in which they live, but they also play a role in influencing their development by interacting with and changing those contexts (Elder et al., 2016). Even infants influence the world around them and construct their own development through their interactions. Consider an infant who smiles at each adult he sees; he influences his world because adults are likely to smile, use “baby talk,” and play with him in response. The infant brings adults into close contact, making one-on-one interactions and creating opportunities for learning. By engaging the world around them, thinking, being curious, and interacting with people, objects, and the world around them, individuals of all ages are “manufacturers of their own development” (Flavell, 1992, p. 998).
It’s easy to see how this baby can influence the world around her and construct her own development through her interactions. By smiling at each adult she sees, she influences her world because adults are likely to smile, use “baby talk,” and play with her in response.
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Nature and Nurture Influence Development
Perhaps the most fundamental question about lifespan human development concerns why people change in predictable ways over the course of their lifetimes. The answer reflects perhaps the oldest and most heated debate within the field of human development: the nature–nurture issue. Is development caused by nature or nurture? Explanations that rely on nature point to inborn genetic traits (heredity), maturational processes, and evolution as causes of developmental change. For example, most infants take their first steps at roughly the same age, suggesting a maturational trend that supports the role of nature in development (Payne & Isaacs, 2016). An alternative explanation for developmental change is nurture, the view that individuals are molded by the physical and social environment in which they are raised, including the home, school, workplace, neighborhood, and society. From this perspective, although most begin to walk at about the same time, environmental conditions can speed up or slow down the process. Infants who experience malnutrition may walk later than well-nourished infants, and those who are given practice making stepping or jumping movements may walk earlier (Siekerman et al., 2015; Worobey, 2014).
Although developmental scientists once attempted to determine whether development depended on nature or nurture, most now agree that both nature and nurture are important contributors (Rutter, 2014; Sasaki & Kim, 2017). Thus, walking is heavily influenced by maturation (nature), but experiences and environmental conditions can influence the timing of a child’s first steps (nurture). Today developmental scientists attempt to determine how nature and nurture interact and work together to influence how people grow and change throughout life (Bjorklund, 2018; Lickliter & Witherington, 2017).
To review, the three basic questions regarding lifespan human development are as follows:
1 Is developmental change gradual, showing continuity, or abrupt, illustrating discontinuity?
2 What role do people play in their own development—how much are they influenced by their surroundings and how much do they influence their surroundings?
3 To what extent is development a function of heredity, and to what extent is it a function of the environment in which individuals live?
Developmental scientists vary in their responses to these questions, as we will see throughout this book.
Thinking in Context 1.2
1 Can you identify ways in which you have changed very gradually over the years? Were there other times in which you showed abrupt change, such as physical growth, strength and coordination, thinking abilities, or social skills? In other words, in what ways is your development characterized by continuity? Discontinuity?
2 What role did your physical and social environment play in your growth? In what ways, if any, did you take an active role in your own development?
3 How much of who you are today is a function of nature? Nurture?
Theoretical Perspectives on Human Development
Over the past century, scientists have learned much about how individuals progress from infants, to children, to adolescents, and to adults, as well as how they change throughout adulthood. Developmental scientists explain their observations by constructing theories of human development. A theory is a way of organizing a set of observations or facts into a comprehensive explanation of how something works. Theories are important tools for compiling and interpreting the growing body of research in human development as well as determining gaps in our knowledge and making predictions about what is not yet known.
Effective theories generate specific hypotheses, or proposed explanations for a given phenomenon, that can be tested by research. It is important to note that this testing seeks to find flaws in the hypothesis—not to “prove” that it is flawless. A good theory is one that is falsifiable, or capable of generating hypotheses that can be tested and, potentially, refuted. As scientists conduct research and learn more about a topic, they modify their theories. Updated theories often give rise to new questions and new research studies, whose findings may further modify theories.
The great body of research findings in the field of lifespan human development has been organized into several theoretical perspectives. As the following sections illustrate, these theoretical perspectives vary greatly in how they account for the developmental changes that occur over the lifespan.
Sigmund Freud (1856–1939), the father of the psychoanalytic perspective, believed that much of our behavior is driven by unconscious impulses.
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Psychoanalytic Theories
Are there powerful forces within us that make us behave as we do? Are we pushed by inner drives? Psychoanalytic theories describe development and behavior as a result of the interplay of inner drives, memories, and conflicts we are unaware of and cannot control. These inner forces influence our behavior throughout our lives. Freud and Erikson are two key psychoanalytic theorists whose theories remain influential today.
Freud’s Psychosexual Theory
Sigmund Freud (1856–1939), a Viennese physician, is credited as the father of the psychoanalytic perspective. Freud believed that much of our behavior is driven by unconscious impulses that are outside of our awareness. As shown in Table 1.2, Freud believed we progress through a series of psychosexual stages, periods in which unconscious drives are focused on different parts of the body, making stimulation to those parts a source of pleasure. Freud explained that the task for parents is to strike a balance between overgratifying and undergratifying a child’s desires at each stage to help the child develop a healthy personality with the capacity for mature relationships throughout life. Notably, Freud did not study children; his theory grew from his work with female psychotherapy patients (Crain, 2016).
In part because of its heavy emphasis on childhood sexuality, Freud’s psychosexual stage framework, especially the phallic stage, is not widely accepted (Westen, 1998). Yet many of Freud’s ideas have stood up well to the test of time and have permeated
