HLD Ch 1 PDF - Human Development

There is nothing permanent except change. OUTLINE —Heraclitus, fragment (sixth century B.C.) Human Development: An Ever-Evolving Field...

There is nothing permanent except change. OUTLINE —Heraclitus, fragment (sixth century B.C.) Human Development: An Ever-Evolving Field Studying the Life Span Human Did You Know... Development Today The Study of Human In some societies there is no concept of adolescence or middle age? Development: Basic Many scholars maintain that races are not physically distinguish- Concepts able categories of people? Domains of Development Periods of the Life Span Within the next 50 years, it has been estimated that about half the Influences on Development U.S. population will be Hispanic, black, or Asian? Heredity, Environment, and More than 36 million people in the United States live in poverty? Maturation Contexts of Development Normative and According to some research, children who have been exposed to Nonnormative Influences Timing of television and computers from an early age develop differently Influences: Critical or Sensitive Periods than children who grow up without them? Paul B. Baltes’s Life-Span Memory, strength, and endurance can be improved with training Developmental Approach and practice, even in late life? Box 1-1: Research in Action: Is There a Critical Period for Language Acquisition? T hese are just a few of the interesting and important topics we will cover in this chapter as you begin your study of human develop- ment. In this introductory chapter, we describe how the field of human development has itself developed. We present the goals and basic concepts of the field today. We identify aspects of human development and show how they interrelate. Next, we summarize major develop- ments during each period of life. Finally, we look at influences on development and the contexts in which it occurs. After you have studied this chapter, you should be able to answer each of the Guidepost questions on the following page. Look for them again in the margins throughout the chapter, where they point to important concepts. To check your understanding of these Guideposts, review the end-of-chapter Summary. Checkpoints throughout the chapter will help you verify your understanding of what you have read. 3  Guideposts for Study 1. What is human development, and how has its study evolved? 2. What do developmental scientists study? 3. What kinds of influences make one person different from another? 4. What are seven principles of the life-span developmental approach? Human Development: An Ever-Evolving Field From the moment of conception, human beings begin a process of change that Guidepost 1 will continue throughout their lives. A single cell becomes a living, breathing, What is human develop- walking, talking person. And though this single cell develops into a unique indi- ment, and how has its study vidual, the changes human beings experience during their lifetimes have certain evolved? common patterns. Babies grow and become children, who grow and become adults. Similarly, some human characteristics have common patterns. Children who are shy are likely to remain shy as adults. human development Scientific Human development is the scientific study of these patterns of change and stabil- study of processes of change and ity. Development is systematic: It is coherent and organized. It is adaptive: It is stability throughout the human life span. aimed at dealing with internal and external conditions of existence. Development may take varied routes and may or may not have a definite goal, but there is some connection between the often-imperceptible changes of which it is composed. Which characteristics are most likely to endure? Which are likely to change, and why? These are among the questions that the study of human development seeks to answer. The professionals who study the science of human development are called developmental scientists. Their work can have a dramatic impact on human lives. Research findings often have direct application to child rearing, education, health, and social policy. For example, researchers in Boston found that public school students who went What’s to school hungry or lacked essential nutrients in their diet had poorer grades and Your View? more emotional and behavioral problems than their classmates. After the schools started a free breakfast program, participating students improved their math grades, How do you think studying were absent and tardy less often, and had fewer emotional and behavioral problems human development will be useful to you? (Kleinman et al., 2002; Murphy et al., 1998). Research showing that the adolescent brain is still immature has prompted suggestions that adolescents accused of crimes be exempt from the death penalty. An understanding of adult development can help people understand and deal with life transitions: a woman returning to work after maternity leave, a person making a career change or about to retire, a widow or widower dealing with loss, someone coping with a terminal illness. Studying the Life Span Developmental scientists have come to recognize human development as a life- life-span development Concept long process—a concept known as life-span development. Early studies such as the of human development as a lifelong process, which can be Stanford Studies of Gifted Children, which traced through old age the develop- studied scientifically. ment of people who had been identified as unusually intelligent in childhood, the 4 Part 1 About Human Development Berkeley Growth and Guidance Studies, and the Oakland (Adolescent) Growth Study have given us much information on long-term development. More recently, Paul B. Baltes’s life- span developmental approach, discussed at the end of this chapter, has provided a comprehensive conceptual framework for the study of life-span development. Human Development Today As the field of human development became a scientific disci- pline, its goals evolved to include description, explanation, prediction, and intervention. For example, to describe when most children say their first word or how large their vocabu- lary typically is at a certain age, developmental scientists observe large groups of children and establish norms, or aver- ages, for behavior at various ages. They then attempt to explain how children acquire language and why some children learn to speak later than usual. This knowledge may make it possible Brain imaging techniques, such as functional magnetic resonance to predict future behavior, such as the likelihood that a child imaging (fMRI), positron emission tomography (PET), and will have serious speech problems. Finally, an understanding electroencephalogram (EEG), are used to map out where certain of how language develops may be used to intervene in develop- thought processes take place within the structure of the brain. ment, for example, by giving a child speech therapy. The scientific study of human development is ever evolving. The questions that developmental scientists seek to answer, the methods they use, and the expla- nations they propose are more sophisticated and more varied than they were even twenty-five years ago. These shifts reflect progress in understanding as new inves- tigations build on or challenge those that went before. They also reflect advances in technology. Sensitive instruments that measure eye movements, heart rate, Checkpoint blood pressure, muscle tension, and the like are turning up intriguing connections Can you... between biological functions and childhood intelligence. Digital technology and computers allow investigators to scan infants’ facial expressions for early signs of ♦ Give examples of practical applications emotions and to analyze how mothers and babies communicate. Advances in of research on human brain imaging make it possible to probe the mysteries of temperament, to pin- development? point the sources of logical thought, and to compare a normally aging brain with ♦ Identify four goals of the the brain of a person with dementia. scientific study of human Almost from the start, developmental science has been interdisciplinary. development? Today students of human development draw collaboratively from a wide range of ♦ Name at least six disciplines, including psychology, psychiatry, sociology, anthropology, biology, disciplines involved in genetics (the study of inherited characteristics), family science (the interdisciplin- the study of human development? ary study of family relations), education, history, and medicine. This book includes findings from research in all these fields. The Study of Human Development: Guidepost 2 Basic Concepts What do developmental scientists study? Developmental scientists study processes of change