Chapter 9.PDF

Chapter 9 Physical, Cognitive, and Identity Development in Adolescence Learning Objectives After reading this chapter, you should be able to: 9.1 Describe sequential processes in adolescent physical development from hormones that trigger events to corresponding changes in the...

Chapter 9 Physical, Cognitive, and Identity Development in Adolescence Learning Objectives After reading this chapter, you should be able to: 9.1 Describe sequential processes in adolescent physical development from hormones that trigger events to corresponding changes in the brain and body and explain how environmental and hereditary factors affect timing of puberty. 9.2 Explain behavioral and emotional changes in adolescence, including a discussion of mood, depression, and the emergence of adult sexuality, and identify factors that shape these changes as well as vulnerabilities that pose threats. 9.3 Describe changes in cognitive functioning in adolescence, charac- terized by Piaget as formal operational thought, and examine broad implications of these cognitive advances including the effects of egocentrism on adolescent life. 9.4 Assess levels of exploration and commitment in adolescent identity formation and support healthy and developmentally appropriate identity construction. Rebecca recently had her 13th birthday. Her Aunt Cathy, who has just returned from a year abroad, hardly recognizes her. When she saw her last, Rebecca was a cute, pug- nosed little girl with a sunny disposition and an easy laugh. Now she is 3 or 4 inches taller. But her rapid growth is not what surprises her aunt; it is the qualitative change in both her appearance and her manner. Her slim, child’s body is softening and chang- ing shape. Her breasts are emerging, her hips spreading. And her face is, well, a little weird. Suddenly she has a big nose and a pimply complexion. Although she seems genuinely happy to see her aunt, within the first hour of her reunion with the family Rebecca begins interjecting sarcastic remarks into the conversation, and she petulantly rolls her eyes at comments made by other members of her family. Little of what is said escapes her biting criticism. When her mildly exasperated father gently suggests that she should spend some time studying for tomorrow’s test, she suddenly seems near tears, whining, “I always have more to do than anyone else!” 341 342 Chapter 9 Clearly, Rebecca has entered the land of puberty and has begun her trek across the divide from childhood to adulthood. Strictly speaking, puberty is a process of sex- ual maturation. When it is complete, boys and girls are fertile: Males can impregnate females, and females can conceive. But as most of us can recall from our own journey, puberty is related to a wide range of emotional, behavioral, and social changes as well. From Shakespeare’s Romeo and Juliet to Salinger’s Holden Caulfield to Marga- ret, the teenager in Judy Blume’s novel who poignantly asked, “Are you there, God?” we have enjoyed many memorable literary examples of adolescents’ coming of age. In many cultures and throughout many different historical periods, adolescence has evoked a certain fascination. We endow it with meaning and celebrate it as the time when innocent, dependent children are transformed into young adults. However, one reason this life stage is so interesting is that, in reality, it defies easy description. What are the tasks of adolescence, and are they completed by a certain chronological age? Are these tasks the same for all adolescents, or are there some that are culture or gen- der specific? Is adolescence a period of storm and stress or a relatively smooth tran- sition? Should adolescents rebel against convention to define their uniqueness, or is rebellion a sign of maladjustment? Is legal adult status a real indicator of adulthood, or should we look to other indicators of cognitive and emotional maturity? And what is really happening within the adolescent brain? These are some of the topics we will discuss in the next two chapters. Because of its child-to-adult metamorphosis, writers have long recognized the centrality of identity development to the adolescent period. Erik Erikson (1950/1963, 1968) is possibly best remembered for his writing on the topic of identity. Sometimes, however, his emphasis on the shaping of identity in adolescence, which has been the popular interpretation of Erikson’s work, inadvertently suggests that there is no real sense of identity beforehand. As we consider this important task of adolescence, we should note that Erikson was careful to emphasize the epigenetic nature of human development. The human being, like any other growing organism, has a “ground plan” (1968, p. 92) composed of parts that unfold or come into ascendancy at certain times, to eventually become a coherent whole. Success at each new developmental task requires qualities and skills acquired from the work of prior life stages and depends upon relative mastery of earlier tasks as a basis for moving ahead. Thus, far from being divorced from the child’s ear- lier sense of self and self-in-relationship, adolescent identity is a synthesis of earlier ele- ments with new, more cognitively and emotionally mature aspects of the self-system. We begin our look at the adolescent period by exploring the physical, emotional, and cognitive changes that mark this time of life. Building on the growth and matu- ration of these systems, we will then consider how they support the process of ado- lescent identity development. In Chapter 10, you will learn about how adolescents’ interactions in their families, in their schools, and with their peers are impacted by the fundamental processes discussed in this chapter. Physical Development 9.1 Describe sequential processes in adolescent physical development from hormones that trigger events to corresponding changes in the brain and body and explain how environmental and hereditary factors affect timing of puberty. The physical changes that startled Rebecca’s Aunt Cathy are just what we see on the surface. Recent discoveries about the adolescent brain have revealed changes that are less obvious externally but no less dramatic. A Glandular Awakening It has been said that “Puberty begins with a Kiss” (e.g., May & Cotton, 2014). That is, it begins with kisspeptin, a signaling chemical produced in the hypothalamus. It is called kisspeptin because it was discovered in Hershey, Pennsylvania, home of  Physical, Cognitive, and Identity Development in Adolescence 343 the famous Hershey Kiss™ (Cortés, Carrera, Rioseco, del Río, & Vigil, 2015). Kiss- peptin combines with receptors in the hypothalamus to trigger a cascade of events in many parts of the brain and body (see Figure 9.1 for a guide to some of the structures involved and the direction of effects). The hypothalamus produces gonadotropin releasing hormone (GnRH), which stimulates the pituitary and sets the reproduc- tive axis into motion. The pituitary releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) that circulate through the bloodstream and stimulate other endocrine glands to increase their hormone production. These glands include the gonads—testes in males, ovaries in females—that now increase their production of both masculinizing hormones (androgens, such as testosterone) and feminizing hor- mones (estrogen). Both masculinizing and feminizing hormones (as well as progesterone, which is involved in the reproductive cycle) are released in males and in females, but they are produced in different ratios. Increases in androgen production are much higher in boys than in girls, whereas estrogen production increases much more in girls. In combination with other hormones circulating in the blood, they cause a series of changes in children’s bodies that promote the maturing of both primary sexual characteristics (those directly involved in reproduction, such as the genita- lia) and secondary sexual characteristics (physical traits not directly involved in reproduction but indicative of sex, such as enlarged breasts in females and deeper voices in males). Early, outward signs of puberty are usually the appearance of pubic hair in both sexes, the growth of the scrotum and testes in boys, and the bud- ding of breasts in girls. Menarche in girls (first menstruation) and spermarche in boys (first ejaculation) usually occur near the end of puberty and are often treated as important social markers of sexual maturation. But fertility—ovulation in girls and adequate sperm production in boys—may not be achieved for a year or more after these outward manifestations of maturity (Cortés et al., 2015). Table 9.1 gives you an overview of some of these changes and the typical order of their appearance in boys and girls. FIGURE 9.1 Key structures affecting changes during puberty. HYPOTHALAMUS PITUITARY GLAND ADRENAL GONADS THYROID GLAND GLAND (TESTES OR OVARIES) COMBINED EFFECTS Boys Girls SOURCE: Adapted from Arnett, J. J. (2013). Adolescence and emerging adulthood (5th Ed.). Upper Saddle River, NJ: Pearson Education, Inc. Used by permission of Pearson Education. 