Chapter 4: Physical Development in Infancy ©2009 The McGraw-Hill Companies, Inc. All rights reserved. Life-Span Development Twelfth Edition

Chapter 4:

Physical Development in Infancy

©2009 The McGraw-Hill Companies, Inc. All rights reserved.

Life-Span Development

Twelfth Edition

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


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


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


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



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



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



Changes in regions of the brain: “Blooming and

pruning” of synapses varies by brain region

Pace of myelination varies as well


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



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


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



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


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


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


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



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


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


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


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


Malnutrition in Infancy: Early weaning and inadequate sources of

nutrients can cause malnutrition Marasmus: a severe protein-calorie deficiency

▪ Results in a wasting away of body tissues Kwashiorkor: a severe protein deficiency that

causes the abdomen and feet to swell with water▪ Causes the vital organs to collect nutrients, depriving

other parts of the body Severe and lengthy malnutrition is detrimental to

physical, cognitive, and social development


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


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


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


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


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


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


Affordances: opportunities for interaction offered by objects that fit within our capabilities to perform activities What affordances can infants or children detect

and use?▪ Children become more efficient at discovering and

using affordances through perceptual development


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



Habituation and Dishabituation Studies: High-amplitude sucking Orienting response Tracking Videotaping Recording heart rate, respiration, body

movement, sucking behavior, visual fixation


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




Perceptual Constancy: sensory stimulation is changing but perception of the physical world remains constant Size Constancy: recognition that an object remains

the same even though the retinal image of the object changes▪ Babies as young as 3 months show size constancy▪ Continues to develop until 10 or 11 years old

Shape Constancy: recognition that an object remains the same shape even though its orientation to us changes▪ 3-month-olds show shape constancy, but not for irregularly

shaped objects


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



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


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


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


Documents

Chapter 4: Physical Development in Infancy ©2009 The McGraw-Hill Companies, Inc. All rights reserved. Life-Span Development Twelfth Edition