9.1 INTRODUCTION: Your Life Story

KEY THEME

Developmental psychology is the study of how people change over the lifespan.

KEY QUESTIONS

One way to look at the “big picture” of your life is to think of your life as a story. You, of course, are the main character. Your life story so far has had a distinct plot, occasional subplots, and a cast of supporting characters, including family, friends, and lovers.

Like every other person’s life story, yours has been influenced by factors beyond your control. One such factor is the unique combination of genes you inherited from your biological mother and father. Another is the historical era during which you grew up. Your individual development has also been shaped by the cultural, social, and family contexts within which you were raised.

The patterns of your life story, and the life stories of countless other people, are the focus of developmental psychology—the study of how people change physically, cognitively, and socially throughout the lifespan. Developmental psychologists investigate the influence of biological, environmental, social, cultural, and behavioral factors on development at every age and stage of life.

developmental psychology

The branch of psychology that studies how people change over the lifespan.

Continuity and Change over the Lifespan The twin themes of continuity and change throughout the lifespan are evident in the changing nature of relationships. Childhood friendships center on sharing activities, while peer relationships in adolescence emphasize sharing thoughts and feelings. Early adulthood brings the challenge of forming intimate relationships and, for some, beginning a family. Close relationships with friends and family continue to contribute to psychological well-being in late adulthood.
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The impact of these factors on individual development is greatly influenced by attitudes, perceptions, and personality characteristics. For example, the adjustment to middle school may be a breeze for one child but a nightmare for another. So, although we are influenced by the events we experience, we also shape the meaning and consequences of those events.

Along with studying common patterns of growth and change, developmental psychologists look at the ways in which people differ in their development and life stories. As we’ll note several times in this chapter, the typical, or “normal,” pattern of development can also vary across cultures (Kagan, 2011; Molitor & Hsu, 2011).

Table : TABLE 9.1
Major Stages of the Lifespan
Stage Age Range
Prenatal Conception to birth
Infancy and toddlerhood Birth to 2 years
Early childhood 2 to 6 years
Middle childhood 6 to 12 years
Adolescence 12 to 18 years
Emerging adulthood 18 to 25 years
Young adulthood 25 to 40 years
Middle adulthood 40 to 65 years
Late adulthood 65 years to death

Developmental psychologists use varied research methods, but two research strategies are particularly important in understanding how people develop: longitudinal and cross-sectional designs (Karmiloff-Smith & others, 2014). Research that utilizes a longitudinal design tracks a particular variable or group of variables in the same group of participants over time, sometimes for years. For example, a longitudinal study of the effects of day care might compare the social development of a matched group of participants, half of whom attended day care and half of whom didn’t, from infancy through high school graduation.

longitudinal design

Research strategy in which a variable or group of variables are studied in the same group of participants over time.

In contrast, research using a cross-sectional design studies a variable or group of variables among a group of participants at different ages or developmental stages. For example, to study the effect of aging on cognitive processes, developmental psychologists might compare memory abilities in 45-year-old, 55-year-old, and 65-year-old participants, looking for age-related differences.

cross-sectional design

Research strategy in which individuals of different ages or developmental stages are directly compared.

The Chapters in Your Life Story If you think of your life as an unfolding story, then the major stages of the human lifespan represent the different “chapters” of your life. Each chapter is characterized by fundamentally different physical, cognitive, and social transitions, challenges and opportunities, demands and adjustments. Comparing different life stories reveals many striking similarities in the developmental themes of any given stage. Nevertheless, every life story is unique.

Developmental psychologists often conceptualize the lifespan in terms of basic stages of development (see TABLE 9.1). Traditionally, the stages of the lifespan are defined by age, which implies that we experience relatively sudden, age-related changes as we move from one stage to the next. Indeed, some of life’s transitions are rather abrupt, such as entering the workforce, becoming a parent, or retiring. And some aspects of development, such as prenatal development and language development, are closely tied to critical periods, which are periods during which a child is maximally sensitive to environmental influences.

Still, most of our physical, cognitive, and social changes occur gradually. As we trace the typical course of human development in this chapter, the theme of gradually unfolding changes throughout the ages and stages of life will become more evident. Another important theme in developmental psychology is the interaction between heredity and environment. Traditionally, this was called the nature–nurture issue. Although we are born with a specific genetic potential that we inherit from our biological parents, our environment influences how, when, and whether that potential is expressed. In turn, our genetic inheritance influences the ways in which we experience and interact with the environment (Diamond, 2009; Meaney, 2010).