Hockenbury Discovering Psychology 5th txtbk

394 CHAPTER 9 Lifespan DevelopmentpubertyThe stage of adolescence in which anindividual reaches sexual maturity andbecomes physiologically capable of sexualreproduction.primary sex characteristicsSexual organs that are directly involved inreproduction, such as the uterus, ovaries,penis, and testicles.secondary sex characteristicsSexual characteristics that develop duringpuberty and are not directly involved in reproductionbut differentiate between thesexes, such as male facial hair and femalebreast development.adolescent growth spurtThe period of accelerated growth duringpuberty, involving rapid increases in heightand weight.menarche(meh-NAR-kee) A female’s first menstrualperiod, which occurs during puberty.Girls Get a Head Start Thesetwo eighth-graders are the sameage! In terms of the progress ofsexual and physical maturation,girls are usually about two yearsahead of boys.and cognitive changes as the individual moves toward independence and adult responsibilities.Outwardly, the most noticeable changes that occur during adolescenceare the physical changes that accompany the development of sexual maturity.We’ll begin by considering those changes, then turn to the aspects of social developmentduring adolescence. Following that discussion, we’ll consider some of thecognitive changes of adolescence, including identity formation.Physical and Sexual DevelopmentNature seems to have a warped sense of humor when it comes to puberty, the physicalprocess of attaining sexual maturation and reproductive capacity that beginsduring the early adolescent years. As you may well remember, physical developmentduring adolescence sometimes proceeds unevenly. Feet and hands get bigger beforelegs and arms do. The torso typically develops last, so shirts and blouses sometimesdon’t fit quite right. And the left and right sides of the body can grow at differentrates. The resulting lopsided effect can be quite distressing: One ear, foot, testicle,or breast may be noticeably larger than the other. Thankfully, such asymmetries tendto even out by the end of adolescence.Although nature’s game plan for physical change during adolescence may seemhaphazard, puberty actually tends to follow a predictable sequence for each sex.These changes are summarized in Table 9.3.Primary and Secondary Sex CharacteristicsThe physical changes of puberty fall into two categories. Internally, puberty involvesthe development of the primary sex characteristics, which are the sex organs thatare directly involved in reproduction. For example, the female’s uterus and the male’stestes enlarge in puberty. Externally, development of the secondary sex characteristics,which are not directly involved in reproduction, signal increasing sexual maturity.Secondary sex characteristics include changes in height, weight, and body shape;the appearance of body hair and voice changes; and, in girls, breast development.As you can see in Table 9.3, females are typically about two years ahead of males interms of physical and sexual maturation. For example, the period of marked accelerationin weight and height gains, called the adolescent growth spurt, occurs abouttwo years earlier in females than in males. Much to thechagrin of many sixth- and seventh-grade boys, it’s notuncommon for their female classmates to be both heavierand taller than they are.The statistical averages in Table 9.3 are informative,but—because they are only averages—they cannot conveythe normal range of individual variation in the timingof pubertal events (see Ellis, 2004). For example, afemale’s first menstrual period, termed menarche, typicallyoccurs around age 12 or 13, but menarche maytake place as early as age 9 or 10 or as late as age 16 or17. For boys, the testicles typically begin enlargingaround age 11 or 12, but the process can begin beforeage 9 or after age 14. Thus, it’s entirely possible for someadolescents to have already completed physical and sexualmaturation before their classmates have even begunpuberty. Yet they would all be considered well within thenormal age range for puberty (Sun & others, 2002).Less obvious than the outward changes associatedwith puberty are the sweeping changes occurring inanother realm of physical development: the adolescent’sbrain. We discuss these developments in theFocus on Neuroscience on page 396.