1. Adolescence 9th edition
Insert Photo from DAL
Chapter One:
Biological Transitions
By Laurence Steinberg, Ph.D.

2. Chapter 1 Overview What is puberty?
What is the endocrine system?
What triggers puberty?
What are the physical changes of puberty?
Variations in the timing and tempo of puberty
What is the psychosocial impact of puberty?
Early vs. late maturation
Eating disorders
Physical health in adolescence

3. Puberty: An Introduction
From Latin word pubertas (adult)
Period of lifespan in which an individual becomes capable of sexual reproduction
Hormones regulated by the endocrine system lead to physical changes
No new hormones are produced and no new bodily systems develop at puberty

4. The Endocrine System
Produces, circulates, and regulates hormone levels in the body
Hormones
Substances secreted by endocrine glands
Glands
Organs that stimulate particular parts of the body to respond in specific ways
Feedback loop (HPG axis)
Set point (Example: thermostat)

5. The Endocrine System: HPG Feedback Loop
HPG Axis:
Hypothalamus
Pituitary gland (master gland)
Gonads (testes and ovaries)
Gonads release sex hormones into bloodstream
Androgens and estrogens

6. What Triggers Puberty?
Although no new hormones in adolescence, something signals the HPG axis to kick on
Presence of mature sexual partners
Nutritional resources
Physically mature enough to begin reproducing
Leptin may be the most important signal
Protein produced by fat cells
Must accumulate enough body fat (~11%)
Rising levels of leptin signal hypothalamus to stop inhibiting puberty (at least in females)
Adrenarche
Maturation of adrenal glands leads to physical (somatic) changes
Not entirely certain but increasing evidence that rising levels of a protein produced by fat cells, leptin, may be the most important signal
(Susman & Rogol, 2004). Page 26

7. What Role Do Hormones Play?
Organizing Role
Prenatal hormones “program” the brain to be masculine or feminine (like setting an alarm clock)
Patterns of behavior as a result of this organization may not appear until adolescence (Ex: sex differences in aggression)
Activating Role
Increase in certain hormones at puberty activates physical changes (Ex: secondary sex characteristics)
Note: There are also changes due to an interaction between the organizational effects of hormones and the activational effects of hormones.
Page 26

8. Puberty is Affected by Context
Timing of physical changes in adolescence varies by
Regions of the world
Socioeconomic class
Ethnic group
Historical era
Example: Menarche (first menstruation)
U.S. average 12 to 13 years
Lumi (New Guinea) average > 18 years
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9. What Are The 3 Major Physical Changes of Puberty?
Adolescent growth spurt
Development of primary sex characteristics (gonads)
Development of secondary sex characteristics (breasts, pubic hair)

10. Physical Changes of Puberty: Adolescent Growth Spurt
Rapid acceleration in growth (height and weight)
Simultaneous release of growth hormones, thyroid hormones, and androgens
Peak Height Velocity (Time that adolescent is growing most quickly)
Average female growth spurt is 2 years earlier than the average male growth spurt

11. Physical Changes of Puberty: Adolescent Growth Spurt

12. Physical Changes of Puberty: Sex Differences in Muscle and Fat
Changes in body composition
Relative proportions of body fat/muscle change
Different for boys (more muscle) and girls (more fat)
Body dissatisfaction among girls
Closing of ends of long bones (epiphysis)
Asymmetry of growth

13. Physical Changes of Puberty: Sexual Maturation
Development of secondary sex characteristics
Measured in boys and girls by Tanner Stages
Changes include
Growth of pubic hair
Changes in appearance of sex organs
Breast development
Boys are generally fertile before they have an “adultlike” appearance.
The opposite is true for girls.
Page 31

14. Sexual Maturation: Boys
Spermarche typically occurs 1 year after accelerated penis growth
Boys capable of fathering a child before they look like adults; opposite true for girls

15. Sexual Maturation: Girls
Sequence less regular than in boys
Menarche typically occurs after other secondary sex characteristics; regular ovulation follows 2 years later
Thus, girls appear physically mature before they are actually capable of reproduction