344 Chapter 9 TABLE 9.1 Typical Sequence of Physical Changes with Puberty BOYS GIRLS CHARACTERISTIC AGE OF ONSET (YEARS) CHARACTERISTIC AGE OF ONSET (YEARS) Growth of testes, scrotal sac 9.5 to 13.5 Growth of pubic hair 8 to 14 Growth of pubic hair 10 to 15 Growth of breasts 8 to 13 Growth spurt 10.5 to 16 Growth spurt 9.5 to 14.5 Growth of penis 10.5 to 14.5 Menarche 10 to 16.5 Change in voice 11 to 15 Growth of underarm hair 10 to 16 Spermarche 12 to 14 Changes in sweat & oil producing 10 to 16 glands Growth of facial & underarm hair 12 to 17 Changes in sweat & oil producing glands 12 to 17 SOURCE: Adapted from Arnett, J. J. (2013). Adolescence and emerging adulthood (5th Ed.). Upper Saddle River, NJ: Pearson Education, Inc. Reprinted and Electronically reproduced by permission of Pearson Education, Inc., New York, NY. The timing of puberty appears to be affected by genetic factors: Identical twins usually begin and end the process within 2 to 3 months of each other, and mothers’ and daughters’ ages at menarche are correlated (Brooks-Gunn, 1991; Day, Perry, & Ong, 2015; Golub, 1992; Mustanski, Viken, Kaprio, Pulkkinen, & Rose, 2004). But environmental factors are clearly important as well. For example, there has been a downward shift in the average age of menarche in many countries (Li et al., 2017). Today, the average age is just under 13 years, with slight variations across racial and ethnic groups, whereas in 1850 it was approximately three years later. Because menarche and spermarche occur later in the maturational process, changes in breast development and pubic hair can be useful markers of pubertal onset. A study conducted in Cincinnati, New York, and San Francisco of over 1,200 girls ages 6 to 7 showed high rates of early puberty. At age 7, early breast development was found for 23% of African American girls, 15% of Hispanic girls, and 10% of Caucasian girls. By age 8, the rates had jumped to 42.9%, 30.9%, and 18.3% respectively. The find- ings for Caucasian girls represented the greatest increase relative to studies conducted 10 years earlier, even though the absolute numbers were lowest for this group. Since early puberty in girls is a risk factor for later breast cancer, cardiovascular problems, elevated BMI, insulin resistance, and a number of mental and behavioral health issues, this study prompts serious concern about the public health issues associated with the trend toward earlier pubertal timing (Biro et al., 2010). Signs of early puberty have been increasing in U.S. boys as well. In a comparable study, the approximate age for early signs of genital development in boys was 10.14 for non-Hispanic White boys, 9.14 for African American boys, and 10.04 for Hispanic boys. The results from this study showed pubertal onset occurring 6 months to 2 years earlier (depending upon groups) than data reported 20 years before (Herman-Giddens et al., 2012). What might be causing this phenomenon? One influence seems to be declining physical activity and increasing intake of high-calorie foods (Herman-Giddens, 2017). Body fat affects the timing of puberty in girls, such that higher ratios of fat are associ- ated with earlier onsets. Whether body fat affects pubertal timing in boys is less clear, although some studies indicate that it does (Lee et al., 2016; see Li et al., 2017). Several mechanisms seem to be involved, including the overproduction of leptin, which is a hormone produced in fat tissue that can affect GnRH levels in the hypothalamus (Fu & Zhou, 2014). Children whose body fat is unusually low, such as those who are mal- nourished, are likely to begin puberty later than other children. One intriguing association between environment and timing of puberty is that the onset of puberty tends to be earlier in families where there is substantial conflict or other significant sources of stress (Rickard, Frankenhuis, & Nettle, 2014). This conclusion  Physical, Cognitive, and Identity Development in Adolescence 345 derives from studies of adolescents around the world. For example, Polish boys and girls living in crowded urban conditions begin puberty earlier than those living in rural areas (Hulanicka, 1999). Puberty is accelerated for Finnish boys and girls reared in father- absent homes as compared to other children (Mustanski et al., 2004). New Zealand girls from divorced families start menstruating earlier than girls whose parents are married (Moffitt, Caspi, Belsky, & Silva, 1992; Tither & Ellis, 2008). Early childhood abuse has also been associated with early menarche (Boynton-Jarrett et al., 2012). A large, longitudinal study of Australian children found that extreme socioeconomic disadvantage put chil- dren at high risk for early onset of puberty. Compared to children in better circumstances, low SES boys showed a four times greater frequency of early onset. For low SES girls, the frequency was two times greater, even though the effects of overweight were controlled (Sun et al., 2017). There could be multiple reasons for the correlations between environ- mental stress and puberty, but one is likely to be that stress affects hormone production. The effects of environmental stress, at least the effects of chronic socioeconomic disadvantage, may be moderated by protective social factors, such as secure attach- ments. For example, in a longitudinal study of U.S. children, low SES was linked to early menarche (Sung et al., 2016). But if low SES girls were securely attached to their mothers as infants, they were less likely to experience early menarche than if they were insecurely attached. Overall, aspects of nutrition and stress may also interact with chemical exposure to disrupt pubertal processes. Certain chemicals used in industrial production (called endocrine-disrupting chemicals or EDCs) interfere with endocrine functions. These chemicals have been linked to changes in pubertal timing and have been shown to affect fat metabolism. EDCs include flame retardants, pesticides, certain pharmaceuti- cal agents, lead, mercury, phthalates found in plastic, and so forth. They have been related to pubertal abnormalities in studies of animals and humans and warrant fur- ther investigation according to experts (see Fisher & Eugster, 2014). The Growth Spurt Puberty corresponds with the adolescent growth spurt, a rapid increase in size accompa- nied by changes in the shape and proportions of the body. Over about a four-year span, the average increase in height is about 10 inches for both boys and girls; boys gain about 42 pounds on average and girls about 38 pounds. Different parts of the body grow at different times. Facial features like the nose and ears usually grow before the skull does, accounting in part for Rebecca’s strange appearance. It is likely that when her head growth catches up with her features, she will no longer seem to have a big nose. Hands, feet, and limbs usually grow before the torso, which can create awkwardness and adds to the odd look. There can even be asymmetries in growth between the two sides of the body, with one breast or one testicle growing before the other (Hofmann, 1997; Tanner, 1990). Some aspects of the growth process play out differently for girls and boys. For girls, the growth spurt begins and ends about two years earlier than for boys (Herting & Sowell, 2017). Besides other obvious differences, such as increased breast size and greater pelvic spread in girls and broader shoulders in boys, there are gender differ- ences in internal growth. The size of the heart and lungs increases more in boys, for example, and boys also develop thicker bones and more muscle tissue than girls. Many of these changes contribute to average differences in physical strength and endurance between the sexes. Adolescent and adult males are typically stronger than females of the same general size. Thus, the adolescent growth spurt increases both internal and external sexual dimorphism, physical differences between the sexes (Malina, 1990). The Changing Brain The adolescent brain is an instrument of change. Its plasticity is its most remarkable characteristic (Giedd, 2015). It is not so much that the brain is growing but that its circuitry is changing. Because it is reorganizing, the teen brain seems especially open to new experiences and learning opportunities, and especially vulnerable to adversity (Byrne et al., 2017; Schultz & Sisk, 2016). We will briefly summarize some changes and then examine how they relate to teen behavior.  346 Chapter 9 The availability of new technologies is rapidly altering our understanding of the processes that contribute to neural reorganization during adolescence. Longitudinal studies of humans and other mammals show that puberty’s hormonal cascade helps trig- ger and moderate changes in brain structure and function (Gur & Gur, 2016; Juraska & Willing, 2017; Schultz & Sisk, 2016). Hormones can modify the brain by influencing the onset or offset of genes. By doing so, they alter protein synthesis, which is important for all neuro-maturational processes. Let’s consider gray matter changes first. Gray matter volume, which appears to peak in early to middle childhood, begins to decrease with puberty (Mills et al., 2016). Pruning of cortical synapses is one likely reason (Kilford, Garrett, & Blakemore, 2016). You will recall that pruning involves carving away unused or dysfunctional synapses (connections between neurons). The pruning we described in the sections on infancy and early childhood take place primarily in the sensory and motor cortices of the brain. In adolescence, pruning occurs primarily in areas of the brain that are related to higher-order functions, especially in the prefrontal cortex. As gray matter volume decreases, white matter increases because of continuing axon myelination. As a result, the relative proportion of white to gray matter rises during the teen years (Mills et al., 2016). As you know, myelination allows faster information processing. Axons transmit impulses up to 100 times faster after myelin- ation than before, and neurons with myelinated axons can fire up to 30 times more frequently (Giedd, 2015). The upshot is more efficient information processing. Myelin also “fine tunes” the timing of signals arriving at any single neuron from multiple parts of the brain. When multiple synapses are activated simultaneously, it is more likely that a neuron will fire and then activate other neurons, further up the line. Firing also strengthens the synapses with the activating neurons. This makes learning, the building or strengthening of associations, more likely. So, while some synapses are pruned, others are strengthening, and brain circuitry is