Physical Changes in Adolescence

Adolescence begins with the onset of pubertyA developmental stage in adolescence in which hormonal changes create rapid physical changes in the body., a developmental period in which hormonal changes cause rapid physical alterations in the body, culminating in sexual maturity. Although the timing varies to some degree across cultures, the average age range for reaching puberty is between 9 and 14 years for girls and between 10 and 17 years for boys (Marshall & Tanner, 1986).Marshall, W. A., & Tanner, J. M. (1986). Puberty. In F. Falkner & J. M. Tanner (Eds.), Human growth: A comprehensive treatise (2nd ed., pp. 171–209). New York, NY: Plenum Press.

Puberty begins when the pituitary gland begins to stimulate the production of the male sex hormone testosterone in boys and the female sex hormones estrogen and progesterone in girls. The release of these sex hormones triggers the development of the primary sex characteristicsThe organs concerned with reproduction, including the testicles and the penis in boys and the ovaries, uterus, and vagina in girls., the sex organs concerned with reproduction (Figure 6.9 "Sex Characteristics"). These changes include the enlargement of the testicles and the penis in boys and the development of the ovaries, uterus, and vagina in girls. In addition, secondary sex characteristicsPhysical features that distinguish the two sexes from each other but that are not involved in reproduction. (features that distinguish the two sexes from each other but are not involved in reproduction) are also developing, such as an enlarged Adam’s apple, a deeper voice, and pubic and underarm hair in boys and enlargement of the breasts, hips, and the appearance of pubic and underarm hair in girls (Figure 6.9 "Sex Characteristics"). The enlargement of breasts is usually the first sign of puberty in girls and, on average, occurs between ages 10 and 12 (Marshall & Tanner, 1986).Marshall, W. A., & Tanner, J. M. (1986). Puberty. In F. Falkner & J. M. Tanner (Eds.), Human growth: A comprehensive treatise (2nd ed., pp. 171–209). New York, NY: Plenum Press. Boys typically begin to grow facial hair between ages 14 and 16, and both boys and girls experience a rapid growth spurt during this stage. The growth spurt for girls usually occurs earlier than that for boys, with some boys continuing to grow into their 20s.

Figure 6.9 Sex Characteristics

Puberty brings dramatic changes in the body, including the development of primary and secondary sex characteristics.

A major milestone in puberty for girls is menarcheThe first menstrual period., the first menstrual period, typically experienced at around 12 or 13 years of age (Anderson, Dannal, & Must, 2003).Anderson, S. E., Dannal, G. E., & Must, A. (2003). Relative weight and race influence average age at menarche: Results from two nationally representative surveys of U.S. girls studied 25 years apart. Pediatrics, 111, 844–850. The age of menarche varies substantially and is determined by genetics, as well as by diet and lifestyle, since a certain amount of body fat is needed to attain menarche. Girls who are very slim, who engage in strenuous athletic activities, or who are malnourished may begin to menstruate later. Even after menstruation begins, girls whose level of body fat drops below the critical level may stop having their periods. The sequence of events for puberty is more predictable than the age at which they occur. Some girls may begin to grow pubic hair at age 10 but not attain menarche until age 15. In boys, facial hair may not appear until 10 years after the initial onset of puberty.

The timing of puberty in both boys and girls can have significant psychological consequences. Boys who mature earlier attain some social advantages because they are taller and stronger and, therefore, often more popular (Lynne, Graber, Nichols, Brooks-Gunn, & Botvin, 2007).Lynne, S. D., Graber, J. A., Nichols, T. R., Brooks-Gunn, J., & Botvin, G. J. (2007). Links between pubertal timing, peer influences, and externalizing behaviors among urban students followed through middle school. Journal of Adolescent Health, 40, 181.e7–181.e13 (p. 198). At the same time, however, early-maturing boys are at greater risk for delinquency and are more likely than their peers to engage in antisocial behaviors, including drug and alcohol use, truancy, and precocious sexual activity. Girls who mature early may find their maturity stressful, particularly if they experience teasing or sexual harassment (Mendle, Turkheimer, & Emery, 2007; Pescovitz & Walvoord, 2007).Mendle, J., Turkheimer, E., & Emery, R. E. (2007). Detrimental psychological outcomes associated with early pubertal timing in adolescent girls. Developmental Review, 27, 151–171; Pescovitz, O. H., & Walvoord, E. C. (2007). When puberty is precocious: Scientific and clinical aspects. Totowa, NJ: Humana Press. Early-maturing girls are also more likely to have emotional problems, a lower self-image, and higher rates of depression, anxiety, and disordered eating than their peers (Ge, Conger, & Elder, 1996).Ge, X., Conger, R. D., & Elder, G. H., Jr. (1996). Coming of age too early: Pubertal influences on girls’ vulnerability to psychological distress. Child Development, 67(6), 3386–3400.