16. Variations in the Timing and Tempo of Puberty
No specific average age at onset or duration of puberty
No relation between the age at which puberty begins and the rate of pubertal development
Timing (early or late) and adult stature
Small effect: late maturers slightly taller as adults, early maturing girls slightly heavier as adults
Childhood height and weight
Stronger correlation with adult height and weight

17. Variations in the Timing and Tempo of Puberty

18. Individual Differences in Pubertal Maturation
Interaction between genes and environment
Differences in timing/rate among individuals in the same general environment result chiefly from genetic factors
Genetic predispositions
Upper and lower age limits, not a fixed absolute
Two key environmental influences
Nutrition
Health
Exposure to pheromones
Insert photo from DAL
Pheromones – a class of chemicals secreted by animals that stimulate certain behaviors in other members of the species. The presence of a stepfather may expose the adolescent girl to pheromones that stimulate pubertal maturation. In general, when mammals live close to biological relatives that slows the pubertal process. Being exposed to unrelated members of the opposed sex may accelerate puberty. Page 36.

19. Group Differences in Pubertal Maturation
Typically studied by comparing average age of menarche
Across countries
Age at menarche younger when not malnourished or suffering from chronic disease (Ex: Africa and United States)
Over time
Changes in the average age of menarche over the past two centuries
Although menarche does not signal the onset of puberty, researchers often use the average age of menarche when comparing the timing of puberty across groups or regions because it can be measured more reliably than other indicators.
The influence of the broader environment on the timing and tempo of puberty can be seen by looking at two sets of findings: (1) comparisons of the average age of menarche across countries, and (2) changes in the average age of menarche over time.
Comparisons of average age of menarche across countries
Western Europe and in the US, the median age of menarche ranges from compared to a range of in Africa

20. Group Differences in Pubertal Maturation
Secular trend (group trend within same region)
Leveling off in industrialized nations
Better sanitation, control of infectious diseases
Onset of puberty has continued to occur earlier among African-American girls in the United States

21. Group Differences in Pubertal Maturation

22. Biological changes affect behavior – Figure 1.9 of the textbook.
Example for Purple squares: Increases in testosterone  increase in boys’ sex drive and sexual activity.
Example for Blue squares: Self-image changes because his body has changed, changes in how he behaves in that boy seeks privacy while bathing.
Example for Orange squares: As her body changes a girl gets attention from older boys that previously didn’t notice her changes in how she behaves in terms of all the extra attention.
Pages 38 and 39 of the textbook.
The biological changes of puberty can affect the adolescent’s behavior in at least three ways

23. How Do Researchers Study The Psychosocial Consequences of Puberty?
Groups compared at different stages of puberty
Cross-sectional study design
Longitudinal study design
Same adolescents tracked over time
Comparison of early vs. late maturers
When interested in the effects of pubertal timing on psychosocial outcomes

24. The Immediate Impact of Puberty
Self-esteem varies by gender and ethnicity
Adolescent moodiness
More fluctuations throughout the day than adults
Not solely due to hormones
Greatly influenced by environmental factors such as shifts in activities

25. The Immediate Impact of Puberty
Changes in patterns of sleep
Delayed phase preference and later melatonin secretion
Environmental influences and school start times

26. The Immediate Impact of Puberty
Family relationships
Increased conflict and distance between parents and children
Peer relationships

27. The Psychosocial Impact of Specific Pubertal Events
Most adolescents react positively to pubertal changes
Especially secondary sex characteristics
Reactions to menarche are less negative than in the past
Less known about boys’ reactions to first ejaculations
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Page 46 notes cultural differences in boys’ responses to first ejaculation.
For example, in Nigeria, boys told their friends about the experience soon after it occurred.
In the United States, boys do not usually discuss this event with parents or with friends.

