The life-span perspective (Baltes et al., 2006; Fingerman et al., 2011; Raz & Lindenberger, 2013) takes into account all phases of life, not just the first two decades (which were once the sole focus of developmental study). By including the entirety of life (see Table 1.1), this perspective has led to the realization that human development is multi-directional, multi-contextual, multi-cultural, and plastic. Now we examine each of these four.

As you will learn, developmentalists are reluctant to specify chronological ages for any period of development, since time is only one of many variables that affect each person. However, age is a crucial variable, and development can be segmented into periods of study. Approximate ages for each period are given here.

Multiple changes, in every direction, characterize the life span: Development is multi-directional. If human traits were all charted over time from birth to death, some traits would appear, others disappear, with increases, decreases, and zigzags (see Figure 1.4). The traditional idea—that all development advances until about age 18, steadies, and then declines—has been refuted by life-span research.

The pace of change varies as well. Sometimes discontinuity is evident: Change can occur rapidly and dramatically, as when caterpillars become butterflies. Sometimes continuity is found: Growth can be gradual, as when redwoods grow taller over hundreds of years.

Even stability is possible. Some characteristics seem not to change. For instance, chromosomal sex is lifelong: A zygote that is XY or XX (male or female) for life. Of course, the power and meaning of that biological fact change, but the chromosomes themselves stay the same.

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There is simple growth, radical transformation, improvement, and decline as well as stability, stages, and continuity—day to day, year to year, and generation to generation. Life-span theorists see gains and losses throughout life (Lang et al., 2011; Villar, 2012). For example, when babies begin to talk, they are less able to distinguish sounds from other languages (a gain and a loss); when adults retire, they may become more creative (a loss and a gain).

CRITICAL PERIODS The speed and timing of impairments or improvements vary as well. Some changes are sudden and profound because of a critical period, a time when something must occur for normal development or the only time when an abnormality can occur. For instance, the critical period for humans to grow arms and legs, hands and feet, fingers and toes, is between 28 and 54 days after conception.

After day 54, that critical period is over. Unlike some insects, humans never grow replacement limbs or digits.

We know the critical period for limb formation because of a tragic occurrence. Between 1957 and 1961, thousands of newly pregnant women in 30 nations took thalidomide, an antinausea drug. This change in nurture (via the mother’s bloodstream) disrupted nature (the embryo’s genetic program).

If an expectant woman swallowed thalidomide between day 28 and 54, her newborn’s arms or legs were malformed or absent (Moore & Persaud, 2007). Whether all four limbs, or just arms, or just hands were missing depended on dose and timing. If thalidomide was ingested only after day 54, the newborn had normal body structures.

SENSITIVE PERIODS Life has few critical periods. Often, however, a particular development occurs more easily—not exclusively—at a certain time. Such a time is called a sensitive period

An example is found in language. If children do not communicate in their first language between ages 1 and 3, they might do so later (hence, these years are not critical), but their grammar is often impaired (hence, these years are sensitive).

Similarly, childhood is a sensitive period for learning to pronounce a second or third language. A new language can be learned in adulthood, but strangers might detect an accent and ask, “Where are you from?”

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Often in development, individual exceptions to general patterns occur. Accent-free speech usually must be learned before puberty, but exceptional nature and nurture (an adult with exceptional hearing and then immersion in a new language) can result in flawless second-language pronunciation (Birdsong, 2006; Muñoz & Singleton, 2011).

Because of sensitive periods, however, such exceptions are rare. A study of native Dutch speakers who become fluent in English found only 5 percent had mastered native English (Schmid et al., 2014).

The second insight from the life-span perspective is that development is multi-contextual. It takes place within many contexts, including physical surroundings (climate, noise, population density, etc.) and family configurations (married couple, single parent, cohabiting couple, extended family, etc.). Each context can influence development, sometimes for a moment, sometimes for years.

A student might choose to go to a party instead of to the library. The social context of the party, such as whether drinks are free, the music lively, and friends are there, influences that student’s next several decisions. As you can imagine, the context of the party, and the decisions influenced by that context, affect later development: It may be hard to go to class the next day, or, in class, hard to apply math formulas or history facts. Each individual is responsible for his or her actions, of course, but social contexts are powerful.

