Transcript Chapter 1

Biological Foundations
in Adolescent Development
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Physical and Hormonal Changes
Cultural & Psychological
Responses to Puberty
Neural Changes
Physical changes
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Puberty – onset of
sexual maturation
Three neuroendocrine
changes:
• Gonadal
• Adrenal androgens
• Growth
Gonadal and adrenal androgen axes
Gonadal (HPG) axis
Gonadotropin releasing hormone
(LH, FSH are gonadotropins)
(testes or ovaries)
(sex hormones – testosterone &
estradiol increase dramatically -gonadarche)
(see next slide)
Sex Characteristics (examples)
Primary Sex
Characteristics
Production of sperm
(spermarche) or
development of eggs
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Development of sex
organs
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Secondary Sex
Characteristics
Pubic and axillary hair growth
 Skin becomes rougher & oily
 Voice deepens
 Slight enlargement of breasts known as
breast buds (also, in ¼ of boys)
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Adrenal androgen (HPA) axis
(ACTH = adrenocorticotropic hormone)
(e.g., testosterone)
(leading to secondary changes)
Growth spurts and height changes
Notice the differential timing in
when growth spurts begin
Notice when the difference
in final height is achieved
Body composition changes
Notice prior to puberty
boys and girls are very
similar in muscle mass
During puberty body
fat increases more for
girls than for boys
Given that girls naturally develop a lower muscle-to-fat ratio than boys during puberty, why would
any culture create physical ideals that demand thinness in females once they reach puberty? AND
what are the health implications?
The Order of Pubertal Events
(see Table 2.2)
GIRLS
Downy
pubic hair
Growth
spurt
Appearance of
breast buds
Growth of
testes
BOYS
Growth of
sexual and
reproductive
organs
Menarche
Growth
spurt
Appearance of
pubic hair
Secretion of
increased
skin oil and
sweat
Increased
growth of
penis
Development
of underarm
hair
Secretion of
increased
skin oil and
sweat
Deepening of
the voice
Development
of facial hair
Pubertal Caveat
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Virtually all the studies considered in
the order of pubertal development
have been conducted with White
adolescents in the West
Variations may exist in other groups
Kikuyu culture in Kenya, Chinese
girls, African-American girls and boys)
(see p. 45; e.g.,
Earlier Puberty
The downward trend in the
age of menarche has
occurred in every Western
country for which records
exist. Why?
Tanner Stage 2
(breast and
pubic hair dev’t)
by age 10 in the
majority of girls
(68% in EuroAmerican girls;
95% in AfricanAmerican girls)
Responses to Puberty
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Homework assignment
Next section:
• Cultural & Psychological responses to
puberty
Cultural Responses to Puberty:
Rituals in Traditional Cultures
• 79% of cultures had
puberty rituals for girls
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• __________ (?) is the
pubertal event that is most
often marked by ritual
• Cultural views are mixed
as to the reaction to
menstruation (see “Historical
Focus” box in chapter)
68% of cultures had
puberty rituals for boys
(e.g., vision quest ) (“Roots”
video)
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Typically rituals require the
young man to display
courage, strength and
endurance (often violent)
NOTE: Globalization has been
credited with the decline in
frequency of these rituals
Personal responses to puberty
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Behavior and emotions
• Problem behavior (e.g., aggression, conduct
disorder symptoms, etc.) has been attributed to
hormonal changes (but also to physical maturation
and brain changes)
• Testosterone (T) can lower boys’ frustration
tolerance  readiness to engage in aggression
• Rapid hormonal changes are associated with
depression, but “hormonal storm” view is far too
simplistic. In fact…
• Hormonal levels account for only a tiny percentage
of the variance in adolescents’ negative affect –
social influences account for considerably more
Pubertal timing and adjustment
• There is a lot of research (which is conflicting) on
the effects of timing of physical development
• Theoretically, being “off-time” creates more
stress and vulnerability to adjustment problems
Maturation - Girls
• According to Arnett, the effects of early
maturation are especially negative for
girls, who are at risk for a variety of
problems:
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Depressed mood, Negative body image,
Eating disorders
Delinquency, Substance use, School
problems, Conflicts with parents
Caveat: Early-maturing girls with no history
of behavior problems experienced fewer
problems than did girls with a history of
behavior problems who matured on time
• Late maturing girls have few of the
problems that early-maturing girls have
Early Maturation - Boys
• The effects of early maturation are more
mixed for boys
• Early maturing boys have:
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More favorable body image
Higher popularity
Earlier involvement in substance use,
delinquency, and sex
Late Maturation – Boys
• Late maturing boys show evidence of
problems
• Compared with boys who mature “on
time” late maturing boys have higher
rates of:
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Alcohol use
Delinquency
Lower grades in school
Neural changes
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New research in cognitive and affective
neuroscience (Intro to “The Teenage Brain” PBS-DVD & Sci American
podcast on the teen brain)
• Brain actively reorganizes itself – cells and connections
are pruned (for efficiency)
• Prefrontal cortex (planning and decision making)
undergoes a growth spurt in early A and continues to
develop throughout A
• Cortical-limbic pathways (thought-emotion connections)
are slowly developing during adolescence (e.g., research
on teens’ difficulty in reading emotions in people’s faces)
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Implications?
• Research example
incarcerated adolescents displayed more
impulsivity and poorer critical thinking than age-matched
students (Chretien & Persinger, 2000).
• Driving and multitasking
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Much more research needed