Cognitive Development in Adolescence

Although the most rapid cognitive changes occur during childhood, the brain continues to develop throughout adolescence, and even into the 20s (Weinberger, Elvevåg, & Giedd, 2005).Weinberger, D. R., Elvevåg, B., & Giedd, J. N. (2005). The adolescent brain: A work in progress. National Campaign to Prevent Teen Pregnancy. Retrieved from http://www.thenationalcampaign.org/resources/pdf/BRAIN.pdf During adolescence, the brain continues to form new neural connections, but also casts off unused neurons and connections (Blakemore, 2008).Blakemore, S. J. (2008). Development of the social brain during adolescence. Quarterly Journal of Experimental Psychology, 61, 40–49. As teenagers mature, the prefrontal cortex, the area of the brain responsible for reasoning, planning, and problem solving, also continues to develop (Goldberg, 2001).Goldberg, E. (2001). The executive brain: Frontal lobes and the civilized mind. New York, NY: Oxford University Press. And myelin, the fatty tissue that forms around axons and neurons and helps speed transmissions between different regions of the brain, also continues to grow (Rapoport et al., 1999).Rapoport, J. L., Giedd, J. N., Blumenthal, J., Hamburger, S., Jeffries, N., Fernandez, T.,…Evans, A. (1999). Progressive cortical change during adolescence in childhood-onset schizophrenia: A longitudinal magnetic resonance imaging study. Archives of General Psychiatry, 56(7), 649–654.

Adolescents often seem to act impulsively, rather than thoughtfully, and this may be in part because the development of the prefrontal cortex is, in general, slower than the development of the emotional parts of the brain, including the limbic system (Blakemore, 2008).Blakemore, S. J. (2008). Development of the social brain during adolescence. Quarterly Journal of Experimental Psychology, 61, 40–49. Furthermore, the hormonal surge that is associated with puberty, which primarily influences emotional responses, may create strong emotions and lead to impulsive behavior. It has been hypothesized that adolescents may engage in risky behavior, such as smoking, drug use, dangerous driving, and unprotected sex in part because they have not yet fully acquired the mental ability to curb impulsive behavior or to make entirely rational judgments (Steinberg, 2007).Steinberg, L. (2007). Risk taking in adolescence: New perspectives from brain and behavioral science. Current Directions in Psychological Science, 16, 55–59.

The new cognitive abilities that are attained during adolescence may also give rise to new feelings of egocentrism, in which adolescents believe that they can do anything and that they know better than anyone else, including their parents (Elkind, 1978, p. 199).Elkind, D. (1978). The child’s reality: Three developmental themes. Hillsdale, NJ: Lawrence Erlbaum Associates. Teenagers are likely to be highly self-conscious, often creating an imaginary audience in which they feel that everyone is constantly watching them (Goossens, Beyers, Emmen, & van Aken, 2002).Goossens, L., Beyers, W., Emmen, M., & van Aken, M. (2002). The imaginary audience and personal fable: Factor analyses and concurrent validity of the “new look” measures. Journal of Research on Adolescence, 12(2), 193–215. Because teens think so much about themselves, they mistakenly believe that others must be thinking about them, too (Rycek, Stuhr, McDermott, Benker, & Swartz, 1998).Rycek, R. F., Stuhr, S. L., Mcdermott, J., Benker, J., & Swartz, M. D. (1998). Adolescent egocentrism and cognitive functioning during late adolescence. Adolescence, 33, 746–750. It is no wonder that everything a teen’s parents do suddenly feels embarrassing to them when they are in public.

Social Development in Adolescence

Some of the most important changes that occur during adolescence involve the further development of the self-concept and the development of new attachments. Whereas young children are most strongly attached to their parents, the important attachments of adolescents move increasingly away from parents and increasingly toward peers (Harris, 1998).Harris, J. (1998), The nurture assumption—Why children turn out the way they do. New York, NY: Free Press. As a result, parents’ influence diminishes at this stage.

According to Erikson (Table 6.1 "Challenges of Development as Proposed by Erik Erikson"), the main social task of the adolescent is the search for a unique identity—the ability to answer the question, “Who am I?” In the search for identity, the adolescent may experience role confusion in which he or she is balancing or choosing among identities, taking on negative or undesirable identities, or temporarily giving up looking for an identity altogether if things are not going well.

One approach to assessing identity development was proposed by James Marcia (1980).Marcia, J. (1980). Identity in adolescence. Handbook of Adolescent Psychology, 5, 145–160. In his approach, adolescents are asked questions regarding their exploration of and commitment to issues related to occupation, politics, religion, and sexual behavior. The responses to the questions allow the researchers to classify the adolescent into one of four identity categories (see Table 6.4 "James Marcia’s Stages of Identity Development").

Figure 6.10

Adolescents search for stable attachments through the development of social identities.

