when she returns. Infants
who are securely attached are more likely to have mothers who are responsive and
accepting and who express affection toward them than are infants who are insecurely
attached (Behrens, Parker, & Haltigan, 2011). The securely attached infant moves freely
away from the mother but also keeps tabs on her by periodically glancing at her. An
insecurely attached infant, in contrast, avoids the mother or is ambivalent toward her. In
the strange situation, such an infant might not even notice the mother has gone (some-
times called avoidant or dismissive attachment style ), or conversely might respond with
intense distress, only to rage at the mother when she returns (sometimes called anxious
or preoccupied attachment style ).
One criticism of attachment theory is that it does not adequately account for cultural
variations (van IJzendoorn & Bakermans-Kranenburg, 2010). For example, in some
cultures infants show strong attachment to many people, not just to their primary
caregiver (Rothbaum & others, 2000, 2007). Infants in agricultural societies tend to
form attachments to older siblings who are assigned a major responsibility for younger
Another critique of attachment theory is that it may not account for temperamental
differences among infants that might color the attachment relationship. In addition, care-
givers and infants likely share genetic characteristics, and it might be that the attachment
relationship is really a product of these shared genes. Despite such criticisms there is
ample evidence that secure attachment is important to development (Sroufe, Cof no, &
Carlson, 2010).
Equipped with the key basic ingredients of temperament and attachment, how does a
human being develop in the socioemotional domain? This question was addressed by
Erik Erikson, who devised a theory of what he called psychosocial development. Erikson’s
Developmental period:
Infancy (Birth to 1
Characterist ics: A sense of
trust requires a feeling of
physical comfort and minimal
amount of fear about the future.
Infants basic needs are met by
responsive, sensitive caregivers.
Developmental period: Early
childhood (preschool years,
ages 3–5)
Characterist ics: As preschool
children encounter a widening
social world, they are challenged
more and need to develop more
purposeful behavior to cope with
these challenges. Children are
now asked to assume more re-
sponsibility. Uncomfortable guilt
feelings may arise, though, if the
children are irresponsible and are
made to feel too anxious.
Developmental period:
Toddlerhood (1
to 3 years)
Characterist ics: After gaining
trust in their caregivers, infants
start to discover that they have
a will of their own. They assert
their sense of autonomy, or
independence. They realize their
will. If infants are restrained too
much or punished too harshly,
they are likely to develop a
sense of shame and doubt.
Developmental period: Middle and
late childhood (elementary school
years, 6 years–puberty)
Characterist ics: At no other time are
children more enthusiastic than at
the end of early childhoods period
of expansive imagination. As chil-
dren move into the elementary school
years, they direct their energy
toward mastering knowledge and
intellectual skills. The danger at this
stage involves feeling
incompetent and
Trust Versus M istrust
Autonomy Versus
Sham e and Doubt
Initiative Ve rsu s G uilt Indu stry Ve rsus Infe riority
Erikson’s Eight Stages
of Psychosocial
Development Erikson
changed the way psychologists
think about development by
tracing the process of growth
over the entire life span.
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Socioemotional Development // 305
theory has powerfully guided thinking about how human beings’ social and
emotional capacities develop throughout the entire life span.
Eriksons Theory of Socioemotional
The life-span development theory of the in uential psychologist Erik Erikson
(1902–1994), who trained as a psychoanalyst under Sigmund Freud, pro-
posed eight psychosocial stages of development from infancy through late
adulthood. In calling the stages psychosocial , Erikson meant to emphasize
how a person’s psychological life is embedded in and shaped by social rela-
tionships and challenges faced by the developing person. Figure 8.15 illus-
trates all of Erikson’s stages.
From Erikson’s (1968) perspective, each stage represents the developmen-
tal task that the individual must master at a particular place in the life span.
