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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