Research on adolescence is over 100 years old and can be characterized by two main trends (Lerner & Steinberg, 2004). In the first 70 years or so, research was mainly confined to separate disciplines. Biologists described physical development and the changes that accompany puberty; psychologists studied cognitive development; sociologists examined how various social arenas influenced adolescents; and educational psychologists studied how adolescents' motivation differed across school and classroom settings. This research produced a detailed account of how adolescents develop. More recently, however, researchers have generated more complex understandings of youth. Instead of, for example, studying biological or social development separately, researchers are increasingly examining how different areas of life interact and affect one another.
Another trend consists of changing assumptions about adolescence. Throughout the first 70 years of research, there was a common assumption that adolescence was a time of “storm and stress” (Hall, 1904). Indeed, many believed that puberty brought an inevitable upheaval that led to antisocial attitudes and recklessness. However, since that time, these generalized assumptions have been challenged. Data suggest that for most, the transition from childhood to adulthood is relatively smooth (Arnett, 1999).
The long history of research into adolescent development has resulted in a wealth of practical implications for educators who work with adolescents and strive to provide proactive, healthy opportunities that will facilitate youth's optimal development.
Notions of adolescence are defined by biology and culture and are best understood in a social-historical context. The most longstanding definition of the onset of adolescence links it to puberty, when hormone activity produces the development of secondary sex characteristics (pubic hair and voice change in males; breast development and menarche in females). However, while these biological changes are evidence of the transition from childhood to adolescence, the transition out of adolescence is less well defined. The adage that “adolescence begins in biology and ends in culture” reflects the variable understanding of when adolescence ends. However, theories and models have emerged to explain the transition out of adolescence into early adulthood (Arnett, 2000).
Culturally, definitions of the timing and meaning of adolescence have changed over the years as expectations of youth shifted. A hundred years ago, notions of adolescence were scarcely understood, since teens did not attend high school and most assumed adult roles of providing for their family and getting married at average ages of 14 and 15. Expectations that teens assume adult roles at young ages precipitated the transition into adulthood at much earlier ages than is the case in the 21st century.
However, during the twentieth century expectations of youth began to shift in response to the demands of a changing economy. The need for a better-educated workforce, along with the child welfare movement, propelled youth out of the workforce and into high schools, thus delaying their entry into adult roles. This trend has continued into the present. Now, young people are expected to stay in school much longer, which means they spend more time with same-age peers and enter adulthood later than ever before. These shifts have influenced views of what it means to be an adolescent (e.g., Nichols & Good, 2004).
As a result of these economic and cultural shifts, the time period of adolescence has been extended to include the ages of 10 through the mid twenties, with most researchers dividing the age span into early (10–13), middle (14–17) and late (18–mid twenties) adolescent (Smetana, Campione-Barr, & Metzger, 2006). This division corresponds to American school structures, allowing analyses of development and context according to middle school, high school, and college.
Adolescence represents a period of significant growth. Individually, adolescents experience rapid physical growth and changes, accompanied by shifts in cognitive and emotional capacities. At the same time, the development from childhood into young adulthood brings new cultural and societal opportunities and expectations. At no other time in life do so many shifts in development and social contexts occur simultaneously.
Physical Growth and Change. Most physical growth occurs during the early and middle phases, with the onset of puberty the most characteristic feature of adolescence. The biological changes of adolescence include hormonal changes leading to growth of secondary sex characteristics, growth in height and weight, and changes in body composition (changes in bone, muscle, and fat). The onset of puberty, as marked by hormone changes, starts as early as age 8 in girls and age 9 in boys, with the development of external characteristics typically appearing a few years later. Over time, females are maturing and developing at younger and younger ages, although this is not the case for males.
