Sometimes referred to as teenage years, youth, or puberty, adolescence covers the period from roughly age 10 to 19 in a child's development.

In the study of child development, adolescence refers to the second decade of the life span, roughly from ages 10 to 19. Some statistics on adolescence narrow the definition to the ages of 12 to 17. In all societies, adolescence is a time of growing up, of moving from the immaturity of childhood into the maturity of adulthood. In 2013, there were 25 million children age 12–17 in the United States, and that number was projected to rise to 26.7 million by 2050.

There is no single event or boundary line that marks the end of childhood or the beginning of adolescence. Rather, experts think of the passage from childhood into and through adolescence as a set of transitions that unfold gradually and that touch upon many aspects of the individual's behavior, development, and relationships. These transitions are biological, cognitive, social, and emotional.

Alfred Adler.

Top 10 causes of disability for adolescents
SOURCE: World Health Organization


The biological transition of adolescence, or puberty, is perhaps the leading sign that adolescence has begun. Technically, puberty refers to the period during which a person becomes capable of sexual reproduction. More broadly speaking, however, puberty is used as a collective term referring to all the physical changes that occur in the growing girl or boy passing from childhood into adulthood.

The timing of physical maturation varies widely. In the United States today, menarche, the first menstrual period, typically occurs around age 12, although some youngsters start puberty when they are only eight or nine. The physical changes of puberty are triggered by hormones, chemical substances in the body that act on specific organs and tissues. In boys a major change is the increased production of testosterone, a male sex hormone, while girls experience increased production of the female hormone estrogen. In both sexes, a rise in growth hormone produces the adolescent growth spurt, the pronounced increase in height and weight that marks the first half of puberty.

Perhaps the most dramatic changes of puberty involve sexuality. As secondary sexual characteristics appear, girls and boys begin to look more like mature women and men. In boys primary and secondary sexual characteristics usually emerge in a predictable order, with rapid growth of the testes and scrotum, accompanied by the appearance of pubic hair. Later comes the growth of facial and body hair, and a gradual lowering of the voice. Around mid-adolescence internal changes begin making a boy capable of producing and ejaculating sperm.

In girls, sexual characteristics develop in a less regular sequence. Usually, the first sign of puberty is a slight elevation of the breasts, but sometimes this is preceded by the appearance of pubic hair. Menarche, the first menstrual period, happens relatively late, not at the start of puberty, as many people believe. Regular ovulation and the ability to carry a baby to full term usually follow menarche by several years.

For many years, psychologists believed that puberty was stressful for young people. We now know that any difficulties associated with adjusting to puberty are minimized if adolescents know what changes to expect and have positive attitudes toward them. Although the immediate effect of puberty on the adolescent's self-image and mood may be very modest, the timing of physical maturation affects the teen's social and emotional development in important ways. Earlymaturing boys tend to be more popular, to have more positive self-conceptions, and to be more self-assured than their later-maturing peers, whereas early-maturing girls may feel awkward and self-conscious.

Cognitive transition

A second element of the passage through adolescence is a cognitive transition. Compared to children, adolescents think in ways that are more advanced, more efficient, and generally more complex. This can be seen in five ways.

First, adolescents become better able than younger children to think about what is possible, instead of limiting their thought to what is real. Whereas children's thinking is oriented to things and events that they can observe directly, adolescents are able to consider what they observe against a backdrop of what is possible.

Second, during the passage into adolescence, individuals become better able to think about abstract ideas. For example, adolescents find it easier than children to comprehend the higher-order, abstract logic of puns, proverbs, metaphors, and analogies. The adolescent's greater ability to think this way also permits him or her to apply advanced reasoning and logical processes to social and ideological issues, as clearly seen in the adolescent's increased interest in and understanding of interpersonal relationships, politics, and morality.

Third, during adolescence boys and girls begin thinking more often about the process of thinking itself, or metacognition. As a result, adolescents may display increased introspection and self-consciousness. Although improvements in metacognitive abilities help adolescents at school or in other intellectual matters, one potentially negative by-product of these advances is that adolescents tend to become egocentrc, or intensely preoccupied with themselves. Sometimes a teenager believes that others are constantly watching and evaluating him or her, much as an audience glues its attention to an actor on a stage. Psychologists refer to this as the imaginary audience.

A fourth change in cognition is that adolescents tend to think about many issues at once, rather than having it limited to a single issue. Adolescents can see things through more complicated lenses than can younger children.

