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Physical and Cognitive Development in Adolescence
Chapter 11
Robert S. Feldman
Growth During Adolescence
Rapid Pace of Physical and
Sexual Maturation

Adolescence: developmental stage that lies between childhood and adulthood
Growth spurt: boys 4 in/yr, girls 3.5 in/yr
Girls begin age 10, boys age 12 (but by 13 are taller)
See How They Grow!
Physical Manifestations of Puberty
Physical maturation begins when pituitary gland signals production of androgens & estrogens at adult levels

Development of primary (development of reproductive organs) and secondary (visible signs of sexual maturity that do not involve sex organs) sex characteristics

Changes in body composition
Puberty in Girls
Begins earlier for girls than for boys
Girls start puberty at around age 11 or 12, and boys begin at around age 13 or 14
Wide variations among individuals
Menarche most obvious sign
Secondary sex characteristics: breast & pubic hair growth
Onset of Menarche
Begins later in poorer, developing countries & in poorer social groups
Influenced by proportion of fat to muscle
Environmental stress can cause early onset
100 years ago average age 14-15, now 11-12
A Cultural View
Puberty in Boys
Genitals begin to grow at accelerated rate around age 12 and reach adult size about 3 or 4 years later
Spermarche around age 13
Secondary sex characteristics: voice change, pubic & facial hair growth
What is a secular trend?
Earlier start of puberty is example of significant secular trend
Pattern of change occurring over several generations
Trends occur when physical characteristic changes over course of several generations
Result of better nutrition over centuries
Body Composition
Weight increase
Muscle (grows faster in males)
Boys end with 3:1 muscle to fat ratio, girls with 5:4
Muscular development is rapid and closely parallels skeletal growth
Strength gains related to size and capacity of heart and lungs (and tolerance to exercise)

Psychological Impact of Puberty
Biological changes can have direct impact on behavior (hormones & mood)
Biological changes can impact self-image, which in turn affects behavior
Biological changes transform appearance, which may affect reactions of others, especially peers
Effects strongest in early puberty when increases may be rapid and variable
Aggressions (males)
Depression (females)

Influenced by environment
Mood changes parallel activity changes
Sleep patterns (delayed phase preference)
Early Maturation
More successful at athletics
More popular
More positive self-concept
Downside: more likely to become involved in delinquency & substance abuse
May lead to ridicule & embarrassment
More popular with older boys
Mixed societal messages?
Late Maturation
Less successful at athletics
Seen as less attractive
May develop healthier self-concept later
May have lower social status early on
Greater satisfaction with bodies by 10th grade because fit societal “ideal”
Nutrition, Food, and Eating Disorders: Fueling the Growth of Adolescence
Nutritional Problems in Adolescence
Poor eating habits
High consumption of junk food/sugar/fats
Large portion sizes
Lack of variety

Related health concerns
Obesity (1 in 20; 1 in 5 overweight)
Heart disease
Why do adolescent women get so little exercise?
Eating Disorders
Anorexia Nervosa
Extreme weight loss
Distorted body image
Binging and purging
Normal weight

Adolescent Health
Unhealthy behaviors
Drug use
Self-inflicted and other-inflicted
Risky activity
Unprotected sexual intercourse
Drunken driving
Brain Development and Thought: Paving the Way for Cognitive Growth
Use It or Lose It
Brain produces oversupply of gray matter in adolescence which is later pruned back at rate of 1% to 2% per year
Number of neurons grows, more complex interconnections
Myelination continues
Prefrontal cortex more efficient in communication
How is this related to adolescent impulse control?
Prefrontal cortex provides for impulse control

Adolescence prefrontal cortex is biologically immature = ability to inhibit impulses is not fully developed
Adolescent Brain & Alcohol
Adolescent brain development produces changes in regions involving dopamine sensitivity and production
Adolescents may become less susceptible to effects of alcohol
More drinks required to experience reinforcing qualities—leading to higher alcohol intake
Alterations in dopamine sensitivity may create more sensitivity to stress, leading to further alcohol use
Yawning of the Age of Adolescence
Sleep Deprivation
Need 9 hours of sleep
Adolescents go to bed later and get up earlier
Sleep deprivation takes its toll
Lower grades
More depressed
Greater difficulty controlling their moods
Greater risk for auto accidents
Cognitive Development

