1. Development Throughout the Life Span
Chapter 12
Development Throughout
the Life Span

2. Objectives 12.1 The Beginnings of Development
Describe the development of the field and explain the prenatal and newborn stages of human development.
12.2 Infancy and Childhood
Discuss physical development in infants and newborns.
Examine Piaget’s stage theory in relation to early cognitive development.
Illustrate the importance of attachment in psychosocial development.

3. Objectives 12.3 Adolescence and Young Adulthood
Discuss the impact of sexual development in adolescence and changes in moral reasoning in adolescents and young adults.
Examine the life stages within Erikson’s theory of psychosocial development.

4. Objectives 12.4 Adulthood and Aging
Illustrate the physical, cognitive, and social aspects of aging.
12.5 Nature and Nurture
Describe the multiple influences of nature and nurture in human development.

5. What Is Development?
Development is one of the most challenging areas within psychology because its focus is on how the individual changes over time.
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Chapter 12: Development Throughout the Life Span
12.1 The Beginnings of Development
LO: Describe the development of the field and explain the prenatal and newborn stages of human development
Development is one of the most challenging areas within psychology because its focus is on how the individual changes over time. If we repeatedly measured aspects of your life over time, we would be conducting a longitudinal study. This type of study compares the same person to him- or herself at different points in time. Alternatively, we can try to understand change by comparing people entering college to others entering high school. This approach, called a cross-sectional study, compares different groups of people at different ages. The problem is that there may be cohort effects; that is, life may be different for those entering high school now than it was for the older group when they entered high school. Psychologists try to identify the “universal” features of development over time. These are features that hold true for everyone, no matter what culture they are raised in or what gender they are, and regardless of any other differences among individuals. However, culture plays a critical role in human development.

6. Prenatal Development
Zygote: An initial stage in development as the fertilized egg grows through cell division and attaches to the uterine wall
Embryo: Prenatal stage following zygote lasting 2 to 8 weeks; in this stage, the heart begins beating
Fetus: The unborn child from around 9 weeks until birth
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Chapter 12: Development Throughout the Life Span
12.1 The Beginnings of Development
LO: Describe the development of the field and explain the prenatal and newborn stages of human development
Maturation refers to biological growth that occurs continuously over time. From the moment of conception, when a sperm cell meets an egg cell and they combine, growth begins. Each cell contains 23 pairs of chromosomes, one of each pair from your father and one from your mother. Each chromosome is made up of more than 2000 genes, for a total of 50,000 genes within each cell. Genotypes provide a “blueprint” for your body’s development; however, genes are expressed flexibly, so that they may be turned on and off and may require specific environmental cues in order to act. As a result, your phenotype (your observed characteristics) may or may not reflect the underlying genetic code. Genetics influence prenatal (before birth) development by directing the growth of the fertilized egg. The initial stage, called the zygote, lasts only between 1 and 2 weeks. If genes or chromosomes are missing or extra copies are present, or if mutations occur, then needed proteins may be absent or made in excess. As a result, abnormal development and growth of the zygote may result. Once implanted in the uterus, the zygote enters the embryo stage for between 2 and 8 weeks. In the embryo, the heart begins beating. By 2 months, sexual differentiation occurs. About 126 male embryos are formed for every 100 female embryos, but male embryos have lower chances of survival, with 105 males born for every 100 females. From around 9 weeks until birth, the now identifiably human fetus continues to develop. But exposure to toxic agents from the environment, called teratogens, is a dangerous problem for fetal development. The fetus is not just growing before birth but also increasing in differentiation; that is, its structures and functions are becoming more specific to perform given tasks. By around 6 months, the fetus has developed enough that it may survive on its own if born prematurely; this is called the age of viability. A full-term birth is typically 37 weeks of prenatal development.

