1.2 The Life-Span Perspective

The life-span perspective (Fingerman et al., 2011; Lerner, 2010) 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 entire life (see TABLE 1.1), this perspective leads to a new understanding of human development as multidirectional, multicontextual, multicultural, multidisciplinary, and plastic (Baltes et al., 2006; Staudinger & Lindenberger, 2003). Ages are only a rough guide to “change over time.”

Development is Multidirectional

The traditional idea—that all development advances until about age 18, steadies, and then declines—has been refuted by life-span research. Multiple changes, in every direction, characterize the life span. If any particular human trait were to be charted over time, it would be apparent that some traits appear and disappear, with increases, decreases, and zigzags (see Figure 1.2).

FIGURE 1.2 Patterns of Developmental Growth Many patterns of developmental growth have been discovered by research. Although linear (or near-linear) progress seems most common, scientists now find that almost no aspect of human change follows the linear pattern exactly.

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. Some characteristics do not seem to change at all: A zygote is XY or XX, male or female, and that chromosomal sex remains throughout the life span. Of course, the significance of that biological fact changes over time.

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. Not only does the direction of change vary over the life span, but each characteristic follows a distinct pattern: Losses in some specific skills and abilities occur at the same time as gains in others. For example, when babies begin talking, they lose some ability to distinguish sounds from other languages; when adults retire, they may become more creative.

The speed and timing of impairments or improvements vary as well. Some changes are sudden and profound because of a critical period, either a time when something must occur to ensure normal development or the only time when an abnormality might occur. For example, the human embryo grows arms and legs, hands and feet, fingers and toes, each over a critical period between 28 and 54 days after conception. After that it is too late: Unlike some insects, humans never grow replacement limbs.

Life-Span Plan This 25-year-old, Diana Truong, is currently in the Master of Teaching program at the Ontario Institute for Studies in Education (OISE). Worldwide, emerging adulthood is a period of exploration and change. Over the next several years, Diana may decide to teach older students rather than younger students, stay in school to get her PhD, or change fields completely.

DIANA TRUONG

Tragically, between 1957 and 1961, thousands of newly pregnant women in 30 nations took thalidomide, an anti-nausea drug. This change in nurture (via the mother’s bloodstream) disrupted nature (the embryo’s genetic program). If an expectant mother ingested thalidomide during the 26 days of that critical period, her newborn’s limbs were malformed or absent (Moore & Persaud, 2007). Specifics (for example, whether arms and legs, or just arms, or only hands were missing) depended on exactly when she swallowed the pill. Surprisingly, if an expectant woman took thalidomide before day 28 or after day 54, no harm occurred.

Life has very few such critical periods. Often, however, a particular development occurs more easily—but not exclusively—at a certain time. Such a time is called a sensitive period. An example is language. If children do not start speaking their first language between ages 1 and 3, they might do so later (hence, the first years are not critical), but their grammar is usually impaired (hence, these years are sensitive). Similarly, childhood is a sensitive period for learning to pronounce a second or third language with a native accent.

As is often the case with development, sweeping generalizations (like those in the preceding sentence) do not apply in every case. Accent-free speech usually must be learned before puberty, but some teenagers or adults with exceptional nature and nurture (naturally adept at hearing and then immersed in a new language) master a second language flawlessly (Birdsong, 2006; Muñoz & Singleton, 2011).

Development is Multicontextual

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, same-sex couple, extended family, and more). Developmentalists who study the life span take dozens of contexts into account, as explained throughout this book. Examining these contexts provides researchers a better understanding of what may be universal or developmental, relevant and similar for all individuals, or dependent on cultural context.

Ecological SystemsThe Russian-American psychologist Urie Bronfenbrenner (1917–2005) stressed contexts by recommending that developmentalists take an ecological-systems approach (see Figure 1.3) (Bronfenbrenner & Morris, 2006). Ecology is the branch of biology that deals with the relation of living things to their environment and to each other; Bronfenbrenner believed that each person is affected by many social contexts and interpersonal relations. Before he died, he renamed his approach the bioecological theory to stress the important role that biology plays in development, recognizing that systems within the body (such as the sexual reproductive system and the cardiovascular system) affect all the external systems.

FIGURE 1.3 The Ecological Model Each person is affected by interactions among overlapping systems, which provide the context of development. Microsystems—family, peer groups, classroom, neighbourhood, house of worship—intimately shape human development. Surrounding and supporting the microsystems are the exosystems— external networks, such as local educational, medical, employment, and communications systems—that influence the microsystems. Influencing both of these systems is the macrosystem, which includes cultural patterns, political philosophies, economic policies, and social conditions. Mesosystems refer to interactions among systems, as when parents and teachers coordinate to educate a child. Bronfenbrenner eventually added a fifth system, the chronosystem, to emphasize the importance of historical time.