Puberty-related changes in the body at earlier ages have implications for how youth cope with these changes—especially for girls. Researchers have investigated how biological and social factors affect one another by looking at puberty status, which refers to the degree of physical maturation (hormone changes, breast development, voice change), and puberty timing, which refers to puberty status relative to same-age peers (Susman & Rogol, 2004). One theory that has been advanced to explain the effects of puberty timing is referred to as the Maturational Deviance Hypothesis. It suggests that adolescents who are “off time (earlier or later) in their pubertal development experience more stress than do on-time adolescents” (Susman & Rogol, 2004, p. 30). Studies reveal that youth who mature earlier or later than their same-age peers are vulnerable to at-risk outcomes such as problems with coping, antisocial behavior, and emotional distress (Brooks-Gunn, Peterson & Eichorn, 1985). Early-developing girls are especially at risk for poor body image, higher levels of depression, and substance abuse. By contrast, late-developing boys seem to be at greater risk for depressed mood, lower self-esteem or confidence, and lower achievement.
While late-maturing boys may be vulnerable to some negative outcomes, this finding is not consistent across studies. By contrast, the finding that early development is disadvantageous for girls is more consistent. Often referred to as the early-maturational or early-timing hypothesis, research studies more or less consistently show how early maturation among girls is associated with negative outcomes. There is also data to suggest that boys too may be disadvantaged if they mature before their peers. In general, research seems to suggest that for both boys and girls, off-timing puberty may have negative effects.
Cognitive Growth and Change. Jean Piaget's theories have provided a starting point in the study of the changing nature of cognitive processing in the development from childhood to adolescence. Piaget described how adolescence brings forth the capacity to think logically and abstractly (Piaget, 1955). Since Piaget's time, researchers have sought to understand more complex questions of how processes such as memory, reasoning or problem-solving skills, and expert knowledge develop through adolescence. In short, these interrelated processes seem to develop together, which means researchers cannot determine their individual developmental paths. Instead, a review of literature on cognitive processing as a whole suggests that adolescence brings the “attainment of a more fully conscious, self-directed, and self-regulating mind” (Keating, 2004, p. 48). Thus, in contrast to children, adolescents become more aware of their surroundings and able to direct their own thinking, learning, and problem solving.
Two areas of cognitive development have received much attention: moral reasoning and changes in interpersonal perspective taking. Lawrence Kohlberg (1984) has significantly contributed to understanding of how adolescents reason in their moral decision-making. Drawing from Piaget's work, Kohlberg theorizes that the capacity to morally reason grows more complex and differentiated over time. Kohlberg argues that in general, data suggest that early adolescents typically reason according to his stage two—individualism, instrumental purpose, and exchange, but by about age 13, reasoning progresses to include mutual understandings. Thus, for a 12-year-old, being “good” is about following the rules for one's own good, whereas in stage three, the capacity to understand another person's experiences broadens notions of morality to include a concern for others and the nature of varying circumstances. In short, one's frame of reference moves from childhood moral reasoning that is based on personal perspectives or “what is right is what is good for me” to adolescent moral reasoning that is based in greater appreciation for others' perspectives and experiences or “what is right is for one may not be right for another.”
Robert Selman's 2003 work on the development of perspective-taking has built on the work of Kohlberg and others to shape understanding of adolescent social and moral cognition. Selman studied the progression of perspective-taking skills, referred to as interpersonal understanding, throughout development to understand how cognitive changes in the capacity to understand someone else's perspective influences relationships. At the earlier stages in childhood, perspectives are limited to a single view of the world with very little back and forth understanding. By level two (around early adolescence), adolescents are better able to understand that people have different perspectives. This stage is marked by reciprocity, in which what they give to others is linked to expectations of what they will receive in return. Level three is also marked by mutual understanding that is characterized by genuine giving and caring for another person without expectation for a return. Early adolescents operate consistently at level two, but as they grow older, they operate more frequently at level three.
Selman's work, along with that of Kohlberg and others (e.g., Gilligan, 1982) suggests that adolescents are cognitively different from their childhood counterparts in that adolescents have the capacity to see and understand the world as others see it. Morally and cog-nitively, this means that adolescents (both early and middle) are more generally prosocial in thought and action than their childhood counterparts (Eisenberg & Morris, 2004). Further, it suggests that for adolescents, fostering and maintaining relationships become more complex as the ability to imagine multiple roles for themselves and multiple perspectives of others deepens.