7. Infancy and Childhood Physical Cognitive Social Neural Plasticity
Rapid Growth
Piaget’s Stage Theory:
Sensorimotor
Preoperational
Concrete Operational
Formal Operational
Touch as Primary
Attachment Bond
Secure
Insecure
Avoidant
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Discuss the physical development in infants and newborns
Most animals enter the world with many “built-in” abilities to help them survive. Newborn humans are also equipped with reflexes present for the first few months of life. Babies have a “rooting” instinct, in which a touch on the cheek causes them to turn and open their mouths. Infants show considerable variability in their natural reactions to stimulation from the environment. Individual differences in temperament, or emotional, motor, and attentional reactions to stimulation, are evident in the first few weeks of life. The visual system is not well developed at birth, and infants see best at a distance of around 8 inches. But newborns have inborn visual preferences that are particularly helpful. Babies are so attentive to faces that they can make surprising distinctions between them. They are not only more interested in faces; they also come prepared to mimic them. Within 72 hours of birth, newborns imitate gestures. Like their vision, newborns’ hearing is also underdeveloped at birth, but infants have been found to like listening to higher-pitched voices. As a result, a “baby talk” voice (called motherese —high in pitch, rhythmic, and simple) is better at attracting responses from babies. These inborn patterns of attention are very helpful in focusing attention on social interactions, a very adaptive behavior in evolutionary terms.

8. Physical Development
Physical growth occurs at a faster rate in the young, with another spurt in adolescence. After the first year, the head becomes proportionally smaller.
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Discuss the physical development in infants and newborns
Physical growth occurs at a faster rate in the young, with another spurt in adolescence. After the first year, the head becomes proportionally smaller. In humans, infant cranial capacity is only 23% of adult capacity; at age 2.5, cranial capacity is 75%; and at age 5, the brain has reached 90% of adult size. But the biological processes of growth are also affected by experience in the world. Stimulating environments produce larger, more interconnected brains. Young children also appear to have greater plasticity in their neural functions. Plasticity is the capacity of the brain to adapt to the “dings, dents, and major insults” that alter it. This is because synaptic connections are created more quickly in younger brains. "Younger people who suffer brain injuries are less likely to have linguistic deficitsthan people whose brains are injured when older. The maturing brain also increases its speed of processing. Between the ages of 8 and 12, the children get much faster at performing a mental task. In addition to continuous maturation or growth, development can take place as an orderly progression of stages, or discrete, qualitative “jumps” over time.

9. Developmental Norms
Developmental norms are milestones that identify when certain behaviors usually occur in normal development.
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Discuss the physical development in infants and newborns
Developmental norms are milestones that identify when certain behaviors usually occur in normal development. Normative stages include motor skills (run, keep balance, use hands to eat and draw), language skills (gestures and communication), cognitive skills (learning, remembering, reasoning), and social skills (cooperating, responding to others). Doctors use norms to identify children who may have disruptions (such as hearing loss) or delays in their development. Though each milestone is associated with age, the actual age when a given child reaches that milestone can vary quite a bit.

10. Piaget’s Stage Theory
Piaget’s theory of cognitive development focused on the formation of concepts, or mental frameworks for organizing and categorizing information.
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Examine Piaget’s stage theory in relation to early cognitive development..
Piaget’s theory of cognitive development focused on the formation of concepts, or mental frameworks for organizing and categorizing information. These concepts change through two processes: (1) assimilation, using current concepts to understand new information, and (2) accommodation, changing concepts to fit new information. Piaget then identified four different stages of thinking, each marked by specific qualities. He proposed all humans go through an orderly sequence of stages in cognitive development and identified when the stages take place.
Sensorimotor Stage: Children focus on developing sensory and motor processes to coordinate their movements and their eyes with their hands. Object permanence is a key sign that a child is moving out of the sensorimotor period and into the preoperational stage.
Preoperational Stage: Preschoolers are still focused on what they perceive. Conservation is the principle that an object maintains the same mass, volume, or number, even if it is displaced across space. Children in the preoperational stage are overwhelmed by what things look like. Preschool children also believe that others know, think, and feel the same way they do, called egocentrism.
Concrete Operational Stage: Around age 7, children achieve conservation and are no longer fooled by appearances. As they enter grade school, they receive some training in logical thinking. But while they are able to learn concrete concepts, they are still limited in their reasoning. The ability to combine two dimensions at once is finally accomplished toward the end of the concrete operational stage.
Formal Operational Stage: Begins at about age 12 and is characterized by reasoning on a logical or hypothetical level. Children around the time of puberty are finally cognitively capable of learning the formal methods of thinking, and formal schooling helps to develop these skills.