ECOLOGICAL SYSTEMS A leading developmentalist, Urie Bronfenbrenner (1917–2005), led the way to considering contexts. Just as a naturalist studying an organism examines the ecology (the multifaceted relationship between the organism and its environment), Bronfenbrenner recommended that developmentalists take an ecological-systems approach (Bronfenbrenner & Morris, 2006).

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The ecological-systems approach recognizes three nested levels that surround individuals and affect them (see Figure 1.5). Most obvious are microsystems, each person’s immediate surroundings, such as family and peer group. Beyond the microsystems are the exosystems (local institutions such as school and church) and macrosystems (the larger social setting, including cultural values, economic policies, and political processes).

Bronfenbrenner also stressed the role of historical conditions and therefore included the chronosystem (literally, “time system”). Further, because he appreciated the dynamic interaction among all the systems, he included a fifth system, the mesosystem, consisting of the connections between and among the other systems.

Throughout his life, Bronfenbrenner studied people in natural settings, interacting with each other at home, at school, or at work instead of coming to a scientist’s laboratory or answering questionnaires. Before he died, he renamed his approach bioecological to highlight the role of biology, recognizing that systems within the body (e.g., the sexual-reproductive system, the cardiovascular system) affect all the external contexts (Bronfenbrenner & Morris, 2006).

As you can see, a contextual approach to development requires simultaneous consideration of many systems. Two contexts—historical and socioeconomic—are crucial in understanding all the systems of life-span development, yet they are often ignored. They merit explanation now.

THE HISTORICAL CONTEXT All persons born within a few years of one another are said to be a cohort, a group defined by its members’ shared age. Cohorts travel through life together, affected by the interaction of their chronological age with the values, events, technologies, and culture of the era.

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If you doubt that historical trends and events touch individuals, consider first names (see Table 1.2). If you know someone named Sophia, she is probably young—Sophia is the most popular name now but was not in the top 100 until 1996. If you know someone named Mary, she is probably old: About 10 percent of all baby girls in the United States were named Mary from 1900 to 1965, but now Mary is unusual.

Data from U.S. Social Security Administration

Two of my daughters, Rachel and Sarah, have names that were common when they were born: One wishes she had a more unusual name, the other is glad she does not. Your own name is influenced by history; your reaction is yours. Nurture and nature again.

Cohort, more than generation, influences attitudes and behavior. Consider marijuana. In the United States in the 1930s, marijuana was declared illegal, but enforcement was erratic, and some cultures encouraged everyone to smoke “weed.” Virtually all the popular musicians of the 1960s—including the Beatles, Bob Dylan, James Brown, and Bob Marley—not only smoked publicly but also sang about it.

Then, during the “war on drugs” in the 1980s, marijuana was labeled a gateway drug, likely to open the floodgates to serious abuse and addiction (Kandel, 2002). People were arrested and jailed for possession of even a few grams.

From 1990 on, attitudes gradually shifted again, such that by 2014 recreational marijuana use became legal in Uruguay and in four U.S. states, with medical use permitted in several others (see Figure 1.6). According to a Gallup poll, more than half (54 percent) of Americans approve legalization of marijuana (Motel, 2014).

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Adolescents are particularly affected by historical shifts, including those regarding marijuana use. In 1978, only 12 percent of high school students thought experimental use of marijuana was harmful, and more than half had tried the drug. Thirteen years later, 80 percent thought there was “great risk” in regular use, and most were suspicious of experimental use.

Every year since then, marijuana use has increased and attitudes have become more accepting. In 2013, about one-third of high school seniors had used it, and only one-third thought there was great risk in regular use (Johnston et al., 2014 and previous years). The developmental consequences of adolescent marijuana use are discussed in Chapter 10; the point here is that cohort effects are sometimes profound.

