Lifespan Development. Tara L. Kuther

      These two cohorts offer striking examples of how sociohistorical context influences development.

      The older Oakland cohort (born in 1920–1921) were children during the affluent 1920s, a time of economic growth in California, and they experienced a prosperous and relatively stress-free childhood. They entered adolescence during the Great Depression, a period of severe economic stress in which unemployment skyrocketed and people’s savings were depleted. As adolescents during the Great Depression, the Oakland cohort tended to behave responsibly and assist their families in coping. The boys often assumed jobs outside the home to aid financially troubled families, which enhanced their social independence and reduced their exposure to family stress. However, girls spent more time at home caring for siblings and performing household chores, as many mothers worked outside the home; they were exposed to greater amounts of family stress and showed poorer adjustment than did the boys. The Oakland cohort completed high school just prior to the onset of World War II, and over time, nearly all of the young men entered the armed forces.

      Unlike the Oakland cohort, individuals in the Berkeley Guidance Study (born in 1928–1929) experienced the Great Depression during their vulnerable early childhood years. The children thus experienced economic scarcity and family discord early in life, at a time when they were very dependent on family. The Berkeley cohort entered adolescence during World War II, a period of additional economic and emotional stress resulting from empty households (as both parents worked to support the war effort) and the military service and war trauma of older brothers. As adolescents, the Berkley boys experienced greater emotional difficulties, poorer attitudes toward school, and less hope, self-direction, and confidence about their future than did the boys in the Oakland cohort. Like the girls in the Oakland cohort, the Berkeley girls spent time at home. They experienced stress but showed better adjustment than the Oakland girls, who experienced multiple stressors and transitions of adolescence (such as puberty and changes in social roles) simultaneously with the onset of the Great Depression.

      Although the Berkeley boys tended to be troubled in adolescence, they demonstrated resilience in adulthood, largely because of the influence of military service. Three quarters of the males in the Berkeley sample served in the military between 1945 and the end of the Korean War in the early 1950s. The most disadvantaged young men tended to join the military early, and early entry into the military predicted personal growth. Military service appeared to offer several opportunities, such as the chance to begin again and reconsider their lives, to travel, and to take advantage of the GI Bill of Rights, which enabled them to expand their education and acquire new skills after the war.

      These two cohorts of young people offer striking examples of how sociohistorical context influences development. Context always plays a role in development—not only in times of social upheaval but every day and for every generation.

      What Do You Think?

      1 Consider the sociohistorical context in which you were raised. What historical and societal events may have influenced you? What events have shaped your generation’s childhood and adolescence?

      2 Consider the societal and cultural events that your parents may have experienced in childhood and adolescence. What technology was available? What historical events did they experience? What were the popular fads of their youth? What influence do you think these sociohistorical factors may have had on your parents’ development?

      A final element of the bioecological system is the chronosystem, which refers to how the bioecological system changes over time. As people grow and change, they take on and let go of various roles. For example, graduating from college, getting married, and becoming a parent involve changes in roles and shifts in microsystems. These shifts in contexts, called ecological transitions, occur throughout life.

      Recently, the bioecological model has been criticized for its vague explanation of development, especially the role of culture (Vélez-Agosto, Soto-Crespo, Vizcarrondo-Oppenheimer, Vega-Molina, & García Coll, 2017). Situated in the macrosystem, culture is said to influence development through the interdependence of the systems. Yet current conceptualizations of culture view it as all the processes used by people as they make meaning or think through interactions with group members (Mistry et al., 2016; Yoshikawa, Mistry, & Wang, 2016). Critics therefore argue that since culture is manifested in our daily activities, it is inherent in each bioecological level (Vélez-Agosto et al., 2017). A second criticism arises from the sheer complexity of the bioecological model and its attention to patterns and dynamic interactions. We can never measure and account for all of the potential individual and contextual influences on development at once, making it difficult to devise research studies to test the validity of the model. Proponents, however, argue that it is not necessary to test all of the model’s components at once. Instead, smaller studies can examine each component over time (Jaeger, 2016; Tudge et al., 2016). In any case, bioecological theory remains an important contribution toward explaining developmental change across the lifespan and is a theory that we will consider throughout this book.

      Shortly after birth, goslings imprint to their mothers, meaning that they bond to her and will follow her to ensure they will be fed and remain protected. Ethologists propose that animal and human caregiving behaviors have an evolutionary basis.

      iStock/EmilyNorton

      Ethology and Evolutionary Developmental Theory

      What motivates parents of most species to care for their young? Some researchers argue that caregiving behaviors have an evolutionary basis. Ethology is the scientific study of the evolutionary basis of behavior (Bateson, 2015). In 1859, Charles Darwin proposed his theory of evolution, explaining that all species adapt and evolve over time. Specifically, traits that enable a species to adapt, thrive, and mate tend to be passed to succeeding generations because they improve the likelihood of the individual and species’ survival. Several early theorists applied the concepts of evolution to behavior. Konrad Lorenz and Niko Tinbergen, two European zoologists, observed animal species in their natural environments and noticed patterns of behavior that appeared to be inborn, emerged early in life, and ensured the animals’ survival. For example, shortly after birth, goslings imprint to their mothers, meaning that they bond to her and follow her. Imprinting aids the goslings’ survival because it ensures that they stay close to their mother, get fed, and remain protected. In order for imprinting to occur, the mother goose must be present immediately after the goslings hatch; mothers instinctively stay close to the nest so that their young can imprint (Lorenz, 1952).

      According to John Bowlby (1969), humans also display biologically preprogrammed behaviors that have survival value and promote development. For example, caregivers naturally respond to infants’ cues. Crying, smiling, and grasping are inborn ways that infants get attention from caregivers, bring caregivers into physical contact, and ensure that they will be safe and cared for. Such behaviors have adaptive significance because they meet infants’ needs and promote the formation of bonds with caregivers, ensuring that the caregivers will feel a strong desire and obligation to care for them (Bowlby, 1973). In this way, innate biological drives and behaviors work together with experience to influence adaptation and ultimately an individual’s survival.

      Another theory, evolutionary developmental theory, applies principles of evolution and scientific knowledge about the interactive influence of genetic and environmental mechanisms to understand the changes people undergo throughout their lives (Bjorklund, 2018; Witherington & Lickliter, 2016). You may have wondered, for example, whether you—your abilities, personality, and competencies—result from your genes or from the physical and social environment in which you were raised. Evolutionary developmental scientists explain that this is the wrong question to ask. From an evolutionary development perspective, genes and context interact in an ever-changing way so that it is impossible to isolate the contributions of each to development (Witherington & Lickliter, 2016) While all of our traits and characteristics are influenced by genes, contextual factors influence the expression