Emotional transition

In addition to being a time of biological and cognitive change, adolescence is also a period of emotional transition and, in particular, changes in the way individuals view themselves and in their ability to function independently.

During adolescence, important shifts occur in the way boys and girls think about and characterize themselves—that is, in their self-conceptions. As individuals mature intellectually and undergo the sorts of cognitive changes described earlier, they come to perceive themselves in more sophisticated and differentiated ways. Compared with children, who tend to describe themselves in fairly simple, concrete terms, adolescents are more likely to employ complex, abstract, and psychological self-characterizations. As adolescents’ selfconceptions become more abstract and as they become more able to see themselves in psychological terms, they become more interested in understanding their own personalities and why they behave the way they do.

Conventional wisdom holds that adolescents have low self-esteem—that they are more insecure and selfcritical than children or adults—but most research indicates otherwise. Although teenagers' feelings about themselves may fluctuate, especially during early adolescence, their self-esteem remains fairly stable from about age 13 on. If anything, self-esteem increases over middle and late adolescence. Most researchers today believe that young people evaluate themselves along several different dimensions. As a consequence, it is possible for an adolescent to have high self-esteem when it comes to his academic abilities, low self-esteem when it comes to athletics, and moderate self-esteem when it comes to his physical appearance.

One theorist whose work has been very influential on our understanding of adolescents’ self-conceptions is Erik Erikson, who theorized that establishing a coherent sense of identity is the chief psychosocial task of adolescence. Erikson believed that the complications inherent in identity development in modern society have created the need for a psychosocial moratorium—a time-out during adolescence from the sorts of responsibilities and obligations that might restrict the young person from pursuing self-discovery. During the psychosocial moratorium, the adolescent can experiment with different roles and identities. Experimenting involves trying out different personalities and ways of behaving. Sometimes, parents describe their teenage children as going through “phases.” Much of this behavior is actually experimentation with roles and personalities.

For most adolescents, establishing a sense of autonomy, or independence, is as important a part of the emotional transition out of childhood as is establishing a sense of identity. During adolescence, there is a movement away from the dependency typical of childhood toward the autonomy typical of adulthood. One can see this in several ways.

First, older adolescents do not generally rush to their parents whenever they are upset, worried, or in need of assistance. Second, they do not see their parents as all-knowing or all-powerful. Third, adolescents often have a great deal of emotional energy wrapped up in relationships outside the family; in fact, they may feel more attached to a boyfriend or a girlfriend than to their parents. And finally, older adolescents are able to see and interact with their parents as people—not just as their parents. Many parents find, for example, that they can confide in their adolescent children, something that was not possible when their children were younger.

Some theorists have suggested that the development of independence be looked at in terms of the adolescent's developing sense of individuation. The process of individuation, which begins during infancy and continues well into late adolescence, involves a gradual, progressive sharpening of one's sense of self as autonomous, competent, and separate from one's parents. Individuation, therefore, has a great deal to do with the development of a sense of identity, in that it involves changes in how we come to see and feel about ourselves.

Being independent means more than merely feel-ing independent, of course. It also means being able to make one's own decisions and to select a sensible course of action by one's self. This is an especially important capability in contemporary society, where many adolescents are forced to become independent decision makers at an early age. In general, researchers find that decision-making abilities improve over the course of the adolescent years, with gains continuing well into the later years of high school.

Susceptibility to the influence of parents and peers changes with development. In general, during childhood, boys and girls are highly oriented toward their parents and less so toward their peers; peer pressure during the early elementary school years is not especially strong. As they approach adolescence, however, children become somewhat less oriented toward their parents and more oriented toward their peers, and peer pressure begins to escalate.

Social transition

Accompanying the biological, cognitive, and emotional transitions of adolescence are important changes in the adolescent's social relationships, or the social transition of adolescence. Developmentalists have spent considerable time charting the changes that take place with friends and with family members as the individual moves through the adolescent years.

One of the most noteworthy aspects of the social transition into adolescence is the increase in the amount of time adolescents spend with their peers. Although relations with peers exist well before adolescence, during the teenage years they change in significance and structure. Four specific developments stand out.

First, there is a sharp increase during adolescence in the amount of time children spend with their peers and in the relative time they spend in the company of peers versus adults. In the United States, more than half of the typical adolescent's waking hours are spent with peers, as opposed to only 15% with adults— including parents. Second, during adolescence, peer groups function much more often without adult supervision than they do during childhood. Third, during adolescence increasingly more contact with peers is with opposite-sex friends.