and stability in all domains, or aspects, of development and throughout all periods of the life span. Domains of Development physical development Growth of Developmental scientists study three major domains: physical, cognitive, and psy- body and brain, including patterns chosocial. Growth of the body and brain, sensory capacities, motor skills, and of change in sensory capacities, health are parts of physical development. Learning, attention, memory, language, motor skills, and health. Chapter 1 The Study of Human Development 5 These children examining snails on a sand table are engaging in all three domains of development: sensory perception (physical development), learning (cognitive development), and social relationships building (psychosocial development). cognitive development Pattern thinking, reasoning, and creativity make up cognitive development. Emotions, per- of change in mental abilities, such sonality, and social relationships are aspects of psychosocial development. as learning, attention, memory, language, thinking, reasoning, and Although we talk separately about physical, cognitive, and psychosocial de- creativity. velopment, these domains are interrelated: Each aspect of development affects the others. As one researcher points out, “Our brains work better, our thinking is psychosocial development Pattern of change in emotions, sharper, our mood brighter, and our vulnerability to disease diminished if we are personality, and social physically fit” (Diamond, 2007, p. 153). For example, a child with frequent ear relationships. infections may develop language more slowly than a child without this physical problem. During puberty, dramatic physical and hormonal changes affect the developing sense of self. In contrast, physical changes in the brains of some older adults may lead to intellectual and personality deterioration. Cognitive advances and declines are closely related to physical, emotional, and social factors. A child who is precocious in language development may evoke positive reactions in others and gain in self-worth. Memory development reflects gains or losses in physical connections in the brain. An adult who has trouble remembering people’s names may feel awkward and reticent in social situations. Psychosocial development can affect cognitive and physical functioning. In- deed, without meaningful social connections, physical and mental health can suf- fer. Motivation and self-confidence are important contributors to school success, whereas negative emotions such as sadness, anger, fear, or anxiety about taking a test can impair performance. Researchers even have identified possible links between personality and length of life. Conversely, physical and cognitive capaci- ties can affect psychosocial development. They contribute greatly to self-esteem and can affect social acceptance and choice of occupation. Thus, although for simplicity’s sake we look separately at physical, cognitive, and psychosocial development, development is a unified process. Throughout the text, we will highlight links among the three major domains of development. social construction A concept or Periods of the Life Span practice that may appear natural Division of the life span into periods is a social construction: a concept or practice and obvious to those who accept it, but that in reality is an invention that may appear natural and obvious to those who accept it, but in reality is an of a particular culture or society. invention of a particular culture or society. There is no objectively definable moment 6 Part 1 About Human Development when a child becomes an adult or a young person becomes old. In fact, the concept of childhood itself can be viewed as a social construction. Some evidence indicates that children in earlier times were regarded and treated much like small adults. However, this suggestion has been disputed (Ariès, 1962; Elkind, 1986; Pollock, 1983). Archaeological finds from ancient Greece show that children played with clay dolls and dice made of bones of sheep and goats. Pottery and tombstones depict children sitting on high chairs and riding goat-pulled carts (Mulrine, 2004). The concept of adolescence as a period of development in industrial societies is quite recent. Until the early twentieth century, young people in the United States were considered children until they left school, married or got a job, and entered the adult world. By the 1920s, with the establishment of comprehensive high schools to meet the needs of a growing economy and with more families able to support extended formal education for their children, the teenage years became a distinct period of development (Keller, 1999). In some preindustrial societies, such as the Chippewa Indians, the concept of adolescence still does not exist. The Chippewa have only two periods of childhood: from birth until the child walks, and from walking to puberty. What we call adolescence is part of adulthood (Broude, 1995). As we discuss in Chapter 16, the Gusii of Kenya have no concept of middle age. In this book, we follow a sequence of eight periods generally accepted in Western industrial societies. After describing the crucial changes that occur in the first period, before birth, we trace all three domains of development through What’s infancy and toddlerhood, early childhood, middle childhood, adolescence, young Your View? adulthood, middle adulthood, and late adulthood (Table 1-1). For each period after infancy and toddlerhood (when change is most dramatic), we have combined Why do you think various societies divide the periods physical and cognitive development into a single chapter. of development differently? The age divisions shown in Table 1-1 are approximate and somewhat arbi- trary. This is especially true of adulthood, when there are no clear-cut social or physical landmarks, such as starting school or entering puberty, to signal a shift from one period to another. Individual differences exist in the way people deal with the characteristic events and issues of each period. Despite these differences, certain basic developmental needs must be met and certain developmental tasks mastered during each period for normal development to occur. A new baby, for example, is dependent on adults to meet his or her basic needs for food, clothing, and shelter as well as for human contact and affection. Babies form attachments to parents or caregivers, who also become attached to them. As babies learn to walk and talk, they become toddlers. Though more self- reliant and able to assert their autonomy, they also need parents or caregivers to provide a safe environment in which to do so. During early childhood, children develop more self-control and more interest in other children. Control over behav- ior gradually shifts from parent to child during middle childhood, when the peer group becomes increasingly important. A main developmental task of adoles- cence is the search for identity—personal, sexual, and occupational. As adoles- Checkpoint cents become physically mature, they must deal with sometimes conflicting needs Can you... and emotions as they prepare to leave the parental nest. During emerging adulthood, an exploratory period in the early to midtwenties, ♦ Identify the three domains of development and give many people are not yet ready to settle down to the typical tasks of young adult- examples of how they are hood: establishing independent lifestyles, occupations, and usually, families. By the interrelated? thirties, most adults have successfully fulfilled those tasks. During middle adulthood, ♦ Name eight periods of some decline in physical capabilities is likely. At the same time, many middle-aged human development (as people find excitement and challenge in life changes—launching new careers and defined in this book) and adult children—while some face the need to care for elderly parents. In late adult- list several key issues or tasks of each period? hood, people need to cope with losses in their faculties, the loss of loved ones, and preparations for death. If they retire, they must deal with the loss of work-based Chapter 1 The Study of Human Development 7  Table 1-1 Typical Major Developments in Eight Periods of Human Development Age Period Physical Developments Cognitive Developments Psychosocial Developments Prenatal Period Conception occurs by normal Abilities to learn and remember Fetus responds to mother’s voice and (conception to fertilization or other means. and to respond to sensory stimuli develops a preference for it. birth) The genetic endowment interacts are developing. with environmental influences from the start. Basic body structures and organs form; brain growth spurt begins. Physical growth is the most rapid in the life span. Vulnerability to