Social and Emotional Changes. Erik Erikson's 1950 theory of identity development has had a significant impact on the understanding of adolescent social and emotional development. According to Erikson, people's sense of who they are unfolds throughout their lives and is driven by the struggle between their “internally defined selves and those selves that are defined, confirmed, or denied by others” (Nakkula & Toshalis, 2006, p. 19). The constant negotiation between these two selves shapes who a person is and who he or she will become. There are eight stages in life during which certain struggles are primary. During adolescence, the primary struggle is over the central question of “Who am I?” Adolescents yearn to be themselves both in relation and reaction to others, and they need relationships in which experiments with identity will be embraced. The struggle to find a balance between individuation and connection drives identity experimentation and the fleeting passions that often accompany it (Nakkula & Toshalis, 2006, p. 22).
Theory on identity development was advanced by James Marcia, who proposed four identity states: foreclosure, moratorium, diffusion, and identity achieved. Each state is characterized by varying levels of exploration and commitments (Marcia, 1966). In Marcia's concept of identity achieved, a person has undergone explorations of possible selves and come to some level of commitment as a result of those explorations. Identity diffusion is the opposite. It applies to someone who has made no commitments and has not gone through any period of exploration. Identity moratorium applies to someone who is actively experimenting or exploring but who has not yet made any commitments, whereas in foreclosure, a person has made commitments without having explored possible options.
The value of these identity status constructs is that they provide a theoretically based framework for understanding the path to healthy identity formation. At the core of these theories is the implication that struggle, experimentation, or exploration is fundamental to the acquisition of healthy identity. Further, these theories imply that the path to an achieved identity involves negotiation between the inner self and social, cultural definitions of the self. Research suggests that identity exploration is often triggered by cognitive and social shifts in which emerging understandings of how others see the world challenge previous definitions. These challenges often unfold in complex social contexts such as schools, peer groups, media environment, and families. In general, at some point, adolescents' views of who they are meet competing definitions that raise the possibility that their own beliefs may be wrong. The resulting challenges often propel teens into exploration, including the taking of risks and pushing of boundaries, in order to better understand their own and others' views of themselves.
Identity struggles emerge because of competing expectations from peers and cultural institutions of which youth are a part. This is true for a wide range of identity constructs, including gender, ethnicity, race, class, and sexual orientation. For example, researchers have long sought to understand the achievement gap between privileged, White cultures and disadvantaged, largely minority cultures. Theorists argue that the achievement gap in the United States is partly explained by a minority culture's distrust of an educational system that is largely based on European values that are perceived as perpetuating segregation and discrimination (Ladson-Billings, 1995). For teens trying to discover their true academic, ethnic, and gendered identity commitments and values, competing expectations cause a dilemma. For minority teens, school may be valued at home, but among peers, doing well in school may be viewed as “acting White” or as abiding by the rules established by another culture. The implicit accusation, that a person has “abandoned” his or her own culture in favor of someone else's, forces minority youth to examine the meaning of school and culture in their lives.
Adolescent physical, cognitive, and emotional development occurs within social institutions, including families, friends, and schools. Therefore, understanding the nature of development necessitates understanding the social contexts in which it occurs. For adolescents, families, peers, and schools constitute the most important cultural contexts in which development unfolds.
Parents and Families. Notions of adolescence as a time of “storm and stress” suggest that this time period will be marked by rebellion, antisocial attitudes, and conflict with parents. However, research suggests that this is the exception rather than the norm. Data reveal that between 5% and 15% of teens are antisocial and excessively rebellious of adult authority (e.g., Collins & Laursen, 2004). Therefore, in family interactions, a majority of youths proceed through adolescence in a relatively stable, healthy, prosocial fashion.
