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Families Can Be Together ForeverClick on the temple to start the video.
The Developing PersonThrough Childhood and Adolescence
Chapter 5The First Two Years: Biosocial Development
➢Body Changes
➢Brain Development
➢Senses and Motor Skills
➢Public Health Measures
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
• At birth the average infant weights 7 ½ lbs.
–Weight typically doubles by 4th month and triples by the first birthday.
–physical growth slows in 2nd year
–By 24 months weight is about 28-30 lbs, height about 32”-36”
–By 2 years height is half the adult height
• percentiles: numbers
fall between 0 and
100, with 50 being
exactly average.
– Actual percentile isn’t
as important as a
change in the
percentile
Percentile
• head-sparing: biological
mechanism that
protects brain
when malnutrition
affects body
growth
Sleep• New babies spend about 17 hours daily
sleeping.
• Regular sleep correlates with:
– normal brain maturation
– learning
– emotional regulation
– psychological adjustment
• 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
– SLOW WAVE SLEEP: The term for a deeper, dreamless sleep state.
Dreaming and transitional sleep decline in the first few weeks.
• co-sleep: custom in which parents and children (usually infants) sleep together in the same room.
• co-bedding or bed-sharing: sleeping in the same bed.
• Breastfeeding is more common, but so is infant death
• Sleeping in the same room is beneficial; being in the same bed is not.
• Parent hear contradictory advice about this practice.– Parents in Asia, Africa, and Latin America favor co-sleeping.
– Western parents put infants to sleep in a crib in a separate bedroom.
Although co-sleeping infants awaken twice as often as
solo-sleeping infants (six versus three times a night)…
…co-sleeping babies got as much sleep as solo sleepers because they went back to sleep more
quickly.
• Newborn’s skull is disproportionately large.– at birth the brain is 25% of
the adult brain weight • body only 5% of the adult
weight
• By age 2 the brain is almost 75% of the adult brain weight.– Increase in brain
weight is due to the proliferation of dendrites in the first year of life.
Brain Development
Baby’s head proportion is large
-Nerve cells, called neurons, are created before birth,
at a peak production
rate of 250,000 new cells
per minute in
mid-pregnancy.
-In infancy, the human brain
has billions of neurons.
• Cortex: outer layers of the brain:
– most thinking, feeling, and sensing involve cortex
– contains all the neurons that make
conscious thought possible (70% of neurons are in the cortex)
– areas devoted to the basic senses mature earlier
• dendrite: fiber
that extends from
the neuron
– receives
electrochemical
impulses
transmitted from
other neurons via
their axons
• axon: fiber that
extends from a
neuron
– transmits
electrochemical
impulses to dendrites of other
neurons
Dendrites Sprouting
• 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.
• 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
– transient - temporary
• Pruning occurs when the unused
neurons and disconnected dendrites
atrophy and die.
Transient Exuberance and Pruning
• self-righting: inborn drive to remedy a
developmental deficit
– Ex: toys
• 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 based on minimal experiences
Because the prefrontal cortex is not developed yet,
telling infants to stop crying is
POINTLESS because they CANNOT decide to stop crying.
Such decisions require brain maturity.
Some adults react by SHAKING A BABY.
This can cause SHAKEN BABY SYNDROME.
Shaken baby syndrome is a life threatening
condition that occurs when
a baby is shaken back and forth.
Although it is successful in making the infant stop
crying, it is also successful in DEATH to the infant
• experience-expectantbrain 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,
specific experiences
that may or may not be available.
Necessary & Possible
Experiences
• Necessary to develop a person’s potential:
– caressing newborn
– talking to preverbal infant
– showing affection toward a small child
– experience expectant: this is the minimum
needed for normal development
Implications
for
Caregivers
Lack of
stimulation-stunts the brain
Overstimulation-waste of time
and money
• Isolation and sensory
deprivation harm the
developing brain,
including social and
emotional development
– Ex: rat studies
– Ex: Romanian orphans
• Experienced catch-up
physical growth but were
emotionally damaged
• Children adopted after 6
months had 15 point lower IQ
Severe Social Deprivation
Romanian orphanages taught us
the importance of contact comfortfor normal development.