environmental influences is great. Infancy and All senses and body systems Abilities to learn and remember are Attachments to parents and others Toddlerhood operate at birth to varying present, even in early weeks. form. (birth to age 3) degrees. Use of symbols and ability to solve Self-awareness develops. The brain grows in complexity and problems develop by end of Shift from dependence toward is highly sensitive to environmental second year. autonomy occurs. influence. Comprehension and use of Interest in other children increases. Physical growth and development language develop rapidly. of motor skills are rapid. Early Childhood Growth is steady; appearance Thinking is somewhat egocentric, Self-concept and understanding of (ages 3 to 6) becomes more slender and but understanding of other emotions become more complex; proportions more adultlike. people’s perspectives grows. self-esteem is global. Appetite diminishes, and sleep Cognitive immaturity results in Independence, initiative, and self- problems are common. some illogical ideas about the control increase. Handedness appears; fine and world. Gender identity develops. gross motor skills and strength Memory and language improve. Play becomes more imaginative, more improve. Intelligence becomes more elaborate, and usually more social. predictable. Altruism, aggression, and fearfulness Preschool experience is common, are common. and kindergarten experience is Family is still the focus of social life, more so. but other children become more important. Middle Childhood Growth slows. Egocentrism diminishes. Children Self-concept becomes more complex, (ages 6 to 11) Strength and athletic skills improve. begin to think logically but affecting self-esteem. concretely. Coregulation reflects gradual shift in Respiratory illnesses are common, but health is generally better than Memory and language skills control from parents to child. at any other time in the life span. increase. Peers assume central importance. Cognitive gains permit children to benefit from formal schooling. Some children show special educational needs and strengths. relationships but may get increased pleasure out of friendships, family, volunteer work, and the opportunity to explore previously neglected interests. Many older people become more introspective, searching out the meaning of their lives. Guidepost 3 Influences on Development What kinds of influences make one person different from What makes each person unique? Although students of development look at the another? universal processes of development experienced by all normal human beings, they must also consider individual differences in characteristics, influences, and 8 Part 1 About Human Development Age Period Physical Developments Cognitive Developments Psychosocial Developments Adolescence Physical growth and other Ability to think abstractly and use Search for identity including sexual (ages 11 to changes are rapid and profound. scientific reasoning develops. identity, becomes central. about 20) Reproductive maturity occurs. Immature thinking persists in some Relationships with parents are Major health risks arise from attitudes and behaviors. generally good. behavioral issues, such as eating Education focuses on preparation Peer group may exert a positive or disorders and drug abuse. for college or vocation. negative influence. Emerging and Young Physical condition peaks, then Thought and moral judgments Personality traits and styles become Adulthood declines slightly. become more complex. relatively stable, but changes in (ages 20 to 40) Lifestyle choices influence health. Educational and occupational personality may be influenced by life choices are made, sometimes stages and events. after period of exploration. Intimate relationships and personal lifestyles are established but may not be lasting. Most people marry, and most become parents. Middle Adulthood Slow deterioration of sensory Mental abilities peak; expertise Sense of identity continues to (ages 40 to 65) abilities, health, stamina, and practical problem-solving develop; midlife transition may occur. and strength may begin, but skills are high. Dual responsibilities of caring for individual differences are wide. Creative output may decline but children and parents may cause Women experience menopause. improve in quality. stress. For some, career success and Launching of children leaves empty earning powers peak; for others, nest. burnout or career change may occur. Late Adulthood Most people are healthy and Most people are mentally alert. Retirement from workforce may occur (age 65 and over) active, although health and Although intelligence and memory and may offer new options for use physical abilities generally may deteriorate in some areas, of time. decline. most people find ways to People develop more flexible Slowing of reaction time affects compensate. strategies to cope with personal some aspects of functioning. losses and impending death. Relationships with family and close friends can provide important support. Search for meaning in life assumes central importance. developmental outcomes. People differ in gender, height, weight, and body build; individual differences Differences in health and energy level; in intelligence; and in temperament, personality, and in characteristics, influences, or developmental outcomes. emotional reactions. The contexts of their lives differ too: the homes, communi- ties, and societies they live in, the relationships they have, the schools they go to (or whether they go to school at all), and how they spend their free time. Heredity, Environment, and Maturation heredity Inborn traits or Some influences on development originate primarily with heredity: inborn traits characteristics inherited from the or characteristics inherited from the biological parents. Other influences come biological parents. Chapter 1 The Study of Human Development 9 environment Totality of largely from the outer and inner environments: the world outside the self beginning nonhereditary, or experiential, in the womb, and the learning that comes from experience. Which of these two influences on development. factors has more impact on development? The issue of the relative importance of nature (heredity) and nurture (environmental influences both before and after birth) historically generated intense debate. Today scientists have found ways to measure more precisely the roles of heredity and environment in the development of specific traits within a popu- lation. When we look at a particular person, however, research with regard to almost all characteristics points to a blend of inheritance and experience. Thus, even though intelligence is strongly influenced by heredity, parental stimulation, education, peer influence, and other variables also affect it. Although there still is considerable dispute about the relative importance of nature and nurture, contemporary theorists and researchers are more interested in finding ways to explain how they work together rather than arguing about which factor is more important. Many typical changes of infancy and early childhood, such as the abilities to maturation Unfolding of a walk and talk, are tied to maturation of the body and brain—the unfolding of a natural sequence of physical and natural sequence of physical changes and behavior patterns. As children grow into behavioral changes. adolescents and then into adults, individual differences in innate characteristics and life experience play a greater role. Throughout life, however, maturation con- tinues to influence certain biological processes, such as brain development. Even in processes that all people undergo, rates and timing of development vary. Throughout this book, we talk about average ages for the occurrence of certain events: the first word, the first step, the first menstruation or nocturnal emission, the development of logical thought, and menopause. But these ages are merely averages. Each individual’s actual age of occurrence for these events will vary. Only when deviation from the average is extreme should we consider devel- opment exceptionally advanced or delayed. In trying to understand human development, then, we need to consider how heredity and environment interact. We need to understand which developments are primarily maturational and which are not. We need to look at influences that affect many or most people at a certain age or a certain time in history and also at those that affect only certain individuals. Finally, we need to see how timing can accentuate the impact of certain influences. All these issues will be discussed throughout this text. Contexts of Development Human beings are social beings. Right from the start, they develop within a social and historical context. For