Human Development

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The You You Used to Be

Take a moment to consider your life in its entirety. On the day you were born, you were a bundle of mystery. Today you might seem like a completely different person—certainly, you are taller and likely have more hair. As you think of all the experiences you have had throughout your life, ask yourself how these have led to the person you are now. To be sure, some characteristics fall by the wayside as we mature, but others are still there, as sure as the freckles from first grade still pepper your arms. What were you like in kindergarten? A shy child or an outgoing little tike? One study found that more socially skilled kindergartners (as rated by their teachers) were, 20 years later, more highly educated and likely to be employed than their less skilled counterparts (Jones, Greenberg, & Crowley, 2015). Children whose mothers worked outside the home are likely to differ from others as adults: Girls whose mothers worked are more likely to be employed themselves and boys whose mothers worked are more likely to have wives who work (Cain Miller, 2015). Such findings demonstrate how, in some ways, our journey from infancy to adulthood can seem like a straight line: A plot without many twists and turns. What such findings do not capture are all the ways we differ in our paths and the active ways we can alter the line of development.

At one time we were all infants and children. Some of the characteristics and experiences that shaped our lives in those earliest days continue to influence us (Nave & others, 2017). Some just happened and others we made happen. As adults, we continue to grow and change and create a future toward which to strive. We can also reach out to change the futures of others. Developmental psychologists probe the process of growth and change throughout the lifespan.

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 PREVIEW

Developmental psychologists are interested in all the ways a person grows and changes throughout life, from its beginning to its inevitable end. We start by defining human development and examining central issues in developmental psychology. In the heart of the chapter, we look at the processes and outcomes of development in three broad domains of life: physical, cognitive, and socioemotional. We then explore the links among these developmental areas by probing gender development, followed by a survey of moral development and death, dying, and grieving. The chapter closes with a look at the positive ways individuals can shape their development in adulthood.

1 Exploring Human Development

Development refers to the pattern of continuity and change in human capabilities that occurs throughout the course of life. Most development involves growth, although it also includes decline (for example, physical abilities may decline with age). Let’s begin our consideration of human development by addressing several key questions and issues that are especially relevant to understanding how human beings grow and change through the life span.

Research Methods in Developmental Psychology

Human development is about changes that occur with age. Sometimes this research involves looking at how people of various ages differ on characteristics. To know what age-related differences mean, however, we must consider the kind of research presented.

In cross-sectional designs, a number of people are assessed at one point in time. Age differences can then be noted. By examining how the ages of these individuals relate to the characteristics measured, researchers can find out whether younger individuals differ from older ones. Age differences, however, are not the same as developmental change.

 Remember, cross-sectional designs involve measuring characteristics at one and only one time point. Longitudinal designs involve measuring the same characteristics in the same people multiple times.

One problem in cross-sectional studies is cohort effects. Cohort effects are differences between individuals that stem not necessarily from their ages but from the historical and social time period in which they were born and developed (Kennison & others, 2017). For instance, individuals who were born in the 1940s might be less likely to have attended college than those born in the 1990s. Differences observed between these groups might be due not to their age but rather to these differing experiences. Consider your own cohort. How might experiences that are unique to your age group lead you and your peers to be different from other generations?

In order to draw more definitive conclusions about human development, researchers must use a different kind of research design. A longitudinal study assesses the same participants multiple times over a lengthy period. A longitudinal study can find out not only whether age groups differ but also whether the same individuals change with respect to a particular characteristic as they age. Strong statements about developmental changes in psychological characteristics require longitudinal designs. Using these and other methods, human development researchers have grappled with big questions that are relevant to all of psychology, as we consider next.

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How Do Nature and Nurture Influence Development?

Developmental psychologists are interested in understanding how nature and nurture contribute to development. Nature refers to a person’s biological inheritance, especially his or her genes. Nurture refers to the individual’s environmental and social experiences. Understanding development requires that we take into account the contributions of both genes (nature) and the environment (nurture).

