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Chapter 4:
PhysicalDevelopment
in Infancy
McGraw-Hill 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
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Lifespan DevelopmentChapter 4
Physical
Growthand
Development
in Infancy
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Infant physical development isextensive in first 2 years of life
Within 1st year
Child grows out of having a gigantichead disproportionate to the body
From some basic reflexes, to capacity to
sit, stand, climb, and walk almost
anywhere During 2nd year: rapid growth sequence
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Cephalocaudal pattern of development
Sequence of growth occurs from top (head) to
bottom (feet)size, weight, and sensory and
motor development
Proximodistal pattern of development
Growth sequence begins at center of body and
moves toward extremities
Average length and average weight of NorthAmerican newborns are 20 inches and 7.5 pounds,
respectively
95% of newborns are full-term
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Brain continues developing past infancy
Shaken baby syndrome: brain swelling and hemorrhaging
from child abuse trauma
At birth, brain is 25% of adult weight; at 2 years of age, it
is 75%
During infancy and toddlerhood, neurons develop as:
They increase in size and connections to one another
The myelin sheath continues to develop
Unimportant neurons die so that more efficient connections
can be formed (synaptic pruning)
Brains primary motor areas develop earlier than other
areas
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Figure 5.2
The Neuron
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Myelination for vision usually completed in 6 months
after birth and for hearing at 4 or 5 years of age
Some myelination continues into adolescence
Most dramatic changes in brain occur in first 2
years of life (see Fig. 5.3)
Synapses are tiny gaps between neurons; chemical
interactions occur here between axons and dendrites
Pruning of connections: overproduction of
synapses leads to gradual retraction
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Development of Dendritic Spreading
At birth1 month
24 months
3 months15 months
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EEG measures brains electrical activity
PET: Positron-emission tomography
MRI: Magnetic resonance imaging
Cerebral cortex divided into 2 hemispheres
Lateralization: Process by which the two halves of
the brain become specialized to perform different
functions.
Each hemisphere is divided into 4 main areas:
Frontal lobe: voluntary thinking and movement
Occipital lobe: vision functions
Temporal lobe: hearing functions
Parietal lobe: processing body sensations
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RightLeft
Approach
behaviors
Withdrawal
behaviors
Joy, bliss,pride, anger,hostility,jealousy,interest,concern,responsibility
Distress,
misery,agony,disgust,contempt,resentment,fear, horror,anxiety
Primaryhearing Primary
visual
Motorcortex
Languagecomprehension
Languagestructure
Sensorycortex
Concentrating,
planning,problem solving
Interpretingexperiences
Based on Figure 5.6
The Brains Hemispheres and Emotions
Front
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Enriched environments promote faster braindevelopment than deprived ones
After birth: sights, sounds, smells, touches,language, and eye contact help shape the brainsneural connections
Cultural variations influence infant sleep patterns;newborns sleep an average of 1617 hours per day
The practice of shared sleeping, in which anewborn shares a bed with mother, varies amongcultures
i.e., Kipsigis of Kenya rarely sleep more than 3 hours at atime until after 8 months.
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SIDS: sudden infant death syndromeinfants stop
breathing and die without apparent cause
Highest risk is in first 46 weeks of life
Highest cause of infant death in U.S. annually
Risk decreases when infant sleeps on its back
Higher risk factors associated with SIDS:
Infants with siblings who died from SIDS
Infants with sleep apnea or low birthweight
Infant passively exposed to cigarette smoke
Being from lower SES or being African
American or Eskimo
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Nutrition is important as infant nearly triplesweight in 1st year
Low-fat, low-calorie foods and skim milk can retard babysdevelopment in first 2 years of life
Benefits for infant from breast milk can include
Denser bones in childhood/adulthood
Reduced incidence of asthma, SIDS, ear infections, diarrhea,respiratory infections, bacterial and urinary tract infections
and overall improved immune function during infancy.