Information processing

Adolescent egocentrism
Piagetian Perspective
Fixed sequence of qualitatively different stages

Fundamentally different than child thinking: more advanced & sophisticated

Utilized in variety of settings and situations
Piagetian Stages Related to Youth Development
Concrete operations
6-11 years
Mastery of logic
Development of rational thinking
Formal operations
11+ years
Development of abstract and hypothetical reasoning
Development of propositional logic
Deductive Reasoning
Developmental of Formal Operations
Early adolescence
Variable usage depends on conditions surrounding assessment

Late adolescence
Consolidated and integrated into general approach to reasoning
Developmental of Formal Operations
Abstract reasoning is hallmark of formal operations
Propositional thought: reasoning that uses abstract logic (i.e. deductive reasoning)
Systematic hypothesis testing is one example of these skills.
Developmental of Formal Operations
Classic experiment gives child a weight hanging from a string & asks child to figure out what determines the speed of the pendulum.
Child can vary length of string, amount of force used to push string, height to which weight is raised before release
Concrete operations approach: haphazard
Formal operations: systematically vary factors
Consequences of Formal Operations
Now may question “rules” and authority figures
May compare their parents to the “ideal” parent and complain
May become very idealistic
Thinking about Thinking…
Metacognition improves during adolescence
Thinks about own thoughts self-consciousness
Monitors own learning processes more efficiently
Paces own studying
Adolescent Egocentrism
Imaginary audience
Belief that one is center of everyone else's concern and attention

Personal fables
Egocentric belief that one’s experiences are unique

Imaginary Audience
School Performance
Students Around the World
Socioeconomic Status and School Performance
Individual Differences in Achievement
Children living in poverty lack many advantages
Later school success builds heavily on basic skills presumably learned or not learned early in school
Middle- and high-SES students earn higher grades, score higher on standardized tests, & complete more years of schooling
Ethnic and Racial Differences in School Achievement
Significant achievement differences between ethnic and racial groups
On average, African-American and Hispanic students tend to perform at lower levels, receive lower grades, and score lower on standardized tests of achievement than Caucasian students
Asian-American students tend to receive higher grades than Caucasian students
Dropping Out of School
Incidence: half a million per year
More males than females
More Hispanics & African-Americans
Poor students 3X more likely
Causes: multiple (support family, pregnancy, language problems, etc.)
Earn 42% less, unemployment rate 50%
Perpetuate cycle of poverty

When Adolescents Do Drugs
50% high school seniors, 20% 8th graders have used marijuana in past year
Why do teens use drugs?
Role models
Peer pressure
Alcohol: Use and Abuse
75% college students past 30 days
40% had 5 or more drinks past 2 weeks
16% have 16 or more per week
76% high school seniors past year
Binge drinking
4 or more drinks (men), 5 or more (women)
50% of male & 40% female college students
Why do adolescents start to drink?
Way of proving themselves
Release of inhibitions and tension
Reduction of stress
False consensus effect
From Activity to Addiction
Adolescent alcoholics
Alcohol use becomes uncontrollable habit
Increasing ability to tolerate alcohol
Increasing need to drink ever-larger amounts of liquor to bring about positive effects craved

The Informed Consumer of Development
Hooked on Drugs or Alcohol?
Identification with the drug culture
Signs of physical deterioration
Dramatic changes in school performance
Changes in behavior
(Adapted from Franck & Brownstone, 1991, p. 593–594)

Tobacco: The Dangers of Smoking
Incidence diminishing somewhat
Gender: on the rise among girls
Racial/SES: White & lower SES more likely
Peer pressure
Role models

Developmental Diversity
Pushing Smoking to the Less Advantaged
Tobacco companies carve out new markets by turning to least advantaged
Tobacco companies aggressively recruit adolescent smokers through ads & free samples

Sexually Transmitted Infections
1 of 4 adolescents will contract STI before graduation, around 2.5 million teens per year

AIDS has killed 20 million, there are 40 million living with it today
Sexually Transmitted Infections

How Many?
Other Sexually Transmitted Infections
Human papilloma virus (HPV)
Can cause cervical cancer in women
Vaccine now available for 11 to 12-yr-old girls
Genital herpes
Gonorrhea and syphilis