Finally, whereas children's peer relationships are limited mainly to pairs of friends and relatively small groups, adolescence marks the emergence of larger groups of peers, or crowds. In contemporary American high schools, typical crowds may be labeled as “jocks” or “brains,” for example. In contrast to cliques, crowds are not settings for adolescents' intimate interactions or friendships, but, instead, help to locate an adolescent within the social structure of the school. Crowds tend to form a sort of social hierarchy or map of the school, and different crowds are seen as having different degrees of status or importance.

The importance of peers during early adolescence coincides with changes in individuals' needs for intimacy. As children begin to share secrets with their friends, a new sense of loyalty and commitment grows, a belief that friends can trust each other. During adolescence, the search for intimacy intensifies, and self-disclosure between best friends becomes an important pastime.

One of the most important social transitions that takes place in adolescence concerns the emergence of sexual and romantic relationships. In contemporary society, most young people begin dating sometime during early adolescence.

Dating during adolescence can mean anything from group activities that bring boys and girls together (without much actual contact between the sexes); to group dates; to casual dating as couples; or to serious involvement with a steady boyfriend or girlfriend. More adolescents have experience in mixed-sex group activities such as parties or dances than dating, and more have experience in dating than in having a serious boyfriend or girlfriend.

Most adolescents’ first experience with sex falls into the category of “autoerotic behavior” —sexual behavior that is experienced alone. The most common autoerotic activities reported by adolescents are erotic fantasies and masturbation. By the time most adolescents have reached high school, they have had some experience with sex in the context of a relationship. About half of all American teenagers have had sexual intercourse by the time of high school graduation.

Estimates of the prevalence of sexual intercourse among American adolescents vary considerably from study to study, depending on the nature of the sample surveyed and the year and region in which the study was undertaken. Although regional and ethnic variations make it difficult to generalize about the average age at which American adolescents initiate sexual intercourse, national surveys of young people indicate that more adolescents are sexually active at an earlier age today than in the recent past.

For many years, researchers studied the psychological and social characteristics of adolescents who engaged in premarital sex, assuming that sexually active teenagers were more troubled than their peers. This view has been replaced as sexual activity has become more prevalent. Indeed, several recent studies show that sexual activity during adolescence is decidedly not associated with psychological disturbance.


Thinking, or the mental processes involved in gaining knowledge and understanding.
A natural process of transforming into a conscious being.
Being aware of one's own cognition, or thought processes.
The relationship of social factors in society to a person's individual behaviors and thoughts.
The biological transition of adolescence, or the period during which a person becomes capable of sexual reproduction.
Secondary sexual characteristics—
Features that develop in boys and girls during puberty (and that were not visible at birth) that show their advancing sexual maturity, such as developing breasts in girls or facial hair in boys.

Although it is incorrect to characterize adolescence as a time when the family ceases to be important, or as a time of inherent and inevitable family conflict, early adolescence is a period of significant change and reorganization in family relationships. In most families, there is a movement during adolescence from patterns of influence and interaction that are asymmetrical and unequal to ones in which parents and their adolescent children are on a more equal footing. Changes in the ways adolescents view family rules and regulations, especially, may contribute to increased disagreement between them and their parents.

Although puberty seems to distance adolescents from their parents, family conflict during this stage is more likely to take the form of bickering over day-today issues than outright fighting. Similarly, the diminished closeness is more likely to be manifested in increased privacy on the part of the adolescent and diminished physical affection between teenagers and parents, rather than any serious loss of love or respect between parents and children. Research suggests that this distancing is temporary, though, and that family relationships may become less conflicted and more intimate during late adolescence.

Generally speaking, most young people are able to negotiate the biological, cognitive, emotional, and social transitions of adolescence successfully. Although the mass media bombard us with images of troubled youth, systematic research indicates that the vast majority of individuals move from childhood into and through adolescence without serious difficulty.



Feldman, S., and G. Elliott, eds. At the Threshold: The Developing Adolescent. Cambridge: Harvard University Press, 1990.

Novak, Gary D., and Martha Palaez. Child and Adolescent Development: A Behavioral Systems Approach. Thousand Oaks, California: Sage Publications, 2003.

Pipher, Mary. Reviving Ophelia. New York: Penguin Group, 2005.

Steinberg, L. Adolescence. 10th ed. New York: McGrawHill, 2013.

Steinberg, L., and A. Levine. You and Your Adolescent: The Essential Guide for Ages 10 to 25. New York: Simon&Schuster, 2011.