Cat, Duck, or Dog? Nine-year-old Sun Minyl is listening to his teacher attentively before circling the correct animal and writing “cat” in his workbook. This activity is not difficult at his age, but Sun Minyl has an extra challenge: he is learning in English, not in his first language, Chinese, at a school near Shanghai.

REUTERS/CLARO ORTES IV CC/DL

Bronfenbrenner developed his theory of ecological systems by stressing that all relationships the individual person has with other people and with various social contexts are interconnected. He started with the most immediate, direct relationships the child has with his or her immediate family and then worked outward to other environments that might affect the child indirectly.

The ecological-systems approach recognizes various systems that surround individuals and have lasting effects on them. Most obvious are microsystems, which are those basic, personal relationships each of us has with family, friends, and peers. Also important are exosystems—relationships between individual people and local institutions such as church and school—and macrosystems, which consist of the broader social setting and include such influences as government policies, economic trends, and cultural values.

Because he appreciated the dynamic interaction among all the systems, Bronfenbrenner included a fourth system, the mesosystem, consisting of the connections among all the other systems. One example of a mesosystem is the interface between employment (exosystem) and family life (microsystem). These connections include not only the direct impact of family leave, retirement, and shift work, but also indirect macrosystem influences from the economy that affect unemployment rates, minimum wage standards, and hiring practices—each of which may affect the family microsystem as well as each individual in the family, always influenced by the overall culture.

For instance, if one person in a dual-earner couple becomes unemployed, he or she usually does more household cooking and cleaning, but specifics depend on whether the unemployed person is a man (3 additional hours per week) or a woman (6 additional hours) (Gough & Killewald, 2011). Gender differences are also affected by national norms: Women in Italy do much more domestic work than men, but this is less true in Sweden (Cooke & Baxter, 2010). It is obvious now, but not when Bronfenbrenner first wrote, that mesosystems provide crucial connections between the various contexts that affect each person.

Twenty-First-Century Manners If this boy removed his elbows from the table but kept texting, what would you say about his manners? What would your parents say? Your grandparents?

WILLIAM HAEFELI/THE NEW YORKER COLLECTION WWW.CARTOONBANK.COM

Throughout his life, Bronfenbrenner also stressed the role of historical conditions on human development, and therefore he included a fifth system, the chronosystem (literally “time system”). For example, children growing up with advanced communication technologies such as cellphones, the Internet, and social networking systems like Facebook and Twitter are experiencing and learning about their world differently than children did 50 years ago.

As you can see, a contextual approach to development is complex; many contexts need to be considered. Two of them, the historical and the economic contexts, merit explanation now, as they affect people throughout their lives. Then in the following section we’ll look at the way multicultural contexts can affect individual people and their families, especially as immigration becomes a global phenomenon.

The Historical ContextAll 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. Ages 18 to 25 are a sensitive period for social values, so experiences and circumstances during emerging adulthood have a lifetime impact. For that reason, attitudes about war and society differ for the Canadian cohorts who were young adults during World War II, during the conflicts in Korea, the Gulf, Afghanistan, or Iraq, or during the wars on poverty, drugs, or terrorism.

As Canadian thinker Marshall McLuhan (1911–1980) pointed out, sometimes advances in communications technology rather than current political issues constitute a historical context. Consider the appearance in 2004 of the social networking service Facebook. Founder Mark Zuckerberg’s mission was to make the world more “connected,” allowing people to express themselves and to communicate in real time with their family members and friends, all the while making new friends. Thanks to the World Wide Web, Facebook quickly became a global phenomenon. By 2013, there were more than 945 million monthly users, more than 80 percent of whom were outside North America (Facebook Newsroom, 2013).

Same Situation, Far Apart: Times are Changing Seniors in the twenty-first century live decades longer than did earlier cohorts, affording them opportunities that were previously unavailable. In 1950 in Peru, average life expectancy was 45. Now in Lima, newlyweds Carmen Mercado, age 64, and Jorge de la Cruz, age 74 (left), can expect a decade of wedded bliss. While Carmen and Jorge were courting, Hazel Soares (right) was studying, which culminated in her graduation from Mills College in Oakland, California, at age 94.

REUTERS/MARIANA BAZO
AP PHOTO/TONY AVELAR

Think of the many ways Facebook may have affected the development of the cohort popularly known as Generation Z, or the Internet Generation: people born roughly between 1990 and 2001. For example, to what extent will this cohort’s notions of privacy and friendship differ from those of their parents and grandparents? These are questions that developmentalists might pose as the basis for research studies. Researchers in Australia who surveyed Internet users there found that Facebook and other online social networks can allow people to develop relationships they would be reluctant to pursue in person. This in turn increases their psychological well-being and strengthens their ties with neighbours and friends (Bargh & McKenna, 2004). These online sites can also decrease the challenges of social interactions and encourage more self-disclosure (Bargh, McKenna, & Fitzsimons, 2002; Tidwell & Walther, 2002).

