CHAPTER 11
Adolescence: Physical and Cognitive
Development
Puberty: The Biological Eruption
Puberty: The Biological Eruption
• Puberty
– Stage of development characterized by reaching sexual maturity
and the ability to reproduce
– Onset of adolescence coincides with advent of puberty
• Feedback loop
– Hypothalamus signals the pituitary gland, which in turn releases
hormones that control physical growth and the gonads
– Gonads respond to pituitary hormones by increasing production
of sex hormones
– Sex hormones further stimulate the hypothalamus, perpetrating
the feedback loop
Puberty: The Biological Eruption (cont’d)
• Primary sex characteristics
– Females: ovaries, vagina, uterus, and fallopian tubes
– Males: penis, testes, prostate gland, and seminal vesicles
• Secondary sex characteristics
– Breast development, deepening of the male voice, and the
appearance of facial, pubic, and underarm hair
– Not involved in reproduction
The Adolescent Growth Spurt
GIRLS
BOYS
• Girls’ growth spurt at age 10
• Growth spurt at age 12
• Girls gain a little more than 13
inches in height; spurt in
weight continues for 2 years
after growth spurt begins
• Peak reached 2 years later
• Gain 14 ½ inches in height
• Hips get wider due to having
twice as much body fat as
boys
• Eventually boys become taller
and heavier than girls
• Girls’ body shape more
rounded
• Boys’ shoulders get broader
Fig. 11-1, p. 228
Fig. 11-2, p. 229
Asynchronous Growth
• Children who spurt earlier more likely to have longer
torsos and shorter legs
• No significant differences between early and late
sprouters in the total height at maturity
• Asynchronous growth
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Different parts of the body grow at different rates
Hands and feet mature before the arms and legs do
Legs reach peak before shoulders and chest
Boys stop growing out of pants about a year before they stop
growing out of their jackets
The Secular Trend
• During the 20th century, children in the Western world
grew more rapidly and wound up taller than children from
earlier times.
– Accompanied by an earlier onset of puberty
– Known as a secular trend
• Occurrence of a secular trend in height and weight has
been documented in nearly all European countries and
the United States.
• Nutrition and medical advances contributed to height
increase.
Fig. 11-3, p. 230
Changes in Boys
• Pituitary gland stimulates the testes to increase output of
testosterone.
– Leads to further development of male genitals
• First sign of puberty is accelerated growth of the testes,
which begins at about 11½ years old.
• Testicular growth accelerates testosterone production
and other pubertal changes.
• Penis begins a spurt of accelerated growth about a year
later
– Still later, pubic hair spurts
• Underarm and facial hair appears about age 15.
Changes in Boys (cont’d)
• Facial hair first appears on upper lip
– Full shaving occurs in half of American boys at age 17
• Voice deepens at age 14 or 15 because of the growth of
the “voice box” or larynx and the lengthening of the vocal
cords.
• Testosterone triggers development of acne.
– Boys more prone to acne
• Males have erections from infancy but not frequent until
age 13 or 14, resulting in nocturnal emissions.
– Wet dreams
Changes in Boys (cont’d)
• Mature sperm found in ejaculatory emissions by age 15
– Ability to ejaculate precedes presence of mature sperm
• Half of all boys experience gynecomastia (enlargement
of the breasts), which declines in a year or two.
• At 20 or 21, young men stop growing taller because
testosterone causes epiphyseal closure, which prevents
the long bones from making further gains in length.
Changes in Girls
• The pituitary gland signals the ovaries to vastly increase
estrogen production at puberty.
• Estrogen may stimulate growth of breast tissue
beginning at age 8 or 9 (breast buds).
• Breasts reach full size in about 3 years.
– Mammary glands are not fully mature until a woman has a baby
• Estrogen also helps widening of pelvis and rounding of
hips.
Changes in Girls (cont’d)
• At about age 11, girls’ adrenal glands produce small
amounts of androgens that contribute to development of
underarm and pubic hair.
• Estrogen causes the labia, vagina, and uterus to develop
during puberty.
– Androgens cause the clitoris to develop
• Vaginal lining varies in thickness according to the
amount of estrogen in the bloodstream.
• Estrogen brakes the female growth spurt before the
ending of the male growth spurt.
Menarche
• Menarche
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First menstruation
Occurs between ages 11 and 14
Some girls as earlier as age 9; some as late as age 16
Height-to-weight ratio contributes to age of menstrual cycle
Average triggering weight depends on the girl’s height
Early starting in Westernized countries has stabilized
Fig. 11-4, p. 232
Regulation of the Menstrual Cycle
• Estrogen and progesterone levels regulate the menstrual
cycle.