11. Challenges to Piaget’s Stage Theory
By depending only on the baby’s motor behaviors, Piaget underestimated their cognitive abilities.
Cognition develops more gradually and continuously.
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Examine Piaget’s stage theory in relation to early cognitive development..
Piaget claimed that, after about 9 months, babies will search for hidden objects, suggesting the infant achieved object permanence. But new studies using looking times showed that infants as young as 5 months thought the hidden object was still there. By depending only on the baby’s motor behaviors, Piaget underestimated the cognitive abilities of babies.
Piaget’s notion of egocentrism has also been expanded to reflect the theory of mind, or the child’s conception of what he or she and others know. Three-year-olds have some understanding of their own and others’ minds; two-year-olds can predict actions and emotions. The idea of false beliefs does not arise until age 4 or 5. Other theorists, such as Lev Vygotksy, proposed that cognition also requires social processes during learning. He proposed a zone of proximal development that predicts what children will learn next. This zone is the range between what the child can already do and what he or she is ready to accomplish.
Studies show that babies know more than Piaget suspected, and that cognition develops more gradually and continuously than he proposed. However, Piaget was accurate in that children do seem to progress through his four stages of thinking in the same order and at about the ages he predicted they would.

12. Social Development
Contact comfort: The need for touch as a primary drive in monkeys and humans
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Illustrate the importance of attachment in psychosocial development
Human infants, like the young of most mammals, are dependent on their parents to help them survive and thrive. One of the primary bonds across species is the mother–infant bond. In evolutionary terms, it is in a mother’s best interest to foster the well-being of her child and for the child to attract and hold the interest of its mother. Attachment refers to this deep, emotional bond that an infant develops with its caregiver. Harlow’s study of monkeys identified the need for contact comfort, or the need for touch, as a primary drive in monkeys. The benefits of child–caregiver touch are readily observed across cultures and childrearing practices.

13. Attachment Theory
John Bowlby developed a theory about the formation of attachment bonds and suggested there is a sensitive period for them.
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Illustrate the importance of attachment in psychosocial development
John Bowlby developed a theory about the formation of attachment bonds and suggested there is a sensitive period for them. This means attachment relationships develop more readily when the child is between 6 and 24 months of age. This sensitive period coincides with a period during which the baby shows an increasing tendency to approach familiar caregivers and to avoid unfamiliar adults. This stranger anxiety refers to the fear reaction infants develop around 12 months of age. A related fear, called separation anxiety, is expressed when babies are separated from a parent, and is observed across cultures. However, developmental psychologists also noticed that children differ in their level of attachment to their caregiver.
Strange situation procedure is a test in which the mother leaves her child alone in a playroom, and a friendly stranger tries to interact with the child. Finally, the mother rejoins them. Results showed that 60% of infants tested at 1 year of age showed a secure attachment to their mother. With secure attachment, the infant feels her caregiver will meet her needs. Secure attachment is more likely to occur when the mother is available and appropriately responsive to her child. What happens when secure attachment is disrupted? Some babies learn they cannot rely upon the caregiver and act this out in the strange situation task mentioned earlier by showing insecure attachment. Some of these children seem to alternately seek out and then avoid their mothers; this is called ambivalent/anxious attachment. Ainsworth’s studies of families in their homes demonstrated that a secure attachment relationship depends on the quality of caregiving the infant receives. Consistent and responsive caregiving leads to a more secure attachment. As adults, our styles in relationships tend to mirror the same pattern of attachment we experienced in our primary relationship.

