Chapter 4: Physical Development in Infancy

Patterns of Growth: • Cephalocaudal Pattern: sequence in which the earliest growth always occurs from the top downward • Also applies to gains in motor development • Proximodistal Pattern: sequence in which growth starts in the center of the body and moves toward the extremities ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Height and Weight: • Average North American newborn is 20 inches long and 7 ½ pounds • 95% of full-term newborns are 18-22 inches long and weigh between 5 ½ and 10 lbs. • Newborns lose 5-7% of their body weight in the first few days of life • They typically gain 5-6 ounces per week during the first month • Weight usually triples by their 1st birthday • Newborns gain approximately 1 inch per month during the first year • Growth slows considerably during the 2nd year ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

The Brain: • Brain continues developing past infancy • Shaken Baby Syndrome: brain swelling and hemorrhaging from child abuse trauma • Brain imaging technologies cannot typically be used with babies • EEGs show regular spurts in the brain’s electrical activity • Spurts may coincide with important changes in cognitive development • At birth, the brain is 25% of its adult weight; at 2 years of age, it is 75% of its adult weight • The brain does not mature uniformly ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Forebrain: portion of the brain farthest from the spinal cord; includes cerebral cortex • Cerebral Cortex: folded surface covering the forebrain • Cerebral cortex is divided into 2 hemispheres, each with 4 lobes • Frontal lobe: voluntary movement, thinking, personality, and intentionality • Occipital lobe: vision functions • Temporal lobe: hearing, language processing, and memory • Parietal lobe: spatial location, attention, and motor control ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Lateralization: specialization of function in one hemisphere of the cerebral cortex or the other • Some functions are lateralized, some are not • Complex functions involve communication between both hemispheres ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Neurons: brain nerve cells that communicate through electrical and chemical signals • Axons carry signals away from the cell body • Dendrites carry signals toward the cell body • Myelin sheath is a layer of fat cells that insulate axons • Helps electrical signals travel faster • Terminal buttons release chemicals (neurotransmitters) into synapses • Synapses: tiny gaps between neurons ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Changes in Neurons: • Myelination: the process of encasing axons with fat cells • Begins prenatally and continues into adolescence • Connectivity among neurons increases • New dendrites grow • Connections among dendrites increase • Synaptic connections increase • More synaptic connections are created than will ever be used • Leads to a “pruning” of unused connections ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Depressed brain activity has been found in children who grow up in a deprived environment • 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 • Repeated experience wires (and rewires) the brain • Brain is both flexible and resilient ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Typical newborns sleep 16-17 hours per day • Infants vary in their preferred times for sleeping • Most have moved closer to adult-like sleep patterns by 4 months of age • Factors involved in night waking: • Daytime crying and fussing • Distress when separated from mother • Breast feeding • Co-sleeping ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Cultural variations influence infant sleeping patterns • Babies average much more REM sleep than do older children or adults • REM sleep may provide infants with added self-stimulation • REM sleep may also promote brain development • We do not know whether infants dream or not ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

The practice of shared sleeping, in which a newborn shares a bed with mother, varies among cultures • Potential benefits: • Promotes breast feeding and a quicker response to crying • Allows mother to detect potentially dangerous breathing pauses in baby • American Academy of Pediatrics discourages shared sleeping • Increases risk of injury (rolling over baby) and SIDS ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

SIDS (Sudden Infant Death Syndrome): infants stop breathing and die without apparent cause • Highest cause of infant death in U.S. annually • Highest risk is 2-4 months of age • Risk decreases when infant sleeps on its back and when a pacifier is used ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Other risk factors associated with SIDS: • Siblings who died from SIDS • Sleep apnea or low birth weight • Infants passively exposed to cigarette smoke • Being from lower SES or being African American or Eskimo • Infants placed in soft bedding • Infants with abnormal brain stem functioning involving serotonin ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Experts recommend that infants consume 50 calories per day for each pound they weigh • U.S. parents typically do not feed infants enough fruits and vegetables • By 15 months, French fries are the most common vegetable eaten • Increasing rates of overweight and obese infants • Other factors: • Mother’s weight gain during pregnancy and pre-pregnancy weight • Breast feeding vs. bottle feeding ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