reshaping in response to the environment. Overall then, white matter expansion means more learning and more complex circuitry within structures (e.g., within the prefrontal cortex) and between structures (e.g., between cortical and subcortical regions; Casey, 2015; Giedd, 2015). There are other important brain changes that are launched at puberty as well. For example, there are large shifts in the production of neurotransmitters and the enzymes that metabolize them. In particular, puberty initiates a slow decrease in serotonin lev- els and a rise in dopamine levels (Casey, 2015). Imbalance in Adolescent Brain Development Brain researchers are finding that adolescence is also a time of uneven brain FIGURE 9.2 A model of timing of development; that is, different regions mature at different rates. However, the functional maturation of the emotional complexity of the processes is so great that researchers do not always agree on and cognitive control systems of the what structures or functions are changing the most quickly, nor do they agree on brain. what the behavioral consequences might be (e.g., compare Shulman et al., 2016, to Romer, Reyna, & Satterthwaite, 2017). The bulk of evidence indicates that sub- cortical areas, such as the limbic system (amygdala, hippocampus, etc.) and the closely related nucleus accumbens, mature at a faster pace than other regions. Functional Development Emotional System These subcortical structures are important for what some call “hot” processes— emotional reactivity, attraction to peers, and the pleasures of risk and reward. The prefrontal cortex, the seat of “cool,” more rational processes, changes at a slower, steadier pace (see Figure 9.2). The prefrontal cortex is also important for Cognitive System emotional and social processing, but it plays a planning and control function, adding a contemplative element to emotional reactions, to social interaction, and to the evaluation of risk and reward (Giedd, 2015). There is a variety of evidence to support the notion of more rapid subcorti- Age cal maturation. For example, dopamine is a neurotransmitter that is important in Adolescence many brain areas, and it is critical for learning, processing emotions, and antici- SOURCE: Based on Casey, B. J., Getz, S., pating and experiencing reward. Studies of animals show that subcortical struc- & ­Galvan, A. (2008). The adolescent brain. ­Developmental Review, 28(1), 62-67. Used with tures like the ventral striatum (part of the nucleus accumbens) reach a peak of permission from Elsevier. responsiveness to dopamine (indicated by the density of dopamine receptors)  Physical, Cognitive, and Identity Development in Adolescence 347 by early adolescence. But the prefrontal cortex does not reach its peak responsiveness to dopamine until early adulthood (Casey, 2015). It is important to keep in mind that despite its more protracted development, the prefrontal cortex still makes substantial maturational progress during the teen years. Improvements in executive functions, in learning, and in logic can be remarkable (Juraska & Willing, 2017; see the next sec- tion on Cognitive Development). But the neural circuitry that connects the prefron- tal cortex to the subcortical, “emotional” brain is in flux and may not fully develop until the maturation of the two systems comes more into alignment. As a result, some researchers argue that sometimes a teen’s choices in emotionally and socially charged situations, especially those involving peers, risk, and/or reward, are driven more by subcortical structures, or “hot” processing, than by the “cool” regulatory processes of the prefrontal cortex (Casey, 2015; Cohen et al., 2016). In addition, you might recall from Chapter 4 that the “emotional” brain gov- erns both an avoidance system (avoiding harm) and an approach system (approach- ing pleasure). These two behavioral systems may not develop at the same pace. The avoidance system is led by the amygdala, which is an important driver of the stress response (see the next section). As you know, this system helps us to interpret stimuli as potentially dangerous and to react in ways that avoid punishment or pain. The approach system, which identifies potentially rewarding situations, is driven by the ventral striatum. Ernst (Ernst, Pine, & Hardin, 2006; Ernst, 2014) proposed a triadic model of neural development to explain increased sensation seeking and risk taking in the teen years. First, the regulatory prefrontal cortex is maturing more slowly than the subcortical structures, as we already described. But also, at the subcortical level, the approach system has a greater effect on teens’ behavior than the avoidance system does. Both systems are maturing, but either the amygdala is developing more slowly than the ventral striatum, or the circuitry that allows each of them to moderate the other’s responses is lagging. As you can see, imbalance in brain development might help explain why ado- lescents tend to score higher than other age groups on sensation seeking (Harden et al., 2017). Sensation seeking is defined as “the need for varied, novel, and complex sensation and experiences and the willingness to take on physical and social risk for the sake of these experiences” (Zuckerman, 1979, p. 10). If sensation seeking is reward- ing, and the emotional brain, especially the subcortical approach system, is maturing more rapidly than regulatory circuitry, then teens might literally anticipate and experi- ence more pleasure from risky behavior than other age groups do. They might also be less able to regulate their behavior in potentially rewarding situations (Casey, 2015). In Chapter 10, you will learn more details on how typical risk taking is for this age group, and how peers, gender, and other individual differences seem to affect it. The Adolescent Brain and Stress Before we take a closer look at teen behavior, let’s examine in more detail what hap- pens to the stress response and the hypothalamic-pituitary-adrenal (HPA) axis during adolescence. You’ll recall from Chapter 2 that when we perceive a stressor, the amyg- dala triggers a chain of reactions in the hypothalamus, the pituitary, and the adrenal glands. The adrenals release cortisol, which travels through the bloodstream to many organ systems, causing the body to ready itself for “fight or flight,” whatever it takes to avoid harm. Under ordinary conditions, cortisol circulates back to the amygdala and the hippocampus, and it binds with receptors there, ending the stress response so that the body can get back to equilibrium and normal functioning. The HPA axis matures in multiple ways during adolescence (Trotman et al., 2013). First, the basal rate of cortisol production increases, and it remains higher in adult- hood than it is in children. Second, the HPA axis grows more sensitive to stressors, secreting more stress-induced cortisol than it did during childhood. In other words, the stress system becomes more responsive, and it remains that way through young adulthood (Holtzman et al., 2013). One often-cited experiment illustrates this altered stress responsiveness. Stroud and colleagues (2009) assessed HPA axis and cardiac functions in children (ages 7 to 12) and adolescents (ages 13 to 17) who were exposed to either performance or social 348 Chapter 9 stressors. To induce performance stress, participants had to make a 5-minute speech, answer mental arithmetic questions, and copy a picture from its mirror image in front of a small audience. Social stress was induced with a social rejection interaction: Con- federates gradually excluded the participant during a conversation. Although the teens did not report feeling more distress than the younger children, they had stronger physiological reactions on all stress-related measures, including cortisol production. We have been describing typical changes to HPA responding during adolescence. Given how much reorganization the teen brain undergoes, you won’t be surprised to learn that severe, unpredictable, or chronic stress can have especially negative effects for this age group. For example, in one study, 16-year-olds who reported experiencing severe social adversity (e.g., violence or bullying) showed a blunting of their stress response by the time they were 19 years old (Laceulle, Nederhof, van Aken, & Ormel, 2017). Animal studies have also found that structures in the limbic system and the prefrontal cortex can show permanent stress-induced atrophy, hypertrophy, or other atypical changes as a result of severe stress during the adolescent period, affecting performance on a variety of behavioral measures (Eiland & Romeo, 2013; Holtzman et al., 2013). MyLab Education Self-Check 9.1. Behavioral and Emotional Changes 9.2 Explain behavioral and emotional changes in adolescence, including a discussion of mood, depression, and the emergence of adult sexuality, and identify factors that shape these changes as well as vulnerabilities that pose threats. The physical changes we have catalogued correspond with many types of behavioral change. You will be reading soon about cognitive developments and about the teen’s reconceptualization of self (identity development) as she experiences the physical transformation puberty initiates. In this section, we will focus on some of the spe- cific behavioral and emotional effects that have been identified, the vulnerabilities that emerge in adolescence, and the advent of adult sexuality. Sleeping—Or Not Puberty’s physiological changes affect Circadian rhythms and homeostasis. The timing of daily hormone release from endocrine glands is delayed, and that shifts the adoles- cent’s sleep-wake cycle to later times, as much as 1 to 4 hours later. Sleep homeostasis, the sleep regulating system, also changes, so that after puberty adolescents can resist sleep pressure (i.e., tolerate the need to sleep) more than before