1.5 Discuss the ethical responsibilities of researchers to protect their participants.
What is Lifespan Human Development?
This is a book about lifespan human development—the ways in which people grow, change, and stay the same throughout their lives, from conception to death. When people use the term development, they often mean the transformation from infant to adult. However, development does not end with adulthood. We continue to change in predictable ways throughout our lifetime, even into old age. Developmental scientists study human development seeking to understand these lifetime patterns of change.
Table 1.1 illustrates the many phases of life through which we progress from conception to death. The phases may have different labels and different sets of developmental tasks, but all have value. The changes that we undergo during infancy, for instance, influence how we experience later changes, such as those during adolescence and beyond. Each phase of life is important and accompanied by its own demands and opportunities.
Change is perhaps the most obvious indicator of development. For example, the muscle strength and coordination needed to play sports increases over childhood and adolescence, peaks in early adulthood, and begins to decline thereafter, declining more rapidly from middle to late adulthood. However, there also are ways in which we change little over our lifetimes. Some personality traits, for example, are highly stable over the lifespan, so that we remain largely the “same person” into old age (Schwaba & Bleidorn, 2018; Wortman, Lucas, & Donnellan, 2012).
Lifespan human development can be described by several principles. As discussed in the following sections, development is (1) multidimensional, (2) multidirectional, (3) plastic, (4) influenced by multiple contexts, and (5) multidisciplinary (Baltes, Lindenberger, & Staudinger, 2006; Overton & Molenaar, 2015).
Development Is Multidimensional
Development is multidimensional and includes changes in the areas of physical, cognitive, and socioemotional development (Baltes et al., 2006). Physical development refers to body maturation and growth, such as body size, proportion, appearance, health, and perceptual abilities. Cognitive development refers to the maturation of thought processes and the tools that we use to obtain knowledge, become aware of the world around us, and solve problems. Socioemotional development includes changes in personality, emotions, views of oneself, social skills, and interpersonal relationships with family and friends. These areas of development overlap and interact. For example, brain maturation, a physical development, underlies advances in cognitive development, which might enable an adolescent to become better at understanding her best friend’s point of view (Braams & Crone, 2017). In turn, she might become more empathetic and sensitive to her friend’s needs and develop a more mature friendship, influencing her socioemotional development. Figure 1.1 illustrates how the three areas of development interact.
Table 1.1
Development Is Multidirectional
Development is commonly described as a series of improvements in performance and functioning, but in fact development is multidirectional, meaning that it consists of both gains and losses, growth and decline, throughout the lifespan (Baltes et al., 2006; Overton & Molenaar, 2015). For example, infants are born with a stepping reflex, an innate involuntary response in which they make step-like movements when held upright over a horizontal surface (for more on infant reflexes, see Chapter 4). The stepping reflex disappears by about 2 months but reemerges as a voluntary action at 8 to 12 months of age as infants begin walking with support (Adolph & Franchak, 2017). Throughout life, there is a shifting balance between gains, improvements in performance (common early in life), and losses, declines in performance (common late in life) (Baltes et al., 2006). At all ages, however, individuals can compensate for losses by improving existing skills and developing new ones (Boker, 2013). The speed at which people think tends to slow in late adulthood, for example, but increases in knowledge and experience enable older adults to compensate for the loss of speed when completing everyday tasks (Hess, Leclerc, Swaim, & Weatherbee, 2009; Margrett, Allaire, Johnson, Daugherty, & Weatherbee, 2010). The brain naturally adapts to a lifetime of sensory experiences in order to portray the world around us efficiently and accurately as we age into older adulthood (Moran, Symmonds, Dolan, & Friston, 2014).
Figure 1.1 Multidimensional Nature of Development
Advances in physical, cognitive, and socioemotional development interact, permitting children to play sports, learn more efficiently, and develop close friendships.
iStock/Essentials; iStock/Signature; Jupiter/Pixland/Thinkstock
We are born with a stepping reflex, an innate involuntary response. When this infant is held under the arms in a standing position on a flat surface, his legs move in a stepping motion.
Phanie / Alamy Stock Photo
Some plasticity is retained throughout life. Practicing athletic activities can help older adults rebuild muscle and improve balance.
Reuters/Mariana Bazo
Development Is Plastic
Development is characterized by plasticity: It is malleable, or changeable. Frequently, the brain and body can compensate for illness and injury. In children who are injured and experience brain damage, for instance, other parts of the brain take on new functions. The plastic nature of human development allows people to modify their traits, capacities, and behavior throughout life (Baltes et al., 2006; Overton & Molenaar, 2015). For example, older adults who have experienced a decline in balance and muscle strength can regain and improve these capabilities through exercise (McAuley et al., 2013). Plasticity generally tends to decline as we age, but it does not disappear entirely. Short instruction, for instance, can enhance the memory capacities of very old adults but less so in younger adults (Brehmer, Westerberg, & Bäckman, 2012; Willis & Belleville, 2016). Plasticity makes it possible for individuals to adjust to change and to demonstrate resilience, the capacity to adapt effectively to adverse contexts and circumstances (Luthar et al., 2015; Masten, 2016).
Development Is Influenced by Multiple Contexts
Context refers to where and when a person develops. Context encompasses many aspects of the physical and social environment, such as family, neighborhood, country, and historical time period. It includes intangible factors, characteristics that are not visible to the naked eye, such as values, customs, ideals, and culture. (For more on the nature of cultural influences, see the accompanying feature Cultural Influences on Development: Defining Culture.) In order to understand a given individual’s development, we must look to his or her context. For example, consider the context in which you were raised. Where did you grow up? City? Suburb? Rural area? What was your neighborhood like? Were you encouraged to be assertive and actively question the adults around you, or were you expected to be quiet and avoid confrontation? How large a part was religion in your family’s life? How did religious values shape your parent’s childrearing practices and your own values? How did your family’s economic status affect your development?