Puberty

Encyclopedia of Psychology, Apr 06, 2001

In boys, as in girls, the first outward sign of sexual maturation is often light-colored pubic hair around the time the growth spurt begins. The testes and scrotum begin to grow, and the scrotum darkens, thickens, and becomes pendulous. About a year after the testes begin to increase in size, the penis lengthens and widens, taking several years to reach its full size. Sperm production increases, and ejaculations-the male counterpart to menarche in girls-begin, occurring through nocturnal emission, masturbation, or sexual intercourse. (It takes from one to three years until ejaculations contain enough sperm for a boy to be really fertile.) Boys' pubic hair, like that of girls, gradually becomes thicker and curlier and covers a wider area, and facial hair appears, first in the mustache area above the upper lip and later at the sides of the face and on the chin. As a boy's larynx grows and the vocal cords lengthen, his voice drops (roughly an octave in pitch) and changes in quality. Although girls' voices also become lower, the change is more dramatic (and less controlled) in boys, whose voices occasionally break, producing an embarrassing high-pitched squeak.

The sequence and age range of the developmental changes associated with puberty can vary widely. Although most children begin puberty between the ages of 10 and 12, it can start at any age from 8 to 16. The most obvious determining factor is gender; on average, puberty arrives earlier for girls than boys. Heredity also appears to play an important role. Compared to an overall age range of nine to 18 for menarche, the age difference for sisters averages only 13 months and for identical twins, less than three months. Body weight is a factor as well: puberty often begins earlier in heavier children of both sexes and later in thinner ones. The onset of menstruation, in particular, appears to be related to amounts of body fat. Girls with little body fat, especially athletes, often start menstruating at a later-than-average age. Over the past 100 years, puberty has tended to begin increasingly early in both sexes (a phenomenon called the secular trend) . In 1997, the results of a study led by Dr. Marcia E. Herman-Giddens of University of North Carolina at Chapel Hill School of Public Health provided evidence that the average age of menarche was declining. Instead of occurring between the ages of 12 and 14, as is typical in the late 1990s, girls' first menstrual periods commonly appeared between the ages of 15 and 17 in the 19th century. Puberty in boys usually didn't begin until the ages of 15 or 16 (in the late 18th and early 19th centuries, boy sopranos in their mid-to-late teens still sang in church choirs). Explanations for this pattern have ranged from evolution to better health, especially as a consequence of improved nutrition.

An important aspect of puberty is the development of body image. Teenagers are often critical of their bodies during this period, either because they feel they are maturing too early or too late, or because they fail to match the stereotyped ideals of attractiveness for their sex (i.e., tall and muscular for men, fashionably thin for women). Girls who mature early have a hard time initially because they feel self-conscious and isolated, but they adjust well and even gain in status once their peers begin to catch up. Some research even suggests that girls who mature early may ultimately be better off than those who mature late because the turmoil of their early teenage years helps them develop coping skills that stand them in good stead later on. For boys, the relative positions of early and late maturers is reversed. Those who are already tall and athletic in junior high school feel better about themselves than those who remain short and skinny. Researchers have linked late physical maturation in boys to the development of both positive personality traits (humor, perceptiveness, flexibility, creativity, and leadership skills) and negative ones (restlessness and lack of poise). In most cases, adolescents gradually become more accepting of their bodies in the years following junior high school.