Kathleen Stassen Berger
Part II
Chapter Five
The First Two Years: Biosocial Development
Body Changes
Brain Development
Senses and Motor Skills
Public Health Measures
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2
Body Changes
• In infancy:
– growth is fast
– consequences of neglect can be severe
– gains need to be monitored
• Check-ups need to include:
– measurement of height
– weight
– head circumference
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• At birth the average
infant weights 7 ½ lbs.
– typically doubles by
4th month
• triples by 1st
birthday
– physical growth slows
in 2nd year
– by 24 months weight
is about 30 lbs, height
about 32”-36”
4
• head-sparing: biological
mechanism that protects
brain when malnutrition
affects body growth
• percentiles: numbers fall
between 0 and 100, with
50 being exactly average
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Sleep
• New babies spend about 17 hours daily
sleeping.
• Regular sleep correlates with:
– normal brain maturation
– learning
– emotional regulation
– psychological adjustment
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Maturation and Sleep Patterns
• Over the first month, amount of time in each stage of
sleep changes.
• Newborns dream a lot with a high proportion of REM
sleep.
• rapid eye movement sleep (REM): stage of sleep
characterized by:
– flickering eyes
– dreaming
– rapid brain waves
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• First-borns typically receive more attention,
which correlates to them having more sleep
problems than later borns.
• Insisting that an infant conform to parents’
sleep-wake schedule can be frustrating.
– in some cases, harmful
• brain patterns and digestion not ready for adult
sleep patterns.
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• co-sleep: custom in which parents and children
(usually infants) sleep together in same bed
• Parent hear contradictory advice about this
practice.
– Parents in Asia, Africa, and Latin America favor cosleeping.
– Western parents put infants to sleep in a crib in a
separate bedroom.
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Brain Development
• Newborn’s skull is disproportionately
large.
– at birth is 25% of the adult brain
• body only 5% of the adult weight
• By age 2 the brain is almost 75% of
the adult brain weight.
– The child’s total body weight is only
about 20% of its adult weight.
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Basic Brain Structures
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• In infancy, human brains have billions of
neurons.
– Some deep inside brain stem, region that
controls automatic responses, such as:
•
•
•
•
heartbeat
breathing
temperature
arousal
• about 70% of neurons are in the cortex
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• cortex: outer layers of the brain
– most thinking, feeling, and sensing involve cortex
• axon: fiber that extends from a neuron
– transmits electrochemical impulses to dendrites of
other neurons
• dendrite: fiber that extends from the neuron
– receives electrochemical impulses transmitted from
other neurons via their axons
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• synapse: intersection between the axon of
one neuron and the dendrites of other
neurons.
• Axons and dendrites do not touch at
synapses.
– the release of chemicals called
neurotransmitters are sent by electrochemical
impulses.
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Transient Exuberance and Pruning
• At birth the brain contains more than 100 billion
neurons.
– more than any person will ever use
• A fivefold increase in dendrites in the cortex
occurs in the 24 months after birth.
– about 100 trillion synapses at age 2
– growth called transient exuberance
• Pruning occurs when the unused
disconneted dendrites atrophy and die.
neurons
and
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Experience Shapes the Brain
• Brain structure and growth depends on genes
and experiences.
• Increasing cognitive complexity of childhood
related to a loss rather than a gain of synapses.
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Necessary and Possible Experiences
• experience-expectant brain functions
– require certain basic common experiences,
which an infant can be expected to have in
order to develop normally
• experience-dependent brain
functions
– depend on particular, variable experience
that may or may not develop
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Implications for Caregivers
• Necessary to develop a person’s
potential:
– caressing newborn
– talking to preverbal infant
– showing affection toward a
small child
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• self-righting: inborn drive to remedy a
developmental deficit
• Human brain designed to grow and adapt.
– some plasticity retained throughout life
– brain protects itself from overstimulation
• overstimulated babies cry or sleep
• understimulated babies adjust by developing
new connections lifelong.
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Sensation and Movement
•
Piaget called the first period of
intelligence the sensorimotor
stage.
–
•
emphasizes that cognition
develops from senses and motor
skills
Infant brain development
depends on sensory experience
and early movement.
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The Five Senses
•
sensation: response of a sensory
system
– eyes, ears, skin, tongue, nose
•
perception: mental processing of
sensory information when brain
interprets a sensation
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Hearing
•
develops during last
trimester
-
•
acute at birth
Young infants are
particularly attentive to
the human voice.
before comprehension
babies understand:
•
-
rhythm
segmentation
cadence of spoken words
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Seeing
•
Vision is the least mature sense at birth.
•
Newborns “legally blind”
–
•
focusing only on objects between 4 and 30 inches
away
binocular vision: ability to focus the two eyes
in coordinated manner in order to see an image
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Smelling, Tasting, and Touching
The senses of smell, taste, and touch function at
birth and rapidly adapt to the social world.
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Motor Skills
•
motor skills: learned ability to move some
part of the body
•
reflex: unlearned, involuntary action or
movement emitted in response to a
particular stimulus
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Reflexes Critical for Survival
• Breathing reflex
– Also hiccups, sneezes, and thrashing
• To Maintain Body Temperature
– Cry, shiver, tuck legs
• To facilitate feeding
– Sucking, rooting, swallowing, spitting up
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Reflexes
•
reflexes that are important signs of normal
brain and body functioning:
–
–
–
Babinski reflex–
• when feet are stroked, toes fan
upward
Stepping reflex–
• held upright move their legs to
walk
Swimming reflex–
• when laid horizontally on their
stomachs, stretch out arms and
legs
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Sensation and Movement
gross motor skills: physical
abilities involving large
body movements, such as
walking and jumping
fine motor skills: physical
abilities involving small
body movement,
especially of hands and
fingers
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Public Health Measures
•
Pubic health refers to the wellness of an entire
population.
– 9 billion children born between 1950 – 2008.
– 2 billion died before age 5
– preventive care includes:
• childhood immunization
• clean water
• adequate nutrition
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•
•
•
immunization: process that stimulates the
body’s immune system to defend against
attack by a particular contagious disease
successes in immunization include:
– smallpox
– polio
– measles
– rotovirus
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Sudden Infant Death Syndrome
•
•
•
Infant mortality worldwide has plummeted in
recent years.
sudden death syndrome (SIDS)– a
seemingly healthy infant suddenly stops
breathing and dies unexpectedly while
sleeping
1990 in the U.S.:
–
5000 babies died of SIDS (about 1 in 800)
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Breast is Best
•
For most newborns, good nutrition starts with
mother’s milk
–
•
Less likely to get sick
• breast milk provides antibodies against any
diseases to which the mother is immune.
colostrum: thick, high-calorie fluid secreted by
woman’s breast for first three days after birth
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Malnutrition
•
Chronically malnourished infants and
children suffer in three ways:
– brains may not develop normally
– have no body reserves to protect against
common disease
– some diseases result directly from
malnutrition
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•
marasmus: disease of severe protein-calorie
malnutrition during early infancy
–
–
–
•
growth stops
body tissues waste away
eventually dies
kwashiorkor: disease of chronic malnutrition
during childhood
–
makes child more vulnerable to other diseases
• measles
• diarrhea
• influenza
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