© Thinkstock

Studies assessing how teens pass through Marcia’s stages show that, although most teens eventually succeed in developing a stable identity, the path to it is not always easy and there are many routes that can be taken. Some teens may simply adopt the beliefs of their parents or the first role that is offered to them, perhaps at the expense of searching for other, more promising possibilities (foreclosure status). Other teens may spend years trying on different possible identities (moratorium status) before finally choosing one.

To help them work through the process of developing an identity, teenagers may well try out different identities in different social situations. They may maintain one identity at home and a different type of persona when they are with their peers. Eventually, most teenagers do integrate the different possibilities into a single self-concept and a comfortable sense of identity (identity-achievement status).

For teenagers, the peer group provides valuable information about the self-concept. For instance, in response to the question “What were you like as a teenager? (e.g., cool, nerdy, awkward?),” posed on the website Answerbag, one teenager replied in this way:

Responses like this one demonstrate the extent to which adolescents are developing their self-concepts and self-identities and how they rely on peers to help them do that. The writer here is trying out several (perhaps conflicting) identities, and the identities any teen experiments with are defined by the group the person chooses to be a part of. The friendship groups (cliques, crowds, or gangs) that are such an important part of the adolescent experience allow the young adult to try out different identities, and these groups provide a sense of belonging and acceptance (Rubin, Bukowski, & Parker, 2006).Rubin, K. H., Bukowski, W. M., & Parker, J. G. (2006). Peer interactions, relationships, and groups. In N. Eisenberg, W. Damon, & R. M. Lerner (Eds.), Handbook of child psychology: Social, emotional, and personality development (6th ed., Vol. 3, pp. 571–645). Hoboken, NJ: John Wiley & Sons. A big part of what the adolescent is learning is social identityThe part of the self-concept that is derived from one’s group memberships., the part of the self-concept that is derived from one’s group memberships. Adolescents define their social identities according to how they are similar to and differ from others, finding meaning in the sports, religious, school, gender, and ethnic categories they belong to.

Developing Moral Reasoning: Kohlberg’s Theory

The independence that comes with adolescence requires independent thinking as well as the development of morality—standards of behavior that are generally agreed on within a culture to be right or proper. Just as Piaget believed that children’s cognitive development follows specific patterns, Lawrence Kohlberg (1984)Kohlberg, L. (1984). The psychology of moral development: Essays on moral development (Vol. 2, p. 200). San Francisco, CA: Harper & Row. argued that children learn their moral values through active thinking and reasoning, and that moral development follows a series of stages. To study moral development, Kohlberg posed moral dilemmas to children, teenagers, and adults, such as the following:

As you can see in Table 6.5 "Lawrence Kohlberg’s Stages of Moral Reasoning", Kohlberg concluded, on the basis of their responses to the moral questions, that, as children develop intellectually, they pass through three stages of moral thinking: the preconventional level, the conventional level, and the postconventional level.

Although research has supported Kohlberg’s idea that moral reasoning changes from an early emphasis on punishment and social rules and regulations to an emphasis on more general ethical principles, as with Piaget’s approach, Kohlberg’s stage model is probably too simple. For one, children may use higher levels of reasoning for some types of problems, but revert to lower levels in situations where doing so is more consistent with their goals or beliefs (Rest, 1979).Rest, J. (1979). Development in judging moral issues. Minneapolis: University of Minnesota Press. Second, it has been argued that the stage model is particularly appropriate for Western, rather than non-Western, samples in which allegiance to social norms (such as respect for authority) may be particularly important (Haidt, 2001).Haidt, J. (2001). The emotional dog and its rational tail: A social intuitionist approach to moral judgment. Psychological Review, 108(4), 814–834. And there is frequently little correlation between how children score on the moral stages and how they behave in real life.

Perhaps the most important critique of Kohlberg’s theory is that it may describe the moral development of boys better than it describes that of girls. Carol Gilligan (1982)Gilligan, C. (1982). In a different voice: Psychological theory and women’s development. Cambridge, MA: Harvard University Press. has argued that, because of differences in their socialization, males tend to value principles of justice and rights, whereas females value caring for and helping others. Although there is little evidence that boys and girls score differently on Kohlberg’s stages of moral development (Turiel, 1998),Turiel, E. (1998). The development of morality. In W. Damon (Ed.), Handbook of child psychology: Socialization (5th ed., Vol. 3, pp. 863–932). New York, NY: John Wiley & Sons. it is true that girls and women tend to focus more on issues of caring, helping, and connecting with others than do boys and men (Jaffee & Hyde, 2000).Jaffee, S., & Hyde, J. S. (2000). Gender differences in moral orientation: A meta-analysis. Psychological Bulletin, 126(5), 703–726. If you don’t believe this, ask yourself when you last got a thank-you note from a man.