Chapter 5: Physical Development in Infancy McGraw-Hill © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.

Physical Growth and Development in Infancy

Infant physical development is extensive in first 2 years of life Within 1st year Child grows out of having a gigantic head disproportionate to the body From some basic reflexes, to capacity to sit, stand, climb, and walk almost anywhere During 2nd year: rapid growth sequence

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 North American newborns are 20 inches and 7.5 pounds, respectively 95% of newborns are full-term

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% Brain’s primary motor areas develop earlier than other areas

The Neuron Figure 5.2

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

Development of Dendritic Spreading At birth 3 months 1 month 15 months 24 months Figure 5.3

EEG measures brain’s electrical activity PET: Positron-emission tomography MRI: Magnetic resonance imaging Cerebral cortex divided into 2 hemispheres Lateralization: hemispheric specialization 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

Language comprehension The Brain’s Hemispheres and Emotions Front Concentrating, planning, problem solving Motor cortex Language structure Sensory cortex Approach behaviors Withdrawal behaviors Left Right Distress, misery, agony, disgust, contempt, resentment, fear, horror, anxiety Joy, bliss, pride, anger, hostility, jealousy, interest, concern, responsibility Interpreting experiences Primary hearing Primary visual Language comprehension Based on Figure 5.6

Enriched environments promote faster brain development than deprived ones After birth: sights, sounds, smells, touches, language, and eye contact help shape the brain’s neural connections Cultural variations influence infant sleep patterns; newborns sleep an average of 16–17 hours per day The practice of shared sleeping, in which a newborn shares a bed with mother, varies among cultures

SIDS: sudden infant death syndrome – infants stop breathing and die without apparent cause Highest risk is in first 4–6 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

Nutrition is important as infant nearly triples weight in 1st year Low-fat, low-calorie foods and skim milk can retard baby’s development in first 2 years of life Benefits for infant from breast milk can include Denser bones in childhood/adulthood Reduced childhood cancers and breast cancer as female adult Improved neurological and cognitive development Improved visual acuity

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 child’s cognitive, physical, and social development Toilet training should be a positive experience starting at around 2 years of age or older

Motor Development

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

Converging factors enabling new behaviors to emerge: Development of nervous system and body’s physical capabilities The goal that the child is motivated to reach The environmental support for the necessary skills used to reach a goal

Baby masters balance and grasping things Baby begins to crawl and grasp things Child is encouraged by grandmother Child is nurtured by mother Perceptions, nurturing, and practice allow baby to fine-tune grasping

Motor development begins with reflexes Sucking and rooting reflexes disappear about 3–4 months after birth Moro reflex (automatic arching of back and wrapping of arms to center of body when startled) disappears about 3–4 months after birth Grasping reflex (infant’s hands close around anything that touches the palms) disappears as voluntary grasp develops Gross motor skills enable large-muscle activities

Support some weight with legs Milestones in Gross Motor Development Stand with support Sit without support Walk alone easily Support some weight with legs Degree of motor development Stand alone easily Roll over Walk using furniture for support Prone, chest up, arms for support Pull self to stand Prone, lift head 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Age in months Figure 5.13

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 2–3 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

Fine motor skills for finely tuned activities Perceptual-motor coupling is necessary for infants 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 while eight-month-olds rely on vision to determine how they will grip an object

Perceptual Development Sensory and Perceptual Development

Information is transmitted through smell, touch, hearing, taste, and vision to sensory receptors Perception is an interpretation of what is sensed Ecological view sees environment as rich with information and sees perceptual system as selecting from it Perception enables interaction with, and adaptation to, one’s environment

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)

Infants aged 6–8 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 mother’s 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

The End