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Chapter 11
Physical and Cognitive Development in Adolescence


ADOLESCENCE is the developmental stage between childhood and adulthood.

The age at which adolescence begins and ends is imprecise, partly because society is unclear about the roles of people in this stage (no longer children, not yet adults).

Physical Maturation

Extreme changes in height and weight are common:

"The adolescent growth spurt"—a period of rapid growth changes in height and weight

The rate of growth matches the high growth rate of infancy.

On average, boys grow 4.1 inches in height each year, girls 3.5 inches.

Girls begin their growth spurts earlier (aprox. 2 years) and complete them earlier.

By age 13, boys are taller on average.

Puberty: The Start of Sexual Maturation

PUBERTY is the period when sexual organs mature, beginning earlier for girls than for boys.

Girls begin puberty about 11 or 12; boys begin at 13 or 14.

What triggers puberty?

Environmental & cultural factors play a role in age of puberty.

MENARCHE, the onset of menstruation, varies in different parts of the world and even with affluence levels.

More affluent, better nourished, healthier girls start menstruation earlier.

Menarche age in the US has declined since 19th century.


The development of PRIMARY SEX CHARACTERISTICS involves organs and structures of the body related to reproduction.

SECONDARY SEX CHARACTERISTICS involve the visible signs of sexual maturity that do not involve sex organs directly.

The Timing of Puberty

Body image involves an adolescent's own reactions to these physical changes.

The timing of puberty is a key factor for how adolescents react to it.

The Timing of Puberty (early maturation)

Early maturation is generally positive for boys.

Early maturing boys tend to be better at athletics, be more popular, have more positive self-esteem, and grow up to be more cooperative and responsible.

On the other hand, these boys also are more likely to have school difficulties and become more involved in delinquency and drug use.

Early maturation is often difficult for girls.

Early maturing girls tend to be more popular but they may not be ready to deal with dating situations.

Reactions depend on cultural norms.

The Timing of Puberty (late maturation)

Late maturation is difficult for boys.

Smaller boys are seen as less attractive and have a disadvantage in sports.

These difficulties often lead to declines in self-concept which can extend into adulthood.

For late maturing girls the picture is complicated.

Late maturing girls can be overlooked and have low social status at first.

However, when they catch up their self-esteem is high.

Nutrition, Food & Eating Disorders During Adolescence

Food and eating disorders become a focus during adolescence.

The adolescent growth spurt requires an increase in food (especially key nutrients such as calcium and iron).

The major nutritional issue for many teens: eating a balance of appropriate foods.

Nutrition, Food & Eating Disorders (cont.)

Obesity is a common concern during adolescence.

1 in 5 adolescents are overweight; 1 in 20 are obese (body weight 20 % above average).

These are book’s figures, American Obesity Assn. says 15% children & teens are obese (95th percentile BMI)

The psychological consequences of adolescent obesity are severe since while body image is a key focus.

Potential health consequences of obesity are also of concern.

High blood pressure; diabetes; likely to be obese adults.

Anorexia Nervosa and Bulimia

ANOREXIA NERVOSA is a severe eating disorder in which individuals refuse to eat, while denying that their behavior and appearance, which may become skeletal, are out of the ordinary.

This disorder primarily affects white women.

These women are often intelligent, successful, attractive, and from affluent homes.

Eating Disorders (continued)

BULIMIA is an eating disorder characterized by binges on large quantities of food, followed by purges of the food through vomiting or the use of laxatives.

A chemical imbalance results from constant vomiting or diarrhea.

This can have serious effects, including heart failure. (It is believed that Terri Schiavo’s heart attack was caused by potassium imbalance that was secondary to bulimia.)

Eating Disorders (continued)

Eating disorders are products of both biological and environmental causes, so treatment involves multiple approaches.


Cognitive-behavioral techniques

Dietary modifications

Stress management

Brain Development

Brain’s oversupply of gray matter is pruned at rate of 1 to 2 percent per year.

Myelination (nerve cells being covered by fat cells) increases, making transmission of neural messages more efficient.

Prefrontal cortex (part of brain that is involved in impulse control, thinking, planning, evaluating, making decisions) develops until early 20s.

Changes in brain chemical dopamine production & sensitivity may make teens less sensitive to effects of alcohol and be able to drink more, and be more susceptible to stress.

Cognitive Development and Schooling

Piaget’s approach to cognitive development has had a significant influence on developmental psychologists.

FORMAL OPERATIONS PERIOD is the stage during which people develop the ability to think abstractly and hypothetically.

Piaget asserted that children enter this stage at about the age of 12.

Using Formal Operations

Full capabilities of using principles of logic unfold gradually, throughout early adolescence (approximately ages 12 to 15).

Not everyone achieves formal operational skills (some studies estimate that 25 to 50 % of college students & adults do not).

Social values/ culture also influence the achievement of these skills.

Isolation, level of formal education, level of scientific sophistication in the community.

Using Formal Operations (continued)

Change in everyday behavior.

Use abstract reasoning abilities to question parents and other authority figures.

Become more argumentative.

Poke holes in others explanations.

Use critical thinking to challenge and see other perspectives.

Coping with these cognitive changes can be challenging for parents.

Information Processing Perspectives to Cognitive Development

The INFORMATION-PROCESSING PERSPECTIVE sees changes in cognitive abilities as gradual transformations in the way that individuals take in, use, and store information.