an infant, the immediate context normally is the family, but the family in turn is subject to the wider and ever-changing influences of neighborhood, community, and society. nuclear family Two-generational Family The nuclear family is a household unit consisting of one or two parents kinship, economic, and household and their children, whether biological, adopted, or stepchildren. Historically, unit consisting of one or two parents and their biological the two-parent nuclear family has been the dominant family unit in the United children, adopted children, States and other Western societies. However, the nuclear family today is differ- or stepchildren. ent from what it used to be. Instead of the large, rural family in which parents and children worked side by side on the family farm, we now see smaller, urban families in which both parents work outside the home and children spend much of their time in school or child care. The increased incidence of divorce also has impacted the nuclear family. Children of divorced parents may live with one or the other parent or may move back and forth between them. The household may 10 Part 1 About Human Development include a stepparent and stepsiblings or a parent’s live-in partner. There are increasing numbers of single and childless adults, unmarried parents, and gay and lesbian households (Hernandez, 1997, 2004; Teachman, Tedrow, & Crowder, 2000). In many societies in Asia, Africa, and Latin America and among some U.S. families that trace their lineage to those countries, the extended family—a multigenerational network of grandparents, aunts, uncles, cousins, and more distant relatives—is the traditional family form. Many or most people live in extended-family households, where they have daily contact with kin. Adults often share breadwin- ning and child-raising responsibilities, and older children are responsible for younger brothers and sisters. Often these households are headed by women (Aaron, Parker, Ortega, & Calhoun, 1999; Johnson et al., 2003). Today the extended-family household is becoming slightly less typical in some developing countries due to industrialization and migration to urban centers (Brown, 1990; Gorman, 1993; Kinsella & Phillips, 2005). At the same time, with the aging of the population, multigenerational family bonds may be increasingly important in Western societies (Bengtson, 2001). Socioeconomic Status and Neighborhood A family’s socioeconomic status (SES) is based on family income and the educational and occupational levels of the adults in the household. Throughout this book, we examine many stud- In the United States, unmarried or divorced parents, stepfamilies, ies that relate SES to developmental processes (such as and gay and lesbian households have increased over the past 150 mothers’ verbal interactions with their children) and to years, requiring adjustments to our understanding of the concept of developmental outcomes (such as health and cognitive family. performance; Table 1-2). SES affects these processes and extended family Multigenerational kinship network of parents, Table 1-2 Poverty Hurts Children children, and other relatives, sometimes living together in an Outcomes Low-Income Children’s Higher Risk extended-family household. Health socioeconomic status (SES) Death, in infancy 1.6 times more likely Combination of economic and Premature birth (under 37 weeks) 1.8 times more likely social factors describing an Low birth weight 1.9 times more likely individual or family, including Inadequate prenatal care 2.8 times more likely income, education, and occupation. No regular source of health care 2.7 times more likely Having too little food sometime 8.0 times more likely in the past 4 months Education Lower math scores at ages 7 to 8 5 test points lower Lower reading scores at ages 7 to 8 4 test points lower Repeating a grade 2.0 times more likely Being expelled from school 3.4 times more likely Being a dropout at ages 16 to 24 3.5 times more likely Finishing a four-year college 50 percent as likely Source: Children’s Defense Fund, 2004. Chapter 1 The Study of Human Development 11  outcomes indirectly, through such associated factors as the kinds of homes and neighborhoods people live in and the quality of nutrition, medical care, and schooling available to them. More than half of the world’s population (53 percent) live on less than the international poverty standard of $2 a day (Population Reference Bureau, 2006). In the United States, where poverty thresholds vary with family size and composi- tion, about 36.5 million people, or 12.3 percent of the population, had incomes below poverty level in 2006 (DeNavas-Walt, Proctor, & Smith, 2005). Poverty, especially if it is long-lasting, is harmful to the physical, cognitive, and psychosocial well-being of children and families. Poor children are more likely than other children to have emotional or behavioral problems, and their cognitive potential and school performance suffer more (Evans, 2004). The harm done by poverty may be indirect, through its impact on parents’ emotional state and par- enting practices and on the home environment they create (see Chapter 10). risk factors Conditions that Threats to well-being multiply if, as often happens, several risk factors—conditions increase the likelihood of a that increase the likelihood of a negative outcome—are present. negative developmental outcome. Affluence doesn’t necessarily protect children from risk. Some children in affluent families face pressure to achieve and are often left on their own by busy parents. Such children have high rates of substance abuse, anxiety, and depression (Luthar & Latendresse, 2005). The composition of a neighborhood affects children as well. Living in a poor neighborhood with large numbers of unemployed people makes it less likely that effective social support will be available (Black & Krishnakumar, 1998). Still, positive development can occur despite serious risk factors. Consider the tele- vision star Oprah Winfrey, the country singer Shania Twain, and the former U.S. president Abraham Lincoln, all of whom grew up in poverty (Kim-Cohen, Moffitt, Caspi, & Taylor, 2004). culture A society’s or group’s total Culture and Race/Ethnicity Culture refers to a society’s or group’s total way of way of life, including customs, life, including customs, traditions, laws, knowledge, beliefs, values, language, and traditions, beliefs, values, language, and physical products— physical products, from tools to artworks—all of the behavior and attitudes that all learned behavior, passed on are learned, shared, and transmitted among members of a social group. Culture from parents to children. is constantly changing, often through contact with other cultures. For example, Europeans arriving on American shores learned how to grow corn from the native Indians. Cultural contact today has been enhanced by computers and telecom- munications. E-mail and instant messaging offer almost instantaneous communi- cation across the globe, and digital services such as iTunes give people around the world easy access to one another’s music and movies. ethnic group A group united by An ethnic group consists of people united by a distinctive culture, ancestry, ancestry, race, religion, language, religion, language, and/or national origin, all of which contribute to a sense of and/or national origins, which contribute to a sense of shared shared identity and shared attitudes, beliefs, and values. Most ethnic groups trace identity. their roots to a country of origin, where they or their forebears shared a common culture that continues to influence their way of life. Ethnic and cultural patterns affect development by their influence on the composition of a household, its eco- What’s nomic and social resources, the way its members act toward one another, the Your View? foods they eat, the games children play, the way they learn, how well they do in How might you be different school, the occupations adults engage in, and the way family members think and if you had grown up in a perceive the world (Parke, 2004). For example, children of immigrants in the culture other than your United States are nearly twice as likely as native-born children to live with ex- own? tended families and are less likely to have mothers who work outside the home (Hernandez, 2004; Shields & Behrman, 2004). The United States has always been a nation of immigrants and ethnic groups, but the primary ethnic origins of the immigrant population have shifted from 12 Part 1 About Human Development KEY: Figure 1-1 Past and projected percentages of Asian/Pacific Islander, non-Hispanic U.S. children in specified racial/ethnic American Indian, non-Hispanic groups. (Source: Hernandez, 2004, Black, non-Hispanic p. 18, Fig. 1. Data from Population Projections Program, Population Division, Hispanic U.S. Census Bureau, issued January 13, White, non-Hispanic 2000.) 