Slide 1
5
Physical Development in
Infancy
John W. Santrock
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Slide 2
Physical Development in
Infancy
• How Do Infants Grow and Develop
Physically?
• How Do Infants Develop Motor Skills?
• How Can Infants’ Sensory and Perceptual
Development Be Characterized?
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 3
Images of Children
• Bottle-feeding in developing countries
– Unsterilized bottles, formula made with unclean
water
– Many children get common illnesses; may die
• Breastfeeding in developing countries
– Breast milk has advantages; immunizes newborn
• Hospitals have vital role in educating mothers
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 4
Patterns of Growth
• Cephalocaudal: size, weight, and
feature differentiation gradually work
from top to bottom
• Proximodistal: growth starts at center
of body and moves toward extremities
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Changes in Proportions of
the Human Body During Growth
Slide 5
Fig. 5.1
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How Do Infants Grow and Develop Physically?
Slide 6
Height and Weight
• Average North American newborn is 20
inches and 7½ pounds
– Birth weight doubled by age 4 months;
tripled at end of first year
– First year growth averages 1 inch per month
– 1½ times birth length at end of 1st year
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 7
Height and Weight
• Average 2-year-old
– 26 to 32 pounds and 32 to 35 inches tall
(almost half of their adult height)
– Growth rate considerably slower in
second year
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 8
Brain Development
• Extensive growth in utero and infancy
• Shaken baby syndrome: brain swelling
and hemorrhaging
• PET and MRI scans may harm infant
• EEG shows brain activity spurt from 1½
to 2 years of age
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 9
Brain Development
• Mapping the brain
– Forebrain
• Cerebral cortex with 2 hemispheres
• 4 lobes in each hemisphere
– Frontal, Occipital, Temporal, Parietal
• Each hemisphere has lateralization
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Slide 10
The Human Brain’s Hemispheres
Fig. 5.3
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Slide 11
The Brain’s Four Lobes
(body sensations)
(voluntary
movement
and thinking)
Prefrontal
cortex
(vision)
(hearing)
Fig. 5.4
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 12
Brain Development
• Neuron: info processing nerve cell
– Axons and dendrites
• Myelin sheath: layer of fat cells
– Encases and insulates most axons
– Myelination continues into adolescence
• Synapses: tiny gaps
– Neurotransmitters
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Slide 13
The Neuron
Fig. 5.5
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
The Development of Dendrite Spreading
At birth
1 month
3 months
15 months
Slide 14
24 months
Fig. 5.6
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 15
Brain Development
• “Blooming” and “pruning”
• Synaptic overproduction peaks about 4
months after birth
• Prefrontal cortex overproduction peaks
about 1 year of age
– Adult density achieved in adolescence
– Heredity and environment affect timing
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Slide 16
Synaptic Density in Human Brain from Infancy to Adulthood
70
Newborn
Adolescence
60
Synaptic density
50
40
30
20
10
adult
0
100
200
300
400
500
600
800
1000
1500
2000
3000
4000
6000
8000 10,000
Age in days (from conception)
Fig. 5.7
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 17
Early Experience
and the Brain
• Environmental experiences important in
brain’s development
• Infant’s brain waiting for experiences to
determine connections among neurons
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 18
Early Experience
and the Brain
• Early experiences affect development
– Enriched environment makes brain
• Heavier in weight with thicker layers
• Develop more neural connections
• Produces higher neurochemical activity
– Impoverished environment
• Depression is common
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 19
Sleep
• After about 4 months, infant has more
adult-like sleep patterns
• Culture Affects Sleep Patterns
– Length of sleep periods related to sleeping
arrangements and parental activities
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 20
Sleep
• Regulation of wake-sleep cycle reflects
neurological maturation; cycles vary
• REM (Rapid Eye Movement) sleep
– Adults—fifth of sleep
– Infants—half of sleep
– May promote brain’s development in infancy
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Fig. 5.10
Slide 21
Sleep Across the Human Life Span
24
16
Total daily sleep (hours)
14
12
10
8
6
4
2
0
1-15
days
Newborn
6
mo
12
mo
18
mo
Infants
2
yrs
10
yrs
20
yrs
Children Adolescents
30
yrs
Adults
40
yrs
50
yrs
60
yrs
70
yrs
80
yrs
90
yrs
Older adults
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 22
Shared Sleeping
• Culture and Sleeping Arrangements
– Sharing bed common in many cultures
– Crib/separate room common in U.S.
– American Academy of Pediatrics
discourages co-sleeping because of
stress and SIDS risk
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 23
Sudden Infant Death
Syndrome (SIDS)
• Infant stops breathing, usually during
night, and dies without apparent cause
– Highest cause of infant death in U.S.
