Adolescence and Emerging Adulthood: A Cultural Approach Chapter 2 Biological Foundations Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Chapter Overview Hormonal Changes Physical Changes Primary Sex Characteristics Secondary Sex Characteristics Cultural, Social, Psychological Responses to Puberty Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Puberty derived from the Latin word ‘pubescere’ which means to “grow hairy” The body undergoes a biological revolution that dramatically changes the adolescent’s anatomy, physiology, and physical appearance Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

The Endocrine System Hormonal changes begin here Fat cells produce leptin that provides the signal to the hypothalamus Gradually increases production of gonadotropin-releasing hormone (GnRH) Recent evidence indicates that this occurs once a threshold level of body fat is reached Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Pituitary Gland and Gonadotropins Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Sex Hormones Compare the differences in hormone production between boys and girls during puberty Testosterone Estradiol Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Endocrine System Feedback Loop Monitor levels of androgens and estrogens in the bloodstream Responds to the reduction in GnRH by reducing production of FSH, LH and ACTH Respond to lower levels of FSH and LH by reducing the amount of sex hormones produced “SET POINT” – when sex hormones reach an optimal level and the hypothalamus reduces GnRH to begin this process Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Physical Growth during Puberty Notice the differential timing in when growth spurts begin Notice when the difference in final height is achieved Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Extremities are the first to hit the growth spurt Growth Spurts Not all parts of the body grow at the same pace Asynchronicity in growth explains the “gangly look” in early adolescence Extremities are the first to hit the growth spurt Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Muscle Mass and Body Fat During puberty body fat increases more for girls than for boys Notice prior to puberty boys and girls are very similar in muscle mass Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Cultural Expectations In many cultures gender differences exist for physical activity Girls are sometimes discouraged from participating in sports (not confirming to “feminine” stereotypes) Boys are more likely to exercise in adolescence This gender difference contributes to differences in athletic performance between adolescent boys and girls Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Is This True? Grip Strength in men peak in emerging adulthood Reaction time is slower in emerging adulthood. Is this true? Is this true? Grip Strength in men peak in emerging adulthood Yes … and followed by a steady decline Reaction time is actually faster in the early twenties than at any other time of life Cardiac output peaks at 18 years of age Is this true? Cardiac output, the quantity of blood flow from the heart, peaks at age 25 Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Physical Functioning in Emerging Adulthood Emerging adulthood is the period of the life span with the least susceptibility to physical illness … but that’s not the whole story Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Physical Functioning in Emerging Adulthood Lifestyles of many emerging adults often include a variety of factors that undermine health such as Poor nutrition Lack of sleep Stress of juggling school/work/multiple jobs Automobile accidents are the leading cause of death among emerging adults in the United States Homicide is another common cause of death in the U.S. during emerging adulthood Rates of contracting sexually transmitted diseases, including HIV are highest in the early twenties Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Primary Sex Characteristics Secondary Sex Characteristics Boys Production of sperm Development of sex organs Hair growth in pubic areas, underneath arms, chests, face, shoulders and back Skin becomes rougher Sweat glands increase production Girls Production of eggs Hair growth in public areas, underneath arms and a slight amount of facial hair Slight enlargement of breasts known as breast buds Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

… the facts about females Women are born with about 400,000 immature eggs (follicles) in each ovary Once a girl reaches her first menstrual period (menarche) one follicle develops into a mature egg (ovum) about every 28 days Females release about 400 eggs over the course of their reproductive lives Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

… the truth about men Males have no sperm in their testes when they are born and do not produce any until they reach puberty The average age that sperm production begins (spermarche) is approximately 12 years old Boys produce sperm in astonishing quantities – there are between 30 and 500 million sperm in the typical male ejaculation, which means they produce millions of sperm everyday Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