14. Family Relationships Parenting Styles Authoritarian Permissive
Authoritative
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Illustrate the importance of attachment in psychosocial development
Studies of parenting have identified differences how parents establish control over their children. The authoritarian parenting style focuses on obedience without question and tends to produce children with low self-esteem. Permissive parents go to an opposite extreme, allowing the children to impose their own control on their behavior. Due to the lack of boundaries, these children are often impulsive and more immature than other children. The authoritative parenting style falls in the middle of these extremes: They have rules to be followed, but the parents are willing to explain the reasons behind them and to allow occasional exceptions to them. Children reporting high levels of self-confidence tend to have authoritative parents.

15. Family Relationships Differential parenting Siblings Daycare Divorce
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Illustrate the importance of attachment in psychosocial development
If children receive equal affection from their parents (in comparison to siblings), they have higher self-esteem, more secure attachment styles, and less romantic relationship distress. However, if parents “play favorites,” the children feel more negative about themselves, whether or not they’re the favored child. The early within-family experiences of childhood appear critical to building healthy self-esteem, and they continue to influence us throughout life.
Sibling relationships also contribute to development. Interactions with older siblings can improve language and cognitive development and the understanding of other people’s emotions and perspectives. However, aggressive older siblings can lead to younger children performing poorly in school and having fewer positive peer experiences.
A major concern for many parents is the effect of daycare on their child’s development. While no research has shown a relationship between working mothers and outcomes of development, a longitudinal study found that children who had spent more time in daycare showed increased aggressive behavior, but only through grade 3.
When divorce occurs, it is often accompanied by a history of family strife and other changes. As a result, it can be difficult to discern the causal factors in adjustment. Children with divorced parents score significantly lower on measures of academic achievement, conduct, psychological adjustment, self-concept, and social relations.

16. Peers
Kindergarteners are much more likely to have same-sex play partners.
Gender differences in observed behavior occur early in development, well before the biological influences.
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Chapter 12: Development Throughout the Life Span
12.2 Infancy and Childhood
LO: Illustrate the importance of attachment in psychosocial development
One of the first self-identifications children make is their gender: They learn to think of themselves as male or female by age 4. They then use this knowledge to self-segregate by gender to form
peer groups. One study found a 10-to-1 ratio in same-sex versus opposite-sex play partners in kindergarteners. Gender roles: Our expectations about how males and females should act—are learned through culture. Gender differences in observed behavior occur early in development, well before the biological influences from reproductive maturation in puberty. Peer relationships in childhood can be important bonds even for very young children like preschoolers. Children who had been together for 3 to 4 years but then transferred to new schools showed increases in desire for physical contact, negative statements and affect, fussiness, and illness, as well as changes in eating and sleeping patterns.
Peer relationships can sometimes be marked by bullying, either as an aggressor or as a victim. Children who are chronic victims of bullying experience more physical and psychological problems than their peers, and they tend not to grow out of the role of victim.

17. Adolescence and Young Adulthood
Physical
Cognitive
Social
Puberty:
Sexual Maturation
Growth Spurt
Neural Growth and Pruning
Emotion over Cognition
Moral Reasoning
Identity Formation
Separation from Parents
Peer Relationships
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Chapter 12: Development Throughout the Life Span
12.3 Adolescence and Young Adulthood
LO: Discuss the impact of sexual development in adolescence and changes in moral reasoning in adolescence and young adults.

18. Physical Development
Primary sexual characteristics: The reproductive organs and external genitalia
Secondary sexual characteristics: Physical changes, along with a spurt in height and changes to the body’s overall shape, that occur during puberty
Menarche: The occurrence of a first menstrual period, indicating the capacity to become pregnant
Spermarche: The first ejaculation occurs around age 14, followed a year later by the development of mature sperm cells
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Chapter 12: Development Throughout the Life Span
12.3 Adolescence and Young Adulthood
LO: Discuss the impact of sexual development in adolescence and changes in moral reasoning in adolescence and young adults.
Adolescence is marked by puberty, or the sexual maturation that occurs as a result of rising hormone levels. Primary sexual characteristics, the reproductive organs and external genitalia, undergo development. Secondary sexual characteristics announce puberty, along with a spurt in height and changes to the body’s overall shape. For girls, the first menstrual period, called menarche, occurs (on average) at age 12, indicating the capacity to become pregnant. For boys, the first ejaculation occurs around age 14, followed a year later by the development of mature sperm cells, called spermarche. The psychological effects of these physical changes can cause girls to focus on their appearance, while boys experience puberty as a more positive change.