Still, parent-adolescent relationships change in certain ways during the transition from childhood to adulthood. For example, disagreements grow in number and severity throughout adolescence as teens seek out autonomy and independence from parental rules. Thus, conflicts, when they do arise, are typically about rule negotiation, with teens seeking more independence and parents struggling to know when and how to accommodate them. One meta-analysis of studies examining longitudinal patterns in parent-child conflict suggests that frequency of conflicts grows from early to mid adolescence and then tapers off in later adolescence, whereas the intensity of conflicts grows through mid adolescence and stays about the same through later adolescence (Laursen, Coy, & Collins, 1998). Data suggest that this pattern holds relatively the same for parent-child relationships in different cultures.
Peers. Research suggests that adolescent peer groups are dynamic systems that grow bigger and more important with the transition from elementary through middle and high school. Although it has been known since 1900 that a teen's peer group is important, recent research has provided a more complex picture of the role and influence of such groups. Brown (2004) comments on a few basic themes uncovered by this rich literature, pointing out that teen friendships are relatively unstable over time. It has been suggested that fewer than half of “reciprop-rated” best friends last more than one full year, and between one third and one half of peer groups dissolve with time (Brown, 2004). One way of studying this is through nomination procedures in which teens identify popular and well-liked kids and those who are not. These status ascriptions are relatively stable in the short term, but they often vary over the long term. Peer groups are therefore fluid systems that change over time.
Another research topic has been how adolescents manage their friendships. As a way of understanding peer-peer relationships, researchers have studied how adolescents manage conflict. In one set of studies, it was found that youth vary with respect to how they respond to aggressive acts. For example, prosocial youth are less likely to attribute aggression to intentional hostility and are more likely to seek out reconciliation than youth who are characterized as withdrawn or rejected.
Bullying has also received increased attention over the years in the wake of incidents such as the shootings at Columbine High School, Colorado, in 1999. A national survey of youth in grades 6–10 reveals that approximately 29% of students report being involved in bullying (as the bully, victim, or both), and that 13% report engaging in moderate or frequent bullying of others (Nansel et al., 2001). Further, bullying more often occurs in grades 6 through 8, with males as the bully and/or victim more often than females. Males are typically more involved in physical bullying whereas females are often more involved in indirect, relational bullying, such as gossip, rumors, and exclusion. The consequences of bullying can be significant because victims often are lonely, depressed, and have low self-esteem. By contrast, students who are infrequently bullied tend to be more strongly bonded to the school and invested in prosocial behaviors and beliefs (Cunningham, 2007).
One consistent theme throughout the literature on adolescence is the notion of “struggle” or “exploration.” The concomitant emergence of cognitive changes, identity conflicts, and changing role expectations as adolescents progress through school requires that they have open, safe places in which to test, explore, and discover for themselves their identities. For cognitive development, this requires having opportunities to form understandings about right and wrong. For emotional development, it means having safe environments for testing identities in multiple contexts (e.g., in peer groups, through school-based and after-school activities). For social development, it means exploring role definitions through interactions with friends, peer groups, and adult role models and mentors. Teachers can help youth manage these learning experiences through active listening, authoritative management styles, and by helping youth feel like they belong and have safe places in which to explore. This is especially important for middle school contexts in which young adolescents are especially vulnerable to disengagement from school (Eccles, 2004).
The Search Institute has summarized developmental assets for positive youth development that offer ideas for helping youth achieve their potential. These include four external and four internal assets. External assets include (a) having supportive, positive fulfilling relationships with members of one's communities (schools, families, friends); (b) empowerment (being perceived positively by members of the community); (c) knowing clearly what family and school expects, (d) a community that provides a safe place with rich opportunities for exploration. Internal assets include (a) being committed to learning, (b) positive values for making good choices, (c) social competencies to engage in familiar and new situations, and (d) positive self concept (Scales & Leffert, 2004). Using these developmental assets as a guide, teachers can assist youth by arranging environments that foster external assets and engaging in relationships that facilitate internal assets.
Teachers play a significant role in the lives of adolescents, and knowledge of adolescence equips them to be sensitive to the diversity in youth's experiences and the competing forces in their lives. Armed with this knowledge, teachers can offer safe spaces for youth to explore and test their emerging ideas of who they are and who they want to become.
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