1. EXPLORING HUMAN DEVELOPMENT
   Historically, researchers and scientists have argued about which governs development: nature or nurture. Is a person's development simply a process of maturation (nature)? Or are we shaped and molded by our surroundings (nurture)? Today, psychologists recognize that both nature and nurture interact to influence the developmental process. The environment (nurture) can determine whether a genetic tendency (nature) is expressed, and genetic tendencies (nature) can evoke particular responses from the environment (nurture). Heredity and environment are correlated, as seen in cases where parents with special talents also nurture those talents in their children.
2. BEGINNINGS
   1. Prenatal Development
      A zygote is the cell that forms when the father's sperm and mother's ovum merge.
      1. Stages of Development. During the first and second weeks after fertilization, the cells divide to become the embryo. During the embryonic stage, all the organs form and cells differentiate into specialized functions. During the fetal stage, from week eight until birth, the organs of the fetus grow and function more efficiently.
      2. Prenatal Risks. Severe damage can occur if the mother takes certain drugs, is exposed to toxins, or contracts certain illnesses (such as rubella) during pregnancy. Teratogens, harmful external substances that result in birth defects, are especially dangerous during critical periods such as the embryonic stage. Babies whose mothers used cocaine are born premature, underweight, and fussy, and are at greater risk for learning and other severe developmental disabilities. Fetal alcohol syndrome is a pattern of defects that can occur as a result of maternal ingestion of even moderate amounts of alcohol. The effects that adverse substances will have depend upon genetic inheritance, their intensity, and the prenatal stage in which they occur.
   2. The Newborn
      The study of newborns is extremely difficult due to their immature motor and language abilities. To learn what infants can see and hear, researchers commonly design studies that record infants' eye movements, heart rates, sucking rates, brain waves, movements, and skin conductance to learn what infants can see and hear.
      1. Vision and Other Senses. Newborns have 20:300 sight. They prefer to look at objects that have contour, contrast, complexity, and movement. Within two to three days after birth, infants can hear soft voices and differentiate tones. They prefer to hear speech, especially speech that is high-pitched, exaggerated, and expressive. Newborns have a good sense of smell and taste and show a preference for the smell of their own mother's milk.
      2. Reflexes and Motor Skills. These are swift and automatic movements that occur in response to external stimuli. Infants have more than twenty reflexes, including the grasping, rooting, and sucking reflexes. As muscle strength increases, infants try out various methods of crawling until they find the most efficient one.
3. INFANCY AND CHILDHOOD: COGNITIVE DEVELOPMENT
   1. Changes in the Brain
      Infants are born with their full quota of brain cells, but neural networks connecting these cells are immature. Over time, as different regions of the brain develop more fully, new cognitive abilities appear.
   2. The Development of Knowledge: Piaget's Theory
      According to Piaget, development proceeds in a series of distinct stages that occur in a specific order; each stage is qualitatively different from the next.
      1. Building Blocks of Development. The movement through stages progresses as children develop schemas through their interaction with the environment. Schemas are elaborated through assimilation, during which information is added to existing schemas, and accommodation, during which existing schemas are modified according to new environmental information.
      2. Sensorimotor Development. During Piaget's first cognitive development stage, the sensorimotor period, infants' mental activity is confined to sensory and motor functions. As infants progress through this stage, they begin to learn object permanence: they become able to mentally represent objects in their minds even when they cannot see or touch them.
      3. New Views of Infants. Psychologists using new research methods find that infants develop some mental representations earlier than Piaget suggested. (See the Focus on Research Methods section for more information.)
      4. Preoperational Development. Lasting from two to seven years, the preoperational period is characterized by intuitive guesses. Symbol usage appears. Children in this stage do not have conservation skills.
      5. Concrete Operational Thought. The concrete operations stage, from age seven to adolescence, is marked by the ability to conserve number and amount. However, children cannot think logically about abstract concepts during this stage. Abstract thinking occurs during Piaget's final development stage: formal operational thought.
   3. Focus on Research Methods: Experiments on Developing Minds
      Renee Baillargeon tested infants' knowledge about objects by measuring the amount of time they spend looking at an event. The independent variable was how much support the objects had. When infants observed an event that was physically impossible (such as a box that appeared to float), they looked longer. Baillargeon proposes that older infants know more about objects because of their increased experience with them rather than because of innate knowledge.
   4. Modifying Piaget's Theory
      Studies show that children are capable of many tasks, such as mental representation, conservation, and nonegocentric thinking, at earlier ages than Piaget predicted. Current psychologists view cognitive development in terms of rising and falling "waves," not fixed stages.
   5. Information Processing During Childhood
      From an information-processing approach, children are viewed as better able to absorb, remember, and store information in more organized ways as they grow older. Memory improves as children learn memory strategies, increase memory storage, and expand their knowledge.