19. Brain Development
Gray matter volume in the cortex increases with maturation from 5 to 20 years of age.
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Chapter 12: Development Throughout the Life Span
12.3 Adolescence and Young Adulthood
LO: Discuss the impact of sexual development in adolescence and changes in moral reasoning in adolescence and young adults.
The physical maturation of the brain goes through its own growth spurt during adolescence. Our brains undergo a massive reorganization between our 12th and 25th years. The neural connections in the brain become increasingly complex and differentiated in their purpose in the adolescent years. As a result, the cortex becomes thinner but more efficient. In addition, the speed of processing in the brain grows to be a hundred times faster due to increased myelination (or covering) of neural axons. The teenage brain is driven by emotion, and cognitive control takes longer to develop. Physical changes in the brain during adolescence start in the rear brain areas and the limbic system and move slowly toward the frontal lobes. This means that more basic functions, such as emotion, vision, and movement, improve in processing speed first. The amygdala areas respond to negative or fearful stimuli more intensely during adolescence, and brain areas involved in rewards are activated more in teens. This means emotional reactivity increases before the development of control provided by the frontal areas. As a result, adolescents’ capacity for cognitive control has not fully matured. By the end of adolescence, there is gradual improvement in the ability to control or inhibit behavior, to weigh decisions, and to consider more information at one time. The consequence of neural development is that thinking is qualitatively different during adolescence. Because teens are less controlled and focused, they may be more flexible in noticing and responding to new situations, just at the time when they are moving from the family into the larger world.

20. Cognitive Development
Preconventional level: Judges the morality of an action based on its consequences, particularly to oneself. An action is morally wrong if you will be punished.
Conventional level: Determines right and wrong based on social roles and society’s laws. Good intentions are taken into account, but the law is the law
Postconventional level: Considers that social contracts, laws, and rules can bend to uphold individual and universal rights
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Chapter 12: Development Throughout the Life Span
12.3 Adolescence and Young Adulthood
LO: Discuss the impact of sexual development in adolescence and changes in moral reasoning in adolescence and young adults.
Lawrence Kohlberg argued that adolescence is a prime time for developing a sense of morality. To investigate this topic, he presented simple scenarios to people and asked their response. Rather than focus on what someone should do, Kohlberg believed that the justification someone offers is what is significant. He devised a theory with three levels of moral thinking, each divided into two stages.
Preconventional level of moral reasoning judges the morality of an action based on its consequences, particularly to oneself. An action is morally wrong if you will be punished.
A conventional level of moral reasoning determines right and wrong based on social roles and society’s laws. Good intentions are taken into account, but the law is the law.
Finally, the postconventional level of moral reasoning considers that social contracts, laws, and rules can bend to uphold individual and universal rights.
Studies have shown that people do pass through the first two stages of moral reasoning in order, just as Kohlberg specified. Before adolescence, most children are preconventional, and during adolescence, they begin to reason in conventional terms. Surprisingly, as far as studies can tell, few adolescents and adults reason using postconventional arguments. Only educated adults from middle-class, urban areas were found to display postconventional reasoning.

