Biological Foundations in Adolescent Development Physical and Hormonal Changes Cultural & Psychological Responses to Puberty Neural Changes

Physical changes Puberty – onset of sexual maturation Three neuroendocrine changes: Gonadal Adrenal androgens Growth

Gonadal and adrenal androgen axes

Gonadal (HPG) axis Gonadotropin releasing hormone (LH, FSH are gonadotropins) (testes or ovaries) (sex hormones – testosterone & estradiol increase dramatically -- gonadarche) (see next slide)

Sex Characteristics (examples) Primary Sex Characteristics Secondary Sex Characteristics Production of sperm (spermarche) or development of eggs Development of sex organs Pubic and axillary hair growth Skin becomes rougher & oily Voice deepens Slight enlargement of breasts known as breast buds (also, in ¼ of boys)

Adrenal androgen (HPA) axis (ACTH = adrenocorticotropic hormone) (e.g., testosterone) (leading to secondary changes)

Growth spurts and height changes Notice the differential timing in when growth spurts begin Notice when the difference in final height is achieved

Body composition changes During puberty body fat increases more for girls than for boys Notice prior to puberty boys and girls are very similar in muscle mass Given that girls naturally develop a lower muscle-to-fat ratio than boys during puberty, why would any culture create physical ideals that demand thinness in females once they reach puberty? AND what are the health implications?

The Order of Pubertal Events (see Table 2.2) GIRLS BOYS Growth of sexual and reproductive organs Secretion of increased skin oil and sweat Growth spurt Downy pubic hair Development of underarm hair Appearance of breast buds Menarche Increased growth of penis Secretion of increased skin oil and sweat Growth of testes Growth spurt Deepening of the voice Development of facial hair Appearance of pubic hair

Pubertal Caveat Virtually all the studies considered in the order of pubertal development have been conducted with White adolescents in the West Variations may exist in other groups (see p. 45; e.g., Kikuyu culture in Kenya, Chinese girls, African-American girls and boys)

Earlier Puberty Tanner Stage 2 (breast and pubic hair dev’t) by age 10 in the majority of girls (68% in Euro-American girls; 95% in African-American girls) The downward trend in the age of menarche has occurred in every Western country for which records exist. Why?

Responses to Puberty Homework assignment Next section: Cultural & Psychological responses to puberty

Cultural Responses to Puberty: Rituals in Traditional Cultures 79% of cultures had puberty rituals for girls __________ (?) is the pubertal event that is most often marked by ritual Cultural views are mixed as to the reaction to menstruation (see “Historical Focus” box in chapter) 68% of cultures had puberty rituals for boys (e.g., vision quest ) (“Roots” video) Typically rituals require the young man to display courage, strength and endurance (often violent) NOTE: Globalization has been credited with the decline in frequency of these rituals

Personal responses to puberty Behavior and emotions Problem behavior (e.g., aggression, conduct disorder symptoms, etc.) has been attributed to hormonal changes (but also to physical maturation and brain changes) Testosterone (T) can lower boys’ frustration tolerance  readiness to engage in aggression Rapid hormonal changes are associated with depression, but “hormonal storm” view is far too simplistic. In fact… Hormonal levels account for only a tiny percentage of the variance in adolescents’ negative affect – social influences account for considerably more

Pubertal timing and adjustment There is a lot of research (which is conflicting) on the effects of timing of physical development Theoretically, being “off-time” creates more stress and vulnerability to adjustment problems

Maturation - Girls According to Arnett, the effects of early maturation are especially negative for girls, who are at risk for a variety of problems: Depressed mood, Negative body image, Eating disorders Delinquency, Substance use, School problems, Conflicts with parents Caveat: Early-maturing girls with no history of behavior problems experienced fewer problems than did girls with a history of behavior problems who matured on time Late maturing girls have few of the problems that early-maturing girls have

Early Maturation - Boys The effects of early maturation are more mixed for boys Early maturing boys have: More favorable body image Higher popularity Earlier involvement in substance use, delinquency, and sex

Late Maturation – Boys Late maturing boys show evidence of problems Compared with boys who mature “on time” late maturing boys have higher rates of: Alcohol use Delinquency Lower grades in school

Neural changes New research in cognitive and affective neuroscience (Intro to “The Teenage Brain” PBS-DVD & Sci American podcast on the teen brain) Brain actively reorganizes itself – cells and connections are pruned (for efficiency) Prefrontal cortex (planning and decision making) undergoes a growth spurt in early A and continues to develop throughout A Cortical-limbic pathways (thought-emotion connections) are slowly developing during adolescence (e.g., research on teens’ difficulty in reading emotions in people’s faces) Implications? Research example -- incarcerated adolescents displayed more impulsivity and poorer critical thinking than age-matched students (Chretien & Persinger, 2000). Driving and multitasking Much more research needed