28. Psychosocial Impact of Early or Late Maturation: Boys
Perception of being an early or late maturer is more important in affecting one’s feelings than the reality
Pros of early maturation
Popularity, better self-esteem
More responsible, cooperative, sociable later in adulthood
Cons of early maturation
More drug and alcohol use, precocious sexual activity, greater impact of victimization
Less creative, more humorless in later adulthood

29. Psychosocial Impact of Early or Late Maturation: Girls
Compared to early maturing boys, early maturing girls have more difficulties
Maturational deviance hypothesis
Developmental readiness hypothesis
Cultural and contextual factors (valuing thinner body types)
Pros of early maturation
Popularity with boys
Cons of early maturation
Heavier and shorter stature later in life
Precocious sexual activity, lowered self-image, higher rates of depression, eating disorders, anxiety

30. Psychosocial Impact of Early or Late Maturation: Girls

31. Eating Disorders Body Dissatisfaction Obesity Disordered eating
Higher among early maturing girls
Obesity
The most common eating disorder among adolescents
Disordered eating
Unhealthy patterns of eating, attitudes, and behaviors

32. Eating Disorders
About ¼ of American adolescents are highly satisfied with their bodies
Over ½ consider themselves overweight and have attempted to diet
Deviation from the “ideal” physique can lead to loss of self-esteem and other problems in the adolescent’s self-image
Studies of magazines, 1970 to 1990
Ideal body shape became slimmer and less curvaceous

33. Eating Disorders: Bulimia & Anorexia Nervosa
Adolescents with these eating disorders have an extremely distorted body image
Bulimia
Eating binges; force themselves to vomit to avoid weight gain
3% of adolescents are genuine bulimics
Anorexia
Starve themselves to keep weight down
Fewer than one-half of 1% of adolescents
Clinically defined bulimia and anorexia are 10 times more common among females
There is a clip on the McGraw-Hill Visual Assets Database that would relate well to this section of the textbook.
Eating Disorders
GRACIELA ANDRESON, CLINICAL PSYCHOLOGIST, STUDENT HEALTH CENTER, UNIVERSITY OF ILLINOIS, U-C. A clinical psychologist describes the types of eating disorders that occur among young women. She states that food is not the main psychological concern for these girls. Instead, the real issue is the need to feel in control.

34. Physical Health and Health Care in Adolescence
Adolescent health care needs differ from those of children and adults
Most health problems are preventable
Field of adolescent health has shifted away from traditional medical models (diagnosis and treatment of disease) toward more educational approaches (prevention and promotion of good health).
Insert photo from DAL
Page 58 of textbook.

35. Physical Health and Health Care in Adolescence
PARADOX: Adolescence is a healthy period of the lifespan
But nearly 1 in 15 adolescents experiences at least one disabling chronic illness:
Mental disorders (depression)
Respiratory illnesses (asthma)
Muscular and skeletal disorders (arthritis)  
Threats to health have psychosocial causes (not natural causes)
Unhealthy behaviors, violence, and risky activity
Page 59 of textbook.

36. Adolescent Mortality Today 50 Years Ago
45% of teen deaths due to car accidents and other unintentional injuries
Less experienced behind the wheel
More likely to take driving risks
27% of teen deaths due to homicide and suicide
50 Years Ago
Most deaths from illness and disease
Two of the most important contributors to serious car accidents involving teenage drivers are driving at night and driving with other teenagers in the car. Page 58
The word “suicide” on this slide has a hyperlink to the website for the:
American Foundation for Suicide Prevention
The American Foundation for Suicide Prevention is a nonprofit organization dedicated to advancing knowledge of suicide and how to prevent it. The site provides links to statistics on suicide rates by gender and age. It also includes links to research findings and useful resources that your students might find interesting.
A link to this site is included in the McGraw-Hill Visual Assets Database (VAD).

37. Promoting Adolescent Health
Particular concern with improving the health of poor and ethnic minority adolescents
Less access to medical care and more likely to:
Suffer from chronic illness
To be obese or have high blood pressure
To be physically inactive
To be victims of violent crimes
To die from drowning
To be murdered (leading cause of Black adolescents is homicide)