Lifespan overheads, chapter 11: physical and cognitive development in adolescence
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Chapter 11: Physical and Cognitive Development in
Adolescence
Adolescence: a period in which the individual will cross the dividing
line between childhood and adulthood.
Puberty
 by age 8 or 9, secretions of growth hormone (GH) and thyroxin
increase, leading to gains in body size and skeletal maturity.
Body growth: the 1st outward sign of puberty is the growth spurt (in
girls, age 10; in boys, age 12 ½).
 for girls body size is complete around age 16; for boys, 17 ½
 adolescents add about 10 inches and 40 pounds during puberty
 body proportions: the proximodistal trend reverses, and growth
of hands, feet, arms and legs accelerate beyond growth of the
trunk. Boys’ shoulders broaden relative to hips and girls’ hips
broaden relative to shoulders and waist.
 Muscle fat: around age 8, girls start to add fat to their arms,
legs, and trunk, which continues throughout puberty, while the
reverse is true for boys.
Motor development: girls’ gains are slow and gradual, leveling off
by age 14. Boys show a dramatic spurt in strength, speed, and
endurance, continuing through the teenage years.
 segregated phys. ed. begins in junior high school because of
these differences in ability
 beginning at an early age, girls get less encouragement and
recognition for athletic achievement
Lifespan overheads, chapter 11: physical and cognitive development in adolescence
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Sexual maturation
In girls: puberty begins with budding breasts and growth spurt. Then
comes menarche (age 12 ½, range 10 ½ - 15 ½). Pubic hair and
breast development are completed, and underarm hair appears.
Takes 3-4 years to be complete. For 12 to 18 months after menarche,
the ovaries usually do not produce mature ova.
In boys: enlargement of the testes at age 11 ½. Pubic hair emerges
and penis begins to enlarge (age 12). Facial and body hair emerge
(age 14). The voice deepens. Spermarche (the first ejaculation)
occurs around age 13; for a while the semen contains few living
sperm.
 heredity is partly responsible for the timing
 for girls, a rise in body fat can trigger menarche, and not
enough body fat can delay it
 in poverty-stricken nations, menarche is greatly delayed
 for people of higher SES, menarche comes 6 to 18 months
earlier
 age of menarche declined steadily from 1860 to 1970 due to
changes in nutrition, health care, sanitation, etc.
The Psychological Impact of Puberty
 for girls who have no warning about menarche, it can be
shocking and disturbing. Girls who are prepared report positive
and negative emotions.
 Boys also report + and – emotions. Boys get less information
and social support.
Adolescent moodiness:
 more negative events than children
 feelings are less stable than adults
 low points occur in adult-oriented settings (class, job, church)
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Relationships with parents: puberty is related to a rise in parentchild conflict (peaking around age 12 for girls, age 14 for boys)
 among nonhuman primates, the young leave the family group
around puberty
Early versus late maturation
 early maturing boys  relaxed, independent, self-confident,
physically attractive
 late maturing boys  anxious, overly talkative, and attentionseeking
 early maturing girls  unpopular, withdrawn, poor selfconfidence, poor body image, psychologically stressed.
 late-maturing girls  attractive, lively, sociable, leaders
 In the long term:
 early maturing boys and late-maturing girls often become rigid,
conforming, discontented
 late maturing boys and early maturing girls often develop into
adults who are independent, flexible, cognitively competent,
and satisfied
Health Issues
Nutritional needs: rapid body growth leads to a dramatic rise in food
intake (2700 calories for males; 2200 calories for females)
Eating Disorders
 anorexia nervosa: 1 in every 50 girls in the US is affected, with
a peak age of onset between 14 and 18. African Americans are
less affected, reporting being more satisfied with their body size
and shape.
o lose 25-50% of weight, halt menstruation/delay menarche
o Pale skin, brittle nails, lanugo, extreme sensitivity to cold
o shrinking heart muscle, kidney failure, permanent loss of
bone mass, brain damage
o 6% mortality rate
o Due to individual factors, the family and the larger culture
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 Bulimia: bingeing followed by purging, vomiting, strict dieting.
o 5% of teenage girls
o may be turning to food to compensate for feelings of
emptiness
o often impulsive in other ways (shoplifting, alcohol abuse)
Sexual activity
 sexual attitudes in the US are relatively restrictive
 among 15-19 years olds, females claiming to have had sex
grew from 28% in 1971 to 55% in 1990, and then dropped to
49% in 1998.
