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What if for your entire life, the image that others held of you was colored by the way in which you were conceived?
In some ways, that’s what it has been like for Louise Brown, who was the world’s first “test tube baby,” born by in vitro fertilization (IVF), a procedure in which fertilization of a mother’s egg by a father’s sperm takes place outside of the mother’s body.
Louise was a preschooler when her parents told her about how she was conceived, and throughout her childhood she was bombarded with questions. It became routine to explain to her classmates that she in fact was not born in a laboratory.
As a child, Louise sometimes felt completely alone. “I thought it was something peculiar to me,” she recalled. But as she grew older, her isolation declined as more and more children were born in the same manner.
In fact, today Louise is hardly isolated. More than 5 million babies have been born using the procedure, which has become almost routine. And at the age of 28, Louise became a mother herself, giving birth to a baby boy name Cameron—conceived, by the way, in the old-fashioned way (Falco, 2012; ICMRT, 2012).
Prologue: New Conceptions
LO 1-1 What is lifespan development?
LO 1-2 What are some of the basic influences on human development?
LO 1-3 What are the key issues in the field of development?
LO 1-4 Which theoretical perspectives have guided lifespan development?
LO 1-5 What role do theories and hypotheses play in the study of development?
LO 1-6 How are developmental research studies conducted?
LO 1-7 What are some of the ethical issues regarding psychological research?
An Orientation to Lifespan Development
Characterizing Lifespan Development: The Scope of the Field
Cohort and Other Influences on Development: Developing with Others in a Social World
Key Issues and Questions: Determining the Nature—and Nurture—of Lifespan Development
Continuous Change versus Discontinuous Change
Critical and Sensitive Periods: Gauging the Impact of Environmental Events
Lifespan Approaches versus a Focus on Particular Periods
The Relative Influence of Nature and Nurture on Development
Theoretical Perspectives on Lifespan Development
The Psychodynamic Perspective: Focusing on the Inner Person
The Behavioral Perspective: Focusing on Observable Behavior
The Cognitive Perspective: Examining the Roots of Understanding
The Humanistic Perspective: Concentrating on the Unique Qualities of Human Beings
The Contextual Perspective: Taking a Broad Approach to Development
Evolutionary Perspectives: Our Ancestors’ Contributions to Behavior
Why “Which Approach Is Right?” Is the Wrong Question
Theories and Hypotheses: Posing Developmental Questions
Choosing a Research Strategy: Answering Questions
Experiments: Determining Cause and Effect
Theoretical and Applied Research: Complementary Approaches
Measuring Developmental Change
Ethics and Research
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4 PART 1 ▸ Beginnings
Louise Brown’s conception may have been novel, but her devel- opment, from infancy, through childhood and adolescence, and to her marriage and the birth of her baby, has followed a predict- able pattern. The specifics of our development vary: some encoun- ter economic deprivation or live in war-torn territories; others contend with genetic or family issues like divorce and step-parents. The broad strokes of the development, however, which were set in motion in that test tube 28 years ago are remarkably similar for all of us. Michael Phelps, Bill Gates, the Queen of England, and each and every one of us, is traversing the terri- tory known as lifespan development.
Louise Brown’s conception in the lab is just one of the brave new worlds of the twenty-first century. Issues ranging from cloning to the consequences of poverty on development, to the prevention of AIDS raise significant developmental concerns that affect human development. Underlying these are even more fundamental issues: How do we develop physically? How does our understanding of the world grow and change throughout our lives? And how do our personalities and our social relationships develop as we move from birth through the entire span of our lives?
Each of these questions, and many others we’ll encounter throughout this book, are cen- tral to the field of lifespan development. As a field, lifespan development encompasses not only a broad span of time—from before birth to death—but also a wide range of areas of develop- ment. Consider, for example, the range of interests that different specialists in lifespan develop- ment focus on when considering the life of Louise Brown:
• Lifespan development researchers who investigate behavior at the level of biological pro- cesses might determine if Louise’s functioning prior to birth was affected by her conception outside the womb.
• Specialists in lifespan development who study genetics might examine how the genetic endowment from Louise’s parents affects her later behavior.
• For lifespan development specialists who investigate the ways thinking changes over the course of life, Louise’s life might be examined in terms of how her understanding of the nature of her conception changed as she grew older.
• Other researchers in lifespan development, who focus on physical growth, might consider whether her growth rate differed from children conceived more traditionally.
• Lifespan development experts who specialize in the social world and social relationships might look at the ways that Louise interacted with others and the kinds of friendships she developed.
Although their interests take many forms, these specialists in lifespan development share one concern: understanding the growth and change that occur during the course of life. Taking many differing approaches, developmentalists study how both the biological inheritance from our parents and the environment in which we live jointly affect our behavior.