21. Social Development
Erik Erikson’s theory of psychosocial development identifies a series of stages in life as we develop from childhood through old age.
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Chapter 12: Development Throughout the Life Span
12.3 Adolescence and Young Adulthood
LO: Examine the life stages within Erikson’s theory of psychosocial development.
Erik Erikson’s theory of psychosocial development identifies a series of stages in life as we develop from childhood through old age. For adolescents, Erikson defined the central task to be the forming of an identity, or a distinct, individualized sense of self. Erikson called this process the “identity crisis,” in which teenagers explore alternative ways of living and describing themselves to the world. In the adolescent years, you break free from your relationship with your parents, going from spending most of your free time with family to spending most of it without them. An evolutionary perspective suggests that the reasons for these family strains lie in the problem of having sexually mature offspring living within the family group.
Another important aspect of social development is gender identity. Cross-cultural studies (including nonindustrial societies) suggest that both biological differences and social roles contribute to observed differences by gender.
An important marker of adolescent social development is increasing emphasis on peer relationships. Moving away from gender segregation, adolescents seek out friendships with the opposite sex, distinguishing between friends and romantic partners. Peer groups provide a reference to compare and evaluate a developing identity. Peer relationships are marked by conformity of behavior, or peer pressure, which peaks in the ninth grade.

22. Adulthood and Aging Physical Cognitive Social Reproductive Maturity
End of Reproduction
Diminished Abilities
Declines in Speed and New Learning
Growth in Knowledge
Choosing a Life Partner
Assessing Contributions
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Chapter 12: Development Throughout the Life Span
12.3 Adolescence and Young Adulthood
LO: Examine the life stages within Erikson’s theory of psychosocial development.

23. Physical Development Successful aging depends on:
Freedom from disability and disease
High cognitive and physical functioning
Social engagement
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Chapter 12: Development Throughout the Life Span
12.4 Adulthood and Aging
LO: Illustrate the physical, cognitive, and social aspects of aging.
By our mid-20s, humans are finally physically mature, and all of our systems are fully developed. After age 20, a 1% loss in muscle mass occurs each year. Delaying parenthood until after age 22 is associated with positive health benefits, and, for women, maximum health benefits are predicted for a first birth at age 30. But reproductive ability diminishes with age, particularly for females. Around age 50, women experience menopause. Men continue to produce sperm, but the number and motility decrease. As we age, we lose strength, speed, and endurance. Our sensory detectors start to fail. However, health and physical abilities are affected more by behavior than by the passing of time: Physical exercise aids brain cells by increasing oxygen and nutrient circulation. Exercise also helps create new neurons in the hippocampus.
Life expectancy in countries with modern medical care now exceeds 80. Those with a positive view toward their own aging live more than 7 years longer than others and have higher rates of engagement in healthy behaviors. Rowe and Kahn define successful aging as: (a) freedom from disability and disease; (b) high cognitive and physical functioning; and (c) social engagement. While people may fear senility, it occurs in less than 5% of people. Alzheimer’s disease is caused by the disruption of the neurotransmitter acetylcholine and is diagnosed in about 3% of elderly patients. It has a genetic component, shown by an identical twin’s 60% likelihood of also getting the disease.

24. Cognitive Development
All adults show a decline in performance on tasks requiring fluid intelligence, or reasoning about new information.
Crystalized intelligence, or reasoning using knowledge already existing in memory, shows no decline with advancing age.
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Chapter 12: Development Throughout the Life Span
12.4 Adulthood and Aging
LO: Illustrate the physical, cognitive, and social aspects of aging.
As physical systems decline with age, cognitive processes show similar impairment. With age, we have more trouble assimilating new information, cannot recall information from memory as accurately, and are slower to learn associations through classical conditioning. In addition, mental processing speed begins to slow down, so it takes longer to recall information, react to signals, and perform mental computations. All adults, not just those at advanced ages, show a decline in performance on tasks requiring fluid intelligence, or reasoning about new information. However, crystalized intelligence, or reasoning using knowledge already existing in memory, shows no decline with advancing age. Individual minds may also be differently resilient when damage occurs. Cognitive reserve refers to the brain’s ability to adapt to damage by recruiting alternate brain regions to perform tasks. Higher education levels, participation in mentally demanding occupations and cognitively stimulating activities, and lifestyle factors, contribute to cognitive reserve. Surprisingly, these age-related slowdowns in cognitive systems and achievements do not show up as changes in perceived performance in real-world settings.