• Ovulation typically begins 12 to 18 months after
menarche.
– Most menstrual cycles begin in the first two years or so after
menarche occurs without ovulation.
– If ovulating, a ripe ovum is released by the ovary when estrogen
reaches peak blood levels.
• Average menstrual cycle is 28 days
– Menstrual cycle irregular for first few years after menarche but
later assumes a regular pattern
Early Versus Late Maturers
• BOYS
– Early-maturing boys tend to be more popular than late-maturing
boys and more likely the leaders in their school.
– Some early-maturing boys engage in delinquency and
aggression as well as sexual encounters they may not be
prepared for.
• GIRLS
– Early-maturing girls tend to have lower self-esteem than male
counterparts.
– Early-maturing girls are conspicuous with height and developing
breasts.
• Even worse if development started in elementary school
• May be teased for it and may get lower grades
Body Image
• Body image refers to how physically attractive we
perceive ourselves to be and how we feel about our
body.
• By age 18, girls and boys are more satisfied with their
bodies than they were in their earlier teens.
• Adolescent females tend to be more preoccupied with
body weight and slimness than adolescent males.
• Adolescent males may want to increase body mass.
Health in Adolescence
Causes of Death
• Greatest causes of adolescent death
– Accidents, mostly with motor vehicles
– Homicides
– Suicides
• Death rates twice higher for males than females
– Males take more risks
• Poor adolescents living in urban areas of high population
at greatest risk of homicidal death
– Homicide rates greater for African-American adolescents than
for European-American adolescents
Fig. 11-5, p. 211
Nutrition
• Average girl needs 1,800 to 2,400 calories per day;
average boy needs 2,200 to 3,200 calories per day
• At peak of spurt, adolescents use twice as much
calcium, iron, zinc, magnesium, and nitrogen as during
the other years of adolescence.
• Irregular eating patterns contribute to adolescents’
nutritional deficits, especially skipping breakfast.
• More likely to obtain less vitamin A, thiamine, and iron
but more fat, sugar, and sodium than recommended
Eating Disorders
• Due to slimming down of American ideal, girls are more
prone to eating disorders
• Anorexia nervosa
– Life-threatening eating disorder characterized by extreme fear of
being heavy, dramatic weight loss, a distorted body image, and
resistance to eating enough to maintain a healthful weight
• Female-to-male ratio of anorexia is 10 to 1
• More affluent European-American females have body
image issues.
Eating Disorders (cont’d)
• Females with anorexia
– Drop 25% of their body weight within a year, resulting in
abnormalities in the endocrine system that prevent ovulation
– General health declines
– Every system in the body is affected, including respiratory and
cardiovascular systems
– At risk for premature development of osteoporosis
– Mortality rate is between 4% and 5%
• Distortion of body image is major feature of the disorder
• Anorexic woman sees self in mirror as too heavy
Bulimia Nervosa
• Bulimia nervosa
– Cyclical binge eating and purging
– May include strict dieting
– Fasting, laxatives, and demanding exercise regime
• Tends to afflict women during adolescence and young
adulthood
• Eating disorders connected with depression
• Eating disorders run in families, indicating genetic
involvement; eating disorders tend to involve
obsessionistic and perfectionistic personality traits
Cognitive Development: Piaget’s Stage
of Formal Operations
Piaget’s Stage of Formal Operations
• Formal operations refers to the ability to abstract reason,
classify objects, hypothesize, and formulate arguments.
• Top level of Piaget’s theory
• Adolescents have reached cognitive maturity in the
formal operations stage.
• Formal operations can begin as early as 11 or 12 years
old.
Hypothetical Thinking
• Adolescents develop concept of “what might be” rather
than “what is”.
• Adolescents “try on” different clothes and attitudes to see
which work best for them.
• Some may experience anxiety due to pressure to pick
the best career fit.
Sophisticated Use of Symbols
• Solving mental activities with “x” as a factor a part of
formal operations stage
• Ability to manipulate symbols a part of formal operations
stage
• Adolescents can analyze metaphors in literature.
• Adolescents may take on “crystal clear” solutions to
religious, political, and social issues without tolerance for
other issues that may be contributory.
Adolescent Egocentrism
• Adolescents have difficulty sorting out issues that
concern others from the things that concern themselves
• Imaginary audience
– Adolescent placed at center stage of fantasies
– Assumes others are concerned with their looks and dress
– Explains why adolescents engage in looking in the mirror so
much
• Personal fable
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Belief that one’s thoughts and emotions are unique and special
Normal for male adolescent to think he is indispensable
Reason STI’s occur – “Can’t happen to me”
Believe that no one has ever experienced the same things as
themselves
Gender Differences
in Cognitive Abilities
Verbal Ability
• As a group, females surpass males in verbal ability.
