1. Physical, Sensory, and Perceptual Development in Infancy
Chapter 4:
Physical, Sensory, and Perceptual Development in Infancy

2. Physical Changes Health and Wellness Infant Mortality Sensory Skills
IN THIS CHAPTER
Physical Changes
Health and Wellness
Infant Mortality
Sensory Skills

3. LEARNING OBJECTIVES
4.1 What important changes in the brain take place during infancy?
4.2  How do infants’ reflexes and behavioral states change?
4.3  How do infants’ bodies change, and what is the typical pattern of motor skill development in the first 2 years?
4.4  What are the nutritional needs of infants?
4.5  How does malnutrition affect infants’ development?
4.6  What are infants’ health-care and immunization needs?
4.7 What have researchers learned about sudden infant death syndrome?
4.8 How do infant mortality rates vary across groups?
4.9 How do infants’ visual abilities change across the first months of life?

4. LEARNING OBJECTIVES (con’t)
4.10 How do infants’ senses of hearing, smell, taste, touch, and motion compare to those of older children and adults?
4.11 How do researchers study perceptual development in infants?
4.12 How do depth perception and patterns of looking change over the first 2 years?
4.13 How do infants perceive human speech, recognize voices, and recognize sound patterns other than speech?
4.14 What is intermodal perception?
4.15 What arguments do nativists and empiricists offer in support of their theories of perceptual development?

5. PHYSICAL CHANGES The Brain and Nervous System
Rapid development during the first 2 years
Midbrain and medulla most fully developed at birth
Cortex is the least developed
The medulla regulates vital functions such as heartbeat and respiration, attention, sleeping, waking, elimination, and movement of the head and neck.
The cortex is responsible for perception, body movement, thinking, and language.

6. PARTS OF THE BRAIN
The medulla and the midbrain are largely developed at birth. In the first 2 years after birth, it is primarily the cortex that develops, with each neuron going through an enormous growth of dendrites and a vast increase in synapses. (Figure 4.1 [p. 83])

7. THE BRAIN AND NERVOUS SYSTEM Physical Changes: Synaptic Development
Synaptogenesis
Creation of synapses or connections between neurons
Synaptic pruning
Elimination of unused neural pathways and connections
Early in development, each muscle cell seems to develop synaptic connections with several motor neurons in the spinal cord. But after the pruning process has occurred, each muscle fiber is connected to only one neuron. Some neurophysiologists have suggested that the initial surge of synapse formation follows a built-in pattern (Greenough et al., 1987). The organism seems to be programmed to create certain kinds of neural connections and does so in abundance, creating redundant pathways. According to this argument, the pruning that takes place beginning at around eighteen months is a response to experience, resulting in selective retention of the most efficient pathways.

8. TV FOR TOTS: HOW MUCH IS TOO MUCH?
Statistics
Ninety percent of U.S. babies watch television and other forms of video entertainment every day.
Infants are exposed to an average of five hours daily of background television.
Research
Excessive television watching during the first three years of life is linked to reduced social interactions as well as AD/HD.
Recommendations
The American Academy of Pediatrics (AAP) calls for no television before age two.
Parents should focus on quality when selecting resources.

9. You Decide
I agree with the AAP’s recommendation that children under age two shouldn’t watch television at all.
I think that the AAP’s recommendation goes too far. There is a place for television in the lives of toddlers.

10. THE BRAIN AND NERVOUS SYSTEM Plasticity
Neural plasticity: the brain’s ability to change in response to experience
Use it or lose it
Changes in psychological functioning
Rat infants reared in a highly stimulating environment have a denser network of neurons, dendrites, and synaptic connections.
Young infants need sufficient stimulation and order in their environments to maximize the early period of rapid growth and plasticity.
Use it or lose it
An intellectually challenging environment creates a more complex network of synapses.
Changes in psychological functioning
Developmental changes in brain across the lifespan
Infant brains have greater plasticity but are more vulnerability to major deficits.

11. THE BRAIN AND THE NERVOUS SYSTEM Myelinization
Myelin: insulating layer of proteins and fatty substances
Description
Timing
Myelin: insulating layer of proteins and fatty substances
Description
Forms myelin sheath covering individual axons
Provides insulation and speeds up neuronal processes
Follows cephalocaudal and proximodistal patterns
Timing
Most rapid during first two years
Continues at a slower pace throughout childhood and adolescence
Cephalocaudal: head to toe
Proximodistal: near to far

12. REFLEXES AND BEHAVIORAL STATES Adaptive Reflexes
Adaptive reflexes: reflexes that aid survival
Warn of possible neuronal development problems when weak or absent
Some persist throughout life.
Help survival
Sucking
Withdrawal from pain
Opening and closing of pupil
Warn of possible neuronal development problems when weak or absent
Some reflexes, such as sucking, will be replaced by voluntary behaviors; others are available throughout the lifespan.

13. REFLEXES AND BEHAVIORAL STATES Primitive Reflexes
Primitive reflexes: reflexes controlled by less sophisticated parts of brain
Should appear at birth and disappear by six to eight months
May indicate neurological problems if persistent
Controlled by less sophisticated parts of brain
Moro (or “startle”) reflex
Babinski reflex (curled toes)
Should disappear by six to eight months
May indicate neurological problems if persistent
Less sophisticated parts of the brain include the medulla and midbrain.