THE SOCIOECONOMIC CONTEXT Another influential context is economic, reflected in a person’s socioeconomic status, abbreviated SES. (Sometimes SES is called social class as in middle class or working class.) SES reflects income and much more, including occupation, education, and neighborhood.

Suppose a U.S. family is comprised of an infant, an unemployed mother, and a father who earns $18,000 a year. Their SES would be low if the wage earner is a high school dropout working 40 hours a week at minimum wage and living in a city slum, but it would be much higher if the wage earner is a postdoctoral student living on campus and teaching part time.

As you see, income alone does not define SES, especially when the historical context is considered. In the United States, the poverty level was set in 1963 by calculating food costs and family size: A family of three is below the 2014 poverty threshold if its household income is less than $19,790 (in Alaska, $24,730).

This way of measuring poverty is less valid currently because food costs are not the most significant family expense: Housing and medical care may be. Ways to measure poverty are complex, especially internationally. The United Nations rates the United States and Canada as rich nations, but some people in those nations might disagree. Another way to measure poverty is to consider the gap between the richest and poorest citizens of a nation (see Figure 1.7). On this, the United States does not do well.

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Every method of calculating poverty within North America finds that citizens whose ancestors were Hispanic or African rather than Asian or European are more often poor. A developmental trend is apparent as well: There are more poor children than adults, and more poor young adults than older adults.

SES brings advantages and disadvantages, opportunities and limitations—all affecting housing, health, nutrition, knowledge, and habits. Although low income obviously limits a person, other factors are pivotal, especially education and national policy. Voters choose leaders who decide policies that differentially affect people of various ages and incomes.

For example, Northern European nations eliminate SES disparities as much as possible. By contrast, the largest gaps between rich and poor tend to be in developing nations, especially in Latin America (Ravallion, 2014). Among advanced nations, the United States has “recently earned the distinction of being the most unequal of all developed countries” (Aizer & Currie, 2014, p. 856), not only by ethnic group but also by age—children and young adults are more often poor compared to middle-aged and old adults.

Worldwide, abject poverty is less common than it was a few decades ago, but the rich are even richer than before. As one economist says, “the rising tide has indeed raised all boats . . . But the big yachts have done better, so overall income inequality is increasing” (Vanneman, quoted in Hvistendahl, 2014, p. 832).

In order to study “all kinds of people, everywhere, at every age,” as developmental science does, it is essential that people of many cultures be considered. For social scientists, culture is “the system of shared beliefs, conventions, norms, behaviors, expectations and symbolic representations that persist over time and prescribe social rules of conduct” (Bornstein et al., 2011, p. 30).

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SOCIAL CONSTRUCTIONS Thus, culture is far more than food, clothes, or rituals; it is a set of ideas that people share. This makes culture a powerful social construction, a concept constructed, or made, by a society. Social constructions affect how people think and behave as well as what they value, ignore, and punish.

Because culture is so basic to thinking and emotions, people are usually unaware that their values are socially constructed. Fish do not realize that they are surrounded by water; people do not realize that their assumptions about life and death arise from their own culture.

One assumption is evident if the word culture is used to refer to large groups of other people, as in “Asian culture” or “Hispanic culture.” That invites stereotyping and prejudice, since such large groups include people of many cultures. For instance, people from Korea and Japan are aware of notable cultural differences between their nationalities, as are people from Mexico and Guatemala.

In today’s United States, most people are influenced by several cultures, not just one. One observer contends that people with Jamaican heritage in the United States are tri-cultural (Jamaican, Black, American) (G. Ferguson et al., 2014). Given our awareness of contexts, each person is also influenced by other cultures, such as middle-class culture, or California culture, or the culture of a particular college.

To appreciate that culture is a matter of beliefs and values more than superficial differences, consider language. Of course, people speak distinct languages, but that in itself is not a cultural difference, although language may reflect culture. However, certain slang words and phrases signal cultural differences: Some people are offended by words that other people proudly say. That is cultural.

More generally, among some English-speaking cultural groups in the United States, linguistic proficiency and independent thinking are encouraged. In families in those groups, children are encouraged to talk freely, and when they do, the adults listen approvingly. Among other U.S. groups, a prime cultural value is that children respect their parents, and, by extension, every adult: Children should never interrupt an adult conversation.