The Socioeconomic ContextAnother influential context of development is a person’s socioeconomic status (SES). Sometimes SES is called social class (as in middle class or working class). SES reflects not just income but other aspects, including level of education and occupational status.

Consider two Canadian families. In both, the family composition includes an infant, an unemployed mother, and a father who earns $15 000 a year. The SES of family 1 would be low if the father were a high school dropout who washes dishes for a living and lives in an urban slum. The SES of family 2 would be higher than that of family 1 if the father were a graduate student who works as a teaching assistant, and his family lived in graduate housing on campus. So, the father’s level of education and social status (a graduate student obviously has a greater potential income than a dishwasher) are taken into consideration when determining the family’s SES.

As this example shows, annual income alone does not determine poverty. Rates of inflation also have to be considered, as when the cost of food or gas or other necessities goes up. In Canada, the federal government has no official definition of poverty, low income, or income adequacy. Statistics Canada uses household income to determine whether a family is “living in straitened circumstances.” If a family spends a greater proportion of its income (at least 20 percent more than the average Canadian family) on basic necessities such as food, clothing, and shelter, then it falls beneath what the agency calls a “low income cut-off,” or LICO rate (Campaign 2000, 2011).

Statistics Canada calculates both a before-tax and after-tax LICO rate. It is the after-tax LICO that most non-governmental agencies and media outlets in Canada use to identify poverty rates in the country. In 2009, the after-tax LICO for one parent with one child under the age of 18 in a large urban centre was $22 420. Nationwide, about 9.5 percent of Canadians fell below this rate, which meant that about 3.2 million people, including 639 000 children, were living in poverty.

Who is at greatest risk of living in poverty in Canada? Female-headed households, Aboriginal peoples, immigrant families, and families that include children with disabilities all have higher-than-average rates of poverty (D. I. Hay, 2009). In 2009, more than half (52 percent) of single mothers with children under the age of 6 were living in poverty. Among First Nations, one in every four children was growing up poor. The extent to which families are vulnerable to poverty also depends on the region in which they live. Comparing child poverty rates among provinces in 2009, Manitoba and British Columbia had the highest rates at 16.8 and 16.4 percent respectively, and Prince Edward Island the lowest rate, at 9 percent (Campaign 2000, 2011).

A question for developmentalists is: At what age does low SES do the most damage? In infancy, a family’s low SES may mean less nutritional foods that could stunt the developing brain. In adolescence, low SES could mean a neighbourhood where guns and drugs are readily available. In adulthood, job and marriage prospects are reduced for those with low SES. In late adulthood, accumulated stress over the decades, including the stress of poverty, overwhelms the body’s reserves, causing disease and death (Hoffmann, 2008).

According to Statistics Canada’s 2009 after-tax LICO rate, seniors had a lower incidence of poverty (5.2 percent) than any other age group, but the fact remains that those seniors who are poor may suffer more. This highlights the role of ideology: SES is a powerful lifelong influence, but the data does not dictate which age group most needs financial relief, nor the problems of the near-poor, who do not qualify for certain social assistance programs.

Also important is how nations differ in their response to SES and whether those responses change over time. For example, in Canada, as in the United States, there is a gap in life expectancy between the rich and poor, as evident from Figure 1.4.

FIGURE 1.4 The Rich Live Longer As you see, there is a difference in life expectancy between the rich and poor, with those in the highest tax bracket (Q5) living the longest.

What to do about age, economic, national, and historical differences is a political rather than a developmental question. Voters choose leaders who decide policies that affect people of various ages and incomes. At best, developmentalists provide data, not prescriptions.

Development is Multicultural

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

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, what they value, ignore, and punish. Because culture is so basic to thinking and emotions, people are usually unaware of their cultural values. Just as fish do not realize that they are surrounded by water, people often do not realize that their assumptions about life and death arise from their own culture.

Family Pride Grandpa Charilaos is proud of his tavern in northern Greece (central Macedonia), but he is even more proud of his talented grandchildren, including Maria Soni (shown here). Note her expert fingering. Her mother and father also play instruments. Is that nature or nature?

KUTTIG-RF-KIDS/ALAMY

Sometimes people use the word culture to refer to large groups of other people, as in “Asian culture” or “Latino 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 themselves, as are people from Mexico and Guatemala. Furthermore, individuals within those cultures sometimes rebel against expected beliefs, conventions, norms, and behaviours.

