Chapter 11


Physical and Cognitive Development

in Adolescence





Chapter Outline



I.        ADOLESCENCE is the developmental stage between childhood and adulthood.

A.     Physical Maturation

1.      Growth During Adolescence:  The Rapid Pace of Physical and Sexual Maturation

a)      Growth spurt during adolescence produces dramatic changes in height and weight.

b)      Girls growth spurt start and stop 2 years earlier than boys.

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

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

b)      There is wide variation among individuals.

c)      Puberty begins when the pituitary gland in the brain signals other glands to begin producing androgens or estrogens at the adult level.

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

(1)   More affluent, better nourished, healthier girls start menstruation earlier.

(2)   Some studies show that the proportion of fat to muscle in the body plays a part in the timing of menarche.

(3)   Environmental stress can bring about early menarche.

(4)   Menarche age in the U.S. has declined since 19th century when menarche began around age 14 or 15.

(a)    The earlier start of puberty is an example of a SECULAR TREND, a statistical tendency observed over several generations.

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

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

g)      Boys’ sexual maturation follows a different course.

(1)   Spermarche, a boy’s first ejaculation, usually occurs around the age of 13, although the body has been producing sperm for about a year.

3.      Body Image involves an adolescents own reactions to these physical changes.

a)      Western societys views of menarche have become more positive than they used to be so girls tend to have higher self-esteem, a rise in status, and self-awareness when they begin menstruating.

b)      Boys first ejaculation is roughly equivalent to girls menarche, but it is rarely discussed.

c)      Girls are often unhappy with their developing bodies, a result of strong societal pressures regarding the ideal female shape.

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

a)      Early maturation is generally positive for boys.

(1)   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.

(2)   On the other hand, these boys also are more likely to have school difficulties and become more involved in delinquency and substance abuse with older friends.

b)      Early maturation is often difficult for girls.

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

(2)   Reactions depend on cultural norms (country and community).

c)      Late maturation is difficult for boys.

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

(2)   Their dating lives may suffer.

(3)   These difficulties often lead to decline in self-concept which can extend into adulthood.

(4)   However, coping with these challenges may help late-maturing boys become assertive, insightful, and more creative.

d)      For late maturing girls the picture is complicated.

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

(2)   However, when they catch up their self-esteem is high with higher body esteem because they are more slender and “leggy” than early maturing girls.

5.      Nutrition, Food, and Eating Disorders:  Fueling the Growth of Adolescence

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

(1)   The average girls requires 2,200 calories and the average boy 2,800.

b)      Obesity is a common concern during adolescence.

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

(2)   Potential health consequences of obesity are also of concern.

(3)   Obese adolescents have an 80 percent chance of becoming obese in adulthood.

c)      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.

(1)   This disorder primarily affects white women between the ages of 12 and 40.

(2)   15 to 20 percent starve themselves to death.

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

(4)   About 10 percent of anorexics are male.

d)      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.

(1)   A chemical imbalance results from constant vomiting or diarrhea.

(2)   This can have serious effects, including heart failure.

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

6.      Brain Development and Thought:  Paving the Way for Cognitive Growth

a)      The prefrontal cortex, the part of the brain that allows people to think, evaluate, and make complex judgments, undergoes considerable development throughout adolescence and is not fully developed until age 20.

b)      Because the prefrontal cortex is also involved in impulse control, the ability to inhibit impulses explains the tendency toward risky and impulsive behaviors in some adolescents.

II.                 Cognitive Development and Schooling

A.     Piagetian Approaches to Cognitive Development:  Using Formal Operations

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

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

b)      Hypothetico-deductive reasoning, in which adolescents start with a general theory and deduce explanations from it, also distinguishes the formal operational period.

(1)   This allows the adolescent to think abstractly.

c)      Adolescents also can employ prepositional thought, reasoning that uses abstract logic in the absence of concrete examples.

d)      Not everyone achieves formal operational skills (some studies estimate that anywhere from 25 to 60 percent of college students do not).

e)      Cultural values also influence the achievement of these skills.

2.      The ability to think abstractly affects everyday behavior.

a)      Adolescents become more argumentative.

b)      This makes adolescents more interesting, but challenging.

3.      There are some criticisms of Piagets theory and approach.

a)      Research finds individual differences in cognitive abilities not universal.

b)      Some researchers suggest that cognitive development is more continuous, less step-like than Piaget proposed.

c)      Piaget underestimated the skills of infants and young children.

d)      Piaget focused only on thinking and knowing, missing other kinds of intelligence.

e)      More sophisticated forms of thinking may follow this stage and do not develop until early adulthood.

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

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

2.      The growth of METACOGNITION, the ability to think about one’s own thinking process and the ability to monitor one’s cognition.