puberty (Hagenauer, Perryman, Lee, & Carskadon, 2009; Hummer & Lee, 2016; Tarokh, Saletin, & Carskadon, 2016). These biological changes mean that adolescents prefer to go to sleep later at night, and they prefer to sleep later in the morning than they did before puberty. This sleep pattern is called delayed phase preference. This preference, along with other adoles- cent experiences––increased autonomy to control bedtime, more time spent on home- work, commitments to extracurricular activities, late night opportunities to socialize via texting and other social media––conspire to make bedtimes later and later. But wake up times, at least during the school week, are usually quite early, and the result is that many teens are sleep deprived. The thing is, adolescents actually need a good deal of regular sleep, between 8 and 10 hours per night, according to the National Sleep Foundation (2017). In one longi- tudinal study, when teens were able to sleep as much as they wished up to 10 hours, they averaged 9.25 hours per night (Tarokh et al., 2016). On school days, most teens get considerably less sleep than they need. Most middle and high schools begin earlier  Physical, Cognitive, and Identity Development in Adolescence 349 than elementary schools, and because adolescents go to bed late, they simply miss out on adequate sleep. They not only are sleep deprived, but their sleep routines tend to vary a great deal. Unfortunately, both sleep deprivation and variability are problematic for the developing brain. “[S]leep itself may play an active role in sculpting the adolescent brain” (Tarokh et al., 2016, p. 184). For example, in one longitudinal study, research- ers asked boys and girls to complete daily sleep diaries for two weeks, once when they were approximately 14 years old and again one year later (Telzer, Goldenberg, Fuligni, Lieberman, & Gálvan, 2015). The participants recorded when they went to bed at night, when they woke up in the morning, and the total time they slept. A few months after the second diary was completed, the teens underwent an imaging pro- cedure called DTI, which can reveal the organization and structural integrity of white matter in the brain. The more variable the teens’ sleep time was at 14 years old, the less white matter integrity their scans showed a year and a half later. At any age, sleep deprivation is associated with poorer performance on execu- tive function tests, learning tasks, and emotion regulation measures (Bryant & Gomez, 2015; Tarokh et al., 2016; Telzer, Fuligni, Lieberman, & Gálvan, 2013). And of course, insufficient sleep makes it more likely that you will be sleepy when you need to be alert. In one well-controlled experiment, 13- to 17-year-olds were allowed to sleep only 6.5 hours per night for five nights. In a school-like context, they learned less, and their attention wandered more frequently, than controls whose sleep was not limited (Beebe, Rose, & Amin, 2010). So, what can we do to protect teens’ sleep in the modern world? One possibil- ity is to start school later in the morning, a solution recommended by the American Academy of Pediatrics (Adolescent Sleep Working Group, Committee on Adoles- cence, & Council on School Health, 2014). Shifting to later start times tends to increase teens’ sleep duration, and longer sleep is associated with better attendance, improved grades, feeling less unhappy, and less risk of driving accidents (Lewin et al., 2017; Minges & Redeker, 2016; Wahlstrom et al., 2014; Wahlstrom, Berger, & Widome, 2017). Even a 30-minute later start seems to improve things for adolescents (Owens, Belon, & Moss, 2010). Parents can also take steps to help their teens. Table 9.2 offers some practical rec- ommendations. One caution: Many people assume that sleep deprivation effects can be managed by “catching up” on weekends. But delaying wake time on weekends is associated with later daily release of melatonin (a sleep hormone) over the next week, making later sleep times even more likely (Bryant & Gómez, 2015). Sleep regularity is a more effective protection. Emotions and Mood You have seen that increased sensation seeking and reward sensitivity can be among the consequences of adolescent brain changes. There are other emotional changes as well. Recall the story of Rebecca at the beginning of this chapter. Part of what surprised her aunt was how moody Rebecca had become. Parents whose children have gone through puberty often warn parents of younger children to “Enjoy them while they’re TABLE 9.2 Teen Sleep Recommendations for Parents Set bedtimes for 10:00 p.m. or earlier. (If the schedule is regular, teens will fall asleep as easily as they do at later times.) Restrict technology use before bedtime and in the bedroom. Limit caffeine and energy drinks, especially in the evening. Keep sleep schedules consistent. Consider advocating for later school start times. SOURCE: Adapted from Bryant, N. B. & Gomez, R. L. (2015). The teen sleep loss epidemic: What can be done? Translational Issues in Psychological Science, 1, 116–125. 350 Chapter 9 young; you don’t know what you’re in for!” Parents of adolescents often assume that hormones are the underlying cause when their adolescents seem emotionally unpre- dictable, making comments such as “Her hormones are raging!” Given that hormones influence brain restructuring and changes in stress respond- ing in the teen years, this is a reasonable statement. But remember, any developmental outcome is usually the result of many contributing factors. Adolescents are adjust- ing to a host of profound changes that can and do affect their moods: new cultural expectations for mature behavior, more difficult academic tasks, the prospect of mak- ing critical life decisions, major changes in friendships and peer experiences, dramatic appearance changes, intensified sexual impulses, and so on. A pioneering study illustrates that teenagers tend to be moodier than other age groups. Larson and Richards (1994) used a technique called the experience sampling method (ESM) to gauge adolescents’ moods in natural settings. A sample of teens and their mothers and fathers wore pagers throughout their waking hours. When the pag- ers beeped, the participants made notes about what they were doing, thinking, and feeling at that moment. In the course of a day, adolescents reported more mood dis- ruptions, more feelings of self-consciousness and embarrassment, more extremes of emotion, and less overall happiness than the adults. In addition, their emotional reac- tions to the very same events tended to be more intense than those of their parents. Many experimental studies have demonstrated that adolescents are more respon- sive to emotional stimuli than younger or older groups are. For example, they show greater pupil dilation to emotion-related words and they tend to remember propor- tionally more emotion-related words in delayed recall tasks than younger children (Silk et al., 2009). Whereas adults show increased amygdala responses only to images of fearful faces, adolescents show greater amygdala activation to both fearful and neu- tral faces (Thomas et al., 2001). So, adolescents are often more emotionally reactive than children or adults. Regard- ing threats, you have seen that teens have a more intense stress response than younger children. Their responses to threats also can be qualitatively different from those of other age groups (Casey, 2015). For example, Pattwell and colleagues (2012) presented chil- dren (ages 5 to 11), adolescents (ages 12 to 17), and adults (ages 18 to 28) with colored squares (neutral stimuli) while blasting a loud, aversive noise (frightening stimulus). Participants of all ages quickly began to show a conditioned fear response to the col- ored squares, based on physiological measures. Participants then experienced several “extinction” trials: The colored squares were presented without the aversive stimulus. The fear response was extinguished for both children and adults, but the adolescents continued to react to the colored squares as though they were frightening. It appears that adolescents may have more difficulty than other age groups suppressing emotional responses to threatening cues when in fact those cues no longer pose a problem. Consider one more example of emotional difference in adolescence. Sebastian, Viding, Williams, and Blakemore (2010) manipulated girls’ social stress by asking them to play a 3-minute computer game called “cyberball.” The girls experienced either inclusion or ostracism as a function of being “thrown” the ball or ignored by two other players. Compared to adult studies using this manipulation, both young (ages 11 to 13) and mid (ages 14 to 15) adolescents reported greater negative mood, and younger girls also showed significant increases in distress. Even a short experi- ence of social stress markedly affected their moods. Such emotional developments are normal for adolescents. But exaggerated emo- tional responding can be a risk factor for the development of mental illness when com- bined with other potential risks (e.g., family dysfunction, childhood trauma, genetic susceptibility, and so on). As you have seen before, risk factors potentiate each other. The diagnosis of serious mental disorders rises dramatically in the teen years. The “intersection of stress and the developing adolescent brain may represent a ‘perfect storm’ in the context of dysfunctional emotional development” (Romeo, 2010, p. 249). First episodes of psychosis, including bipolar disorder and schizophrenia, often occur in the later teen years or soon afterward (Holtzman et al., 2013). Half of social anxiety disorder cases are first diagnosed by age 13, with 90% being diagnosed by age 23 (Kilford et al., 2016). Rates of clinical depression increase in adolescence as well.  