Culture influences everything we say, do, or think, but the term “culture” needs to be carefully used. Ideally, pride in one’s national heritage adds to personal happiness, but sometimes cultural pride is destructive of both the individual and the community (Morrison et al., 2011; Reeskens & Wright, 2011).

Deficit, or Just Difference?Humans tend to believe that they, their nation, and their cultures are a little better than others. This way of thinking has benefits. Generally, people who like themselves are happier, prouder, and more willing to help others. However, that belief becomes destructive if it reduces respect and appreciation for others. Developmentalists recognize the difference-equals-deficit error, the assumption that people unlike us (different) are inferior (deficit). Think back to high school and the various cliques and groups of people there. Did some groups of students think that they were better than the rest?

The difference-equals-deficit error is one reason a multicultural approach is necessary. 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 may be connected to an asset (Marschark & Spencer, 2003). For example, cultures that discourage dissent also foster harmony. The opposite is also true—cultures that encourage conflict also value independence. Whatever your personal judgment on this, the opposite opinion has some merit. A multicultural understanding requires recognition that some differences signify strengths, not weaknesses.

A multicultural perspective helps researchers realize that whether a difference is an asset or not depends partly on the cultural context. Is the toddler who has a large vocabulary better than the one who knows few words? Is the mother who reads to her child every day better than the mother who does not? Yes to both questions in middle-class United States culture. A European-American criticism of Mexican-Americans is that parents rarely read to their children. But this criticism may reflect the difference-equals-deficit error; cross-cultural research finds that many Mexican-American families use other ways to foster language, such as storytelling (Hammer et al., 2011).

Another important reason to have a multicultural perspective is to be more sensitive to our biases and how we socially construct our knowledge. For example, for a long time, many researchers concluded that Chinese societies promote interdependence whereas Western countries such as Canada and the United States promote independence. However, researchers such as Chao (1994, 1995) and Chuang (2006) have found that Chinese-American and Chinese-Canadian mothers do support their young children’s independence, even though how they define independence may vary. Chinese-American mothers define independence as self-reliance, the ability to do things without the parents’ assistance; American parents define it as self-expression (Chao, 1994). As for Chinese-Canadian mothers, they define independence both as self-reliance and as an expression of self (Chuang, 2006). For all these reasons, it is important for researchers to understand how people are defining, interpreting, and making meaning of their development and their world around them.

Feet Between Feet This child is completely enclosed by his mother’s body as she reads to him, unlike the side-by-side position typical among European-Canadians. What cultural values does each position teach?

ARNELL MANALANG/ALAMY

The Multicultural Context in CanadaThe Canadian identity is rooted in multiculturalism and the diversity it encourages. Historically, this diversity has had two major manifestations—among the “three founding peoples” at the time of Confederation, and among the waves of immigrants who arrived after the country’s immigration policies were liberalized in the 1960s.

The three founding peoples consist of the Aboriginal peoples, the French, and the English. As the Constitution Act acknowledges, the Aboriginal peoples themselves are subdivided as First Nations, Inuit, and Métis. Among the various First Nations peoples across the country, there is also much diversity of languages and cultures.

For various reasons, the English gradually came to be the “dominant” culture in Canada as a whole, and both the Aboriginal peoples and the French have struggled to maintain their distinct identities in the face of this dominance.

For the French, language has always been key to their sense of identity. The right to use French in the courts and Parliament was enshrined in the British North America Act, 1867 and the Constitution Act, 1982, and over the years various federal and provincial/territorial laws have further defined and strengthened these rights. Canada is officially a bilingual nation, and the Official Languages Act states that all federal services must be available in both English and French. It’s also important to remember that the French presence is not limited to Quebec; there are significant francophone communities in New Brunswick (the only officially bilingual province in Canada), Ontario, Manitoba, Saskatchewan, and Alberta.

One question we’ll pursue throughout this text is: What are the developmental implications of living in a bilingual country? What effects might this have on patterns of language acquisition, on education in general, and on a person’s world view? Could it be that Canadians are a little more cosmopolitan, a little more open to other opinions than their American neighbours, because of the presence of the French and official bilingualism?

Another question we’ll consider is: To what extent have cultural conflicts between Aboriginal peoples and the rest of Canadian society had developmental impacts on Aboriginal persons of all ages? Perhaps the most dramatic example of these conflicts is the residential school system of the twentieth century, when Aboriginal children were taken from their parents and home communities and sent away to schools run by Christian churches. In these schools, young people were forbidden to speak their own language, to participate in their own cultural practices, and for the most part to communicate with their own family members.