American Academy of Pediatrics strongly endorses breast feeding throughout the first year • Benefits for baby can include: • Fewer gastrointestinal and lower respiratory tract infections • Potentially decreased risk of asthma • Less likely to become overweight or obese • Less incidence of diabetes • Less likely to experience SIDS ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Benefits for mother can include: • Lower incidence of breast and ovarian cancer • Lower incidence of Type 2 diabetes • Breast feeding does not: • Help mother return to pre-pregnancy weight • Guard against osteoporosis • Decrease likelihood of experiencing post-partum depression ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Women less likely to breast feed: • Mothers who work full-time outside of the home • Mothers under age 25 • Mothers without a high school education • African-American mothers • Mothers in low-income circumstances ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Mother should not breast feed if: • She has AIDS or other infectious diseases that can be transmitted through milk • She has active tuberculosis • She is taking a drug that may not be safe for the infant • No psychological differences have been found between breast-fed and bottle-fed infants • Most breast- vs. bottle-feeding studies are correlational and do not imply causation ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Dynamic Systems View: • Infants assemble motor skills for perceiving and acting • Motor skills represent solutions to goals • Development is an active process in which nature and nurture work together • Development of nervous system • Body’s physical properties and possibilities for movement • Goal the child is motivated to reach • Environmental support for the skill ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Reflexes: built-in reactions to stimuli; generally carry survival mechanisms • Rooting Reflex: when the infant’s cheek is stroked, the infant will turn its head to the side that was touched • Moro Reflex: automatic arching of back and wrapping of arms to center of body when startled • Grasping Reflex: infant’s hands close around anything that touches the palms • Some reflexes continue throughout life; others disappear several months after birth ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Gross Motor Skills: skills that involve large-muscle activities • Walking, grabbing for objects • Gross motor skills require postural control • Posture is a dynamic process linked with sensory information in the skin, joints, and muscles • Infants can produce stepping movements needed for walking from a very early age • They lack the ability to stabilize balance on one leg at a time • Infants learn what kinds of places and surfaces are safe for locomotion ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Development in the 2nd Year: • Toddlers become more skilled and mobile • Motor activity is vital to the child’s development of competence and independence • By 18-24 months, toddlers can: • Walk quickly or run stiffly • Balance on their feet in a squat position • Walk backward • Stand and kick a ball without falling • Jump in place ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Cultural Variations: mothers in developing countries tend to stimulate their infants’ motor skills more than mothers in more modern countries • Infants can reach motor milestones slightly earlier if provided with physical guidance or given opportunities for exercise • Even when activity is restricted, many infants still reach milestones at a normal age ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Fine Motor Skills: involve finely tuned movements • Reaching and grasping is a significant milestone for infants • Palmer grasp: grasping with the whole hand • Pincer grip: grasping with the thumb and forefinger • 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 ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Sensation: occurs when information interacts with sensory receptors (eyes, ears, tongue, nostrils, and skin) • Perception: the interpretation of what is sensed • Ecological View: we directly perceive information that exists in the world around us • The perceptual system selects from the rich information provided by the environment • Perception enables interaction with, and adaptation to, one’s environment ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Visual Preference Method: infants look at different things for different lengths of time • They look at preferred objects longer • Habituation: decreased responsiveness to a stimulus after repeated presentations • Dishabituation: recovery of a habituated response after a change in stimulation ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Newborn’s vision is about 20/600 (an object 20 feet away appears as if it were 600 feet away) • By the age of 6 months, vision is 20/100 or better • Vision approximates that of an adult by the infant’s first birthday • Infants show an interest in human faces soon after birth • The way they gather information about the visual world changes rapidly with age ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Eleanor Gibson and Richard Walk studied development of depth perception using a “visual cliff” • Infants 6-12 months old can distinguish depth • Infants 2-4 months old show heart rate difference when placed on deep side of cliff • Infants develop binocular depth cues by about 3-4 months of age ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Fetuses can hear and learn sounds during the last two months of pregnancy and can recognize their mother’s voice at birth • Newborns: • Cannot hear soft sounds as well as adults • Are less sensitive to pitch • Are fairly good at determining the location of a sound ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Touch and Pain: newborns respond to touch and can feel pain • Smell: newborns can differentiate odors • Preference for mother’s smell by 6 days • Taste: sensitivity to taste may be present before birth ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Intermodal Perception: the ability to integrate information from two or more sensory modalities • Babies are born with some innate abilities to perceive relations among senses • Their abilities improve considerably through experience • Perceptual–Motor Coupling: action guides perception, and perception guides action ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Chapter 4: Physical Development in Infancy