Some developmentalists focus on explaining how our genetic background can determine not only how we look but also how we behave and relate to others in a consistent manner—that is, matters of personality. They explore ways to identify how much of our potential as human beings is provided—or limited—by heredity. Other lifespan development specialists look to
Louise Brown and son.
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ChAPTeR 1 ▸ An Introduction to Lifespan Development 5
the environment, exploring ways in which our lives are shaped by the world that we encounter. They investigate the extent to which we are shaped by our early environments, and how our current circumstances influence our behavior in both subtle and evident ways.
Whether they focus on heredity or environment, all developmental specialists acknowl- edge that neither heredity nor environment alone can account for the full range of human development and change. Instead, our understanding of people’s development requires that we look at the joint effects of the interaction of heredity and environment, attempting to grasp how both, in the end, underlie human behavior.
In this chapter, we orient ourselves to the field of lifespan development. We begin with a discussion of the scope of the discipline, illustrating the wide array of topics it covers and the full range of ages it examines. We also survey the key issues and controversies of the field and consider the broad perspectives that developmentalists take. Finally, we discuss the ways developmentalists use research to ask and answer questions.
An Orientation to Lifespan Development LO 1-1 What is lifespan development?
LO 1-2 What are some of the basic influences on human development?
Have you ever wondered how it is possible that an infant tightly grips your finger with tiny, perfectly formed hands? Or marveled at how a preschooler methodically draws a picture? Or at the way an adolescent can make involved decisions about whom to invite to a party or the ethics of downloading music files? Or the way a middle-aged politician can deliver a long, flawless speech from memory? Or wondered what it is that makes a grandfather at 80 so simi- lar to the father he was when he was 40?
If you’ve ever wondered about such things, you are asking the kinds of questions that scientists in the field of lifespan development pose. Lifespan development is the field of study that examines patterns of growth, change, and stability in behavior that occur throughout the entire life span.
Although the definition of the field seems straightforward, the simplicity is somewhat misleading. In order to understand what development is actually about, we need to look un- derneath the various parts of the definition.
In its study of growth, change, and stability, lifespan development takes a scientific approach. Like members of other scientific disciplines, researchers in lifespan development test their assumptions about the nature and course of human development by applying scientific methods. As we’ll see later in the chapter, they develop theories about development, and they use me- thodical, scientific techniques to validate the accuracy of their assumptions systematically.
Lifespan development focuses on human development. Although there are developmentalists who study the course of development in nonhuman species, the vast majority examines growth and change in people. Some seek to understand universal principles of development, whereas others focus on how cultural, racial, and ethnic differences affect the course of development. Still others aim to understand the unique aspects of individuals, looking at the traits and characteristics that differentiate one person from another. Regardless of approach, however, all developmentalists view development as a continuing process throughout the life span.
As developmental specialists focus on the ways people change and grow during their lives, they also consider stability in people’s lives. They ask in which areas, and in what periods, people show change and growth, and when and how their behavior reveals consistency and continuity with prior behavior.
How people grow and change over the course of their lives is the focus of lifespan development.
lifespan development the field of study that examines patterns of growth, change, and stability in behavior that occur throughout the entire life span.
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6 PART 1 ▸ Beginnings
Finally, developmentalists assume that the process of development persists through- out every part of people’s lives, beginning with the moment of conception and continuing until death. Developmental specialists assume that in some ways people continue to grow and change right up to the end of their lives, while in other respects their behavior remains stable. At the same time, developmentalists believe that no particular, single period of life governs all development. Instead, they believe that every period of life contains the potential for both growth and decline in abilities, and that individuals maintain the capacity for sub- stantial growth and change throughout their lives.
Characterizing Lifespan Development: The Scope of the Field Clearly, the definition of lifespan development is broad and the scope of the field is extensive. Consequently, lifespan development specialists cover several quite diverse areas, and a typical developmentalist will choose to specialize in both a topical area and an age range.
TOPICAL AReAs IN LIfesPAN DeveLOPMeNT. Some developmentalists focus on physical development, examining the ways in which the body’s makeup—the brain, nervous system, muscles, and senses, and the need for food, drink, and sleep—helps determine behav- ior. For example, one specialist in physical development might examine the effects of malnu- trition on the pace of growth in children, while another might look at how athletes’ physical performance declines during adulthood (Fell & Williams, 2008).
Other developmental specialists examine cognitive development, seeking to understand how growth and change in intellectual capabilities influence a person’s behavior. Cognitive developmentalists examine learning, memory, problem-solving skills, and intelligence. For example, specialists in cognitive development might want to see how problem-solving skills change over the course of life, or whether cultural differences exist in the way people explain their academic successes and failures. They would also be interested in how a person who experiences significant or traumatic events early in life would remember them later in life (Alibali, Phillips, & Fischer, 2009; Dumka et al., 2009; Penido et al., 2012).