100 80 Percent of Children 60 40 20 1980 1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 Projected Europe and Canada to Asia and Latin America (Hernandez, 2004). In 2007, more than 20 percent of the population were immigrants or children of immigrants. More immigrants came from Mexico, 40 percent, than from any other country, and the remaining 60 percent came from nations in the Caribbean, East and West Asia, Australia, Central and South America, Indochina, the former Soviet Union, and Africa. By 2040 the minority population is projected to rise to 50 percent (Hernandez, Denton, & Macartney, 2007; Figure 1-1). Wide diversity exists within broad ethnic groups. The European-descended “white majority” consists of many distinct ethnicities—German, Belgian, Irish, French, Italian, and so on. Cuban Americans, Puerto Ricans, and Mexican Americans—all Hispanic Americans—have different histories and cultures and may be of African, European, Native American, or mixed descent (Johnson et al., 2003; Sternberg, Grigorenko, & Kidd, 2005). African Americans from the rural South differ from those of Caribbean ancestry. Asian Americans hail from a vari- ety of countries with distinct cultures, from modern, industrial Japan to commu- nist China to the remote mountains of Nepal, where many people still practice their ancient way of life. Native Americans consist of hundreds of recognized nations, tribes, bands, and villages (Lin & Kelsey, 2000). Many scholars now agree that the term race, historically and popularly viewed as an identifiable biological category, is a social construct. There is no clear scientific consensus on its definition, and it is impossible to measure reli- ably (Bonham, Warshauer-Baker, & Collins, 2005; Helms, Jernigan, & Mascher, 2005; Smedley & Smedley, 2005; Sternberg et al., 2005). Human genetic varia- tion occurs along a broad continuum, and 90 percent of such variation occurs within rather than among socially defined races (Bonham et al., 2005; Ossorio & Duster, 2005). Nevertheless, race as a social category remains a factor in research because it makes a difference in “how individuals are treated, where they live, their employment opportunities, the quality of their health care, and Chapter 1 The Study of Human Development 13  whether [they] can fully participate” in their society (Smedley & Smedley, 2005, p. 23). Categories of culture, race, and ethnicity are fluid (Bonham et al., 2005; Sternberg et al., 2005), “continu- ously shaped and redefined by social and political forces” (Fisher et al., 2002, p. 1026). Geographic dispersion and intermarriage together with adaptation to varying local conditions have produced a great heterogeneity of physical and cultural characteristics within populations (Smedley & Smedley, 2005; Sternberg et al., 2005). Thus, the golf champion Tiger Woods, who has a black father and an Asian American mother, may fall into more than one racial/ethnic category and may identify more strongly with one or another at different times (Hitlin, Brown, & Elder, 2006; Lin & Kelsey, 2000). A term such as black or Hispanic can be an ethnic gloss—an overgeneralization that obscures or blurs such variations (Parke, 2004; Trimble & Dickson, 2005). The Historical Context At one time developmental scien- Golf legend Tiger Woods is one of many Americans with dual or multiple ethnic backgrounds. tists paid little attention to the historical context—the time in which people live. Then, as early longitudinal studies of ethnic gloss Overgeneralization childhood extended into the adult years, investigators began to focus on how cer- about an ethnic or cultural group tain experiences, tied to time and place, affect the course of people’s lives. Today, that obscures differences within the group. as we will discuss in the next section, the historical context is an important part of the study of development. Checkpoint Normative and Nonnormative Influences Can you... To understand similarities and differences in development, we need to look at two types of normative influences—biological or environmental events that affect ♦ Give examples of the influences of family and many or most people in a society in similar ways—and also at events that touch neighborhood composi- only certain individuals (Baltes & Smith, 2004).* tion, socioeconomic sta- Normative age-graded influences are highly similar for people in a particu- tus, culture, race/ethnicity, lar age group. The timing of biological events is fairly predictable within a and historical context? normal range. For example, people don’t experience puberty at age 35 or meno- pause at 12. normative Characteristic of an Normative history-graded influences are significant environmental events that event that occurs in a similar way shape the behavior and attitudes of an age cohort, a group of people born at for most people in a group. about the same time, or a historical generation, a group of people who experience cohort A group of people born at the same life-changing event at a formative time in their lives. A historical gen- about the same time. eration may contain more than one cohort, but not all cohorts are part of his- historical generation A group of torical generations. Depending on when and where they live, cohorts or genera- people strongly influenced by a major historical event during their tions may feel the impact of famines, wars, or major epidemics and of such formative period. societal and technological developments as the changing roles of women and the impact of television and computers. For example, the generations that came of What’s age during the Great Depression and World War II tend to show a strong sense Your View? of social interdependence and trust that is not as evident among more recent generations (Rogler, 2002). The strength of a history-graded influence may Can you think of a historical depend on the type of event, the age of the person, and the short-term and long- event that has molded your term personal and social effects of the event. life? If so, in what ways? *Unless otherwise noted, this section is based largely on Baltes & Smith, 2004. 14 Part 1 About Human Development  Widespread use of computers is a normative history-graded influence on children’s development, which did not exist in earlier generations. Nonnormative influences are unusual events that have a major impact on indi- nonnormative Characteristic of vidual lives because they disturb the expected sequence of the life cycle. They are an unusual event that happens to a particular person or a typical either typical events that happen at an atypical time of life (such as the death of event that happens at an unusual a parent when a child is young) or atypical events (such as winning the lottery). time of life. Some of these influences are largely beyond a person’s control and may present rare opportunities or severe challenges that the person perceives as turning points. On the other hand, people sometimes help create their own nonnormative life Checkpoint events—say, by deciding to have a baby in their midfifties or taking up a risky hobby such as skydiving—and thus participate actively in their own development. Can you... Taken together, normative and nonnormative influences contribute to the unpre- ♦ Give examples of norma- dictability of human development as well as to the challenges people experience tive age-graded, norma- in trying to build their lives. tive history-graded, and nonnormative influences? Timing of Influences: Critical or Sensitive Periods In a well-known study, Konrad Lorenz (1957), an Austrian zoologist, waddled, honked, and flapped his arms—and got newborn ducklings to follow him as they would the mother duck. Lorenz showed that newly hatched ducklings will instinc- tively follow the first moving object they see, whether or not it is a member of their species. This phenomenon is called imprinting, and Lorenz believed that it imprinting Instinctive form of was automatic and irreversible. Usually, this instinctive bond is with the mother; learning in which, during a critical period in early development, a but, if the natural course of events is disturbed, other attachments, such as the young animal forms an attachment one to Lorenz, can form. Imprinting, said Lorenz, is the result of a predisposition to the first moving object it sees, toward learning: the readiness of an organism’s nervous system to acquire certain usually the mother. information during a brief critical period in early life. Chapter 1 The Study of Human Development 15  BOX 1-1 Research in Action Is There a Critical Period for Language Acquisition? In 1967 Eric Lenneberg (1967, 1969) proposed a critical period acquisition is possible. Some researchers consider the prepubertal for language acquisition beginning in early infancy and ending years a sensitive rather than critical period for learning language around puberty. Lenneberg argued that it would be difficult, if (Newport, Bavelier, & Neville, 2001; Schumann, 1997). Brain not impossible, for a child who had not yet acquired language by imaging research has found that even if the parts of the brain best the onset of puberty to do so after that age. suited to language processing are damaged early in childhood, In 1970, a 13-year-old girl called Genie (not her real name) nearly normal language development can continue as other parts offered the opportunity for a test of Lenneberg’s hypothesis. of the brain take over (Boatman et al., 1999; Hertz-Pannier et al., Genie was discovered in a suburb of Los Angeles (Curtiss, 1977; 2002; M. H. Johnson, 1998). In fact, shifts in brain organization Fromkin, Krashen, Curtiss, Rigler, & Rigler, 1974; Pines, 1981; and utilization occur throughout the course of normal language Rymer, 1993). The victim of an abusive father, she had been con- learning (M. H. Johnson, 1998; Neville & Bavelier, 1998). fined for nearly 12 years to a small room in her parents’ home, If either a critical or a sensitive period for language learning tied to a potty chair and cut off from normal human contact. exists, what explains it? Do the brain’s mechanisms for acquiring When found, she recognized only her name and the word sorry. language decay as the brain matures? That would seem strange, Could Genie be taught to speak, or was it too late? The National as other cognitive abilities improve. An alternative hypothesis is Institutes of Mental Health (NIMH) funded a study to provide that this very increase in cognitive sophistication interferes with intensive testing and language training for Genie. an adolescent’s or adult’s ability to learn a language. Young chil- Genie’s progress during the study both supported and chal- dren acquire language in small chunks that can be digested lenged the idea of a critical period for language acquisition. readily. Older learners, when they first begin learning a language, She learned some simple words and could string them together tend to absorb a great deal at once and then may have trouble into primitive sentences. She also learned the fundamentals of analyzing and interpreting it (Newport, 1991). sign language. But “her speech remained, for the most part, like a somewhat garbled telegram” (Pines, 1981, p. 29). Her mother regained custody, cut her off from the NIMH researchers, and then eventually sent her into the foster care system. A series of What’s Your View? abusive foster homes rendered Genie silent once more. What explains Genie’s initial progress and her inability to Have you had difficulty learning a new language as an adult? sustain it? Her understanding of her name and the single word If so, does this box help you understand why? sorry may mean that her language-learning mechanisms had been triggered early in the critical period, allowing later learning Check It Out to occur. The timing of the NIMH language training and her For more information on language learning go to ability to learn some simple words at age 13 may indicate that she www.facstaff.bucknell.edu/rbeard/acquisition.html. This was still in the critical period, though near its end. On the other website was developed by Professor Robert Beard of hand, her extreme abuse and neglect may have retarded her so the Linguistics Program at Bucknell University. The page much that she could not be considered a true test of the critical cited gives a brief, accurate overview of the nature-nurture period concept (Curtiss, 1977). question as it concerns language acquisition. Links to other Genie’s case dramatizes the difficulty of acquiring language related sites of interest are given. after the early years of life, but, because of the complicating fac- tors, it does not permit conclusive judgments about whether such critical period Specific time when A critical period is a specific time when a given event, or its absence, has a a given event or its absence has a specific impact on development. specific impact on development. Critical periods are not absolutely fixed; if ducklings’ rearing conditions are varied to slow their growth, the usual critical period for imprinting can be lengthened, and imprinting itself may even be reversed. The window of opportunity, some scientists now believe, may never completely shut (Bruer, 2001). Do human beings experience critical periods, as ducklings do? If a woman receives X-rays, takes certain drugs, or contracts certain diseases at certain times during pregnancy, the fetus may show specific ill effects, depending on the nature of the shock and on its timing. If a muscle problem interfering with the ability 16 Part 1 About Human Development Newly hatched ducklings followed and became attached to the first moving object they saw, which just happened to be ethologist Konrad Lorenz. Lorenz called this behavior imprinting. plasticity Range of modifiability of to focus both eyes on the same object is not corrected within a critical period performance. early in childhood, depth perception probably will not develop (Bushnell & sensitive periods Times in Boudreau, 1993). development when a person is particularly open to certain kinds However, the concept of critical periods in humans is controversial. Because of experiences. many aspects of development, even in the physical domain, have been found to show plasticity, or modifiability of performance, it may be more useful to think about sensitive periods, when a developing person is especially responsive to Checkpoint certain kinds of experiences (Bruer, 2001). Further research is needed to dis- cover “which aspects of behavior are likely to be altered by environmental Can you... events at specific points in development and which aspects remain more plastic ♦ Contrast critical and sen- and open to influence across wide spans of development” (Parke, 2004, p. 8). sitive periods and give examples? Box 1-1 discusses how the concepts of critical and sensitive periods apply to language development. Paul B. Baltes’s Life-Span Guidepost 4 Developmental Approach What are seven principles of Paul B. Baltes (1936–2006) and his colleagues (1987; Baltes & Smith, 2004; Baltes, the life-span developmental approach? Lindenberger, & Staudinger, 1998; Staudinger & Bluck, 2001) have identified seven key principles of a life-span developmental approach that sum up many of the concepts discussed in this chapter. Together these principles serve as a widely accepted conceptual framework for the study of life-span development: 1. Development is lifelong. Development is a lifelong process of change. Each period of the life span is affected by what happened before and will affect what is to come. Each period has unique characteristics and value; no peri- od is more or less important than any other. 2. Development is multidimensional. It occurs along multiple interacting dimensions—biological, psychological, and social—each of which may develop at varying rates. 3. Development is multidirectional. As people gain in one area, they may lose in another, sometimes at the same time. Children grow mostly in one direction— up—both in size and in abilities. Then the balance gradually shifts. Adolescents typically gain in physical abilities, but their facility in learning a new language typically declines. Some abilities, such as vocabulary, typically continue to increase throughout most of adulthood; others, such as the ability to solve unfamiliar problems, may diminish; but some new attributes, such as exper- tise, may increase with age. People seek to maximize gains by concentrating Chapter 1 The Study of Human Development 17  on doing things they do well and to minimize losses by learning to manage or compensate for them—for example, by writing “to-do” lists when memory flags. 4. Relative influences of biology and culture shift over the life span. The process of development is influenced by both biology and culture, but the balance between these influences changes. Biological abilities, such as sensory acu- ity and muscular strength and coordination, weaken with age, but cultural supports, such as education, relationships, and technologically age-friendly environments, may help compensate. 