According to Erikson, these developmental tasks are represented by two pos-
sible outcomes, such as trust versus mistrust (Erikson’s rst stage). If an
infant’s physical and emotional needs are well taken care of, he or she will
experience an enduring sense of trust in others. If, however, these needs are
frustrated, the person might carry concerns about trust throughout life, with bits of this
un nished business being re ected in the rest of the stages. For Erikson, each stage is a
turning point with two opposing possible outcomes—one, greater personal competence;
the other, greater weakness and vulnerability. Using Erikson’s stages as a guide, let’s
consider the various ways that human beings develop in terms of their capacities for
interpersonal relationships and emotional well-being.
Erik Erikson (1902–1994)
Erikson generated one of the most
important developmental theories of the
twentieth century.
Developmental period:
Adolescence (10–20 years)
Characterist ics: Individuals are
faced with finding out who they are,
what they are all about, and where
they are going in life. An important
dimension is the exploration of
alternative solutions to roles. Career
exploration is important.
Developmental period:
Middle adulthood (40s, 50s)
Characterist ics: A chief concern
is to assist the younger genera-
tion in developing and leading
useful lives.
Developmental period:
Eary adulthood (20s, 30s)
Characterist ics: Individuals face
the developmental task of
forming intimate relationships
with others. Erikson described
intimacy asnding oneself yet
losing oneself in another person.
Developmental period:
Late adulthood (60s )
Characterist ics: Individuals look
back and evaluate what they have
done with their lives. The retro-
spective glances can be either
positive (integrity) or negative
Ide n tity Ve rs us
Ide n tity Co nfusion
Intim a cy Ve rs us Iso la tion
Generativity Versus
Inte grity Ve rsus D e spa ir
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306 // CHAPTER 8 // Human Development
TO INDUSTRY Erikson’s rst four stages apply to childhood. Each stage is inti-
mately linked with the kinds of activities associated with human life at each age:
Trust versus mistrust: Infancy (birth to 1½ years) is concerned with establishing trust
in the social world. At this stage, the helpless infant depends on caregivers to establish
a sense that the world is a predictable and friendly place. Once trust is established,
toddlers begin to see themselves as independent agents in the world.
Autonomy versus shame and guilt: During toddlerhood (1½ to 3 years), children, many
of whom are going through toilet training, experience the beginnings of self-control.
When these young children have the opportunity to experience control over their own
behaviors, they develop the capacity for independence and con dence.
Initiative versus guilt: In early childhood (ages 3 to 5), preschoolers experience what
it is like to forge their own interests and friendships and to take on responsibilities.
If you have ever spent time with a 3-year-old, you know how often the child wants
to help with whatever an adult is doing. When they experience a sense of taking on
responsibility, preschoolers develop initiative. Otherwise, according to Erikson, they
may feel guilty or anxious.
Industry versus inferiority: During middle and late childhood (6 years to puberty),
children enter school and gain competence in academic skills. Just as the label indus-
try would suggest, children nd that this is the time to get to work, learn, achieve,
and learn to enjoy learning.
From Erikson’s perspective, then, children should grow toward greater levels of auton-
omy and self-con dence as they progress from infancy to school age and beyond. Is
there a particular parenting style that is most likely to lead to these sorts of outcomes?
Let’s nd out.
Parenting and Childhood Socioemotional Development Researchers have
tried to identify styles of parenting associated with positive developmental outcomes.
Diana Baumrind (1991, 1993) described four basic styles of interaction between parents
and their children:
Authoritarian parenting i s a s t r i c t p u n i t i v e s t y l e . T h e a u t h o r i t a r i a n p a r e n t rmly
limits and controls the child with little verbal exchange. In a difference of opinion
about how to do something, for example, the authoritarian parent might say, “You do
it my way or else. Children of authoritarian parents sometimes lack social skills,
show poor initiative, and compare themselves with others.
Authoritative parenting encourages the child to be independent but still places lim-
its and controls on behavior. This parenting style is more collaborative. Extensive
verbal give-and-take is allowed, and parents are warm and nurturing toward the child.
An authoritative father might put his arm around the child in a comforting way and
say, “You know you should not have done that; let’s talk about how you can handle
the situation better next time. Children of authoritative parents tend to be socially
competent, self-reliant, and socially responsible.