The negative consequences of these schools were so obvious and grave that the entire system was eventually dismantled and the Canadian government issued a formal apology to all Aboriginal peoples in 2008, calling the residential school system “a sad chapter in our history.” Developmentally speaking, are there lessons to be learned, not just from the residential schools legacy, but from traditional Aboriginal teachings on child rearing and education?

To a large extent, residential schools were an attempt by the government to assimilate Aboriginal peoples into the dominant culture of the time to, in the chilling words of one government official, “kill the Indian in the child.” As the government began to abandon this policy in the 1960s, Aboriginal peoples also acquired, for the first time in Canadian history, the rights of full citizenship. At the same time, Canada began to liberalize its immigration laws, which had always favoured white Europeans and discouraged immigration from Asia, Africa, and South America.

Slowly and sometimes grudgingly, Canadian society began to welcome, even to celebrate, diversity. Part of what makes this cultural diversity possible is what John Berry, emeritus professor at Queen’s University in Kingston, calls acculturation. This is the process of cultural and psychological changes that individuals face as they come into contact with a new culture (Berry et al., 1989). Specifically, it involves all the adjustments immigrants have to make to adapt to their new surroundings while still maintaining their own cultural practices and beliefs.

In Canada, the acculturation process has been made easier than in some other countries because of certain government policies and programs that are rooted in the country’s history. As noted above, before the 1960s, Canada’s ethnoprofile was largely European, white, and, except in Quebec, English speaking. Then in 1962 and 1967, largely for economic reasons, the federal government reformed the Immigration Act to remove all existing racial barriers. The result was a major transformation in the number of immigrants coming to Canada from countries in the developing world, a transformation that over the years has completely changed the ethnic profile of Canadian immigration (see Figure 1.5).

FIGURE 1.5 A Changing Society The liberalization of Canadian immigration laws in the 1960s had obvious and long-term impacts on the ethnic composition of Canadian society. In terms of the regional origin of immigrants, which region had the greatest decline over the 45-year period illustrated here? Which had the greatest increase? How might these changes affect human development in this country?

To accommodate this change in its immigrant population, the Canadian government under Pierre Trudeau adopted an official policy of multiculturalism in 1971. In 1988, this policy became law through the adoption of the Canadian Multiculturalism Act, whose stated objective is to “recognize and promote the understanding that multiculturalism reflects the cultural and racial diversity of Canadian society and acknowledges the freedom of all members of Canadian society to preserve, enhance and share their cultural heritage” (Minister ofJustice, 1988).

To strengthen the country’s commitment to immigrant Canadians, the federal and provincial/territorial governments now provide funds to support numerous services and programs specifically targeted to newcomers. By 2011, there were close to 1000 immigrant serving agencies (ISAs)—largely community-based, not-for-profit organizations—across Canada. Numerous community organizations also provide free services and programs for local immigrant families. From a developmental point of view, these types of social support systems help mitigate some of the negative experiences that are often associated with the acculturation process, such as poverty, depression, and family conflicts.

Mentoring Children Lev Vygotsky lived from 1896 to 1934, when war, starvation, and revolution led to the deaths of millions. Throughout this political turmoil, Vygotsky focused on the role of parents in their children’s learning. Here he is shown with his daughter Gita, who later worked with some of her father’s students to publish his manuscripts.

LEV VYGOTSKY

Learning Within a CultureRussian cognitive 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 Russian cultures (Asians and Europeans, of many religions) taught their children whatever beliefs and habits they might need as adults.

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). One example is book reading, as just explained.

Inspired by Vygotsky, Barbara Rogoff studied cultural transmission in Guatemalan, Mexican, Chinese, and American families. Adults always guide children, but clashes occur if parents and teachers are of different cultures. In one such misunderstanding, a teacher praised a student to his mother:

Ethnic and Racial GroupsIt is easy to confuse culture, ethnicity, and race, because these terms sometimes overlap (see Figure 1.6). People of an ethnic group share certain attributes, almost always including ancestral heritage and usually national origin, religion, and language (Whitfield & McClearn, 2005). As you can see from this definition, ethnic groups often share a culture, but this is not necessary. Some people of a particular ethnicity differ culturally (consider people of Irish descent in Ireland, Australia, and Canada), and some cultures include people of several ethnic groups (consider British culture).

FIGURE 1.6 Overlap—But How Much? Ethnicity, culture, and race are three distinct concepts, but they often—though not always—overlap. Which set of circles do you think is more accurate?

Ethnicity is a social construction, affected by the social context, not a direct outcome of biology. That makes it nurture, not nature. For example, African-born people who live in Canada typically consider themselves African, but African-born people living on that continent identify with a more specific ethnic group.

Similar identity becomes strengthened and more specific (Sicilian, not just Italian; South Korean, not just East-Asian) when others of the same ethnic group are nearby and when members of other groups emphasize differences. 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 section explains.

