Theories of Human Development
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Transcript Theories of Human Development
Physical Development
Chapter 6
Prolonged period of physical growth
Period between birth/puberty mice/rats
(2% of lifespan)
7 years in chimpanzees (17% of lifespan)
20% of total years to growth
Why?
Changes in Body Size
Rapid changes during infancy
– By end of first year, height 50% greater than
birth
– End of second year, 75% greater
– Weight shows similar gains
– If rate maintained, children would be 10 feet
tall and weigh over 200 pounds by age 10; 12
feet tall and weigh several tons by age 18
Changes in Body Size
Slows in early and middle childhood
Sharp acceleration in puberty
•
Figure 6.1 Gain
in height per
year by males
and females from
birth through
adolescence. At
age 10 ½ , girls
begin their
growth spurt.
Boys follow some
2 ½ years later
and grow faster
than girls once
their growth
begins. BASED
ON TANNER,
WHITEHOUSE, &
TAKAISHI, 1966.
Changes in Body Proportions
Different rates
Cephalocaudal
Proximodistal
Exceptions to growth trends in
adolescence
Changes in Body Proportions
Body proportions similar in infancy and
childhood
Major differences occur during
adolescence
Changes in Body Composition
Changes in muscle-fat makeup
Body fat increases pre/postnatally
Peak 9 months
Slender starting in second year until
middle childhood
Changes in Body Composition
Girls more body fat at birth – increases
Around 8, changes begin through puberty
for girls
Opposite happens for boys
Changes in Body Composition
Muscle different rate than fat
Infancy/childhood slow
Adolescence rises
In children, muscle composes 18-24% of
body weight for both males and females
By their mid-twenties, percent of body
that is muscle averages 24% for females
and about 40% for males
Changes in Body Composition
Both sexes gain muscle at puberty, gain is
greater for boys
– Develop larger skeletal muscles
– Larger hearts
– Greater lung capacity
– Number of blood cells increases
– Thus…?
Skeletal Development
Different rates
Skeletal age
Embryonic skeleton cartilage
Beginning at 6th week of pregnancy, bones
harden (ossify) – process continues
throughout childhood and adolescence
Skeletal Development
Skull fontanelles and sutures
Ankles, feet, wrists, hands develop more
bones
Individual and Cultural Differences
Most differences within normal range
Children at extremes
What accounts for differences in growth?
Secular trends in physical growth
Individual and Cultural Differences
May be due to improved nutrition and
health
– Orphaned babies from developing countries
– Low-income children
– Regions where poverty, famine, and disease
are widespread
Development of the Brain
100-200 billion neurons
Neural tube of embryo
Migrate and differentiate
By end of second trimester, most neurons
are formed
– Produce neurons?
– Brain can compensate
Development of the Brain
Synaptogenesis
– Infants more connections than adults
– Neurons in synapse get crowded and die
Neurons need stimulation to survive
– Synaptic pruning
Development of the Brain
If most neurons are produced prenatally,
what accounts for increase in size of
brain?
– Glial cells
– Myelinization
Development of the Brain
Cerebral Cortex
– Largest structure
– Responsible for intelligence
– Order of development
Development of the Brain
3-6 frontal lobes
6-puberty temporal and parietal lobes
MRIs were used to compare brain activity
in adolescents (10-18) and adults (20-40)
while processing emotional information
Development of the Brain
Lateralization
– When does it occur?
– Tells us about brain plasticity
– Lateralization has already begun at birth
– Lateralization not complete…
Motor Development
Sequence of motor skills same
Large individual variation
Rate of motor development ≠ future
development outcomes
Motor Development
Gross motor development
Fine motor development
•
Table 6.1 Age Norms (in Months) for Important Motor Developments (Based on European
American, Latino, and African American Children in the United States)
Motor Development
Not a series of isolated, unrelated
accomplishments
Cross-cultural research
Motor Development
Beyond Infancy: Motor Development in
Childhood and Adolescence
– Each year, skills improve
Large muscles, eye-hand coordination
– Young children overestimate
– Puberty – males increase in muscle
development; females tend to become less
active
Hormonal Influences on Physical
Growth
Physical changes endocrine system
Hormones
Pituitary gland
Growth hormone (GH)
Hormonal Influences on Physical
Growth
GH body tissues except CNS and
genitals
No prenatal growth, essential from birth
on
Lack GH average mature height of 4
feet 4 inches
Catch-up growth
Hormonal Influences on Physical
Growth
Sexual maturation pituitary secretions
Estrogens female hormones
Androgens male hormones
Both in each sex, different amounts
Hormonal Influences on Physical
Growth
Boys’ testes release large quantities of
testosterone, which leads to muscle
growth, body and facial hair, and other
male sex characteristics, also contributes
to gains in body size
Estradiol causes the breasts, uterus, and
vagina to mature and the body to take on
feminine proportions, also help regulate
menstrual cycle
Hormonal Influences on Physical
Growth
Adrenal androgens
Not sure what sets hormonal processes in
motion
– Combination of heredity, hormones, and body
fat
•
Figure 6.10 Hormonal influences on physical development.
Hormonal Influences on Physical
Growth
In girls, rise in body weight and fat
appears to play a role in sexual maturation
– Serious athletic training/eat little
– Overweight
– Body fat ≥ 17%
– Athletes, eating disorders
Puberty
Physically mature; produce offspring
Changes in physical features related to
sexual functioning
– Primary sexual characteristics
– Secondary sexual characteristics
Puberty
Boys
– Early maturation: advantaged in emotional
and social functioning (seen as more relaxed,
independent, self-confident, and physically
attractive; also tend to be more popular, hold
leadership positions, and are athletic stars)
– Late maturation: not well liked (seen as
anxious, overly talkative, and attention
seekers)
Puberty
Girls
– Early maturation: social difficulties (below average in
popularity, withdrawn, lack self-confidence, hold few
positions of leadership, more likely to be depressed,
smoke/drink, have an eating disorder)
– Late maturation: physically attractive, lively, sociable,
leaders at school
Advantages of maturing early and the
disadvantages of maturing late are greater for
boys than for girls
Heredity vs. Environment
Heredity hormones
Nutrition
– Dietary diseases
Marasmus
Kwashiorkor
Infectious disease
Heredity vs. Environment
Emotional Well-Being
– Nonorganic failure to thrive
– Deprivation dwarfism