From this view, thinking advances during adolescence result from the ways people organize their thinking and develop new strategies.

Information processing perspectives assert that one of the key reasons that mental abilities advance during adolescence is the growth of METACOGNITION, the ability to think about one's own thinking process and their ability to monitor their cognition.

Egocentrism in Adolescent Thinking

ADOLESCENT EGOCENTRISM is a stage of self-absorption where the world is seen only from one's own perspective.

Thus adolescents are highly critical of authority figures, unwilling to accept criticism, and quick to find fault with others.

Adolescent egocentrism helps explain why teens often think they are the focus of everyone’s attention.

Adolescent egocentrism leads to two distortions:

IMAGINARY AUDIENCE, where adolescents think they are the focus of everyone else's attention.

PERSONAL FABLES, the belief that the adolescent is unique and exceptional.

No one understands me

Risk-taking behavior


School Performance

While cognitive abilities increase, school performance tends to decline.

Reasons not completely clear.

More strict grading?

There is a strong relationship between educational achievement and socioeconomic status (SES).

Poorer children have fewer resources, lower health, more inadequate schools, and less involved parents.

School Performance (cont.)

There are ethnic and racial differences in school achievement, but the reason for them is not clear.

In general, African-American and Hispanic students perform at lower levels than Caucasians, and Asians perform at higher levels.

When socioeconomic levels are taken into account, achievement differences diminish.

Additional success factors are the cultural value of school success, attributions of school success, and consequences for not doing well.

Achievement Test Results






Dropping Out of School

Most students complete high school, but half million each year drop out.

Consequences of dropping out are severe.

Students leave schools for many reasons.


Economic reasons

Problems with English language

Dropping Out of School (cont.)

Dropout rates differ between groups:

Males, African-American and Hispanic students are more likely to leave.

Poverty plays a huge rule in determining who drops out.

Lower-income students are three times more likely to drop out than middle- or higher-income students.

Drug Use in Adolescence

The use of illegal drugs in adolescence is very prevalent and rising.

In the 1990's drug use rose, after a decline in the 1980's.

Almost 20% of eighth graders and 40% of seniors say they smoked marijuana at least once in the last year.

More than half of high school seniors have used an illegal drug at least once in their lives.

Drug Use (cont.)

Why do teens use illegal drugs?

Perceived pleasurable experience.

Escape from daily pressures.

The thrill of doing something illegal.

A number of role-models use drugs.

Peer pressure.


ADDICTIVE DRUGS produce a biological or psychological dependence in users, leading to increasingly powerful cravings for them.

Drug use carries the risk of numerous legal and physical consequences.

A major danger of drugs as escapism is that the adolescent never learns to confront the original problem and therefore never learns effective problem-solving skills.

Alcohol: Use and Abuse

76% of high school students reported having consumed an alcoholic drink in the past year in a study by the Center on Addiction and Substance Abuse.

75+% of college students report that they have consumed at least one alcoholic drink during the last 30 days.

40+% have had 5+ drinks in the last 2 weeks

16% drink 16 or more drinks each week.

Alcohol (cont.)

Binge drinking is a particularly troubling pattern in college students.

5+drinks in one sitting for men; 4 for women

50% of male college students and 39% of females say they have participated in binge drinking in the previous 2 weeks.

Adolescents drink because they think it is an adult thing to do.



ALCOHOLICS are persons with alcohol problems who have learned to depend on alcohol and are unable to stop their drinking.

Stress may trigger drinking and alcoholism for some teens.

Alcoholism tends to run in families (genetic predisposition or environmental stress).


Smoking among adolescents has declined, but the number of teen smokers is still substantial.

Smoking is considered cool.

Nicotine can produce biological and psychological dependency.

Smoking produces a pleasant emotional state that smokers seek to maintain.

Exposure to parents’ smoking and peer smoking increases the chances that an adolescent will take up the habit.


Tobacco Use

Smoking is sometimes seen as an adolescent rite of passage, a sign of growing up.

Less advantaged are targeted.

People who smoke as few as ten cigarettes early in their lives have an 80% chance of becoming habitual smokers.

Smoking will prematurely kill some 200 million of the world’s children & teens.


Sexually Transmitted Diseases

AIDS (ACQUIRED IMMUNODEFICIENCY SYNDROME) a sexually transmitted disease, produced by the HIV virus, has no cure, and ultimately causes death.

AIDS is a SEXUALLY TRANSMITTED DISEASE transmitted through the exchange of bodily fluids (usually sexual contact).

AIDS is one of the leading causes of death among young people.



AIDS and Adolescent Behavior

It has been difficult to motivate adolescents to use safe sex measures and change their sexual behavior.

Feelings of invulnerability


Sense of privacy


Other Sexually Transmitted Diseases

CHLAMYDIA is the most common sexually transmitted disease, caused by a bacteria. It can lead to pelvic inflammatory disease.

GENITAL HERPES is a common sexually transmitted disease caused by a virus, and not unlike cold sores that sometimes appear around the mouth.

Trichomoniasis is an infection caused by a parasite.

Gonorrhea and syphilis used to be deadly but can now be treated with antibiotics.


Prevention of STDs

Abstinence is the only certain way to avoid AIDS and other sexually transmitted diseases.

If they plan to engage in sexual activity, adolescents should be encouraged to practice safe sex:

Use condoms.

Avoid high risk behaviors.

Know your partner’s sexual history.