John W. Santrock

1. Children 6 Physical Development in Infancy John W. Santrock

2. Physical Development in Infancy • How Do Infants Grow and Develop Physically? • How Do Infants Develop Motor Skills? • How Can Infants’ Sensory and Perceptual Development Be Characterized?

3. How Do Infants Grow and Develop Physically? Images of Children • Bottle-feeding newborns in impoverished countries has become a trend • Formula mixed with unclean water • Bottles often unsterilized • Many children get common illnesses; may die • Breast milk would immunize newborn • Hospitals have vital role in educating mothers

4. How Do Infants Grow and Develop Physically? Cephalocaudal and Proximodistal Patterns • Cephalocaudal: size, weight, and feature differentiation gradually work from top to bottom • Proximodistal: growth starts at center of body and moves toward extremities

5. Changes in Proportions of the Human Body During Growth Fig. 6.1

6. How Do Infants Grow and Develop Physically? Height and Weight • Average North American newborn is 20 inches and 7½ pounds • Birthweight doubled by age 4 months; tripled at end of first year • Growth during first year averages 1 inch per month • 1½ times birth length at end of 1st year

7. How Do Infants Grow and Develop Physically? Height and Weight • Average 2-year-old • 26 to 32 pounds and 32 to 35 inches tall (almost half of their adult height) • Growth rate considerably slower in second year

8. How Do Infants Grow and Develop Physically? Brain Development • Extensive growth in uteroand infancy • Shaken baby syndrome: brain swelling and hemorrhaging • Neuron: nerve cell; all present at birth • Dendrites

9. How Do Infants Grow and Develop Physically? Brain Development • Myelin sheath: layer of fat cells • Encases most axons • Insulates nerve cells • Synapses: tiny gaps • EEG activity spurts about 1½ to 2 years of age

10. The Neuron Fig. 6.2

11. At birth 1 month 15 months 24 months 3 months The Development of Dendrite Spreading Fig. 6.3

12. How Do Infants Grow and Develop Physically? Brain Development • “Blooming” and “pruning” • Synaptic overproduction peaks about 4 months after birth • Prefrontal cortex overproduction peaks about 1 year of age • Adult density achieved in adolescence • Heredity and environment affect timing

13. Synaptic Density in Human Brain from Infancy to Adulthood 70 Newborn Adolescence 60 50 40 Synaptic density 30 20 10 adult 0 6000 10,000 100 200 300 400 500 600 800 1000 1500 2000 3000 4000 8000 Age in days (from conception) Fig. 6.4

14. How Do Infants Grow and Develop Physically? Brain’s Lobes and Hemispheres • Four lobes and two hemispheres • Cerebral cortex • Frontal lobe • Occipital lobe • Temporal lobe • Parietal lobe • Lateralization of hemispheres

15. (body sensations) (voluntary movement and thinking) Prefrontal cortex (vision) (hearing) Fig. 6.6 The Brain’s Four Lobes

16. The Human Brain’s Hemispheres Fig. 6.7

17. How Do Infants Grow and Develop Physically? Brain’s Lobes and Hemispheres • Frontal lobe is immature in newborn • Ability to regulate physiological states and control reflexes in first year • Cognitive skills emerge later • More electrical activity in left hemisphere than right hemisphere when listening

18. How Do Infants Grow and Develop Physically? Early Experience and the Brain • Environmental experiences important in brain’s development; enriched environments enhance growth • Infant’s brain waiting for experiences to determine connections among neurons

19. How Do Infants Grow and Develop Physically? Sleep • Regulation of wake-sleep cycle reflects neurological maturation; cycles vary • REM (Rapid Eye Movement) sleep • Adults—fifth of sleep • Infants—half of sleep • May promote brain’s development in infancy

20. How Do Infants Grow and Develop Physically? Sleep • After about 4 months, infant has more adult-like sleep patterns • Culture Affects Sleep Patterns • Length of sleep periods related to sleeping arrangements and parental activities

21. How Do Infants Grow and Develop Physically? Sleep and Culture • Culture and Sleeping Arrangements • Sharing bed common in many cultures • Crib/separate room common in U.S. • American Academy of Pediatrics discourages co-sleeping because of stress and SIDS risk

22. 24 16 14 12 10 Total daily sleep (hours) 8 6 4 2 0 6 mo 12 mo 18 mo 2 yrs 10 yrs 20 yrs 30 yrs 40 yrs 50 yrs 60 yrs 70 yrs 80 yrs 90 yrs 1-15 days Newborn Infants Children Adolescents Adults Older adults Fig. 6.7 Sleep Across the Human Life Span

23. How Do Infants Grow and Develop Physically? Sudden Infant Death Syndrome (SIDS) • Infant stops breathing, usually during night, and dies without apparent cause • Also known as “crib death” • Prone sleeping reduces risk by 5 to 10 times

24. How Do Infants Grow and Develop Physically? Sudden Infant Death Syndrome (SIDS) • Increased risks if: • Lower birthweight • Siblings with SIDS • Sleep apnea • Lower SES groups • Exposure to cigarette smoke • Placement in soft bedding