Development is Multidisciplinary

Scientists often specialize, studying one phenomenon in one species at one age. Such specialization provides a deeper understanding of the rhythms of vocalization among 3-month-old infants, for example, or of the effects of alcohol on adolescent mice, or of widows’ relationships with their grown children. (The results of these studies inform later sections of this book.)

However, human development requires insights and information from many scientists, past and present, in many disciplines. Our understanding of every topic benefits from multidisciplinary research; scientists hesitate to apply conclusions about human life until they are substantiated by several disciplines.

Genetics and EpigeneticsThe need for multidisciplinary research became particularly apparent with the onset of genetic analysis. The final decades of the twentieth century witnessed dozens of genetic discoveries, leading to a momentous accomplishment at the turn of the century: The Human Genome Project mapped all the genes that make up a person. To the surprise of many, it is now apparent that every trait—psychological as well as physical—is influenced by genes (see Chapter 2).

At first, it seemed that genes might determine everything, that humans became whatever their genes destined them to be—heroes, killers, or ordinary people. However, research from many disciplines quickly revealed the limitations of genetic research. Yes, genes affect every aspect of behaviour. But even identical twins, with identical genes, differ biologically, psychologically, and socially (Poulsen et al., 2007).

The realization that genes alone do not determine development soon led to the further realization that all important human characteristics are epigenetic. The prefix epi- means “with,” “around,” “before,” “after,” “beyond,” or “near.” The word epigenetic, therefore, refers to the environmental factors that surround the genes, affecting genetic expression.

Some “epi” influences occur in the first hours of life as biochemical elements silence certain genes, in a process called methylation. The degree of methylation for people changes over the life span, affecting genes (Kendler et al., 2011). In addition, other epigenetic influences occur, including some that impede development (e.g., injury, temperature extremes, drug abuse, and crowding) and some that facilitate it (e.g., nourishing food, loving care, and active play). Research far beyond the discipline of genetics, or even the broader discipline of biology, is needed to discover all the epigenetic effects.

The inevitable epigenetic interaction between genes and the environment (nature and nurture) is illustrated in Figure 1.7. That simple diagram, with arrows going up and down over time, has been redrawn and reprinted dozens of times to emphasize that genes interact with environmental conditions again and again in each person’s life (Gottlieb, 2010).

FIGURE 1.7 An Epigenetic Model of Development Notice that there are as many arrows going down as going up, at all levels. Although development begins with genes at conception, it requires that all four factors interact.

Epigenetic research is especially important in treating diseases that impair the brain and devastate human development. As one group of researchers explains, “Clearly, the brain contains an epigenetic ‘hotspot’ with a unique potential to not only better understand its most complex functions, but also to treat its most vicious diseases” (Gräff et al., 2011). Genes are always important; some are expressed, affecting development, and some are never noticed, from generation to generation, unless circumstances change. The reasons are epigenetic; factors beyond the genes are crucial (Issa, 2011; Skipper, 2011).

Multidisciplinary Research On DepressionConsider the importance of many disciplines in understanding depression, which results in 65 million lost years of productive life per year around the world (P. Y. Collins et al., 2011). There is no doubt that depression is partly genetic and neurological—certain brain chemicals make people sad and uninterested in life. There is also no doubt that depression is developmental: Depression increases and decreases throughout the life span (Kapornai & Vetró, 2008; Kendler et al., 2011).

For instance, the incidence of clinical depression suddenly rises in early adolescence, particularly among girls. Throughout life, whether or not a person becomes depressed is affected by chemicals in the brain—not only by neurotransmitters such as dopamine and serotonin, but also by growth factors such as GDNF (glial cell line-derived neurotrophic factor), the product of one gene that makes neurons grow or stagnate (Uchida et al., 2011).

Child-rearing practices have an impact as well. Typically, depressed mothers smile and talk to their infants less than other mothers, and then the infants become less active and verbal. A researcher who studies mother–infant interaction told non-depressed mothers with their 3-month-olds to do the following for only three minutes:

Red Means Stop The red areas on the top PET scan show abnormally low metabolic activity and blood flow in a depressed person’s brain, in contrast to the normal brain shown in the bottom scan.

WDCN/UNIV. COLLEGE LONDON/SCIENCE SOURCE

Thus, even three minutes of mock-depressive behaviour makes infants act depressed. If a mother is actually depressed, her baby will be, too.

