Chapter 5: Physical and Cognitive Development in Infancy

“A great blooming, buzzing confusion” -William James

“A lively squirmingt bit of flesh capable of making a few simple responses.”

-John Watson

The Design of the Newborn

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

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, interactionGlobal terms: worrisome, normal, superior

Reflexes

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

Orienting response Habituation Non-nutritive sucking

Nutrition and Brain Development

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

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

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

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

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

As brain develops, so do motor skills Some reflexes become more controlled

Moro disappears Sucking Rooting

Perceptual Development

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

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

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

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

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

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)