C.     ADOLESCENT EGOCENTRISM is a stage of self-absorption where the world is seen only from ones own perspective.

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

2.      Adolescent egocentrism leads to two distortions:

a)      IMAGINARY AUDIENCE, where adolescents think they are the focus of everyone elses attention.

b)      PERSONAL FABLES, the belief that the adolescent is unique and exceptional and shared by no one else.

D.     School Performance

1.      On average, students’ grades decline during adolescence.

a)      One reason may be that the material is getting more complex.

b)      Another is that teachers grade older adolescents more stringently.

c)      This decline may also reflect broad educational difficulties, especially in the U.S.

E.      Socioeconomic Status and School Performance:  Individual Differences in Achievement

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

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

b)      A controversial theory (The Bell Curve) identifies genetics as the source of this SES-achievement correlation.

c)      The differences in educational achievement start from the beginning of school with the gap widening throughout the years.

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

a)      African-American and Hispanic families are more likely to live in poverty

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

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

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

F.      Dropping Out of School

1.      One-half million students drop out each year.

a)      Pregnancy

b)      Problems with the English language

2.      Hispanic and African-American students are more likely to leave school.

3.      Asians, however, drop out at a lower rate than Caucasians.

4.      23 percent of students who live in households in the lowest 20 percent of income drop out.

a)      This rate is 8 times greater than the dropout rate for incomes in the highest 20 percent.

b)      Dropping out perpetuates the cycle of poverty.

III.               Threats to Adolescents Well-Being

A.     Illegal Drugs

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

a)      More than 33 percent of eighth graders and close to 40 percent of seniors said they had smoked marijuana at least once in the last year.

b)      Illegal drug use is on the rise.

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

2.      Some theories of why adolescents try illegal drugs are:

a)      Perceived pleasurable experience

b)      Escape from daily pressures

c)      The thrill of doing something illegal

d)      A number of role-models use drugs

e)      Peer pressure.

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

4.      A major danger of drugs as escapism is that adolescents never learn to confront original problems and learn problem-solving skills.

5.      Casual users can escalate to more dangerous forms of substance abuse.

B.     Alcohol:  Use and Abuse

1.      More than 75 percent of college students have consumed at least one alcoholic drink during the last 30 days.

2.      More than 40 percent say they’ve had 5 or more drinks within the past 2 weeks.

3.      76 percent of high school seniors drink alcohol.

4.      Binge drinking – drinking 5 or more drinks for men and 4 or more for women in one sitting -- is a particularly troubling pattern in college students.        

a)      50 percent of males and 39 percent of females report binge drinking in the past 2 weeks.

5.      Why do adolescents drink?

a)      It is an adult thing to do.

b)      Maintaining a “macho” image for male athletes

c)      It releases inhibitions and tension.

d)      The false consensus effect – assumption that everyone else is doing it.

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

a)      Teens may be genetically prone to become alcoholic.

b)      Stress may trigger drinking and alcoholism for some teens.

C.     Tobacco:  The Dangers of Smoking

1.      There are significant numbers of adolescents smoking still, although the overall proportion has decreased.

2.      Smoking is more prevalent among girls.

3.      Whites smoke more than African Americans.

4.      Why do adolescents smoke?

a)      Smoking is considered hip and sexy.

b)      Nicotine can produce biological and psychological dependency.

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

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

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

5.      People who smoke as few as ten cigarettes early in their lives stand an 80 percent chance of becoming habitual smokers.

D.     Developmental Diversity:  Selling Death:  Pushing Smoking to the Less Advantaged

1.      As smoking rates in the U.S. go down, tobacco companies are seeking new markets.

a)      African Americans in urban areas.

b)      Free samples to adolescents in other countries.

E.      Sexually Transmitted Diseases:  One Cost of Sex

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

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

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

(2)   African Americans and Hispanics account for nearly 40% of AIDS cases.

(3)   16 million people have died of AIDS, and the number of people living with the disease is 34 million worldwide.

2.      Other sexually transmitted diseases include:

a)      CHLAMYDIA is the most common sexually transmitted disease, caused by a parasite.

b)      GENITAL HERPES is a common sexually transmitted disease which is a virus ( not unlike cold sores that sometimes appear around the mouth).

c)      Trichomoniasis, is an infection caused by a parasite.

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


Key Terms and Concepts







Secular trend

Primary sex characteristics

Secondary sex characteristics

Anorexia nervosa


Formal operational stage

Information-processing perspective


Adolescent egocentrism

Imaginary audience

Personal fables

Addictive drugs


Acquired immunodeficiency

  Syndrome (AIDS)

Sexually transmitted disease


Genital herpes