Many genetic, biochemical, and neurological factors distinguish adults with depression from other adults (Kanner, 2012; Poldrack et al., 2008). However, their moods and behaviours are powerfully affected by experience and cognition (Huberty, 2012; van Praag et al., 2004). Again, nature is affected by nurture. A person with depressing relationships and experiences is likely to develop the brain patterns characteristic of depression, as well as vice versa. Overall, at least 12 factors are linked to depression:

• Low serotonin in the brain, as a result of an allele of the gene for serotonin transport (neuroscience)

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• Childhood caregiver depression, especially postpartum depression with exclusive mother-care (psychopathology)
• Low exposure to daylight, as in winter in higher latitudes (biology)
• Malnutrition, particularly low hemoglobin (nutrition)
• Lack of close friends, especially when a person enters a new culture, school, or neighbourhood (anthropology)
• Diseases, including Parkinson’s and AIDS, and drugs to treat diseases (medicine)
• Disruptive event, such as a breakup with a romantic partner (sociology)
• Death of mother before age 10 (psychology)
• Absence of father during childhood—especially because of divorce, less so because of death or migration (family studies)
• Family history of eating disorders (not necessarily of the depressed person) (genetics)
• Poverty, especially in a nation where some people are very wealthy (economics)
• Low cognitive skills, including illiteracy and lack of exposure to other ideas (education).

As you see, each of these factors arises from research in a different discipline (italicized). Of course, disciplines overlap. Lack of close confidants, for instance, is noted by anthropologists, but also by sociologists and psychologists. Furthermore, culture, climate, and politics all have an effect, although the particulars are debatable. For example, consider the national differences in Figure 1.8. There are at least six explanations for the disparity in the incidence of depression between one nation and another—some genetic, some cultural, and some a combination of the two.

FIGURE 1.8 Why? Interpretation of these data depends on the interpreter’s assumption. The low rate of depressive episodes in Japan could be caused by something wonderful in Japanese culture—close human bonds, for instance. Or it could be something that North Americans might consider negative—repression of emotions, perhaps, which would reduce only the rate of diagnosed depression, not the rate of actual depression. As with the results of most research, data often raise new questions.

A multidisciplinary approach is crucial in alleviating every impairment, including depression. Currently in North America, a combination of cognitive therapy, family therapy, and antidepressant medication is often more effective than any one of these three alone. International research finds that depression is relatively high in some populations in some places (e.g., among half the women in Pakistan) and low in others (e.g., among about 3 percent of the non-smoking men in Denmark), again for a combination of reasons (Flensborg-Madsen et al., 2011; Husain et al., 2011; von dem Knesebeck et al., 2011).

As already noted in our discussion of nature and nurture, of SIDS, and of the story of watching Caleb’s birth, no single factor determines any outcome. In fact, some people who experience one, and only one, of the factors above never experience depression. It is a combination that makes a person depressed. As you will now learn, for genetic and other reasons, some people are severely affected by circumstances that do not bother others. The multidisciplinary approach to the life span adds a measure of caution to every scientist: No one is able to predict with certainty the future developmental path for anyone.

Development is Plastic

The term plasticity denotes two complementary aspects of development: Human traits can be moulded (as plastic can be) and yet people maintain a certain durability of identity (as plastic does). The concept of plasticity in development provides both hope and realism—hope because change is possible, and realism because development builds on what has come before.

Dynamic SystemsThe concept of plasticity is basic to the contemporary understanding of human development. This is evident in one of the newest approaches to understanding human growth, an approach called dynamic systems. The idea is that human development is an ongoing, ever-changing interaction between the body and mind and between the individual and every aspect of the environment, including all the systems described in the ecological approach. The dynamic-systems approach began in disciplines that focus on changes in the natural world.

Note the key word dynamic: Physical and emotional influences, time, and each person and every aspect of the environment are always interacting, always in flux, always in motion. This approach builds on many aspects of the life-span perspective already described, including that development is multidirectional, multicontextual, multicultural, and multidisciplinary. With any developmental topic, stage, or problem, the dynamic-systems perspective urges us to consider all the interrelated aspects, every social and cultural factor, over days and years.

An Example of Interacting Systems

My sister-in-law contracted rubella (called German measles) early in her third pregnancy, a fact not recognized until David was born, blind and dying. Heart surgery two days after birth saved his life, but surgery at 6 months to remove a cataract destroyed that eye. Malformations of his thumbs, ankles, teeth, feet, spine, and brain became evident. David did not walk or talk or even chew for years. Some people wondered why his parents did not place him in an institution. Yet dire early predictions—from me as well as many others—have proven false. David is a productive adult, and happy. When I questioned him about his life he said, “I try to stay in a positive mood” (David Stassen, personal communication, 2011).

Remember, plasticity cannot erase a person’s genes, childhood, or permanent damage. David’s disabilities are always with him (he still lives with his parents). But his childhood experiences gave him lifelong strengths. His family loved and nurtured him (consulting the Kentucky School for the Blind when he was a few months old, enrolling him in four preschools and then in public kindergarten at age 6). By age 10, David had skipped a year of school and was a fifth grader, reading at the eleventh-grade level. He learned a second and a third language. In young adulthood, after one failing semester (requiring family assistance again), he earned several As and graduated from college.