Reduced childhood cancers and breast cancer as female
adult
Improved neurological and cognitive development
Improved visual acuity
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Mother should not breast-feed if she has AIDS or other
infectious diseases or active tuberculosis or is taking drugs
that can be transmitted through breast milk
Prolonged and severe malnutrition can be detrimental to
childs cognitive, physical, and social development
Marasmus: results from protein-calorie deficiency during
first year and causes wasting away of tissues.
Kwashiorkor: results from deficiency in protein; causes
distended belly and usually appears between ages 1 and 3.
Toilet training should be a positive experience starting at
around 2 years
of age or older
Intensive toilet training before 27months is ineffective.
readiness includes social, cognitive and biological factors.
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Dynamic systems view:
Motor development is not a result of nature alone
but an active process in which nature and nurture
work together Infants assemble motor skills for perceiving and
acting, as solutions to goals
Environment motivates infants to act
Perceptions help infants fine-tune movements
Three factors enable new behaviors to emerge
Motor Development
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Converging factors enabling newbehaviors to emerge:
Development ofnervous system and bodys
physical capabil i ties
The goalthat the child is motivated to reach
The environmental supportfor the necessary
skills used to reach a goal
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Child is encouragedby grandmotherChild is nurtured
by mother
Babymastersbalance
andgrasping
things
Perceptions, nurturing, and practiceallow baby to fine-tune grasping
Baby begins tocrawl and grasp
things
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Motor development begins with reflexes
Sucking and rooting reflexes disappear about
34 months after birth Moro reflex (automatic arching of back
and wrapping of arms to center of body
when startled) disappears about
34 months after birth Grasping reflex (infants hands close
around anything that touches the palms)
disappears as voluntary grasp develops
Gross motor skills enable large-muscle
activities
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Age in monthsFigure 5.13
1 2 3 4 5 6 7 8 9 110 12 13 1410
D
egreeofmo
tordevelopm
ent
Prone, lift head
Prone, chest up,arms for support
Roll over
Sit without support
Support some weight with legs
Stand with support
Pull self to stand
Walk using furniture for support
Walk alone easily
Stand alone easily
Milestones in Gross Motor Development
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Cultural variations: mothers in developing
countries treat infants differently from mothers
in developed cultures
Jamaican mothers
Regularly massage infants and stretch their
arms and legs
On average, their babies sit and walk alone
23 months earlier than English babies
Algonquin infants in Quebec, Canada
Strapped to cradleboard for 1st year
Sit, crawl, and walk about same time as
those in cultures raised without cradleboard
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Fine motor skills for finely tuned activities
Perceptual-motor coupling (using perception
and motor skills together) is necessary forinfants to coordinate grasping
Experienced infants look at objects longer,
reach for them more, and are more likely to
mouth the objects
Four-month-olds often rely on touch whileeight-month-olds rely on vision to determine
how they will grip an object
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Information is transmitted through smell, touch,
hearing, taste, and vision to sensory receptors
Perceptionis an interpretation of what is sensed
Ecological viewsees environment as rich with
information and sees perceptual system as
selecting from it
Perception enables interaction with, andadaptation to, ones environment
Sensation and Perception
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Infants gain adult-like color vision by 2 months
Two-month-olds scan wide areas of faces and
show preferences for target and stripped patterns
Perceptual constancy in seeing sizes and shapes starts
to develop between 3 and 5 months of age
Depth perception as tested by visual cliff is evident
in 2- to 4-month-old infants
Infants develop expectations about future events at
about 3 months of age (on average)
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Studying Infants Perceptual
Abilities Habituation: gradual reduction in the strength of a
response due to repetitive stimulation (getting a baby used
to a stimulus so it no longer responds to it as if it is new)
Dishabituation: Introducing a new stimulus to cause
responsiveness to return to a high level.
Visual Preference Method: a method used to determine
whether infants can distinguish one stimulus from another
by measuring the length of time they attend to differentstimuli.
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Infants aged 68 months can perceive gravity and
understand that objects can fall or roll
Fetuses can hear sounds during the last 2 months of
pregnancy and recognize the mothers voice at birth
Newborns
Show a preference for human speech
Are born deaf in about 1 in 1,000 cases
Can feel pain at birth
Are sensitive to taste before birth
Sensory input detection is affected by experience
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