– Highest risk is 4 to 6 weeks of age
– Prone position increases risk
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 24
Sudden Infant Death
Syndrome (SIDS)
• Increased risks if:
– Highest risk in
– Lower birth weight
African American
– Siblings with SIDS
and Inuit infants
– Sleep apnea
– Lower SES groups
– Exposure to cigarette smoke
– Placement in soft bedding
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 25
Nutrition
• Healthy infants need
– Loving, supportive feeding environment
– 50 calories per day per pound of weight
– Fat; very important for growth
– Breast milk (nature’s food)
– Demand feeding becoming more popular
– More fruits and vegetables, less junk food
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 26
Breast Versus Bottle Feeding
• Breastfeeding is better
– Appropriate weight gain, lowers obesity risk
– Prevents or reduces allergies and infections
– Promotes neurological and cognitive growth
– Lowers risk of SIDS and cancers
– Better visual acuity and bone density
– The only option in poor countries
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 27
Malnutrition in Infancy
• Infants can develop
– Marasmus: wasting away of body tissues
in infant’s first year, severe lack of protein
– Kwashiorkor: deficiency in protein; child’s
abdomen, feet become swollen with water
–
– If not fatal, effects are detrimental; lowest
SES aided most by supplementary feeding
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Grow and Develop Physically?
Slide 28
Health
• Immunization begins in infancy
• Accident Prevention
– Increased monitoring needed in infancy
– Asphyxiation: leading cause of death under 1
– Chocking hazards: toys, chunky foods
– Burn risks: sun, electrical, heaters, hot water
– Other risks: car accidents, cuts, pet bites
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Develop Motor Skills?
Slide 29
Dynamic Systems Theory
• Gesell revealed motor skill development
– Maturation: unfolding genetic plan
• Perceptions and motivation lead to new
motor skills or fine tuning
– Nervous system maturation
– Repeated “cycles” of actions
– Nature, nurture, and environment interact
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Develop Motor Skills?
Slide 30
Reflexes
• Built-in reactions to stimuli
– Rooting: reaction to cheek/mouth touched
– Sucking: automatic sucking object in
mouth
– Moro reflex: startle response causes back
arching, rapid closing of arms and legs
– Grasping: when something touches palm
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Develop Motor Skills?
Slide 31
Gross Motor Skills
• Milestones for large muscle activities
– Development of posture
– Learning to walk; locomotion, balance,
and practice (crawling to walking)
– Development in second year
• Skilled and mobile: pull toys, climb stairs
• Natural exercise: walk quickly, run stiffly
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Slide 32
Milestones in Gross Motor Development
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Develop Motor Skills?
Slide 33
Cultural Variations in Guiding
Infants’ Motor Development
• Infants reach motor milestones
in different cultures based on
activity opportunities
– Variations not large
– Milestones reached within normal
age ranges
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Do Infants Develop Motor Skills?
Slide 34
Fine Motor Skills
• Finely tuned (coordinated) movements
– Perceptual-motor coupling necessary
• Finger dexterity (thumb and forefinger)
• Two types of grasps: Palmar and Pincer
• Wrists and hands turn and rotate more
– Experience and exercise have impact
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 35
What Are Sensation and
Perception?
• Sensation: occurs when information
contacts sensory receptors – eyes,
ears, tongue, nostrils, and skin
• Perception: interpretation of sensation
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 36
The Ecological View
• People directly perceive information in
the world around them
– Perception allows human-environmental
interaction and adaptation
– Affordances: opportunities for interaction
offered by objects; enhanced by previous
experiences
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 37
Studying Infant Perception
• Infant cannot talk
– Head movement indicates some vision
– Visual preference method: Fantz
measured length of gaze and patterns
of preference in “looking chamber”
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 38
Habituation and Dishabituation
• Habituation: decreased responsiveness
to stimulus after repeated presentations
• Dishabituation: recovery of habituated
response after change in stimulation
• Tracking: applied to vision and hearing
– High-amplitude sucking, videos, computers
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 39
Visual Perception
• Visual acuity and color in newborn
• Perceiving patterns – patterns preferred
• Perceptual constancy – size, shape
• Depth perception
– ‘visual cliff’ study and visual expectations
– Binocular cues and stereoacuity
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 40
Perceptual Constancy
– Size constancy
– Shape constancy
Recognition that
object remains the
same even though
the retinal image
changes
Recognition that
object remains the
same even though
its orientation
changes
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 41
Other Senses
• Hearing: begins in womb
– Infancy changes: volume, pitch, localization
• Touch and Pain
• Smell: present shortly after birth
• Taste: may exist before birth
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 42
Intermodal Perception
• Ability to relate and integrate
information from two or more
sensory modalities
– Exist in world of objects and events
– Crude exploratory forms of intermodal
perception exist in newborns
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
How Can Infants’ Sensory and Perceptual Development Be Characterized?
Slide 43
Perceptual-Motor Coupling
• Perception and activity were traditionally
considered separate.
• Dynamic systems approach and ecological
approach both suggest they are linked.
– Dynamic systems: infants assemble motor
behavior for perceiving and acting
– Ecological: action can guide perception and
perception can guide action
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.
Slide 44
5
The End
© 2009 The McGraw-Hill Companies, Inc. All rights reserved.