• Boys in the U.S. are more likely to be dyslexic and read
below grade level.
• Culture and heredity play a role in the mastery of verbal
ability.
Visual-Spatial Ability
• Visual-spatial ability (VSB)
– The ability to visualize objects or shapes and to mentally
manipulate and rotate them
– Important ability in art, architecture, and engineering
• By age 8 or 9, boys begin outperforming girls in VSB.
– Most notable on mental rotation tasks
• VSB ability of boys may be due to evolutionary factors as
well as sex hormones.
• Environment plays a role
– Ex.: toys for boys (Legos, Erector sets) versus the toys for girls
– Boys engage in more sports, which is associated with better
performance of visual-spatial skills
Fig. 11-6, p. 239
Mathematical Ability
• Male adolescents generally outperform female
adolescents especially in geometry and word problems.
• No sex differences in understanding math concepts at
any age.
• Teaching expectations and involvement with math from
dad contribute to mathematical advancement of boys;
girls less likely to be encouraged in math; advanced
teachers more likely male; teachers spend more time
helping males with math
Moral Development
Moral Development
• Many adolescents engage in postconventional moral
reasoning.
– They deduce proper behavior
• Postconventional moral reasoning based on person’s
own moral standard and personal values
– Stages 5 and 6
• Stage 5
– Legalistic and contractual
– Laws stem from agreed upon procedures; many rights have
great value and should not be violated
• Stage 6
– Based on universal ethical principles of human life, individual
dignity, and reciprocity (behavior that is consistent with these
principles is considered right)
Moral Behavior and Moral Reasoning
• Positive relationship between a person’s level of moral
development and his or her behavior
• Group discussion of moral dilemmas elevates
delinquents’ level of moral reasoning
Evaluation of Kohlberg’s Theory
• Evidence supports that moral judgment develops in
children in upward sequence.
• Postconventional thought first found in adolescents;
formal operational thinking a prerequisite
• Kohlberg underestimated the role of cultural, social, and
educational institutions as well as parents.
• Postconventional thinking absent in developing countries
and infrequent in the U.S.; e.g., principles such as
freedom and tolerance of differences are not universally
admired
The Adolescent in School
The Adolescent in School
• Adolescents are influenced by opinions of peers and
teachers.
– Self-esteem reflective of their skills
• Middle-school teachers more likely to exert more
behavioral control than teachers in elementary school
– Conflict arises
• Transition to middle and high school results in decline in
grades and participation in school activities.
– More difficult for girls due to puberty
• Drop in self-esteem and increase in psychological
distress
• Schools can ease distress by creating a warmer climate
and establishing schools within a school.
Dropping Out
• Early predictors
– Below grade-level reading and excessive absences
• Other factors
– Low SES, low grades, poor problem-solving ability, low selfesteem, problems with teachers, dissatisfaction with school,
substance abuse, being old for one’s grade level (retention is
not the same as remediation), and being male
• Middle-class youth who feel bored with school,
alienated, or strongly pressured to succeed are at risk.
Preventing Drop Out
• Successful prevention programs include
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early preschool interventions
identification and monitoring of high-risk students
small class size, individualized instruction, and counseling
vocational components that link learning to community work
experiences
– involvement of families or community organizations
– positive school climate that provides clear and reasonable
educational goals, student accountability for behavior, and
motivational systems that involve penalties and rewards
Adolescents in the Workforce
Prevalence of Adolescent Employment
• One-half of high school sophomores, two-thirds of
juniors, and almost three-fourths of seniors have a job
during the school year.
• 2 to 3 million adolescents work illegally.
• Employed lower-income adolescents work longer hours
than working middle-class teens.
Pros and Cons of Adolescent Employment
• Potential benefits of employment include
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developing a sense of responsibility, self-reliance, and discipline
learning to appreciate value of money and education
acquiring positive work habits and values
enhancing occupational aspirations
• Lower SES adolescents work to supplement family
income.
• Middle-class teens use income for personal purchases,
such as clothing, iPods, CDs, DVDs, gear, and car
payments.
Pros and Cons of Adolescent Employment
(cont’d)
• Most working teens in jobs with low pay, high turnover,
little authority, and little chance of advancement; typically
perform repetitive tasks.
• Teens working more than 11 to 13 hours per week have
– lower grades, higher rates of drug and alcohol use, more
delinquent behavior, lower self-esteem, and higher levels of
psychological problems than other students not working
• Working teens less monitored, spend fewer hours with
family, and granted more decision-making power
• Hours worked per week needs to be limited