   6. Linkages: Development and Memory
      We may be unable to recall memories from before age three because of poor encoding and storage or because the memories are implicit rather than explicit. Another possibility is that such early experiences are joined into generalized event representations, like "going to the park."
   7. Culture and Cognitive Development
      Children's interaction with their culture and language has significant effects on their development. Children form scripts, or mental representations of common cultural activities. A child will be much better able to perform a given task if it is presented in a familiar "script." The influence of language, teaching methods, and parental emphasis on education all contribute to cultural differences in cognitive development.
      H. Variations in Cognitive Development
      Cognitive development can be influenced to some degree by the environment. Stimulating surroundings and positive experiences tend to enhance a child's cognitive development.
4. INFANCY AND CHILDHOOD: SOCIAL AND EMOTIONAL DEVELOPMENT
   Infants and parents bond during the first few months of life; infants respond to parental behavior, and parents respond to the infant.
   1. Individual Temperament
      Temperament, an individual's style and frequency of expressing needs and emotions, is genetically influenced and obvious at birth. If the child's temperament matches the parents' expectations, the parent-child interaction will most likely be positive. Culture and innate tendencies interact in the development of temperament throughout childhood.
   2. The Infant Grows Attached
      During the first year of life, infants form an attachment to their parents.
      1. Motherless Monkeys and Children. The Harlow attachment studies demonstrate that infant monkeys are motivated by contact comfort needs. Monkeys raised in isolation exhibit severe deficits in social and emotional development. Similar problems have been noted in abandoned and neglected children.
      2. Forming an Attachment. In most cultures the mother is the first person to whom the baby becomes attached. Infants also become attached to fathers. Fathers are more likely to play with infants, while mothers are more likely to feed, cuddle, and talk with them.
      3. Variations in Attachment. Many factors, including the infant's temperament, the caretaker's responsiveness, and cultural variability, can influence the development of attachments. Securely attached children tend to be more socially and emotionally competent; more cooperative, enthusiastic, and persistent; better problem solvers; more compliant and controlled; and more playful and popular.
   3. Thinking Critically: Does Day Care Harm the Emotional Development of Infants?
      What am I being asked to believe or accept?
      Separation created by day care can damage the mother-infant attachment and harm the child's emotional development.
      What evidence is available to support the assertion?
      While children who attend day care do form attachments and prefer the company of their mothers, some research suggests that these children have a greater tendency to be insecurely attached.
      Are there alternative ways of interpreting the evidence?
      Infants in day care may be more independent than those children who stay at home. In addition, mothers who work may reward more independent behavior in their children.
      What additional evidence would help to evaluate the alternatives?
      Research must measure aspects of emotional adjustment other than secure attachments. Infant relationships with other caregivers in other situations must also be examined.
      What conclusions are reasonable?
      According to a recent study, infants in quality day-care situations with sensitive and responsive mothers were no more likely to develop emotional or attachment problems than those not in day care. So, day care itself does not lead to problems, but poor quality day care may interact with already risky home situations to have a negative effect on attachment.
   4. Relationships with Parents and Peers
      According to Erik Erikson's theory of social development, individuals pass through eight qualitatively different stages, each one associated with an issue that the individual must resolve. Positive resolution provides the basis for developing trust, autonomy, and initiative, whereas negative resolutions may leave a person psychologically troubled and less able to cope effectively with future situations.
      1. ParentingStyles. Socialization is the method by which authority figures teach children the skills and rules needed to function in their society. Socialization is shaped by cultural values.
         • Authoritarian parents are firm, punitive, and unsympathetic. Permissive parents give children complete freedom and use lax discipline. Authoritative parents are firm but understanding, increase children's responsibility as they grow older, and reason with their children.
         • Authoritarian parents tend to have children who are unfriendly, distrustful, and withdrawn. Permissive parents tend to have children who are immature, dependent, and unhappy, and who exhibit little self-control. Authoritative parents tend to have children who are friendly, cooperative, self-reliant, and socially responsible.
         • However, correlational socialization studies do not show causation, and their results are not strong. Hence researchers cannot conclude that parental behavior causes a particular social outcome. Children's temperaments, physical health, and cultural environment influence social and scholastic development.
      2. Relationships with Peers. Two-year-olds play with the same toys that their playmates do but do not interact with one another. By age four, children begin to interact socially through play. In the final stages of the preschool years, children learn to cooperate or compete. Schoolchildren develop friendships based on feelings. Children who do not develop friendships have problems later in life.
   5. Social Skills
      Cooperation, understanding, empathy, and self-regulation can be taught at home. Aggressive and depressed children tend to lack social skills.
   6. Gender Roles
      Through socialization, children learn the norms governing gender roles in their culture. Differences between boys and girls have some roots in biological makeup, but these differences are amplified by gender schemas, as boys and girls learn "appropriate" behaviors for boys and girls through modeling and encouragement.