Neglectful parenting is distinguished by a lack of parental involvement in the child’s
life. Children of neglectful parents might develop a sense that other aspects of the
parents’ lives are more important than they are. Children whose parents are neglectful
tend to be less competent socially, to handle independence poorly, and (especially) to
show poor self-control.
Permissive parenting places few limits on the child’s behavior. A permissive parent
lets the child do what he or she wants. Some parents deliberately rear their children
this way because they believe that the combination of warm involvement and few
limits will produce a creative, con dent child. However, children with very permissive
parents typically rate poorly in social competence. They often fail to learn respect for
others, expect to get their own way, and have dif culty controlling their behavior.
authoritarian parenting
A restrictive, punitive style
in which the parent exhorts
the child to follow the par-
ent’s directions.
authoritative parenting
A parenting style that en-
courages the child to be
independent but that still
places limits and controls on
neglectful parenting
A parenting style character-
ized by a lack of parental in-
volvement in the child’s life.
permissive parenting
A parenting style character-
ized by the placement of
few limits on the child’s
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Socioemotional Development // 307
Recall that socioemotional development means becoming
increasingly adept at controlling and regulating one’s emotions
and behaviors. Children may require structure from their care-
givers to acquire these skills.
The Cultural Context of Parenting Culture in uences the
effects of parenting on children, especially authoritarian parenting.
In one study, mothers from four collectivistic cultures (Iran, India,
Egypt, and Pakistan) described themselves as authoritarian but did
not express negative attitudes about their children, and the children
did not show negative outcomes (Rudy & Grusec, 2006). For
Latino families, some psychologists have suggested that authoritar-
ian parenting may express culturally valued childrearing goals such
as family, respect, and education and that this parenting style must
be understood in the context of these cultural ideals (Halgunseth,
Ispa, & Rudy, 2006). On the basis of her research, Ruth Chao
(2001, 2007; Chao & Otsuki-Clutter, 2011) has argued that many
Asian American mothers and fathers function as “training parents”
who focus exclusively on directing and guiding their children to
high academic achievement.
S O C I O E O M O T I O N A L D E V E L O P M E N T I N A D O L E S C E N C E : T H E E M E R -
GENCE OF IDENTITY Erikson (1968) viewed the key challenge of adolescence
as identity versus identity confusion. In seeking an ide n tity, adolescents must nd out
who they are, what they are all about, and where they are going in life. Adolescents are
confronted with many new roles and adult statuses—from the vocational to the romantic.
If they do not adequately explore their identities during this stage, they emerge confused
about who they are. Adolescents who spend this time in their lives exploring alternatives
can reach some resolution of the identity crisis and emerge with a new sense of self.
Those who do not successfully resolve the crisis become confused, suffering what Erikson
calls identity confusion . This confusion is expressed in one of two ways: Either indi-
viduals withdraw, isolating themselves from peers and family, or they lose themselves in
the crowd.
Marcia’s Theory of Identity Status Building on Erikson’s ideas, James Marcia
proposed the concept of identity status t o d e s c r i b e a n a d o l e s c e n t s p o s i t i o n i n t h e
development of an identity (Kroger, Martinussen, & Marcia, 2010; Marcia, 1980,
2002). In Marcias view, two dimensions of identity, exploration and commitment, are
important. Exploration refers to a person’s investigating various options for a career
and for personal values. Commitment involves deciding which identity path to follow
and personally investing in attaining that identity. Various combinations of exploration
and commitment give rise to one of four identity statuses, according to Marcia
( F i g u r e 8 . 1 6 ) :
Identity diffusion : The adolescent has neither
explored nor committed to an identity. Adolescents
experiencing identity diffusion may describe them-
selves as not caring about much in the world. They
have not confronted the crisis of identity or are so
overwhelmed by the challenge of answering the
question “Who am I?” that they have withdrawn.
These individuals may nd themselves in crisis.
Eventually, as they engage in life, these adolescents
will begin the process of thinking about what matters
(and what does not) and enter into the stage of explo-
ration called morat o rium .
“Relax, Ted, it’s only a phase.”
Used by permission of CartoonStock,
Ye s
Ye s
Has the person
some identity
Has the person made a commitment?