 A substantial minority are sexually active early, by 9th grade
 Males have their first intercourse earlier than girls
 Sexual activity is high among male African-Americans
 Early and frequent teenage sexual activity is associated with
early physical maturation, parental divorce, large family size,
sexually active friends and older siblings, poor school
performance, lower educational aspirations, and normviolations (e.g., alcohol/drug use, delinquency)
 Contraceptives are not used at all by 1/3 to ½ of American
sexually active teenagers
Sexual orientation: 3 to 6% discover that they are gay or lesbian.
 heredity
 might be X-linked
 certain genes affect prenatal sex hormone levels, which modify
brain structures
 most are not “gender deviant” in dress or behaviour.
 18% of heterosexual boys and 6% of girls report participating in
at least one homosexual act
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Adolescent pregnancy & parenthood
 900 000 American teenage girls become pregnant annually
 40% end in abortion
 14% end in miscarriage
 320 000 keep their baby
o much more likely to be poor
o low parental warmth and involvement; poor school
performance; alcohol and drug use; adult models of
unmarried parenthood
o low income minorities, especially African-American,
Native-American, and Hispanic teenagers.
o 50% graduate with a diploma or a GED
o reduces the chances of marriage, and increases the
chances of divorce.
o on welfare or in jobs that are low-paying and unsatisfying.
o babies often experience prenatal and birth complications
o more likely to be inadequate parents
Substance use and abuse
 By age 14:
o 56% have tried cigarettes
o 81% drinking
o 39% at least one illegal drug, usually marijuana
 by end of high school:
o 16% are regular smokers
o 30% have engaged in heavy drinking at least once
o over 45% have experimented with illegal drugs. Of these,
about 1/3 have tried at least one highly addictive and toxic
substance, like amphetamines, cocaine, PCP, or heroin
o most teenagers are experimenters
o a minority move from use to abuse
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 Correlates of adolescent drug abuse:
o seriously troubled, express unhappiness through
antisocial acts
o low SES, family mental health problems, parental and
older sibling drug abuse, lack of parental warmth and
involvement, poor school performance, peers who
encourage the abuse
o serious adjustment problems, including depression and
antisocial behaviour.
o often enter into marriage, parenthood, and the work world
prematurely and fail at them.
Cognitive Development
Piaget’s theory: the formal operational stage
 hypothetico-deductive reasoning becomes possible
o E.g. the pendulum problem
 propositional thought
 40 -60% of college students fail Piaget’s formal operation tasks
The Information Processing view of cognitive development
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attention becomes more thorough
strategies become more effective
knowledge increases, easing strategy use
metacognition expands
processing capacity increases
Consequences of abstract thought
 argumentativeness:
 self-consciousness
o The imaginary audience
o The personal fable
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Idealism and criticism: construct grand visions of the world with no
injustice, no discrimination. As a result, they may become fault-finding
critics
Sex differences in mental abilities
 by adolescence, girls’ language advantage isn’t meaningful.
 boys get better than girls at math
 Some believe that this gap in math skills is genetic
o Social pressures also contribute
o Sex differences in cognitive abilities of all kinds have
been declining over the past several decades
Academic achievement
 child rearing practices:
o in Caucasian kids, authoritative parenting is linked to
achievement in adolescence
o In Asian kids, high parental control is linked to better
grades than other styles
o In low-SES African-American kids, high parental control is
associated with better grades than other styles
 peer influences
o sometimes low-SES minority students react against
working hard, convinced that getting good grades will
have little payoff for them, and seeing it as a threat to
their ethnic identity
School characteristics: adolescents seek out adult models other
than their parents
 the quality of public education in the US is uneven
Part-time work:
 half of US high school students work part time
 low-level and repetitive
 more than15 hours a week: poorer school attendance, lower
grades, less time for extracurricular activities, more drug and
alcohol use, more distant from parents, cynical about the work
world
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Dropping out: 11% of US young people leave high school without
a diploma.
 less likely to become employed
 greater chance of working in menial, low-paying jobs
 factors related to dropping out:
o parents who are less involved in their child’s education
o parents who never finished high school
o parents who are unemployed, on welfare, divorced
o parents who respond to poor grades with anger and
punishment
 prevention strategies
o high quality vocational training
o remedial instruction and counseling
o efforts to address the many factors in students’ lives
related to leaving school early
o participation in extra-curricular activities
On the positive side:
 nearly 40% of 18 to 24 year-olds are working towards college
degrees - the highest rate in the world
 about 1/3 of all college dropouts return to finish later