 What factors in your childhood environment influenced your expression of your gifts and abilities?

Recall that a genotype is the individual’s genetic heritage—the actual genetic material. We also examined the idea of a phenotype (the person’s observable characteristics). The phenotype shows the contributions of both nature (genetic heritage) and nurture (environment). Whether and how the genotype is expressed in the phenotype may depend on the environment. For example, a person might be born with the genes to be the next LeBron James but without the necessary environmental factors such as good nutrition, sound medical care, access to a basketball court, and superb coaching, that potential might never be reached.

Consider the genetic condition called phenylketonuria (PKU). Caused by two recessive genes, PKU results in an inability to metabolize the amino acid phenylalanine. Decades ago, it was thought that the genotype for PKU led to a specific phenotype, namely, irreversible brain damage, intellectual disability, and seizures. However, experts now know that as long as individuals with the genotype for PKU stick to a diet that is very low in phenylalanine, these characteristics in the phenotype can be avoided (Bernstein & others, 2017). These environmental precautions can change the phenotype associated with this genotype.

 A flock of birds flying in formation illustrates an emergent property. The birds may appear to be following a leader, but they aren’t. Instead, each individual bird is following its own local rules. What you see as a flock of birds is in fact a collection of individual birds, each one “doing its own thing” but creating the formation (the emergent property) you recognize as a flock.

The PKU example tells us that a person’s observable characteristics (phenotype) might not reflect his or her genetic heritage (genotype) very precisely because of the particular experiences the person has had.

Instead, for each genotype, a range of phenotypes may be expressed, depending on environmental experiences. The person whom we see before us emerges out of an interplay of genetic and environmental experiences. Development is the product of nature, nurture, and the complex interaction of the two (Meaney, 2017).

Although it might be easy to think of genes as the blueprint for a person, development is not a process that follows a genetic master plan (Turkheimer, 2011). In fact, it is difficult to tell a simple story about how development occurs. One way that scientists and philosophers think about complex processes such as development is through the concept of emergent properties. An emergent property is a big entity (like a person) that is a consequence of the interaction of multiple lower-level factors (Gottlieb, 2007; Nalepka & others, 2017). Development is about the complex interactions of genes and experience that build the whole person.

Concept Clip: Nature/Nurture Debate

Do Early Experiences Rule Us for Life?

The PKU example above suggests the power of early experience (nurture) in human development. A key question in developmental psychology is the extent to which childhood experiences determine aspects of later life. Some research shows that unless infants experience warm, nurturing caregiving in the first year or so of life, they will not develop to their full potential (Boldt, Kochanska, & Jonas, 2017; Phillips & Lowenstein, 2011). Other studies demonstrate the power of later experience in influencing development in adulthood (Antonucci, Ajrouch, & Birditt, 2014; Kjellström & Stålne, 2017). Life-span developmentalists stress that experiences throughout life contribute to development (Dunlop, Bannon, & McAdams, 2017; Park & others, 2014). Both early and later experience make significant contributions to development, so no one is doomed to be a total prisoner of his or her childhood.

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Human development is complex because it is the product of several processes. The hormonal changes of puberty, a baby’s playing with blocks and an older couple’s embrace reflect physical, cognitive, and socioemotional processes, respectively.

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A key concept in understanding the role of negative early experiences in later development is resilience. Resilience refers to a person’s ability to recover from or adapt to difficult times. Resilience means that despite encountering adversity, a person shows signs of positive functioning (Labella & Masten, 2018; Taylor & Conger, 2017). Resilience can involve factors that compensate for difficulties, buffering the individual from the effects of these hardships. Moderate difficulties early in life can be strengthening experiences that lay the groundwork for effective future coping (Ager, 2013; Dooley & others, 2017; Seery, Holman, & Silver, 2010). Although often studied as an aspect of childhood (Masten, 2014) and adolescence (Montgomery, 2010), resilience can also characterize development in adulthood and old age (Bradley & Hojjat, 2017; Kuchel, 2017).