Physical, Cognitive, and Identity Development in Adolescence 351 Depression in Adolescence Let’s take a closer look at the rise in depression during adolescence. Compared to much lower rates in childhood, about one third of teens experience depressed mood, defined as a subclinical level of depression, at any given time (Petersen, Compas, Brooks-Gunn, Ey, & Grant, 1993). Rates of clinical depression are also higher for teen- agers than for children. In fact, by mid-adolescence, clinical depression rates reach adult levels. As we have noted before, both depressed mood and clinical depression occur more often in females than in males, beginning in adolescence. Depending on the measurement techniques used, large studies report major depression rates for 12- to 19-year-olds ranging from 5% to 20%, with girls’ rates as much as triple that of boys (SAMHSA, 2017; Thapar, Collishaw, Pine, & Thapar, 2012). What accounts for the adolescent rise in depression rates? As with most behav- ioral outcomes, there appear to be multidimensional processes at work here. Physical changes brought on by puberty interact with other causal factors to affect adolescent emotions and behavior, especially mental health. We will examine these multidimensional factors by considering why girls are more susceptible to depression than boys. Sex differences in circulating hormones may directly contribute to sex differences in depression rates (Hamilton, Hamlat, Stange, Abramson, & Alloy, 2014). But most developmentalists argue that social stressors can play as great or a greater role in the mix of causes. Both boys and girls experience increased stress of various kinds after puberty. But on the whole, it may be that girls face more chal- lenges in early adolescence than boys do (Petersen, Sarigiani, & ­Kennedy, 1991). That is, girls must deal with more stressors simultaneously. In comparison to their male coun- terparts, females report experiencing more stressors from early adolescence onward (Compas, Howell, Phares, Williams, & Giunta, 1989; Wichstrom, 1999). Let’s start by looking at what happens when puberty is “off time,” especially when the onset is early. Going through puberty before one’s peers can create social and emotional problems, especially for girls (Galvao et al., 2014; Mendle, 2014). Even though early and late maturers are subject to the same hormonal influences once puberty begins, early maturers are more susceptible to depression, suicidal thoughts, panic attacks, substance use, and many other problems. The reasons must depend on factors other than hormones. For example, partly because most girls begin puberty before most boys, an espe- cially early-maturing girl is bigger than most of the other children her age. She is also heavier and so is more likely than other girls to be unhappy with her body in a cul- ture that prizes slimness (Wichstrøm & von Soest, 2016). Early sexual maturation (e.g., breast development) can also make her a target for teasing or innuendo from peers or even outright rejection by less mature girls (Hamilton et al., 2014). Parents of early-maturing girls often worry about their daughters being at risk for sexual experiences that they are not ready to handle, and they may limit their daughters’ independence in ways that are grating. Their concerns may not be exag- gerated. Behavior problems for early-maturing girls are more likely if the girls become involved with older boys, which is more probable with low levels of parental supervi- sion (Skoog & Stattin, 2014). Early-maturing girls are also more likely to be targets of sexual victimization and partner violence than other girls (Mendle, 2014). For early-maturing boys, the picture is less clear. Older studies indicate that early puberty might be helpful to boys, giving them an edge in socially approved activities such as athletics, or in romantic relationships, given that their pubertal timing may be more in line with that of typical girls. Late-maturing boys could be at a disadvan- tage in such activities. This is probably true in some cases, but newer, longitudinal studies often find that early-maturing boys have some of the same disadvantages as girls. Being different is a social liability and can lead to peer rejection. Early-maturing boys, like girls, show less social competence than their “on time” peers as they move through adolescence (Westling, Andrews, & Petersen, 2012). On the whole, it appears that for boys as well as girls, early puberty creates some risk of both internalizing and externalizing problems, although the list of negative consequences is longer for girls than for boys (Hamilton et al., 2014; Mendle, 2014). 352 Chapter 9 Box 9.1: The Limits of Guilt in Adolescence Steven Drizin, a defense attorney who works with juvenile clients, states were required to revisit such sentences delivered prior to provides the following case description: the 2012 ruling (Steinberg, 2017). In November 1999, a Michigan jury convicted thirteen In making these landmark decisions, the U.S. Supreme Court year old Nathaniel Abraham of second degree murder in took into account information that was presented by develop- the shooting death of Ronnie Greene, a crime committed mental scientists on adolescents’ cognitive functioning, on brain when Abraham was only eleven years old. Under Michigan development, on identity development, and on social interactive law, Judge Eugene Moore could have sentenced processes, like peer relations (Cohen & Casey, 2014; Steinberg, Nathaniel as a juvenile, as an adult, or given him a blended 2017). Such research has been brought to bear on two critical sentence that treated Nathaniel initially as a juvenile and questions. First, are teens as fully culpable as adults when com- then later as an adult if he failed to rehabilitate himself with mitting the same crimes? And second, are adolescents compe- services provided in the juvenile system. Judge Moore tent to participate in the adult justice system? gave the boy the break of his life, sentencing Abraham as a juvenile and sparing him a sentence of between 8 and Adolescent Culpability 25 years in prison. But the boy, who fidgeted and doodled Even when an individual is found guilty of a crime, her guilt can during the judge’s twenty-minute speech, didn’t appreci- be mitigated under the law. “Mitigation places the culpability of ate the judge’s generosity. Reportedly, he turned to his a guilty actor somewhere on a continuum of criminal culpability attorney after the judge had concluded, and asked, ‘What and, by extension, a continuum of punishment” (Steinberg & Scott, happened?’ (Drizin, 2003, p. 8) 2003, p. 1010). Mitigation does not mean excusing the crime. The Drizin suggests that Nathaniel’s response to his trial illus- perpetrator is held responsible, but she is considered less than fully trates an important reason for treating juvenile offenders dif- blameworthy. If by virtue of being an adolescent a guilty party’s ferently from adults: They are not necessarily fully capable of culpability were mitigated, then the punishments that would be understanding the proceedings of a trial, participating in their appropriate would be altered as well. Indeed, interventions aimed own defense, or of making the many decisions that are required at rehabilitation rather than punishment might be the wisest course. of an adult defendant. Steinberg and Scott (2003) indicate that there are roughly The first juvenile justice system was established in Illinois in three sources of mitigation in adult criminal law. The first is 1899. Within 25 years, in every part of the United States there were diminished capacity, which could be due to mental illness, two systems of justice for individuals charged with crimes, one for emotional distress, intellectual impairment, or “susceptibility to adults and the other for juveniles (usually defined as those under influence or domination” (p. 1011). The second, compelling the age of 18). The juvenile system emphasizes rehabilitation rather circumstances, occurs when an individual faces such pressure than punishment, and it reflects that focus even in the terminology that even an ordinary, reasonable person could be expected that is used: “petition instead of indictment, respondent instead of to give in, such as acting in the face of extreme need or under defendant, and disposition instead of sentencing” (Trivits & Repucci, threat of injury. The third source of mitigation is when the crime 2002, p. 694). The emphasis on rehabilitation is based on the belief represents uncharacteristic behavior on the part of the perpe- that juvenile offenders are immature, not fully formed, and so can trator, as in the case of a first offense or when the crime is “aber- be reshaped or reformed. Further, the state’s role is a parental one, rant in light of the defendant’s established character traits and to provide the right environment for future development. respect for the law’s values” (p. 1011). But by the 1990s, “a legislative tsunami was washing over Are teens as fully culpable as adults? Steinberg (2017; Schul- the United States” (Wilcox, 2003, p. 12). In one state after man & Steinberg, 2016; Steinberg & Scott, 2003) argues that another, laws were altered to allow juveniles, especially ado- if we look at the developmental evidence, adolescents should lescents, to be tried in adult criminal court, facing the same be considered less culpable on the basis of all three sources of penalties that adults would face. A sense that predatory teens mitigation. First, their cognitive and psychosocial development is with well-established and irremediable character flaws were vic- likely to affect their choices in ways not characteristic of adults. timizing citizens and getting off too lightly in the juvenile justice In essence, their decision making tends to be immature (or we system seemed to prevail. This “tough on crime” attitude over- could say impaired) in comparison to that