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One of my students remembered:

My mom was outside on the porch talking to my aunt. I decided to go outside; I guess I was being nosey. While they were talking I jumped into their conversation which was very rude. When I realized what I did it was too late. My mother slapped me in my face so hard that it took a couple of seconds to feel my face again.

[C., personal communication]

Notice how my student reflects her culture; she labels her own behavior “nosey” and “very rude.” She later wrote that she expects children to be seen but not heard and that her own son makes her “very angry” when he interrupts. Whether you agree depends on your culture.

DEFICIT OR JUST DIFFERENCE? Whatever a person’s culture or cultures may be, humans tend to believe that they, their nation, their group, and their culture are better than others. That belief becomes destructive if it reduces respect and appreciation. Developmentalists recognize the difference-equals-deficit error, the assumption that people who are different are thereby deficient, which means lacking in some important ways. Too quickly and without thought, differences are assumed to be problems (Akhtar & Jaswal, 2013).

Negative judgments are often made about how other people raise children, or worship God, or even eat. Age differences are also stereotyped. Have you heard adults complain about the attitudes, abilities, or actions of teenagers, or of senior citizens? Such age stereotypes are evidence of judging a difference as a deficit.

Gender differences are another easy example. We are amused when young girls say, “Boys stink,” or their male classmates say, “Girls are stupid.” However, even though the sexes have far more similarities than differences, humans of all ages tend to notice differences and then make sexist judgments.

According to one scholar, even neuroscientists make that mistake. They are susceptible to “neurosexism,” seeing and explaining gender differences “in the absence of data” (Fine, 2014, p. 915).

One of the very few proven gender differences is that women are more tenderhearted and men more sexually driven (Hyde, 2014). If you are male, do you think that women are weak because they are too emotional; if you are female, do you think men are too obsessed with sex? If you answer yes, how human of you. And how mistaken.

The difference-equals-deficit error is one reason a multi-cultural approach is crucial. Various ways of thinking or acting are not necessarily wrong or right, better or worse. The scientific method, which requires empirical data, is needed for accurate assessments.

Sometimes a difference is actually an asset (Marschark & Spencer, 2003). For example, cultures that discourage dissent also foster harmony. The opposite is also true—cultures that encourage dissent also value independence. Whatever your personal judgment on this cultural difference, the opposite opinion has some merit. A multi-cultural understanding requires recognition that some differences signify strengths, not weaknesses.

LEARNING WITHIN A CULTURE Russian developmentalist Lev Vygotsky (1896–1934) was a leader in describing the interaction between culture and education (Wertsch & Tulviste, 2005). He noticed that adults from the many cultures of the Soviet Union (Asians and Europeans, of many religions) taught their children whatever beliefs and habits they might need as adults within their local community.

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Vygotsky (discussed in more detail in Chapter 5) believed that guided participation is a universal process used by mentors to teach cultural knowledge, skills, and habits. Guided participation can occur via school instruction but more often happens informally, through “mutual involvement in several widespread cultural practices with great importance for learning: narratives, routines, and play” (Rogoff, 2003, p. 285).

ETHNIC AND RACIAL GROUPS It is easy to confuse culture, ethnicity, and race because these terms sometimes overlap (see Figure 1.8). People of an ethnic group share certain attributes, almost always including ancestral heritage and usually national origin, religion, and language (Whitfield & McClearn, 2005). That means that ethnic groups often share a culture, but this is not a requirement. Some people of a particular ethnicity differ culturally (consider people of Irish descent in Ireland, Australia, and North America), and some cultures include people of several ethnic groups (consider British culture).

Ethnic groups are primarily social constructions, dependent on context. For example, African-born people who live in North America typically consider themselves African, but African-born people living on that continent identify with a more specific ethnic group, Yoruba not Ibo or Hausa (Nigeria), or Kikuyo not Luhya or Luo (Kenya). Although many Americans consider warring participants within distant nations (e.g., Syria, Iraq, Russia) to be of the same ethnicity as their enemies, the rivals themselves do not.

