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Chapter 5:
Physical and Cognitive Development in Infancy
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“A great blooming, buzzing confusion”
 -William James
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“A lively squirmingt bit of flesh capable of making a few
simple responses.”
 -John Watson
The Design of the Newborn
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Neonates have little physical or motor control.
Does the newborn have ideas?
What does the newborn feel?
Does it feel sadness when it cries?
Neonatal Tests
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APGAR (appearance, pulse, grimace, activity, respiration)
 1-5 minutes after birth
Brazelton Neonatal Behavioral Assessment Scale
Given several days after birth (day 3), then a few days later
 Assess neurological dvmt, reflexes, reactions to people
 Looks at 20 reflexes and reactions to circumstances
 Rate newborn on 26 items, each has specific
measurements
 4 major categories
 Physio, motoric, state, interaction
 Global terms: worrisome, normal, superior
Reflexes
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Development occurs in physical, social, and cognitive ways
Neonate has the primitive reflexes that allow it to survive
(with assistance)
 Sucking reflex (disappears 3-4 mos)
 Babinski reflex (diminishes 1 mo, gone by 5-6)
 Rooting reflex (becomes voluntary during 1st year)
 Moro or startle (disappears 3-4 mos)
 Grasping (gone by 9 mos. -1 year)
 Others
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Orienting response
Habituation
Non-nutritive sucking
Nutrition and Brain Development
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Newborn’s central nervous system is immature at birth
Activity in association areas of the brain – cortex – increases
rapidly as child experiences the world
Optimal brain development is influenced by sensory/cognitive
stimulation & nutrition
Got breastmilk?
Figure 5.1 Percentage of
mothers breast-feeding in
the world. Source: Based on
Bellamy (1999a), page 101.
Brain & Behavior in Newborns
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At birth infant brain weighs 25% of adult weight
Brainstem is most highly developed at birth (necessary for
survival – heart rate and breathing)
Major early development involves the interconnections in the
brain – forming of new connections among and between
neurons
Brain Development
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Brain reaches 75% of adult weight by age 2 years
Development of protective coatings on neurons (myelin
sheaths) occurs rapidly
Brain proliferation – 2 year old has an enormous number of
potential connections among neurons – allows for rapid
learning, especially language
Figure 5.6 The main structures of the brain. The various substructures of the cerebrum are
intimately involved in “higher” mental functions. In particular, the frontal lobe is associated with
speech and reasoning. The cerebrum’s 1/8-inch-thick covering, the cerebral cortex, is so
convoluted that its surface area is actually much larger than the space it occupies.
Infant States
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Six distinct infant states:
 Regular sleep
 Irregular sleep
 Drowsiness
 Alert inactivity
 Alert activity
 Crying
Figure 5.8 The infant’s state reflects level of alertness or responsiveness to the environment.
States are closely related to the infant’s level of brain activity (arousal). Source: Based on
Wolff (1966).
Physical Growth
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Average infant 20 inches long, 7.5 lbs
Babies lose 5-7% of weight as newborn
Then, gain 5-6 oz. Per week for the first mo.
Doubled weight by 4 mos, 3x at 1 yr
Grow 2 inches per month, 1.5x length at 1 yr
Almost 3 ft by 2 yrs, 26-32 lbs.
Figure 5.2 Height at the 50th
percentile for U.S. infants,
birth to 24 months. Source:
Adapted from Health
Department, Milwaukee,
Wisconsin; based on data by
H. C. Stuart and H. V.
Meredith, prepared for use in
the Children’s Medical Center,
Boston. Used by permission
of the Milwaukee Health
Department.
Figure 5.3 Weight at the 50th percentile for U.S. infants, birth to 24 months. Source: Adapted
from Health Department, Milwaukee, Wisconsin; based on data by H. C. Stuart and H. V.
Meredith, prepared for use in the Children’s Medical Center, Boston. Used by permission of the
Milwaukee Health Department.
Figure 5.4 Manifestations of malnutrition in non-industrialized countries. Source: Based on
data from Bellamy (1999a), p. 101.
Figure 5.5a Decline in infant mortality rates from all causes and from SIDS for infants under 1
year, 1980–1995. Source: Based on U.S. Bureau of the Census (1998), p. 99.
Figure 5.5b Decline in infant mortality rates in Canada from all causes, 1975–1995. Source:
Based on Canada Yearbook, 1999.
Motor Development
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As brain develops, so do motor skills
Some reflexes become more controlled
 Moro disappears
 Sucking
 Rooting
Perceptual Development
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Sensation – physical stimuli converted into neural impulses
Perception – brain’s interpretation of sensation
Conceptualization – intellectually understanding what is
perceived
From Infant Perception…Infant visual preferences
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Prefer patterns of faces to colors/brightness
Even at 2 days, prefer mother’s face
Newborn vision 20/200 or 20/600 vs our 20/20
1 day old, prefer stripes vs. gray patch if stripes are
1/10th inch thick
 At 2 mos, 1/20 inch
 At 8 mos. 1/80 inch
 6 yr old/adult can see stripes at 1/300 inch thick
More infant vision
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Color vision well developed by 2-4 mos.
At 4 mos, red/blues preferred
Depth Perception
 Visual cliff (Gibson & Walk, 1960)
 Experienced crawlers afraid of cliff
 Others not
Infant Hearing
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Prefer mother’s voice
At 3 days can discriminate among voices
Figure 5.9 Relative percentage of time infants looked at six circular visual stimuli. The graph
depicts infants’ preference for the human face and for more complex stimuli. Source: Based on
data in Robert L. Fantz (1963). Pattern vision in newborn infants. Science 40: 296–297.
Copyright 1963 by the American Association for the Advancement of Science. Used by
permission of the American Association for the Advancement of Science and the author.
Sudden Infant Death Syndrome
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An infant death attributed to an unknown cause
Some common characteristics are associated with SIDS
 Age – peaks between age 2 and 4 months
 Gender – males account for 60% of cases
 Maternal smoking
 Paternal smoking (less predictive than maternal)
 Sleeping in a face down position
Preventing SIDS
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SIDS is most common under 3 simultaneous conditions
 A vulnerable infant (poor lung development, etc.)
 A critical developmental period (2-4 months of age)
 An external stressor (parental smoking, temperature
changes, infant infection, sleeping in a prone position)