9.10 CHAPTER REVIEW

KEY POINTS

• Developmental psychologists study the many ways in which people change over the lifespan. Key themes in developmental psychology include understanding the stages of lifespan development, the nature of change, and the interaction between heredity and environment. Research in developmental psychology may incorporate either a longitudinal design or a cross-sectional design.

• At conception, the union of the sperm and egg result in the single-celled zygote. The zygote contains genetic instructions inherited from the biological parents, encoded in the chromosomes. Chromosomes are made of deoxyribonucleic acid (DNA). Each chromosome has thousands of DNA segments called genes, which encode instructions for making a particular protein.

• An organism’s unique genotype is found in almost every body cell. Cells differ not because they carry different genes but because they result from different genes being activated or expressed. Mapping of the human genome resulted in the discovery that humans have only 20,000–25,000 genes. Gene variations are called alleles. Most characteristics involve the interaction of multiple genes.

• The phenotype results from the interaction of genes and environmental factors. Different genotypes respond differently to the same environmental factors. Epigenetics is the study of the factors that control gene expression.

• During the nine months that make up the prenatal stage, the zygote develops into a full-term fetus. The prenatal stage includes the germinal period, the embryonic period, and the fetal period. Stem cells can divide indefinitely and give rise to other types of cells. The greatest vulnerability to teratogens occurs during the embryonic stage, when major bodily systems are forming.

• Newborns are equipped with reflexes and sensory capabilities that enhance their chances for survival. Vision, hearing, and smell are attuned to interaction with caregivers. The brain develops rapidly after birth. The sequence of motor skill development is generally universal, although there is individual variation in the rate of development.

• Thomas and Chess demonstrated that infants seem to be born with different temperaments. They identified three basic temperamental patterns: easy, difficult, and slow-to-warm-up. According to Kagan, infants can be classified in terms of reactivity. Temperamental qualities seem to have a biological basis and persist through life, although they can be modified by environmental influences.

• According to attachment theory, the infant’s ability to thrive is dependent on the quality of his or her attachment to caregivers. Secure attachment develops when parents are sensitive and responsive to the infant’s needs. Insecure attachment may develop when parents are insensitive to the infant’s needs.

• Infants are biologically predisposed to learn language. Adults encourage language development in infants by using motherese, also called parentese or infant-directed speech.

• The stages of language development include cooing, babbling, the one-word stage, and the two-word stage. At every stage, comprehension vocabulary is larger than production vocabulary.

• According to Jean Piaget’s theory of cognitive development, children progress through distinct cognitive stages, each of which represents a shift in how they think and understand the world.

• Object permanence is acquired during the sensorimotor stage. Symbolic thought is acquired during the pre-operational stage. Preoperational thought is egocentric and characterized by irreversibility and centration. Thus, the preoperational child is unable to grasp the principle of conservation. Children become capable of logical thought during the concrete operational stage, but thinking is limited to tangible objects and events. During the formal operational stage, the adolescent can engage in logical mental operations involving abstract concepts and hypothetical situations.

• Criticisms of Piaget’s theory include the following: Piaget underestimated the cognitive abilities of infants and children; he underestimated the impact of the social and cultural environment on cognitive development; and he overestimated the degree to which people achieve formal operational thought processes. In contrast to Piaget’s theory, Vygotsky’s idea of the zone of proximal development emphasizes that children can progress to higher cognitive levels through the assistance of others who are more competent.

• The information-processing model is a description of cognitive development that emphasizes basic mental processes and stresses that cognitive development is a process of continuous change.

• During adolescence, puberty occurs. Puberty involves the development of primary and secondary sex characteristics, the adolescent growth spurt, and, in females, menarche. While the sequence of pubertal changes is relatively predictable, the timing of puberty varies. Factors that affect the timing of puberty include gender, nutrition, body weight, family stress, and absence of the biological father.

• In general, when parent–child relationships are good before adolescence, they continue to be positive during adolescence. Relationships with peers become increasingly important. Peer influence is just as likely to be positive as negative. Romantic relationships can have a significant impact on the adolescent’s psychological and social development.

• Erik Erikson’s theory of psychosocial development stresses that every stage of life is marked by a particular psychosocial conflict. Identity versus role confusion is the conflict associated with adolescence; however, the process of identity formation does not end in adolescence.

• Lawrence Kohlberg described the types of moral reasoning used in making moral decisions. His theory of moral development includes the preconventional, conventional, and postconventional levels; each level has two stages. Other researchers study the role of emotion, culture, and gender in moral decision making.

• Although there are general patterns in adult development, individual variation becomes increasingly significant. The three phases of adulthood are early adulthood, middle adulthood, and late adulthood. Genetics, environment, and an individual’s lifestyle all influence physical changes during adulthood and aging. Women experience menopause and men experience andropause during middle adulthood as the production of sex hormones declines in both sexes.

• Love and work are two key themes that dominate adult development. Friends continue to be important in adulthood. Forming a committed, intimate relationship is one important task traditionally associated with early adulthood.

• Marital satisfaction tends to decline after the first child is born and to increase after children leave home. Family structures and relationships have become increasingly diverse in the United States.

• Late adulthood does not necessarily involve a steep decline in physical and cognitive functioning. Mental abilities begin to decline slightly only at around age 60, and these declines can be minimized or eliminated with an active and mentally stimulating lifestyle.

• Many older adults do not disengage from life but remain socially active. According to the activity theory of aging, life satisfaction in late adulthood is highest when people maintain their previous levels of activity. Older adults differ in their optimal level of activity. Erikson identified ego integrity versus despair as the key psychosocial conflict of old age.

• Although commonly associated with old age, death can occur at any point in the lifespan. Anxiety about death tends to peak in middle adulthood and decrease in late adulthood. Elisabeth Kübler-Ross proposed a five-stage model of dying: denial, anger, bargaining, depression, and acceptance. However, individuals respond in diverse ways to impending death.

KEY TERMS

KEY PEOPLE