ChapTer 3 Development Over the Life Span 101You are about to learn...
• the physiological changes of adolescence.
• the psychological issues of adolescence.
• findings on brain development in adolescence.
adolescence
In middle childhood (ages 6 to 12), children go
through a period called adrenarche (a-DREN-ar-
kee), when the adrenal glands begin pumping out
hormones that affect brain development, most
notably an androgen called DHEA (Campbell,
2011). These hormones divert glucose in the
brain to foster the maturation of brain regions
vital to interpreting social and emotional cues.
Children’s brains during these years are at
their most flexible and responsive to learning.
Children become able to control their impulses,
reason better, focus and plan for the future, and
understand mortality and death. Their friend-
ships flourish.
All over the world, cultures acknowledge
that middle childhood is an important station on
the road to adulthood. Adults begin giving chil-
dren responsibilities—hunting, gardening, care of
younger children, chores—though these tasks vary
in seriousness (Lancy & Grove, 2011). Ariaal girls
in northern Kenya work the hardest, putting in 9.6
hours of farm work daily; but among the Pumé, a
foraging group in Venezuela, preadolescent girls
do almost nothing. “Pumé girls spend their time
socializing, talking and laughing with their friends,
beading and resting,” observed the researchers
who lived among them (Kramer & Greaves, 2011).
And then... adolescence strikes. Adolescence
refers to the period of development between
puberty, the age at which a person becomes ca-
pable of sexual reproduction, and adulthood. In
some cultures, the time span between puberty and
adulthood is only a few months; a sexually ma-
ture boy or girl is expected to marry and assume
adult tasks. In modern Western societies, however,
teenagers are not considered emotionally mature
enough to assume the full rights, responsibilities,
and roles of adulthood.
The Physiology of adolescence
Lo 3.13
Until puberty, boys and girls produce roughly
the same levels of androgens (masculinizing
puberty The age at
which a person becomes
capable of sexual
reproduction.adrenarche [a-Dren-
ar-kee] A time in middle
childhood when the
adrenal glands begin
producing the adrenal
hormone DHEA and
other adrenal hormones
that affect cognitive and
social development.hormones) and estrogens (feminizing hormones).
But from puberty on, boys have a higher level of
androgens than girls do, and girls have a higher
level of estrogens than boys do. In boys, the re-
productive glands are the testes (testicles), which
produce sperm; in girls, the reproductive glands
are the ovaries, which release eggs. During pu-
berty, these organs mature and the individual
becomes capable of reproduction. In girls, signs
of sexual maturity are the development of breasts
and menarche, the onset of menstruation. In boys,
the signs are the onset of nocturnal emissions
and the growth of the testes, scrotum, and penis.
Hormones are also responsible for the emergence
of secondary sex characteristics, such as a deepened
voice and facial and chest hair in boys and pubic
hair in both sexes.
The onset of puberty is determined by both
biological and environmental factors. Menarche
depends on a female’s having a critical level of
body fat, which is necessary to sustain a preg-
nancy and which triggers the hormonal changes
associated with puberty. An increase in body fat
among children in developed countries may help
explain why the average age of puberty declined
in Europe and North America until the mid-
twentieth century. The average age of menarche
is now about 12 years and 6 months in white
girls and a few months earlier in black girls.
Other signs of puberty in girls, such as pubic
hair and breast buds, are appearing at younger
and younger ages. In boys, the average age of
puberty (as measured by testicular size) used
to be 11 years and 6 months, and a few months
earlier in black boys; but boys, too, are entering
puberty from seven months to two years sooner
than that (Herman-Giddens et al., 2012). Various
reasons for the earlier ages for puberty have been
suggested—rising obesity rates, environmental
pollution, childhood stress—but the answer is still
unknown.
The onset and length of puberty vary con-
siderably from one person to another. Some
girls go through menarche at 9 or 10, or even
earlier, and some boys are still growing in height
after age 19. Early-maturing boys generally have
a more positive view of their bodies than late-
maturing boys do, and their relatively greater
size and strength give them a boost in sports
and the prestige that being a good athlete brings
young men. But they are also more likely to
smoke, drink alcohol, use other drugs, and break
the law than later- maturing boys (Cota-Robles,
Neiss, & Rowe, 2002). Some early-maturing
girls have the prestige of being socially popular,menarche [men-
arr-kee] The onset
of menstruation during
puberty.