of adults, suggesting whelmed the reasoning that had inspired a different approach to diminished capacity. Reasoning ability improves throughout ado- juveniles a century before. Yet an appreciation for that reasoning lescence into adulthood. By mid-adolescence, many youngsters has re-emerged, and is reflected in U.S. Supreme Court deci- do well on tests of formal logic if they are given hypothetical prob- sions in the early years of this century. The Court ruled in 2005 lems that have logical solutions under conditions of low emotional that sentences of capital punishment are unconstitutional for arousal (like the scientific problem solving described later in this any defendant under age 18. They later limited sentences of life chapter). But as you will see in Chapter 11, teens do not perform without parole. In 2010, these were deemed unconstitutional for as well as young adults on the more ambiguous problems of individuals under 18 for crimes other than homicide. In 2012, real life, especially when they are emotionally invested in an issue states were first enjoined from automatically sentencing juveniles (Blanchard-Fields, 1986). In addition, teens’ decisions in real-life to life sentences even when the crime was homicide; in 2016, situations may be influenced by their psychosocial immaturity and  Physical, Cognitive, and Identity Development in Adolescence 353 lack of experience. As you will see in Chapter 10, adolescents are Adolescent Competence to Stand Trial particularly susceptible to peer influence, they are high risk takers, The same characteristics that may mitigate adolescents’ culpa- and their self-control is not fully developed. Their capacity or ten- bility raise questions about their competence to be processed in dency to think about future consequences is beginning to develop, the system of justice designed for adults. In this system, a crimi- but is quite limited. Teens heavily weigh short-term gains in their nal defendant must be competent to stand trial, meaning that decision making and tend to discount long-term considerations she must be able to assist her counsel in preparing her defense, (e.g., Halpern-Felsher & Cauffman, 2001). When they are asked to understand the court proceedings well enough to participate, imagine themselves or their circumstances in the future, teens use and be capable of making decisions about her rights, like a much shorter time frame than adults do (e.g., Nurmi, 1991). whether or not to waive a jury trial or to accept a plea bargain. Adolescent characteristics that suggest diminished capac- Fortunately, a research consortium, the MacArthur Research ity from a legal standpoint appear to be linked to immature, and Network on Adolescent Development and Juvenile Justice, is changing, neurological processes. As this chapter makes clear, undertaking studies that are designed to assess the degree to the teen brain shows gradual maturing of precisely those regions which teens have these capabilities. In one study (reported in that affect long-term planning, judgment, decision making, regu- Grisso et al., 2003, and in Steinberg et al., 2003), 1,000 juveniles lation of emotion, impulse control, and the evaluation of risk and (ages 11 to 17) and 500 young adults (ages 18 to 24) partici- reward. Change in these areas continues throughout adoles- pated. Half of the participants were either in juvenile detention cence and into young adulthood. centers or adult jails, and the other half were drawn from the Not only could adolescents be considered less culpable community (and matched for socioeconomic status, ethnicity, than adults on the basis of diminished capacity, but also they are and so on). Each of them completed two measures. One was more vulnerable to compelling circumstances. As Steinberg and designed to assess competence to stand trial, including factors Scott (2003) argue, “ordinary adolescents may respond adversely such as “understanding” (e.g., comprehension of courtroom to external pressures that adults are able to resist” (p. 1014). For procedures) and “reasoning” (e.g., recognition of information many of the reasons already indicated, they may be more easily relevant to a legal defense). The other measure was designed to provoked to aggressive responses by perceived threats. Their identify the kinds of choices that might be characteristic of the emotional lability and intensity seem to make many situations different age groups with regard to legal decisions. Participants more stressful for adolescents than for adults. Also, their need heard stories about individuals charged with crimes and were for peer support and approval makes them especially susceptible asked to make decisions for them (e.g., about how to respond to to peer influence, whether in the form of direct pressure or as a police interrogation, whether to disclose information during con- result of the adolescent’s own concern for fitting in. sultation with an attorney, and how to respond to a plea agree- Finally, adolescents’ criminal actions may well qualify as ment that would involve a guilty plea and testifying against other uncharacteristic behaviors on the grounds that a teen’s character defendants). and identity is relatively unformed. Identity formation is a major The results support the conclusion that juveniles from ages developmental task in adolescence and can involve assessment 11 to 15 are significantly less competent than young adults to and reassessment of every aspect of the developing self, includ- stand trial, whereas 16- to 17-year-olds are not significantly ing the moral self. Teens who are immersed in this process often different from young adults. Substantially more young teens experiment with (or “try on”) behaviors that are potentially dan- showed impairments in understanding or reasoning about court- gerous, like drug use or antisocial acts, but for most adolescents related matters in comparison to young adults. Only age and this delinquent activity is relatively short-lived. It is referred to as intelligence were significant predictors of competence—gender, “adolescence limited” behavior (see Chapter 10). ethnicity, current status as an offender, and socioeconomic sta- One arena in which this adolescence limited behavior has tus were not important. been observed is the perpetration of sex offenses. Trivits and A similar pattern was obtained on the measures of decision Repucci (2002) examined recidivism rates across a wide range of making. Younger teens, ages 11 through 15, were significantly studies of adolescents and adults convicted of sex crimes, such more likely to make decisions based on what authorities dictated. as rape, child molesting, and exhibitionism. On the whole, ado- “Thus, compared with older adolescents and young adults, lescents’ recidivism rates over many years ranged from about 8% adolescents aged 15 and younger are more likely to recommend to 12% and were substantially lower than those of adult offend- confessing to the police rather than remaining silent and accept- ers, which ranged from about 20% to 40%. Other studies have ing a plea bargain offered by a prosecutor rather than going to reported similar differences in recidivism rates between adoles- trial” (Steinberg et al., 2003, p. 10). The researchers looked at cents and adults (e.g., Caldwell, 2010). what considerations were involved in making these decisions and As Trivits and Repucci point out, sexual offenses may tend found that, compared to older adolescents and adults, younger to have very different etiologies in adolescents as compared juveniles often failed to identify or to adequately evaluate risks or to adults, and patterns of sexual behaviors are likely to be less to take into account the long-range, as opposed to short-term, established among adolescents. Sexual misconduct in teens may consequences of their choices. often represent the kind of experimentation described earlier, In general, the results support Drizin’s (2003) judgment associated with the fact that the adolescent’s identity and char- that juvenile offenders, at least those under the age of 16, are acter is very much a “work in progress.” Adolescent sex offend- substantially less likely than adults to have the ability to function ers are also more likely than adults to respond well to treatment adequately in the adult justice system. (Harris, Walfield, Shields, & Letourneau, 2016). 354 Chapter 9 Other stressors, beyond the impact of early puberty, can contribute to sex differ- ences in depression rates. We will consider a few of the challenges that seem to espe- cially affect girls regardless of pubertal timing. First, by age 11, children are aware that the female gender role is less valued than the male role. They believe that there are greater restrictions on behavior for females and that there is gender-based discrimina- tion (Brown & Bigler, 2005). They recognize that females are seen as less competent than males, and that traditional female occupations are less prestigious than male occupations (Ruble, Martin, & Berenbaum, 2006). As they integrate these beliefs into MyLab Education their self-concept, girls may begin to feel less worthwhile than boys, or at least less Video Example 9.1 appreciated. Second, although both boys and girls are concerned about body image 16-year-old Josh describes his expe- (their concept of, and attitude toward, their physical appearance), girls worry more riences entering high school as an than boys about appearance and weight after puberty (Dion et al., 2015). And, adoles- early-maturing freshman boy who cents’ dissatisfaction with their bodies is predictive of declining self-esteem and stands inches taller and speaks with depressive symptoms (Solomon-Krakus et al., 2017). a deeper voice than many of his We should note, as we did in Chapter 7, that ethnicity moderates body satisfac- friends. tion. For