Self-
righting:
toys don’t
have
to be
expensive!
Piaget called the first
period of intelligence
the sensorimotor stage.
– Emphasized that
cognition
develops from
senses and motor
skills
Sensation
and
Movement
• Sensation: response of a sensory system to a stimulus
– eyes, ears, skin, tongue, nose
• Perception: mental processing of sensory information
when brain interprets a sensation
• Cognition: the mental action or process of acquiring
knowledge and understanding through thought,
experience, and the senses.
The Five Senses
• develops during last trimester
- acute at birth
- certain sounds trigger reflexes
• Young infants are particularly attentive to the human voice
• before comprehension babies understand:
- Rhythm
- Which syllable to stress
- Inflection (Chinese).
Hearing
• Vision is the least
mature sense at birth.
• Newborns are “legally
blind”
– focusing only on
objects between 4 and
30 inches away
• binocular vision: ability
to focus the two eyes
in coordinated
manner, usually
develops at 2-4 mos.
Seeing
Infant vision still undeveloped
The senses of smell, taste, and touch function at birth
and rapidly adapt to the social world.
Smelling, Tasting, and Touching
• Touch is comforting to normally developing
babies. Many different kinds of touch:
“wrapping,” caressing, patting, massage
etc.
• It is unknown when infants first feel pain;
they appear to feel it differently (both less
and more) than adults.
Touch
and
Pain
Babies need
touch!
• motor skills: learned
ability to move some
part of the body
• reflex: unlearned,
involuntary action or
movement emitted in
response to a
particular stimulus
Motor Skills
• All healthy babies
develop motor skills
in the same
sequence.
• The age of
acquisition varies
according to
culture.
• Depends on brain
maturation, muscle
development, and practice.
• Unusual delays are
a cause for
concern.Cultural Variations
FINE MOTOR SKILLS:
physical abilities involving
small body movement,
especially of hands and
fingers.
-2 months: excitedly wave
arms
-3 months: can touch
precise objects
-4 months: can grab, but
their timing is off
-6 months: with
concentration, can reach
for, grab, and hold onto an
object
gross motor skills:
physical abilities involving large
body movements, such as walking
and jumping
Sensation and Movement
Sitting:•By three months, babies
have sufficient muscle
control to be lap-sitters if
support is provided.
•By six months they can
usually sit unsupported.
Crawling:•By five months, babies can
use their arms and legs to
inch forward.
•By eight to ten months
they can usually lift their
midsection and crawl.
Walking:Walking progresses from
reflexive, hesitant, adult-
supported stepping to a
smooth, coordinated walk.
• By nine months , can step
while holding on
• By ten months, can alone
momentarily
• By twelve months, can
walk well, unassisted
Three needed factors:
• Muscle strength
• Brain maturation
• Practice
Infants respond to motion:
Ex: Driving, swinging the carseat, rocking
By six months, infants have learned to
coordinate the senses.
Dynamic Sensory Systems
Rocking, cars, swinging – baby loves
motion!Just don’t turn on their favorite song!
Click the baby to start the video.
• Immunization
– Dramatic Successes:
smallpox, polio, measles,
rotavirus.
– Problems with
Immunization: parental
concerns, more
independent studies needed.
– Autism rate is 1/45.
– What causes autism?
Surviving
in Good
Health
• sudden death syndrome (SIDS)– a seemingly healthy infant suddenly stops breathing and dies unexpectedly while sleeping
• “Back to sleep”
Sudden Infant
Death
Syndrome
• 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
Nutrition: Breast is Best
Although breast is
best, breast milk may
be deficient in
Vitamin D.
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
Stunting: The failure
of children to grow
to a normal height
for their age due to
severe and chronic
malnutrition.
Wasting: The
tendency for
children to be
severely
underweight for
their age as a result
of malnutrition.
• kwashiorkor: disease of chronic malnutrition during childhood. Causes a distended belly.– makes child more
vulnerable to other diseases • measles
• diarrhea
• influenza
• Breathing reflex
– Also hiccups, sneezes, and thrashing
• To Maintain Body Temperature
– Cry, shiver, tuck legs
• To facilitate feeding
– Sucking, rooting, swallowing, spitting up
Reflexes
Critical for
Survival