25. How Do Infants Grow and Develop Physically? Nutrition • Healthy infants need • Loving, supportive feeding environment • 50 calories per day per pound of weight • Fat; very important for growth • Breast milk (nature’s food) • Demand feeding becoming more popular

26. How Do Infants Grow and Develop Physically? Breast-Feeding Versus Bottle-Feeding • Breast-feeding recommended • Appropriate weight gain, lowers obesity risk • Prevents or reduces allergies and infections • Promotes neurological and cognitive growth • Lowers risk of SIDS and cancers • Better visual acuity and bone density • The only option in poor countries

27. How Do Infants Grow and Develop Physically? Malnutrition in Infancy • Infants can develop • Marasmus: wasting away of body tissues in infant’s first year, severe lack of protein • Kwashiorkor: deficiency in protein; child’s abdomen, feet become swollen with water • If not fatal, effects are detrimental; lowest SES aided most by supplementary feeding

28. How Do Infants Grow and Develop Physically? Toilet Training • Ability to control affected by muscular maturity and motivation • Average child ready at age 2 • Controversy exists over “delaying” training • Readiness approach recommended

29. How Do Infants Grow and Develop Physically? Health • Immunization begins in infancy • Accident Prevention • Increased monitoring needed in infancy • Asphyxiation: leading cause of death under 1 • Chocking hazards: toys, food • Burn risks: sun, electrical, heaters, hot water • Other risks: car accidents, cuts, pet bites

30. How Do Infants Develop Motor Skills? Dynamic Systems Theory • How infants acquire motor skills • Perceptions and motivation leads to new motor skills or fine tuning • Nervous system maturation • Repeated “cycles” of actions • Nature, nurture, and environment create ever-changing system

31. How Do Infants Develop Motor Skills? Reflexes • Rooting: reaction when infant’s cheek is stroked or side of the mouth is touched • Sucking: automatic sucking when something is placed in newborn’s mouth • Moro reflex: startle response causes rapid closing of arms and legs • Grasping: when something touches palm

32. How Do Infants Develop Motor Skills? Gross Motor Skills • Large muscle activities • Development of posture • Learning to walk; locomotion, balance, and practice • Development in second year • Pull toys, climb stairs • Walk quickly, run stiffly

33. Stand with support Sit without support Degree of motor development Support some weight with legs Walks alone easily Roll-over Stands alone easily Prone, chest up, arms for support Walk using furniture for support Pull self to stand Prone, lift head 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Age (months) Milestones in Gross Motor Development Fig. 6.15

34. How Do Infants Develop Motor Skills? Cultural Variations in Guiding Infants’ Motor Development • Infants reach motor milestones in different cultures based on activity opportunities • Variations not large • Milestones reached within normal age ranges

35. How Do Infants Develop Motor Skills? Fine Motor Skills • Reaching and grasping • Perceptual-motor coupling necessary • Initially move shoulders and elbows crudely; later move wrists and rotate hands • Coordinate thumb and forefinger • Experience affects reaching and grasping; becomes more refined during first 2 years

36. How Can Infants’ Sensory and Perceptual Development Be Characterized? Defining Sensation and Perception • Sensation: occurs when information contacts sensory receptors—eyes, ears, tongue, nostrils, and skin • Perception: interpretation of sensation

37. How Can Infants’ Sensory and Perceptual Development Be Characterized? The Ecological View • People directly perceive information in the world around them • Perception allows human-environmental interaction and adaptation • Affordances: opportunities for interaction offered by objects; enhanced by previous experiences

38. How Can Infants’ Sensory and Perceptual Development Be Characterized? Studying Infant Perception • Infant cannot talk • Head movement indicates some vision • Visual preference method: Fantz measured length of gaze and patterns of preference in “looking chamber”

39. How Can Infants’ Sensory and Perceptual Development Be Characterized? Studying Infant Perception • Habituation and Dishabituation • Habituation: decreased responsiveness to a stimulus after repeated presentations • Dishabituation: recovery of a habituated response after change in stimulation • Tracking: applied to vision and hearing • Equipment: high-amplitude sucking

40. How Can Infants’ Sensory and Perceptual Development Be Characterized? Visual Perception • Visual acuity and color • Perceiving patterns • Perceptual constancy—size, shape • Depth perception • Visual expectations

41. How Can Infants’ Sensory and Perceptual Development Be Characterized? Perceptual Constancy • Size constancyRecognition that object remains the same even though the retinal image changes • Shape constancyRecognition that object remains the same even though its orientation changes

42. How Can Infants’ Sensory and Perceptual Development Be Characterized? Other Senses • Hearing: begins in womb • Touch and Pain • Smell: present shortly after birth • Taste: may exist before birth

43. How Can Infants’ Sensory and Perceptual Development Be Characterized? Intermodal Perception • Ability to relate and integrate information from two or more sensory modalities • Exist in world of objects and events • Crude exploratory forms of intermodal perception exist in newborns

44. How Can Infants’ Sensory and Perceptual Development Be Characterized? Perceptual-Motor Coupling • Perception and activity were traditionally considered separate. • Dynamic systems approach and ecological approach both suggest they are linked. • Dynamic systems: infants assemble motor behavior for perceiving and acting • Ecological: action can guide perception and perception can guide action

45. Children 6 The End