5. Development involves changing resource allocations. Individuals choose to invest their resources of time, energy, talent, money, and social support in varying ways. Resources may be used for growth (for example, learning to play an instrument or improving one’s skill), for maintenance or recovery (practicing to maintain or regain proficiency), or for dealing with loss when maintenance and recovery are not possible. The allocation of resources to these three functions changes throughout life as the total available pool of resources decreases. In childhood and young adulthood, the bulk of resources typically goes to growth; in old age, to regulation of loss. In midlife, the allocation is more evenly balanced among the three functions. 6. Development shows plasticity. Many abilities, such as memory, strength, and endurance, can be improved significantly with training and practice, even late in life. However, even in children, plasticity has limits that depend in part on the various influences on development. One of the tasks of developmental research is to discover to what extent particular kinds of development can be modified at various ages. 7. Development is influenced by the historical and cultural context. Each person Checkpoint develops within multiple contexts—circumstances or conditions defined in part by maturation and in part by time and place. Human beings not only Can you... influence but also are influenced by their historical-cultural context. As ♦ Summarize the seven prin- we will discuss throughout this book, developmental scientists have found ciples of Baltes’s life-span significant cohort differences, for example, in intellectual functioning, in developmental approach? women’s midlife emotional development, and in the flexibility of personality in old age. Now that you have had a brief introduction to the field of human development and some of its basic concepts, it’s time to look more closely at the issues devel- opmental scientists think about and how they do their work. In Chapter 2, we discuss some influential theories of how development takes place and the meth- ods investigators commonly use to study it. Summary and Key Terms Human Development: Developmental research has important applications in An Ever-Evolving Field various fields. As researchers have become interested in following Guidepost 1: What is human development, and how development through adulthood, life-span development has its study evolved? has become a field of study. Human development is the scientific study of processes The study of human development seeks to describe, of change and stability. explain, predict, and, when appropriate, intervene in development. 18 Part 1 About Human Development  Students of human development draw on such Important environmental influences stem from culture, disciplines as psychology, psychiatry, sociology, race/ethnicity, and historical context. Race is viewed by anthropology, biology, genetics, family science, most scholars as a social construction. education, history, philosophy, and medicine. Influences may be normative (age-graded or history- Methods of studying human development are still graded) or nonnormative. evolving, making use of advanced technologies. There is evidence of critical or sensitive periods for human development (4) certain kinds of early development. life-span development (4) individual differences (9) heredity (9) The Study of Human Development: environment (10) Basic Concepts maturation (10) Guidepost 2: What do developmental scientists nuclear family (10) study? extended family (11) Developmental scientists study change and stability in all socioeconomic status (SES) (11) domains of development throughout the life span. risk factors (12) The three major domains of development are physical, culture (12) cognitive, and psychosocial. Each affects the others. ethnic group (12) The concept of periods of development is a social ethnic gloss (14) construction. In this book, the life span is divided into normative (14) eight periods: prenatal, infancy and toddlerhood, early childhood, middle childhood, adolescence, emerging and cohort (14) young adulthood, middle adulthood, and late adulthood. historical generation (14) In each period, people have characteristic developmental nonnormative (15) needs and tasks. imprinting (15) physical development (5) critical period (16) cognitive development (6) plasticity (17) psychosocial development (6) sensitive periods (17) social construction (6) Paul B. Baltes’s Life-Span Influences on Development Developmental Approach Guidepost 3: What kinds of influences make one Guidepost 4: What are seven principles of the person different from another? life-span developmental approach? Influences on development come from both heredity and The principles of Baltes’s life-span developmental environment. Many typical changes during childhood approach include the propositions that (1) development are related to maturation. Individual differences tend to is lifelong, (2) development is multidimensional, increase with age. (3) development is multidirectional, (4) the relative In some societies, the nuclear family predominates; in influences of biology and culture shift over the life span, others, the extended family. (5) development involves changing resource allocations, Socioeconomic status (SES) affects developmental (6) development shows plasticity, and (7) development processes and outcomes through the quality of home is influenced by the historical and cultural context. and neighborhood environments, nutrition, medical care, and schooling. Multiple risk factors increase the likelihood of poor outcomes. Chapter 1 The Study of Human Development 19 2 Theory and Research There is one thing even more vital to science than OUTLINE intelligent methods; and that is, the sincere desire Basic Theoretical Issues to find out the truth, whatever it may be. Issue 1: Is Development Active or Reactive? Issue 2: Is Development —Charles Sanders Peirce, Collected Papers, vol. 5, 1934 Continuous or Discontinuous? Theoretical Perspectives Perspective 1: Psychoanalytic Did You Know... Perspective 2: Learning Perspective 3: Cognitive Perspective 4: Theories are never set in stone; they are always open to change as Contextual Perspective 5: Evolutionary/ a result of new findings? Sociobiological A Shifting Balance Research Methods People shape their world as it shapes them? Sampling Forms of Data Cross-cultural research enables us to learn which aspects of Collection Basic Research Designs development are universal and which are culturally influenced? Developmental Research Designs An experiment is the only way to demonstrate that one event Ethics of Research causes another? BOX 2-1: Window on the The results of laboratory experiments may be less applicable to World: Purposes of Cross- Cultural Research real life than experiments carried out in a home, school, or public setting? T hese are just a few of the interesting and important topics we will cover in this chapter. Here, we present an overview both of major theories of human development and of research methods used to study it. In the first part of the chapter, we explore major issues and theoretical perspectives that underlie much research in human development. In the remainder of the chapter, we look at how researchers gather and assess information so that, as you read further in this book, you will be better able to judge whether research findings and conclusions rest on solid ground. After you have studied this chapter, you should be able to answer each of the Guidepost questions on the following page. 21  Guideposts for Study 1. What purposes do theories serve, and what are two basic theoretical issues on which developmental scientists differ? 2. What are five theoretical perspectives on human development, and what are some theories representative of each? 3. How do developmental scientists study people, and what are some advantages and disadvantages of each research method? 