FIGURE 8.16 Marcia’s Four Statuses of Identity
Who are you? When you think of how you have come to identify yourself,
which of these four statuses does your answer best represent?
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308 // CHAPTER 8 // Human Development
Identity moratorium : The adolescent is actively exploring and trying on new roles but
has not committed to a particular identity. For example, consider an adolescent who
passionately throws himself into a variety of internship opportunities to see what
different jobs might be like, or the rst-year college student who takes a range of
different classes to explore potential careers.
Identity foreclosure: The adolescent has committed to a particular identity but has
done so without actually exploring his or her options. An example is a girl who
decides to pursue accounting as a major in college because everyone in her family is
an accountant.
Identity achievement : After exploring the options and committing to an identity, the
adolescent emerges with a sense of his or her own values and principles, a sense of
the kind of person he or she wishes to be, and goal commitments that provide his or
her life with a feeling of purpose.
Marcia therefore views identity as an active construction, an outcome of a process of
thinking about and trying on different identities (Klimstra & others, 2009, 2010). Some
of the things we associate with adolescence, then—such as rebelling against one’s
p a r e n t s , a s s e r t i n g o n e s o w n s e n s e o f s t y l e , a n d d e v e l o p i n g o n e s o w n i n t e r e s t s a n d
relationships—are part of the active developer’s assertion of himself or herself in the
service of identity.
Ethnic Identity Within a Larger Culture D e v e l o p i n g a n i d e n t i t y i n a d o l e s c e n c e
can be especially challenging for individuals from ethnic minority groups (Syed, 2010;
Syed, Azmitia, & Cooper, 2011). As they mature cognitively, many adolescents become
acutely aware of the evaluation of their ethnic group by the majority culture. In addition,
an increasing number of minority adolescents face the challenge of b i cultura l ism
identifying in some ways with their ethnic minority group and in other ways with the
majority culture (Marks, Patton, & Coll, 2011).
Research has shown that for ethnic minority youth, feeling both a positive attachment
to their minority group and an attachment to the larger culture is related to more positive
academic and emotional outcomes (Umaña-Taylor, Updegraff, & Gonzales-Bracken,
2011). Although it might seem that being a member of an ethnic minority would make
life more stressful, studies have indicated that having a strong ethnic identity can buffer
adolescents from the effects of discrimination (Iturbide, Raffaelli, & Carlo, 2009). For
both minority and majority adolescents, developing a positive identity is an important
life theme (Kort-Butler & Hagewen, 2011; Oyserman & others, 2003; Umaña-Taylor,
Gonzales-Backen, & Guimond, 2009). In addition to ethnic identity, adolescence can be
a time when other aspects of one’s identity come to the fore, such as sexual orientation
or gender roles. We will examine the latter later in this chapter.
Parents and Peers Parents and peers can help the adolescent answer the central
questions of identity, “Who am I, and who do I hope to become?” To help adolescents
reach their full potential, a key parental role is to be an effective manager—one who
locates information, makes contacts, helps to structure offsprings’ choices, and provides
guidance. By assuming this managerial role, parents help adolescents to avoid pitfalls
and to work their way through the decisions they face (Simpkins & others, 2009).
For parents to play an active role in the development of their sons and daughters, they
have to know what is going on in their adolescent’s life. Research on adolescents’ man-
agement of their parents’ access to information, especially disclosing or concealing strat-
egies about their activities, shows that adolescents are more willing to disclose
information to parents when parents ask teenagers questions and when the parent–child
relationship is characterized by a high level of trust, acceptance, and quality (Smetana
& others, 2010; Tasopoulos-Chan, Smetana, & Yau, 2009).
During adolescence, individuals spend more time with peers than they did in child-
hood. These peer in uences can be positive or negative. A signi cant aspect of positive
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Socioemotional Development // 309
peer relations is having one or more close friends. Adolescents can learn to be skilled
and sensitive partners in intimate relationships by forging close friendships with
selected peers. However, some peers and friends can negatively impact adolescents’
development. Researchers have found that hanging out with delinquent peers in
adolescence can be a strong predictor of substance abuse, delinquent behavior, and
depression (Laursen & others, 2012).
