Chapter 4:

Physical Development in Infancy

Life-Span Development

Twelfth Edition

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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

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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

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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

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Forebrain: portion of the brain farthest from the spinal cord; includes cerebral cortex

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

$$ Electroencephalogram (EEG) is commonly used to study the brain in infancy.

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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

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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

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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

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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

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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

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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

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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

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

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Dynamic Systems View: Infants assemble motor skills for perceiving and

acting▪ Motor skills represent solutions to goals▪ $$ Arnold Gesell believed that motor skills come about

through maturation 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

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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

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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

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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

Cultural Variations: mothers in developing countries tend to stimulate their infants’ motor skills more than mothers in more modern countries

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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

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$$ Affordances: When we sense information from the environment, we are given the opportunity to interact with the environment Eleanor and James Gibson What affordances can infants or children detect

and use?▪ Children become more efficient at discovering and

using affordances through perceptual development

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$$ Visual Preference Method: the studying of whether an infant can distinguish between two objects is done by measuring the length of time the infant looks at an object.

Habituation: decreased responsiveness to a stimulus after repeated presentations

Dishabituation: recovery of a habituated response after a change in stimulation

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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

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Perceptual Constancy: sensory stimulation is changing but perception of the physical world remains constant

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$$ Two types of Perceptual Constancy

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

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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

$$ Stereoacuity: Fine-detail depth perception

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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

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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

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