The Order of Pubertal Events 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 Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Pubertal Caveat Virtually all the studies considered in the order of pubertal development have been conducted with White adolescents in the West Three studies demonstrate the variations that may exist in other groups Worthman, 1987 Lee, Chang, and Chan, 1963 Herman-Giddens et al., 1997; 2001 Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Kikuyu culture in Kenya (Worthman, 1987) Boys show the first physical changes of puberty before their female peer a reversal of the Western pattern African American Girls (Herman-Giddens et al., 1997; 2001) Many Black girls were found to begin developing breast buds and pubic hair considerably earlier than White girls Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Chinese Girls (Lee, Chang, and Chan, 1963) Pubic hair began to develop in most girls about 2 years after the development of breast buds and only a few months before menarche In sharp contrast to the Western studies that found pubic hair and breast buds developed together about 2 years before menarche These three studies show the importance of investigating ethnic differences in the rates, timing, and order of pubertal events Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Culture and Pubertal Timing The secular trend downward in the age of menarche has occurred in every Western country for which records exist Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

How do your answers compare to the following slide? Discussion Stop Why is the secular trend for the age of menarche going down in Western countries? How do your answers compare to the following slide? Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Downward Secular Trend of Menarche Puberty begins earlier in cultures where good nutrition and medical care are widely available Illness and thinness tend to inhibit the development of body fat resulting in delayed puberty Advances in food production have enhanced nutrition and therefore puberty has come sooner Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Cultural Responses to Puberty: Rituals Traditional Cultures 79% of cultures had puberty rituals for girls Menarche is the pubertal event that is most often marked by ritual Cultural views are mixed as to whether menstrual blood is an omen or a positive sign of fertility 68% of cultures had puberty rituals for boys Typically rituals require the young man to display courage, strength and endurance The rituals are often violent, requiring boys to submit to and sometimes engage in bloodletting of various kinds NOTE: Globalization has been credited with the decline in frequency of these rituals Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

How do parent-adolescent relations change at puberty? Conflict increases Closeness decreases Parents and adolescents seem less comfortable in each other’s presence Distancing hypothesis: it may be adaptive for young people to move away from closeness to their parents once they reach sexual maturity so that they mate and reproduce with persons outside the family, thus avoiding the genetic problems that often result from incest Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Frequency of Adolescent-Mother Touching and Talking Research based on 122 pairs of mother and children aged 6 to 16 Mothers and early adolescents talked more than mothers and younger children, suggesting that parent-child communication styles shift toward talking and away from touching when puberty is reached Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Early Maturation - Girls The effects of early maturation are especially negative for girls Early maturing girls are at risk for a variety of problems: Depressed mood Negative body image Eating disorders Substance use Delinquency School problems Conflicts with parents Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Late Maturation - Girls Late maturing girls have few of the problems that early-maturing girls have Although they can suffer from: Teasing Negative body image (during the years when other girls have begun to develop) However, by their late teens they tend to have a more favourable body image than other girls They are more likely to end up with the lean body build that tends to be regarded as attractive in Western majority cultures. Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Early Maturation - Boys The effects of early maturation tend to be positive for boys Early maturing boys have: More favorable body image Higher popularity Although not everything is favorable. They tend to be involved in: Substance use Delinquency Sex Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

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 Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Genotype-Environment Interactions A person’s inherited genes According to the theory Both genotype and environment make essential contributions to human development Genotype-environment interactions take three forms: Passive Evocative Active Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Genotype-Environment Interactions Description Passive Occur in biological families when parents provide both genes and environment Evocative Occur when a person’s inherited characteristics evoke responses from others in their environment Active Occur when people seek out environments that correspond to their genotypic characteristics Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.

Unravelling genotype-environment interactions Adoption studies These studies avoid the problem of passive genotype-environment effects because one set of parents provided the adolescent’s genes but a different set of parent provided the environment Adolescence and Emerging Adulthood: A Cultural Approach by Jeffrey Jensen Arnett. Copyright © 2004 by Pearson Education. All rights reserved.