25. Social Development
Erikson’s theory of development noted many important stages in adulthood, focusing on love, caring, and wisdom. Across time and age, personality traits are largely unchanged.
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Chapter 12: Development Throughout the Life Span
12.4 Adulthood and Aging
LO: Illustrate the physical, cognitive, and social aspects of aging.
Erikson’s theory of development noted many important stages in adulthood, focusing on love, caring, and wisdom. Across time and age, personality traits are largely unchanged. A cross-sectional study comparing personality traits like extroversion over age groups found consistent patterns across nationalities, including Turkey, Germany, Spain, Britain, and Czechoslovakia. Individual differences in personality traits show some continuity from early childhood onward and are essentially fixed by age 30. However, there is also evidence that people can change over time: With increased age, people show increased self-confidence, warmth, self-control, and emotional stability. Life experiences in young adulthood may be the most likely reason for changes in personality with age. As they age, people’s social vitality (a facet of extraversion), openness, agreeableness, and neuroticism decrease. Older people tend to be a little less sociable but also less worried about life.
Divorce is one of the most difficult transitions encountered in life. In the middle 1800s, only 4% of marriages ended in divorce; today, about half of all first marriages in the United States end in divorce. Because women tend to marry older men and are more likely to live longer, many women experience the loss of a husband in later life. There are perhaps 10 times as many women as men who have lost their spouses.

26. Ages and Stages of Adulthood
People who are out of sync with the social clock experience more stress than those who are “on time.”
The pressure to make choices and move ahead can grow throughout adulthood.
Adults often try to identify a purpose in life.
Life satisfaction ratings are similar across age ranges.
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Chapter 12: Development Throughout the Life Span
12.4 Adulthood and Aging
LO: Illustrate the physical, cognitive, and social aspects of aging.
For certain milestones, people are sensitive to a social clock, or norms for ages at which these events occur. People who are out of sync with these expectations experience more stress than those who are “on time.” Because opportunities often depend on chance encounters, the pressure to make choices and move ahead can grow throughout adulthood. An additional task in this phase of life is identifying a “purpose” in life, or something personally meaningful to pursue. During middle adulthood, climbing the professional ladder or accomplishing financial goals becomes a central focus in order to support a family, desired lifestyle, or future retirement. An additional demand arises in middle age: Elderly parents often need care from their children, both in social support and financial contributions. In later adulthood, people find increasing satisfaction by “giving back,” an action called generativity. Life satisfaction ratings are similar across age ranges, suggesting that around 75 to 80% of people feel satisfied with their lives and that satisfaction does not decrease in later life.

27. Nature and Nurture
Nature: Biological influences including genetics, hormones, and evolutionary tendencies
Nurture: Environmental influences such as family life, schooling, culture, and experiences
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Chapter 12: Development Throughout the Life Span
12.5 Nature and Nurture
LO: Describe the multiple influences of nature and nurture in human development.
One of the ongoing questions about development is the relative importance of nature (biological influences including genetics, hormones, and evolutionary tendencies) and that of nurture (environmental influences such as family life, schooling, culture, and experiences). Learning theorist John B. Watson claimed that nurture could change the future of any child, and much of the evidence about development points to environmental factors (caregivers, peers, rich environments) as important influences in development. At the same time, some environmental variables that would seem to be very important in development have been found to have little effect. The shared environment of family life has clear influences on development, yet it appears to have little impact on personality.
Nature weighs in on development early: The temperaments of newborns is heritable. Evidence from behavioral genetics suggests that virtually all individual differences, when reliably measured, are moderately to substantially heritable. We are born with a biological predisposition that is fixed by genetics and hormones, so that certain sexual and gender behaviors are likely to be expressed. But which patterns are expressed also depends on societal and cultural gender roles and the degrees of tolerance our culture allows.
Nature and nurture can interact to create patterns of development. Studies show that biology plays a role in intelligence test scores for some children, but only for those raised in high-socioeconomic status (SES) homes. For the low-SES children, genetics does not predict their intelligence test scores, while their disadvantaged homes provide a good predictor of their cognitive ability.