For Erikson, once the issues of identity have been resolved, the young adult turns to the
important domain of intimate relationships. However, recently, scholars have noted that dur-
ing the life stage after adolescence, many young people seem to be putting off the kinds of
commitments to marriage, family, and career that we associate with adult life. Jeffrey Arnett
(2004, 2007, 2010) introduced the concept of emerging adulthood t o d e s c r i b e t h i s t r a n s i -
tional period that is partly an extended adolescence and partly a phase of experimenting
with adult roles. If you are a traditional-age college student, you are at this point in the life
span. Let’s brie y examine socioemotional development typical to this life stage.
Emerging adulthood is the transitional period from adolescence to adulthood (Arnett,
2004, 2006, 2007). The age range for emerging adulthood is approximately 18 to 25
years of age. Experimentation and exploration characterize the emerging adult. At
this point in their development, many individuals are still investigating their career
path, their identity, and the kinds of close relationships they will have.
Jeffrey Arnett (2006, 2010) identi ed ve main features of emerging adulthood:
Identity exploration, especially in love and work: Emerging adulthood is the time
of signi cant changes in identity for many individuals.
Instability: Residential changes peak during emerging adulthood, a time during which
there also is often instability in love, work, and education.
Self-focus: Emerging adults “are self-focused in the sense that they have little in the
way of social obligations, little in the way of duties and commitments to others, which
leaves them with a great deal of autonomy in running their own lives” (Arnett, 2006,
p. 10).
Feeling “in between”: Many emerging adults consider themselves neither adolescents
nor full- edged adults.
The age of possibilities, a time when individuals have an opportunity to transform
their lives: Arnett (2006) describes two ways in which emerging adulthood is the age
of possibilities: (1) Many emerging adults are optimistic about their future, and (2)for
emerging adults who have experienced dif cult times while growing up, emerging
adulthood presents an opportunity to guide their lives in a more positive direction.
Emerging adults have more choices—and more control over those choices—in their
daily life. The choices emerging adults make with regard to their life goals have implica-
tions for their later well-being. A longitudinal study spanning 17 years showed that the
changes emerging adults made in their goals predicted their levels of well-being as adults
(Hill & others, 2011), suggesting that this time of life sets the stage for later develop-
ment. Eventually, though perhaps later than previous generations, emerging adults adopt
the mantle of adulthood. According to Erikson, the early part of adulthood is occupied
with the experience of loving, intimate relationships .
VERSUS ISOLATION E r i k s o n s ( 1 9 6 8 ) s i x t h s t a g e , intimacy versus isolation,
refers to the challenge of forming intimate relationships with others or becoming
socially isolated. Erikson describes intimacy as both nding oneself and losing oneself
in another. If the young adult develops healthy friendships and an intimate relationship
with a partner, intimacy will likely be achieved. One key way that young adults
The transitional
period from
adolescence to
adulthood, span-
ning approxi-
mately 18 to 25
years of age.
If you could travel
back i n t i me and vi si t your
adol escent s el f , what woul d
you t el l hi m or her ?
Some peopl e ent er
adul t hood ear l i er t han
ot her s. Some mar r y, st ar t
a f ami l y, and t ake up f ul l -
time employment right out
of hi gh school . Do you t hi nk
these individuals experience
“emerging adult hood”?
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310 // CHAPTER 8 // Human Development
achieve intimacy is through long-term relationships with a romantic partner, often
including marriage.
Marriage J u s t a s t h e n o t i o n o f e m e r g i n g a d u l t h o o d w o u l d i n d i c a t e , i n t h e l a s t t w o
decades or so, men and women are waiting longer to marry. For example, in
2010, the average age for a rst marriage in the United States climbed to just
over 28 years for men and 26 years for women (Copen & others, 2012). This
may be good news for marital stability. Women who marry before age 20
are three times more likely to divorce within ve years than those who
marry after age 20 (Copen & others, 2012).
What makes for a successful marriage? John Gottman has been study-
ing married coupleslives