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Who We Are and What We Study

Lifespan development is a mega-discipline encompassing child development, gerontology, and adult development. Developmental scientists, or developmentalists, chart universal changes from birth to old age, explore individual differences in development, study the impact of normative and non-normative life transitions, and explore every other topic relevant to our unfolding lives.

Several major contexts of development shape our lives. The first is our cohort, or the time in history in which we live. The huge baby boom cohort, born in the years following World War II, has changed society as it passes through the lifespan. Cohorts of babies born before the twentieth century faced a shorter, harsher childhood, and many did not survive. As life got easier and education got longer, we first extended the growing-up phase of life to include adolescence and, in recent years, with a new life stage called emerging adulthood, have put off the starting date of full adulthood to our late twenties.

The early-twentieth-century life expectancy revolution, with its dramatic advances in curing infectious disease and shift to deaths from chronic illnesses, allowed us to survive to later life. Average life expectancy is now within striking distance of the maximum lifespan in affluent nations, and we distinguish between the healthy young-old (people in their sixties and seventies) and the frail old-old (people in and over their eighties). The second major twentieth-century change occurred in the 1960s with the lifestyle revolution, which has given us freedom to engineer our own adult path. Today, the Internet and social networking sites have transformed relationships, while the lingering effects of the Great Recession of 2008 and widening income inequalities are still clouding the economic landscape of twenty-first century life.

Socioeconomic status (SES) greatly affects our lifespan—with poor people in each nation facing a harsher, more stressful, and shorter life. The gaps between developed world countries and developing world countries are even more dramatic, with the least-developed countries lagging well behind in terms of health, wealth, and technology.

Our cultural and ethnic background also determines how we develop. Scientists distinguish between collectivist cultures (typically non-Western), which stress social harmony and extended-family relationships, and individualistic cultures (often Western), which value independence and personal achievement. We need to be aware, however, that residents living in all nations have a mix of individualistic and collectivist worldviews; the practice of lumping people into broad ethnic labels masks diversity within each group. Finally, our gender influences our travels through life. Women outlive men by at least two years in the developed world.

Theories offer explanations about what causes people to act the way they do. The main theories in developmental science offering general explanations of behavior vary in their position on the nature versus nurture question. Behaviorists believe nurture is all-important. Traditional behaviorists, in particular B. F. Skinner, believe operant conditioning and reinforcement determine all voluntary behaviors. According to cognitive behaviorism/social learning theory, modeling and self-efficacy—our internal sense that we can competently perform given tasks—predict how we act.

Sigmund Freud, in his psychoanalytic theory, believed our adult personality is shaped by the way our parents treated us during the first five years of life. Freud also felt human beings are dominated by unconscious drives, mental health depends on self-awareness, and sexuality (different erogenous zones) motivates behavior during the early childhood years. John Bowlby’s attachment theory draws on the psychoanalytic principle that parenting during early life (or our attachment relationships) determines later mental health, but he believes that the attachment response is genetically built in to our species to promote survival. Evolutionary psychologists adopt this nature perspective, seeing actions and traits as programmed into our DNA. Behavioral genetic research—in particular, twin studies, adoption studies, and occasionally twin/adoption studies—convinced developmental scientists of the power of nature, revealing genetic contributions to almost any way we differ from each other as human beings.

Developmental scientists today, are exploring how nature and nurture combine. Due to evocative and active forces, we shape our environments to go along with our genetic tendencies, and human relationships are bidirectional—our temperamental qualities and actions influence the others, just as their actions influence us. A basic developmental science challenge is to foster an appropriate person–environment fit. We need to match our genetically based talents and abilities to the right environment. New research suggests that people differ genetically in how responsive they are to environmental events, and that early life environments may alter our genome, producing long-lasting epigenetic effects.

Erik Erikson spelled out eight psychosocial tasks that we must master as we travel from birth to old age. According to Jean Piaget’s cognitive developmental theory, children progress through four qualitatively different stages of intellectual development, and all learning occurs through assimilation and accommodation.

Most developmental scientists today adopt the developmental systems perspective. They welcome input from every theory and realize that many interacting influences shape who we are. They understand that diversity among people and change processes is the essence of development.

The two main research strategies scientists use are correlational studies, which relate naturally occurring variations among people, and true experiments, in which researchers manipulate a variable (or give a specific treatment) and randomly assign people to receive that intervention or not. With correlational studies, there are always competing possibilities for the relationships we find. While experiments do allow us to prove causes, they are often unethical and impractical. In conducting research, it’s best to strive for a representative sample, and it’s essential to have accurate measures. Naturalistic observation, self-reports, and observer evaluations are three common measurement strategies developmental scientists use.

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The two major designs for studying development are longitudinal and cross-sectional research. Cross-sectional studies, which involve testing people of different age groups at the same time, are very easy to carry out. However, they may confuse differences between age groups with true changes that occur as people age, and they can’t tell us about individual differences in development.

Longitudinal studies can answer vital questions about how people develop. However, they involve following people over years and may sample atypical, elite groups.

Quantitative research—studies involving groups of participants, and using statistical tests—is still the standard way we learn the scientific truth. But developmentalists are now occasionally conducting qualitative research—interviewing people in depth. Our research is generally getting more global and sophisticated, too.