example, African American youth are more likely to report positive body images than White youth. Body ideals among African Americans are more consistent with actual body characteristics, which serves as a protective factor for adolescents (Paxton, Eisenberg, & Neumark-Sztainer, 2006). For other ethnic groups, especially for girls, thinness as a body ideal is well established by early adolescence (Carey, Dono- hue, & Broderick, 2014). As Harter (2006) points out, such “images of female attractive- ness are very punishing in that they are unattainable by the vast majority of girls and women in the culture” (p. 556). Third, girls historically have more often had lower expectations of success than boys (Ruble, Gruelich, Pomerantz, & Gochberg, 1993). Despite much cultural change, lingering inequalities may still affect girls’ beliefs about their future possibilities as they navigate adolescence. Fourth, girls may be more stressed by the burgeoning of their sexuality and their sexual desirability. The traditional double standard, by which female sexual behavior is judged more harshly than male sexual behavior, has clearly diminished over the last half century, as the rates and acceptability of premarital sex have increased among teens of both sexes. Yet, in the United States there is still a tendency for girls who have engaged in sex between ages 11 and 16 to experience increased peer rejection over time, whereas the opposite is true for boys (Kraeger, Staff, Gauthier, Lekowtiz, & Feinberg, 2016). Girls and young women who have had multiple sexual partners are still considered to be more immoral than boys and young men who have (Crawford, 2003; Jones, 2016). Thus, even though girls’ acceptance of and experience with sexual- ity is increasing rapidly, they are still more subject to ambiguous messages about the acceptability of sex and seem to be more uncertain about what is appropriate for them in a world of shifting values (Collins & Steinberg, 2006). In addition, the physical and social consequences of sexual activity are greater for girls. They are still the ones who get pregnant. Fifth, after puberty, girls and boys start interacting more in mixed-sex groups and in heterosexual dyads. In these contexts, the differences in their discourse styles may create more stress for girls. You’ll recall from Chapter 8 that girls tend to acquire a more cooperative discourse style and boys a more domineering style during child- hood. One result is that when adolescent girls socialize with boys, they are less likely to influence the outcome of a discussion (Maccoby, 1990). Also, boys do not offer as much support to their conversation partners as girls do (Davies, 2003). Sixth, early adolescent romantic involvement is also linked to depression, espe- cially for girls. Sexual debut refers to age of first intercourse, and in the United States an early debut is usually defined as before age 15. For girls (but not boys) who expe- rience an early debut, depression tends to increase over time, and self-esteem tends to decrease (Golden, Furman, & Collibee, 2016). In early adolescence, especially for girls, even typical romantic behaviors, such as flirting and kissing, are associated with increased depressive symptoms (Steinberg & Davila, 2008). Why this is so is not yet understood. Girls tend to report more feelings of guilt and shame than boys do (Golden et al., 2016), so issues such as a lingering double standard and low levels of  Physical, Cognitive, and Identity Development in Adolescence 355 support from male partners may certainly be important (Davila, 2008). (We discuss sexuality and sexual debut more fully later in this chapter.) Seventh, because puberty comes earlier for girls, they are more likely than boys to simultaneously face both the changes of puberty and the difficult transition to second- ary school (i.e., junior high or middle school; Petersen, Kennedy, & Sullivan, 1991; see Chapter 10 for a discussion of this transition). Girls may be more subject to depression than boys not only because they face more challenges but also because they often adopt a coping style, rumination, that increases the risk of depression (Hilt, Armstrong, & Essex, 2017; Nolen-Hoeksema, 2012). Rumination may be defined as a stable, emotion-focused coping style that involves responding to problems by directing attention internally toward negative feelings and thoughts. Ruminating about problems includes both cognitive (self-focused cogni- tions) and affective (increased emotional reactivity) elements. Ruminative strategies may include isolating oneself to dwell on a problem, writing in a diary about how sad one feels, or talking repetitively about a negative experience with the purpose of gain- ing increased personal insight. In general, however, ruminative focusing on problems while in a depressed mood may actually make the depression worse. This type of heightened focus on negative feelings and issues increases the dura- tion and intensity of depressive episodes, particularly in adolescent and adult females, who are much more likely to exhibit this style of coping than are males (Butler & Nolen-Hoeksema, 1994; Hilt et al., 2017). Adolescents and adults who ruminate are more likely to experience depression. There are other coping styles that seem to help minimize depression, or at least do not exacerbate it. These include, for example, distraction, which involves divert- ing attention away from a problem towards more positive thoughts or actions. Males appear to be more likely to use such approaches than females (Broderick & Korteland, 2004; Nolen-Hoeksema, 1987). However, gender role also influences how children and early adolescents cope with problems. A ruminative coping style is most pronounced among girls and some boys whose gender roles are stereotypically feminine. These individuals identify themselves as relatively passive and nondominant, and they are less likely to cope by using active problem solving or distraction. Having a rumina- tive coping style, or being uncomfortable with or incapable of psychological distrac- tion, may be a particularly heavy burden for feminine-identified boys, for whom such behavior is clearly contrary to the peer group’s expectations for appropriate masculine behavior (Broderick & Korteland, 2004). The Emergence of Sexuality and Sexual Preference Sexual pleasure is a part of human functioning even in early childhood. Preschoolers and school-aged children may fondle their own genitals for the pleasure of it, and many engage in sex play with others. “Playing doctor,” for example, has been known to involve disrobing or fondling the genitals of other children. On average, children begin to show sexual attraction at adrenarche, when the adrenal glands increase their activity just before puberty, at about age 10 (Diamond, Bonner, & Dickenson, 2015). However, the strength and urgency of the adult sex drive, emerging as a function of puberty, is a new experience to young adolescents. They are more sensitive to, and interested in, sexually relevant stimuli than younger children. Despite having spent most of childhood spontaneously segregating into single-gender groups, young ado- lescents begin to seek out opportunities to socialize in mixed-gender groups (Maccoby, 1998; Rubin, Bukowski, & Bowker, 2015). Faced with their increased sexual interest, most adolescents begin to explore their sexuality. The earliest and most common activity throughout adolescence is sexual fanta- sizing, and the next step tends to be masturbation. It is reported more by boys than by girls, but this seems to be more socially and culturally determined than driven by any differences in sexual desire (Diamond et al., 2015; Fortenberry, 2013). Girls with more education about how their bodies function are more likely to engage in mas- turbation (Bancroft, Herbenick, & Reynolds, 2003) as are girls living in countries with greater gender equality (Peterson & Muehlenhard, 2007). Although some religions 356 Chapter 9 and cultures frown on masturbation, and adolescents often report feeling guilty or ashamed about masturbating, it actually seems to be associated with some valuable health outcomes. It benefits the development of sexual self-awareness and as a result, more satisfying partner relationships. It also provides youth with an option for sexual release that doesn’t carry the health risks of pregnancy and sexually transmitted diseases (STDs) (Diamond et al., 2015). Partnered sex tends to begin with kissing and fondling (making out) and for some, moves on to oral-genital contact, which is more often received by boys than by girls (Chandra, Mosher, Copen, & Sionean, 2011). Participation in oral-genital sex is increas- ing in frequency, but little is really known yet about how typical it is for teens, or what effects such practices might have on them (Fortenberry, 2013). Some young people see it as a way of maintaining their virginity or as safer than intercourse. Unfortunately, when teens define activities other than intercourse as not really “counting” as sex, they seem to be less likely to use condoms or other protection. That may be why adolescents who take a virginity pledge have STD rates as high as those who do not take a pledge (Bruckner & Bearman, 2005). Another problem may be that if males are more often recipients of oral-genital stimulation than females, kids of both genders may begin to see girls more as givers than as receivers of sexual pleasure (Diamond et al., 2015). The most often researched sexual activity is coitus, which is defined as penile- vaginal intercourse. Data on sexual debut usually refers to first coitus. This aspect of adolescent sexual behavior is important, of course, because of the implications it has both for social adjustment and for health. Around the world, sexual debut is most likely to occur between the ages of 12 and 24, and for most