1. 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.

2. 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.

3. 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.

4. 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.

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

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. … 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.

17. … 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. 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.

23. 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.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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.

30. 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.

31. 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.

32. 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.

33. 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.

34. 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.