David now works as a translator of German texts, which he enjoys because, he says, “I like providing a service to scholars, giving them access to something they would otherwise not have” (David Stassen, personal communication, 2007). As his aunt, I have seen him repeatedly defy predictions. All five of the characteristics of the lifespan perspective are evident in David’s life, as summarized in TABLE 1.2.

Differential SensitivityAs just noted, plasticity emphasizes that people can and do change, that predictions are not always accurate. This is sometimes frustrating to scientists, who seek to prevent problems by learning what is particularly risky or helpful for healthy development.

Kathleen’s Nephews Michael, Bill, and David (left to right) are adults now, with quite different personalities, abilities, offspring (4, 2, and none), and contexts (in Massachusetts, Pennsylvania, and California). Yet despite distinct genes, prenatal life, and childhood influences, they shared the influence of Glen and Dot, Kathleen’s brother and sister-in-law—evident here in their similar, friendly smiles.

GREG STASSEN

Three insights have improved predictions. Two of them you already know: (1) nature and nurture always interact, and (2) certain periods of life are sensitive periods, more affected by particular events than others. This was apparent for David: his inherited characteristics affected his ability to learn and his early childhood education (a sensitive period for language learning) has helped him throughout his life.

The third factor to aid prediction and thus target intervention is a more recent discovery, differential sensitivity. The idea is that some people are more vulnerable than others to particular experiences.

Can you remember something you heard in childhood that still affects you, such as a criticism that stung or a compliment that motivated you? Now think of what that same comment meant to the person who uttered it, or what it might have meant to another child. A particular comment stayed with you, but for most people, the same words would be forgotten. That is differential sensitivity.

Generally, many scientists have found many genes, or circumstances, that work both ways—they predispose people to being either unusually successful or pathological (Belsky et al., 2012; Kéri, 2009). This idea is captured in the folk saying “Genius is close to madness”: The same circumstance (brilliance) can become a gift for an entire society or a burden for the affected individual, or it can have little effect.

Many Brain Regions More than a dozen brain areas are more reactive to stress when a person has only the short allele of 5-HTTLPR. That is shown in these brain scans from a study of healthy college women who were paid to undergo an experiment involving 12 episodes without shocks, 13 with moderate shocks, and 13 with stronger (painful but not extreme) shocks. Uncertainty increased stress: The women did not know exactly when or how strong the shocks would be. People with only the short version of 5-HTTLPR were much more anxious overall, with more areas of their brains activated (shown here in red), compared with those who had the long version.

© AMERICAN PSYCHIATRIC ASSOCIATION, 2012

Here is one example that began with African-American 11-year-old boys in rural Georgia (Brody et al., 2009). Early puberty is a sensitive period, when young adolescents seek to rebel against parents, preachers, and teachers, and when the allure of alcohol, marijuana, and sexual intercourse is strong. Yet if a boy can resist those hazards until he is more mature, his future is much brighter. A team of researchers hoped they could protect these Georgia boys from future harm, and they sought scientific evidence to prove or disprove their hypothesis.

Accordingly, they randomly divided parents and sons into two groups: (1) a group that had no intervention, and (2) a group that attended seven seminars designed to increase racial pride, family support, honest communication, and compliance with parents’ rules. These features are in keeping with replicated research that finds that pride and parental involvement protect against early sex and drug use.

FIGURE 1.9 Differential Sensitivity The risk score for these boys was a simple 0 to 3, with 1 point for each of the following: drank alcohol, smoked marijuana, had sex. As shown, most had done none of these at age 11, and, by age 14, most had done one (usually drunk beer). However, some of those at genetic risk had done all three, and many had done two. For them, and only them, the seven-session intervention made a difference.

The first follow-up, five years later, was disappointing. The intervention seemed to have had almost no effect. Both groups of boys drank, smoked, or had sex at similar rates. However, remember that scientists constantly keep up with the work of other scientists, reading published research from many disciplines. By the first follow-up, research on genetics and differential sensitivity had begun appearing in the academic literature, so the Georgia researchers decided to assess (via a saliva test) whether each boy had the short or long version of a particular gene (called 5-HTTLPR).

That small genetic difference turned out to be critical: Those with the long version developed just as well whether they were in the intervention group or not. However, teenagers with the short version who attended the seminars were less likely to have early sex or to use drugs than those who had the short gene but not the family training (see Figure 1.9). The sensitivity provided by nature (the small difference in the code for 5-HTTLPR) allowed the special nurture (the seminars) to have an impact.