Race is also a social construction—and a misleading one. There are good reasons to abandon the term, and good reasons to keep it, as the following explains.

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Both brain and behavior are far more plastic than once was thought. The term plasticity denotes two complementary aspects of development: Human traits can be molded (as plastic can be), and yet people maintain a certain durability (as plastic does). This provides both hope and realism—hope because change is possible and realism because development builds on what has come before.

Plasticity is basic to our contemporary understanding of human development because it simultaneously incorporates two facts: People can change over time, and new behavior depends partly on what has already happened.

This is evident in the dynamic-systems approach, a framework many contemporary developmentalists use. The idea behind this approach is that human development is an ongoing, ever-changing interaction between the individual and all the systems, domains, and cultures.

Note the word dynamic: Physical contexts, emotional influences, the passage of time, each person, and every aspect of the ecosystem are always interacting, always in flux, always in motion. For instance, a useful strategy for developing motor skills in children with autism spectrum disorder (described in Chapter 7) is to think of the dynamic systems that undergird movement—the changing physical and social contexts (Lee & Porretta, 2013). Systematically considering contexts helps such children—not to make the autism disappear (past conditions are always influential) but to improve the child’s ability to function.

The most surprising example of plasticity in recent years involves the brain. Expansion of neurological structures, networks of communication between one cell and another, and even creation of neurons (brain cells) occurs in adulthood. This neurological plasticity is evident in hundreds of studies mentioned later in this text (see Figure 1.9).

Plasticity is especially useful when anticipating growth of a particular person: Everyone is constrained by past circumstances, but no one is confined by them. Consider David.

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Plasticity emphasizes that people can and do change, that predictions are not always accurate. Three insights already explained have improved predictions: (1) Nature and nurture always interact. (2) Certain ages are sensitive periods for particular kinds of development. (3) Genes predispose people to respond to certain circumstances, in differential susceptibility.

This was apparent for David: His inherited characteristics (from his smart parents) affected his ability to learn, his four preschools in early childhood (a sensitive period for language) helped him lifelong, and his inborn temperament (he is still devastated by criticism but overjoyed by praise) helped him flourish because he was easily influenced by his parents’ devoted guidance. If I had known more about human development when he was born with multiple disabilities, I would have predicted a brighter—and more accurate—future for him.

WHAT HAVE YOU LEARNED?

Question 1.11

Development is multi-directional; if human traits were all charted over time from birth to death, some traits would appear while others disappear, with increases, decreases, and zigzags.

Question 1.12

Development takes place within many contexts, including one’s physical surroundings (climate, noise, population density, etc.) and family configurations (married couple, single parent, cohabiting couple, extended family, etc.).

Question 1.13

Exosystems (community structures, and local educational, medical, employment, and communications systems) influence microsystems, which intimately and immediately shape human development. In this example, the school’s structure and administration (the exosystem) influence a child’s classroom and teacher (the microsystem), which intimately and immediately shape his or her development.

Question 1.14

Answers can include (but are not limited to) the values, events, technologies, and culture of each era.

Question 1.15

Answers can include (but are not limited to) income, occupation, education, neighborhood, and family size.

Question 1.16

Stereotypes—such as assuming from media coverage that Catholic priests are sexual predators (the vast majority of them are most certainly not)—are social constructions.

Question 1.17

The term race has been used to categorize people on the basis of physical differences, particularly outward appearance. Ethnicity is a different social construction, affected by the social context rather than a direct outcome of biology.

Question 1.18

Vygotsky believed mentors use the universal process of guided participation to teach children cultural knowledge, skills, and habits. Guided participation often happens informally, through mutual involvement in several widespread cultural practices with great importance for learning: narratives, routines, and play.

Question 1.19

The term plasticity denotes two complementary aspects of development: Human traits can be molded (as plastic can be), and yet people maintain a certain durability of identity (as plastic does).

Question 1.20

Human development is an ongoing, ever-changing interaction between the body and mind and between the individual and every aspect of the environment.