Finally, some developmental specialists focus on personality and social development. Personality development is the study of stability and change in the enduring characteristics that differentiate one person from another over the life span. Social development is the way in which individuals’ interactions with others and their social relationships grow, change, and remain stable over the course of life. A developmentalist interested in personality develop- ment might ask whether there are stable, enduring personality traits throughout the life span, whereas a specialist in social development might examine the effects of racism or poverty or divorce on development (Evans, Boxhill, & Pinkava, 2008; Lansford, 2009). These four ma- jor topic areas—physical, cognitive, social, and personality development—are summarized in Table 1-1.
Age RANges AND INDIvIDuAL DIffeReNCes. In addition to choosing to spe- cialize in a particular topical area, developmentalists also typically look at a particular age range. The life span is usually divided into broad age ranges: the prenatal period (the pe- riod from conception to birth); infancy and toddlerhood (birth to age 3); the preschool period (ages 3 to 6); middle childhood (ages 6 to 12); adolescence (ages 12 to 20); young adulthood (ages 20 to 40); middle adulthood (ages 40 to 65); and late adulthood (age 65 to death).
It’s important to keep in mind that these broad periods—which are largely accepted by lifespan developmentalists—are social constructions. A social construction is a shared notion of reality, one that is widely accepted but is a function of society and culture at a given time. Consequently, the age ranges within a period—and even the periods themselves—are in many
physical development development involv- ing the body’s physical makeup, including the brain, nervous system, muscles, and senses, and the need for food, drink, and sleep.
cognitive development development in- volving the ways that growth and change in intellectual capabilities influence a person’s behavior.
personality development development in- volving the ways that the enduring characteris- tics that differentiate one person from another change over the life span.
social development the way in which in- dividuals’ interactions with others and their social relationships grow, change, and remain stable over the course of life.
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ChAPTeR 1 ▸ An Introduction to Lifespan Development 7
ways arbitrary and often culturally derived. For example, later in the book we’ll discuss how the concept of childhood as a special period did not even exist during the seventeenth cen- tury; at that time, children were seen simply as miniature adults. Furthermore, while some periods have a clear-cut boundary (infancy begins with birth, the preschool period ends with entry into public school, and adolescence starts with sexual maturity), others don’t.
For instance, consider the period of young adulthood, which at least in Western cultures is typically assumed to begin at age 20. That age, however, is notable only because it marks the end of the teenage period. In fact, for many people, such as those enrolled in higher edu- cation, the age change from 19 to 20 has little special significance, coming as it does in the middle of the college years. For them, more substantial changes may occur when they leave college and enter the workforce, which is more likely to happen around age 22. Furthermore, in some non-Western cultures, adulthood may be considered to start much earlier, when chil- dren whose educational opportunities are limited begin full-time work.
In fact, some developmentalists have proposed entirely new developmental periods. For instance, psychologist Jeffrey Arnett argues that adolescence extends into emerging adulthood, a period beginning in the late teenage years and continuing into the mid-twenties. During emerging adulthood, people are no longer adolescents, but they haven’t fully taken on the responsibilities of adulthood. Instead, they are still trying out different identities and engage in self-focused exploration (Schwartz, Côté, & Arnett, 2005; Lamborn & Groh, 2009; Arnett, 2010, 2011; de Dios, 2012).
In short, there are substantial individual differences in the timing of events in people’s lives. In part, this is a biological fact of life: People mature at different rates and reach develop- mental milestones at different points. However, environmental factors also play a significant role in determining the age at which a particular event is likely to occur. For example, the typi- cal age of marriage varies substantially from one culture to another, depending in part on the functions that marriage plays in a given culture.
TAbLe 1-1 Approaches to Lifespan Development
Orientation Defining Characteristics examples of Question Asked*
Physical development Emphasizes how brain, nervous system, muscles, sensory capabilities, needs for food, drink, and sleep affect behavior
• What determines the sex of a child? (2) • What are the long-term results of premature birth? (3) • What are the benefits of breast milk? (4) • What are the consequences of early or late sexual maturation? (1) • What leads to obesity in adulthood? (13) • How do adults cope with stress? (15) • What are the outward and internal signs of aging? (17) • How do we define death? (19)
Cognitive development Emphasizes intellectual abilities, including learning, memory, problem solving, and intelligence
• What are the earliest memories that can be recalled from infancy? (5) • What are the intellectual consequences of watching television? (7) • Do spatial reasoning skills relate to music practice? (7) • Are there benefits to bilingualism? (9) • How does an adolescent’s egocentrism affect his or her view of the
world? (11) • Are there ethnic and racial differences in intelligence? (9) • How does creativity relate to intelligence? (13) • Does intelligence decline in late adulthood? (17)
Personality and social development
Emphasizes enduring characteristics that differentiate one person from another, and how interactions with others and social relationships grow and change over the lifetime
• Do newborns respond differently to their mothers than to others? (3) • What is the best procedure for disciplining children? (8) • When does a sense of gender identity develop? (8) • How can we promote cross-race friendships? (10) • What are the causes of adolescent suicide? (12) • How do we choose a romantic partner? (14) • Do the effects of parental divorce last into old age? (18) • Do people withdraw from others in late adulthood? (18) • What are the emotions involved in confronting death? (19)
*Numbers in parentheses indicate in which chapter the question is addressed.