4. What ethical problems may arise in research on humans? Basic Theoretical Issues Guidepost 1 When Ahmed earned an engineering degree from M.I.T. with honors, his father, an What purposes do theories serve, and what are two award-winning engineer, beamed. “The apple doesn’t fall far from the tree,” he said. basic theoretical issues Statements like that one, which abound in everyday life, are informal, or intui- on which developmental tive, theories about why people develop as they do. Scientists have formal theories scientists differ? about human development. Like laypeople’s informal theories, scientific theories are not dry, abstract, or esoteric. They deal with the substance of real life. A scientific theory is a set of logically related concepts or statements that seek, theory Coherent set of logically related concepts that seeks to in this field, to describe and explain development and to predict what kinds of organize, explain, and predict behavior might occur under certain conditions. Theories organize and explain data. data, the information gathered by research. As painstaking research adds, bit by bit, to the body of knowledge, theoretical concepts, such as the idea of an iden- tity crisis, discussed later in this chapter, help us make sense of, and see connec- tions between, isolated pieces of data. Theory and research are interwoven strands in the seamless fabric of scien- tific study. Theories inspire further research and predict its results. They do this hypotheses Possible explanations by generating hypotheses, tentative explanations or predictions that can be tested for phenomena, used to predict by further research. Research can indicate whether a theory is accurate in its pre- the outcome of research. dictions but cannot conclusively show a theory to be true. Theories change to incorporate new findings. Sometimes research supports a hypothesis and the theory on which it was based. At other times, scientists must modify their theories to account for unexpected data. Research findings often suggest additional hypotheses to be examined and provide direction for dealing with practical issues. A theory is based on certain assumptions, which may or may not turn out to be true. A theorist’s assumptions may be influenced by his culture and time in history. For example, Charles Darwin’s theory of evolution, which preceded mod- ern cell biology, assumed that all life forms evolved from a single ancestor. This assumption has been challenged by newer evolutionary research. One such model suggests that a loose grouping of cells eventually split into three primary lines of descent (Liu, 2006; Woese, 1998). Developmental science cannot be completely objective. Theories and research about human behavior are products of very human individuals, whose inquiries and interpretations are inevitably influenced by their own values and experience. In striving for greater objectivity, researchers must scrutinize how they and their 22 Part 1 About Human Development colleagues conduct their work, the assumptions on which it is based, and how they arrive at their conclusions. Throughout this book, we examine many, often conflicting, theories. In Checkpoint assessing them, it is important to keep in mind that they reflect the outlooks of the human beings who originated them. The way theorists explain development Can you... depends in part on their assumptions about two basic issues: (1) whether people ♦ Explain the relationships are active or reactive in their own development, and (2) whether development is among theories, continuous or occurs in stages. A third issue, whether development is more influ- hypotheses, and research? enced by heredity or by environment, was introduced in Chapter 1 and will be discussed more fully in Chapter 3. Issue 1: Is Development Active or Reactive? Are people active in their own development? This controversy goes back to the eighteenth century. The English philosopher John Locke held that a young child is a tabula rasa—a “blank slate”—on which society “writes.” In contrast, the French philosopher Jean Jacques Rousseau believed that children are born “noble savages” who develop according to their own positive natural tendencies if not corrupted by society. We now know that both views are too simplistic. Children have internal drives and needs that influence development, but children also are social animals who cannot develop optimally in isolation. Mechanistic Model The debate over Locke’s and Rousseau’s philosophies led to two contrasting models, or images, of development: mechanistic and organismic. Locke’s view was the forerunner of the mechanistic model. In this model, people mechanistic model Model that are like machines that react to environmental input (Pepper, 1942, 1961). A views human development as a series of predictable responses machine is the sum of its parts. To understand it, we can break it down into its to stimuli. smallest components and then reassemble it. Machines do not operate of their own volition; they react automatically to physical forces or inputs. Fill a car with gas, turn the ignition key, press the accel- erator, and the vehicle will move. In the mechanistic view, human behavior is much the same: It results from the operation of biological parts in response to external or internal stimuli. If we know enough about how the human “machine” is put organismic model Model that together and about the forces acting on it, we can predict what the person will do. views human development as internally initiated by an active Mechanistic research seeks to identify the factors that make people behave as organism and as occurring in a they do. For example, in seeking to explain why some college students drink too sequence of qualitatively different much alcohol, a mechanistic theorist might look for environmental influences, such stages. as advertising and whether the student’s friends are heavy drinkers. Organismic Model Rousseau was the precursor of the organismic model. This model sees people as active, growing organisms that set their own development in motion (Pepper, 1942, 1961). They initiate events; they do not just react. Thus, the driving force for change is internal. Environmental influences do not cause development, though they can speed or slow it. Because human behavior is viewed as an organic whole, it cannot be predicted by breaking it down into simple responses to environmen- tal stimulation. The meaning of a family relationship, for example, goes beyond what can be learned from studying its individual members and their day-to-day interactions. An organismic theorist, in studying why some students drink too much, would be likely to look at what Are more women becoming doctors today because of inner motivation or environmental influences? kinds of situations they choose to participate in, and with whom. Do Mechanistic and organismic theorists might give they choose friends who prefer to party or to study? different answers to that question. Chapter 2 Theory and Research 23  Table 2 -1 Five Perspectives on Human Development Perspective Important Theories Basic Propositions Psychoanalytic Freud’s psychosexual theory Behavior is controlled by powerful unconscious urges. Erikson’s psychosocial theory Personality is influenced by society and develops through a series of crises. Learning Behaviorism, or traditional learning theory People are responders; the environment controls behavior. (Pavlov, Skinner, Watson) Social learning (social cognitive) theory Children learn in a social context by observing and imitating models. (Bandura) Children are active contributors to learning. Cognitive Piaget’s cognitive-stage theory Qualitative changes in thought occur between infancy and adolescence. Children are active initiators of development. Vygotsky’s sociocultural theory Social interaction is central to cognitive development. Information-processing theory Human beings are processors of symbols. Contextual Bronfenbrenner’s bioecological theory Development occurs through interaction between a developing person and five surrounding, interlocking contextual systems of influences, from microsystem to chronosystem. Evolutionary/ Bowlby’s attachment theory Human beings have the adaptive mechanisms to survive; critical or sensitive sociobiological periods are stressed; evolutionary and biological bases for behavior and predisposition toward learning are important. For organicists, development has an underlying, orderly structure, though it may not be obvious from moment to moment. As a fertilized egg cell develops into an embryo and then into a fetus, it goes through a series of qualitative changes not overtly predictable from what came before. Swellings on the head become eyes, ears, mouth, and nose. The brain begins to coordinate breathing, digestion, and elimination. Sex organs form. Similarly, organicists describe development after birth as a progressive sequence of stages, moving toward full maturation. Issue 2: Is Development Continuous or Discontinuous? The mechanistic and organismic models also differ on the second issue: Is devel- opment continuous, that is, gradual and incremental, or discontinuous, that is, abrupt or uneven? Mechanistic theorists see development as continuous, like walking or crawling up a ramp. Development, in mechanistic models, is always governed by the same processes, allowing prediction of earlier behaviors from later ones. quantitative change Change Mechanistic theorists deal with quantitative change—changes in number or in number or amount, such as amount, such as in height, weight, size of vocabulary, or frequency of communi- in height, weight, or the size of vocabulary. cation. A baby who gains three pounds in his first three months of life experi- ences a quantitative change. Quantitative researchers may measure how much a person can remember, rather than what