   7. Risk and Resilience
      Family instability, child abuse, homelessness, poverty, substance abuse, and domestic violence produce serious short- and long-term consequences for children. However, some children show resilience. These children tend to be intelligent, easy going, and self-confident, and they have a close caring relationship with at least one adult.
5. ADOLESCENCE
   Owing to the interplay of nature and nurture, adolescents experience changes in physical size, shape, and capacity. Changes also occur in social life, reasoning ability, and self-perception.
   1. The Challenges of Change
      1. With the onset of puberty, sudden growth spurts occur, sexual characteristics develop, sexual interest stirs, and opportunities to experience drugs arise. Many problems of adolescence are associated with challenges to self-esteem. Conflicts between parents and teens develop as a result of the adolescent's attempt to become independent and cope with the challenges brought on by puberty. However, most teens do not experience major personal or family turmoil.
      2. When there is trouble, sex is often involved, resulting in lower scholastic achievement, sexually transmitted diseases, and unplanned, unwanted pregnancies.
   2. Identity and Development of the Self
      A century ago, adulthood began at approximately fourteen years of age. Today, however, many people don't make the transition into adulthood until their early twenties in Western societies. Lengthened adolescence has created difficulties in identity formation.
      1. Forming a Personal and Ethnic Identity. A person's sense of self develops throughout middle childhood, then erupts during adolescence through self-consciousness and self-awareness. The personal identity is affected by ethnic identity, reflecting racial, religions, or cultural groups to which the person belongs.
      2. Facing the Identity Crisis. Identity formation is the adolescent's central task, according to Erikson's psychosocial development theory. If the individual has developed trust, autonomy, and initiative in early childhood, the identity crisis will be positively resolved.
   3. Abstract Thought and Moral Reasoning
      Piaget's formal operational period first occurs during adolescence. Hypothetical thinking, hypothesis generation, and abstract conceptual thinking are now possible. However, only half of Western cultural populations reach the formal operational period; the failure to reach this stage is highly correlated with a lack of education.
      1. Kohlberg's Stages of Moral Reasoning. Kohlberg proposed that moral reasoning develops in six stages that progress from avoiding punishment and attaining pleasure (preconventional), to following rules as part of social duty (conventional), and finally to principles of justice, equality, and respect for human life (postconventional).
      2. Limitations of Kohlberg's Stages. Research generally supports the sequence of Kohlberg's stages. In addition, however, culture and gender influence people's definition of the moral "ideal."
      3. Moral Reasoning and Moral Action. The relationship between level of moral reasoning and behavior is complex, in part because the situation or context may be a large determinant of behavior. The development of moral behavior requires more than just cognitive knowledge; children also require experience, role models, and authoritative socialization.
6. ADULTHOOD
   Development is a lifelong process. Adults, too, experience physical and cognitive transitions.
   1. Physical Changes
      In early adulthood, shoulder width, height, and chest size increase. The body begins to show signs of aging in middle adulthood. Sensory acuity begins to decrease, fertility declines (a process known as menopause in women), and susceptibility to heart disease is heightened. In late adulthood, the body continues to deteriorate and blood flow to the brain slows.
   2. Cognitive Changes
      Cognitive abilities continue to improve until late adulthood. Because of years of experience and information accumulation, an older adult may be better able to handle complex situations than a younger adult.
      1. Early and Middle Adulthood. Cognitive abilities improve as young and middle-aged adults get new information, learn new skills, and refine old skills. Adults become more adept at problem solving and decision making; adult thought is more complex and adaptive than adolescent thought.
      2. Late Adulthood. After age sixty-five, the speed of information absorption slows and memory declines. Unfamiliar tasks, complex problems, and tasks that require divided attention are more difficult for older than for younger people. However, if mental faculties are used throughout the life span, these skills are less apt to diminish.
   3. Social Changes
      1. Early Adulthood. In early adulthood (ages twenty to forty), intimate relationships and parenting styles may reflect earlier attachment relationships. About half of married adults will have to face the challenges of divorce.
      2. Middle Adulthood (ages forty to sixty-five). Around age forty, many people become concerned with the crisis of generativity--that is, producing something that will outlast them, usually children or job achievements. People may experience a mid-life transition, when they feel compelled to reappraise or modify their lives in some way. Afterwards, the middle years are often a time of satisfaction and happiness.
      3. Late Adulthood (ages sixty-five to seventy-five). Most people in this age group consider themselves to be middle-aged. Retirement usually occurs and is a positive experience if viewed as a choice. In late adulthood, people become more reflective, cautious, and conforming, and they value relationships more.
   4. Death and Dying
      A few years or months before dying, many people experience a sharp decline in mental functioning known as terminal drop. The awareness of impending death, according to Erikson, brings about the last social crisis. People reminisce and evaluate the meaningfulness of their lives.
   5. Longevity
      People want to live as long as possible. Longevity is greater among women, those without histories of heavy drinking or heart problems, and those who live independently. Longevity is also related to conscientiousness and curiosity.