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8 PART 1 ▸ Beginnings
It is important to keep in mind, then, that when developmental specialists discuss age ranges, they are talking about averages—the times when people, on average, reach particular milestones. Some people will reach the milestone earlier, some later, and many will reach it around the time of the average. Such variation becomes noteworthy only when children show substantial deviation from the average. For example, parents whose child begins to speak at a much later age than aver- age might decide to have their son or daughter evaluated by a speech therapist.
The LINKs beTweeN TOPICs AND Ages. Each of the broad topical areas of lifes- pan development—physical, cognitive, social, and personality development—plays a role throughout the life span. Consequently, some developmental experts focus on physical devel- opment during the prenatal period, and others during adolescence. Some might specialize in social development during the preschool years, while others look at social relationships in late adulthood. And still others might take a broader approach, looking at cognitive development through every period of life.
In this book, we’ll take a comprehensive approach, proceeding chronologically from the prenatal period through late adulthood and death. Within each period, we’ll look at different topical areas: physical, cognitive, social, and personality. Furthermore, we’ll also be consider- ing the impact of culture on development, as we discuss next.This wedding of two children in India is an
example of how environmental factors can play a significant role in determining the age when a particular event is likely to occur.
Developmental Diversity anD your life
How Culture, Ethnicity, and Race Influence Development Mayan mothers in Central America are certain that almost con- stant contact between themselves and their infant children is nec- essary for good parenting, and they are physically upset if contact is not possible. They are shocked when they see a North American mother lay her infant down, and they attribute the baby’s crying to the poor parenting of the North American. (Morelli et al., 1992)
What are we to make of the two views of parenting expressed in this passage? Is one right and the other wrong? Probably not, if we take into consideration the cultural context in which the mothers are operating. Different cultures and subcultures have their own views of appropriate and inappropriate childrearing, just as they have different developmental goals for children (Feldman & Masalha, 2007; Huijbregts et al., 2009; Chen & Tianying Zheng, 2012).
It has become clear that in order to understand development, devel- opmentalists must take into consideration broad cultural factors, such as an orientation toward individualism or collectivism. They must also consider finer ethnic, racial, socioeconomic, and gender differences if they are to achieve an understanding of how people change and grow throughout the life span. If developmentalists succeed in doing so, not only can they achieve a better understanding of human development, but they may be able to derive more precise applications for improving the human social condition.
Efforts to understand how diversity affects development have been hindered by difficulties in finding an appropriate vocabulary. For example, members of the research community—as well as society at large—have sometimes used terms such as race and ethnic group in inappropriate ways. Race is a biological concept, which should be employed to refer to classifications based on physical and structural characteristics of species. In contrast, ethnic group and ethnicity are
broader terms, referring to cultural background, nationality, religion, and language.
The concept of race has proven especially problematic. Although it formally refers to biological factors, race has taken on substantially more meanings—many of them inappropriate—that range from skin color to religion to culture. Moreover, the concept of race is exceed- ingly imprecise; depending on how it is defined, there are between 3 and 300 races, and no race is genetically distinct. The fact that 99.9 per- cent of humans’ genetic makeup is identical in all humans makes the question of race seem comparatively insignificant (Bamshad & Olson, 2003; Helms, Jernigan, & Mascher, 2005; Smedley & Smedley, 2005).
In addition, there is little agreement about which names best reflect different races and ethnic groups. Should the term African American— which has geographical and cultural implications—be preferred over black, which focuses primarily on skin color? Is Native American preferable to Indian? Is Hispanic more appropriate than Latino? And how can researchers accurately categorize people with multiethnic backgrounds? The choice of category has important implications for the validity and usefulness of research. The choice even has political implications. For example, the decision to permit people to identify themselves as “multiracial” on U.S. government forms and in the U.S. Census initially was highly controversial (Perlmann & Waters, 2002).
In order to fully understand development, then, we need to take the complex issues associated with human diversity into account. It is only by looking for similarities and differences among various ethnic, cultural, and racial groups that developmental researchers can distin- guish principles of development that are universal from principles that are culturally determined. In the years ahead, then, it is likely that lifes- pan development will move from a discipline that focuses primarily on North American and European development to one that encompasses development around the globe (Fowers & Davidov, 2006; Matsumoto & Yoo, 2006; Kloep et al., 2009).
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