young people by age 20 (Diamond et al., 2015). In the United States, “debut is considered ‘early’ if it occurs prior to age 15, ‘normative’ if it occurs between 15 and 19 years of age, and ‘late’ if it occurs after 19 years of age” (Golden et al., 2016, p. 1). Table 9.3 indicates gender, eth- nic, and grade differences among U.S. high school students reporting ever having had intercourse in a large, 2015 survey Similar annual surveys indicate that percentages have steadily declined for all gender and ethnic groups since 1991, perhaps in part MyLab Education because of increases in other types of sexual behavior (Kann, McManus et al., 2016). Video Example 9.2 Sexual maturation is a key determiner of sexual behavior, but many other factors Josh says there’s no peer pressure come into play. Adolescents are often moved to engage in sexual behavior out of curi- to have a girlfriend, but he also says osity or because of their peer culture (Collins & Steinberg, 2006). Peers can affect teens’ that some classmates brag or lie sexual behavior in many ways. One large meta-analysis of peer influence studies about having a sexual relationship. showed that adolescents are more likely to have sex if their peers are sexually active, if On this topic, consider the range of their peers approve of having sex, or if their peers pressure them to be sexually active perspectives among adolescents. (van de Bongardt, Reitz, Sandfort, & Dkovic, 2015). Table 9.3 Percentage of U.S. High School Students by Gender, Race, and Grade Endorsing “Ever Had Intercourse” BOYS GIRLS Ethnicity/Race White 39.5 40.3 Black 58.8 37.4 Hispanic 45.1 39.8 Grade   9 27.3 20.7 10 37.9 33.5 11 51.2 48.2 12 59.0 57.2 SOURCE: Kann, L., McManus, T., Harris, W. A., Shanklin, S. L., Flint, K. H., Hawkins, J.... Zaza, S. (2016). Youth risk behavior surveillance—United States, 2015. MMWR Surveillance Summaries, 65(SS06), 1–174.  Physical, Cognitive, and Identity Development in Adolescence 357 Myriad other influences—from social class and ethnicity to religious background, geographic setting (urban versus rural), popular culture (as portrayed in movies, music, teen magazines, and Internet sites), the quality of sex education in schools, and personality factors—play a part in when and whether adolescents become sexually active (Baams, Overbeek, Dubas, & van Aken, 2014; Collins & Steinberg, 2006; Mad­ kour et al, 2014). Clearly, sexuality is a normative part of adolescent development, but early sexual debut is associated with more negative outcomes. Pregnancies and STDs are more likely with early debut than with normative or late debuts, and so is depres- sion, especially in girls. The causal relationship between early debut and depres- sion seems to be bidirectional. That is, early debut predicts the onset of depression, and depression in young adolescents increases the likelihood of early debut (Davila, Capaldi, & La Greca, 2015). Sexual Orientation A central feature of sexual development in adolescence is the emergence of sexual orientation, referring to a preference for sexual partners of the opposite sex (heterosexuality), the same sex (homosexuality; “gay” males and “lesbian” females) or both (bisexuality). Researchers often refer to individuals who identify as either homosexual or bisexual as nonheterosexual. Most adolescents eventually identify themselves as heterosexual. For example, in a recent Youth Risk Behavior Surveillance (YRBS) survey of high school students across the United States, approximately 89% identified as heterosexual. Girls were more likely to identify as bisexual (9.8%) than lesbian (2%), which is a pattern that is also typical of large adult samples. Boys were about evenly divided between identifying as bisexual (2.4%) or as gay (2%), whereas by adulthood, males are more likely to be exclusively homosexual than bisexual. The survey also inquired about type of sexual contact in which youth engaged. Most stu- dents reported only heterosexual contact (median = 48%). A smaller proportion (1.7%) reported sexual activity only with same-sex partners, 4.6% reported bisexual contact, and 45.7% reported no sexual contact (Kann, Olsen et al., 2016). Young adolescents are especially likely to have some sexual contact with members of the same sex, primarily displaying and touching genitals, and engaging in mutual masturbation. These activities seem to be partly a function of opportunity, because young adolescents still spend more of their time with same-sex than opposite-sex peers. For most youngsters, these sexual contacts are not indicators of a homosexual orientation (Diamond et al., 2015). For example, in one large longitudinal study, only 1 in 5 girls and fewer than 1 in 25 boys who reported same-sex contact during their teens actually identified as nonheterosexual by the time they were in their 20s (Savin- Williams & Ream, 2007). Adolescence is a time of exploration and sensation seeking when it comes to many kinds of behavior, including sexual behavior. For some, more often for girls, adolescence and young adulthood is also a time of sexual fluidity, meaning change in sexual interest in same-sex versus opposite-sex partners. In one longitudinal study, females who identified initially as nonheterosex- ual were interviewed repeatedly from age 16 to 23. Many participants changed their reported sexual identity to “adjacent” categories, such as from bisexual to heterosex- ual, or from lesbian to bisexual (Diamond, 2008). If heterosexuality is by far the most typical pattern for adolescents and adults, and one that clearly benefits the survival of the species, what causes homosexuality or bisexuality? Available theories that postulate social causes have no empirical sup- port. The most famous of these is Freud’s account (e.g., Freud, 1935/1960). As you will recall from Chapter 8, Freud proposed in his psychoanalytic theory that 3- to 5-year- olds compete with the same-sex parent for the attentions of the opposite-sex parent. To avoid the punitive consequences of such competition, Freud believed that boys even- tually identify with their fathers and girls with their mothers, imitating the behaviors and internalizing the values of that parent. According to Freud, this identification pro- cess explains why most children eventually adopt a heterosexual orientation. It is just one more way in which the child becomes like the same-sex parent. Homosexuality or bisexuality results when something goes wrong with the identification process: The 358 Chapter 9 process cannot unfold in the usual way because there is only one parent in the home, the same-sex parent is too weak or shows little interest in the child, or the opposite-sex parent lacks sufficient warmth to be attractive or is too dominant. Freud’s theory of identification is not supported by the evidence. Adults who are homosexual or bisexual are not more likely than heterosexuals to come from one- parent homes or to have weak fathers or dominant mothers. Even modeling by parents does not seem to affect children’s sexual preference. Children raised by homosexual partners (lesbian or gay couples) are no more likely to become homosexual themselves than children raised by heterosexuals (Miller, Kors, & Macfie, 2017; Patterson, 2017). Other theories that pose social causes are also unsupported. One view, for exam- ple, is that homosexuality is “socially contagious,” that is, when it is encouraged by removing legal or moral restrictions or by sexual recruiters (enticements by others), nonheterosexuality spreads. Although tolerance does increase the open expression of homosexuality, there is currently no scientific evidence that rates of heterosexuality and nonheterosexuality differ across cultures or religious groups (Bailey et al., 2016). There is better evidence for nonsocial influences on sexual orientation. One well- supported finding is that nonheterosexual adults are likely to have been gender non- conformists in childhood, showing a strong and persistent tendency to behave like the other sex, such as in playmate or toy preferences (Karson, Kung, & Hines, 2017). Both retrospective interview studies and longitudinal studies following individuals from childhood to adulthood have demonstrated this behavioral thread, although there are, of course, many exceptions. Children often show signs of gender nonconformity by age 2, and it usually does not seem to be a function of parents or others pushing the child to act in gender atypical ways. This suggests that there are often differences among children that emerge early in development and are precursors of heterosexual and nonheterosexual attraction later. Such findings suggest that biological causes are at work, causes that are likely to result from the coaction of genes and early (perhaps prenatal) environment. There is good evidence for genetic influence. If one identical twin is nonheterosexual, there is a significantly greater chance that the other twin will be nonheterosexual (a higher concordance rate) than we find between less closely related family members, includ- ing fraternal twins (Chaladze, 2016). The same is true for males and females, although the concordance rates appear to be lower for female twins (Burri, Spector, & Rahman, 2015). Sexual orientation researchers have identified some candidate genes, but there is still much to learn about which genes are important and how they might influence sexual orientation (e.g., Sanders et al., 2015). Prenatal hormones appear to play an organizing role. You will recall that male fetuses produce androgens in large quanti- ties while female fetuses usually do not. Androgens, especially testosterone, mascu- linize the developing reproductive systems and brains of mammals. And exposure to androgens, especially testosterone, during prenatal development has been linked to the development of sexual orientation. There are several lines of evi