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182 PILLAR 2 Development and LearningOne of the most obvious changes is a growth spurt. Sixth- or seventh-grade girls often tower over their male classmates. But, given time, boys tend to wind up taller than girls.5During the growth spurt, both primary and secondary sex characteristics develop (Figure 11.1). The primary sex characteristics are the reproductiveorgans%u2014the testes in males and the ovaries in females. The secondary sex characteristics arenonreproductive sexual characteristics, such as breast and hip development in girls and voice quality and facial hair in boys.Two of the more obvious events of puberty are the first menstrual period (known as menarche) for females and the first ejaculation for boys (called spermarche), which often happens during sleep as a nocturnal emission. Each is a memorable event that produces a variety of emotions in the young person. Puberty can be a distressing experience for some children.6 Teens who have been prepared to expect these events are more likely to view them as positive, rather than frightening or negative, experiences.7%u20139During adolescence, we also usually begin to recognize our sexual orientation, the direction of our romantic, emotional, and sexual attraction.10,11 We may be attracted to people of the opposite sex (heterosexual orientation), to our own sex (same-sex orientation), to both males and females (bisexual orientation), or to no one at all (asexual orientation). According to more than a dozen surveys in Europe and the United States, about 3 to 4 percent of men and 2 percent of women report having exclusively same-sex attractions.12,13 Most of the remaining men and women are heterosexual, although a growing number identify as bisexual.Sexuality is certainly a biological event, but cognitive and cultural factors also govern sexual behaviors. Our culture is saturated with sexual imagery. Hit television shows often contain 15 or more sexual references per hour, most of which ignore the risks of unwanted pregnancy and sexually transmitted infections.14%u201316The amount of sexual content and nudity available on television has increased sharply with the advent of streaming video services.17 Social media often deliver primary sex characteristicsThe reproductive organs%u2014ovaries, testes, and external genitalia.secondary sex characteristicsNonreproductive sexual characteristics, such as breast and hip development in females and voice quality and facial hair in males.sexual orientation The direction of our sexual attractions, as reflected in our enduring romantic, emotional, and sexual attraction toward other people.The Growth SpurtGirls tend to get their growth spurt in middle school. But the boys in this photo will likely be as tall or taller than their female classmates%u2014and their teacher%u2014by the time they finish high school.kali9/E+/Getty ImagesPituitary glandreleaseshormonesthat stimulateAdrenalglandsAdrenalglandsOvaries TestesTo release hormonesthat stimulateUnderarmhair growthBreastdevelopmentEnlargementof uterusBeginning ofmenstruationPubic hairgrowthFacial andunderarmhair growthLarynx(voice box)enlargementPubic hairgrowthGrowth of penisand testesBeginning ofejaculationFIGURE 11.1 The Changes of PubertyThe release of hormones during puberty triggers changes in the body. Some of those changes are illustrated here.%u00a9 Bedford, Freeman & Worth Publishers. For review purposes only. Do not distribute.