14. REFLEXES AND BEHAVIORAL STATES States of Consciousness
Sleep, Baby, Sleep
Patterns of sleep and wakefulness stabilize with age.
Neonates sleep 80 percent of the time.
By eight weeks of age, babies begin to sleep through the night.
By six months of age, babies average fourteen hours of sleep per day.
Sleep patterns are individualized; some babies may not develop nighttime patterns until one year of age.
Patterns of sleep and wakefulness stabilize with age.
Neonates sleep 80 percent of the time.
By eight weeks of age, babies begin to sleep through the night.
By six months of age, babies average fourteen hours of sleep per day.
Clear nighttime patterns and daytime naps are established.

15. REFLEXES AND BEHAVIORAL STATES Five States of Sleep and Wakefulness
Deep sleep
Light sleep
Alert wakefulness
Fussing
Drowsy
Sleep patterns are individualized; some babies may not develop nighttime patterns until one year of age.
Patterns of sleep and wakefulness stabilize with age.
Neonates sleep 80 percent of the time.
By eight weeks of age, babies begin to sleep through the night.
By six months of age, babies average fourteen hours of sleep per day.
Clear nighttime patterns and daytime naps are established.
Most infants move through these states in the same sequence every two hours

16. REFLEXES AND BEHAVIORAL STATES Crying Baby, Not Crybaby!
Cries differ by need.
Cross-cultural studies suggest crying increases until six weeks and then tapers off.
Prompt attention to crying in the first three months leads to less crying later.
Cries differ by need.
Basic cry: signals hunger; rhythmic pattern
Anger cry: louder and more intense
Pain cry: very abrupt onset
Colic: a pattern involving intense bouts of crying for no immediately apparent reason, as much as three hours a day; appears at about two weeks and then disappears by three to four months of age.

17. GROWTH, MOTOR SKILLS, AND DEVELOPING BODY SYSTEMS Physical Changes: Growth
By Age One
10 to 12 inches of growth
Infants triple body weight
Around Age Two
Toddlers reach half their adult height.
Proportionately much larger heads than adults

18. GROWTH, MOTOR SKILLS, AND DEVELOPING BODY SYSTEMS Growth and Motor Skills: Overview
A person’s inborn timetable of motor skills development interacts with other aspects of physical development (Thelen).
Muscles, bones, and weight all work together.
Opportunities to practice motor skills are important.

19. STOP AND THINK!
Researchers suggest there is a difference in the rate but similarity in the sequence of motor skill development.
Using this information as a base, what advice would you give to parents of toddlers?

20. DEVELOPING BODY SYSTEMS AND MOTOR SKILLS Bones
Ossification: the process of hardening of the bones
Begins during prenatal development
Continues through puberty
Motor development depends to a large extent on ossification.
Changes in the number and density of bones are responsible for improved coordination.
At birth, the wrist is cartilage; by one to three years of age, it is separate bones: by adolescence, it is made up of nine separate bones. This improves manipulative skills.
Standing is impossible without ossification.

21. DEVELOPING BODY SYSTEMS AND MOTOR SKILLS Muscles
A full complement of muscle fibers is present at birth.
A decline in the muscle tissue to fat ratio occurs by age one.
A change in muscle composition leads to an increase in strength.
Stamina: the ability to maintain activity
Gross motor skills exhibit predictable changes over time.
Fine motor skills, such as palmar grasp and pincer grasp, take longer to develop.
Motor skills follow cephalocaudal and proximodistal development.
Gallaway and Thelen (2004): infants can reach for objects more efficiently with their legs—just the opposite of cephalocaudal development.

22. DEVELOPING BODY SYSTEMS AND MOTOR SKILLS Lungs and Heart
Rapid growth during the first two years leads to stamina.
Ability to sustain motor activity without rest by end of infancy
Stamina: the ability to maintain activity
Gross motor skills exhibit predictable changes over time.
Fine motor skills, such as palmar grasp and pincer grasp, take longer to develop.
Motor skills follow cephalocaudal and proximodistal development.
Gallaway and Thelen (2004): infants can reach for objects more efficiently with their legs—just the opposite of cephalocaudal development.

23. DEVELOPING BODY SYSTEMS AND MOTOR SKILLS Cross-Cultural Research
Experience influences motor development!
African infant precocity
A pattern of traditional cultural practices intentionally and coincidentally promotes motor development.
Precocity does not persist into early childhood.
Stamina: the ability to maintain activity
Gross motor skills exhibit predictable changes over time.
Fine motor skills, such as palmar grasp and pincer grasp, take longer to develop.
Motor skills follow cephalocaudal and proximodistal development.
Gallaway and Thelen(2004): infants can reach for objects more efficiently with their legs—just the opposite of cephalocaudal development.

24. HEALTH AND WELLNESS Nutrition: Breastfeeding and Bottle Feeding
Nutritionally superior: more rapid weight gain and size Early health benefits Only nutrition needed for first four to six months of life May not be possible for all mothers
May be a needed supplement for preterm babies Special-needs formulas available Can be high quality Allows more paternal participation
Common illnesses: diarrhea, gastroenteritis, bronchitis, ear infections, and colic, as well as infant death
Mothers should not breastfeed if they are using drugs, if they are substance abusers, or if they have AIDS.

25. HEALTH AND WELLNESS Nutrition: Solid Food
Solid Foods
Early introduction can interfere with nutrition.
Do not help babies to sleep through the night
Should start between four and six months of age
Baby is ready for solid foods when he or she can:
Hold head in steady, upright position
Sit with support
Show interest in what you are eating

26. HEALTH AND WELLNESS Malnutrition
Macronutrient malnutrition
Marasmus
Kwashiorkor
Micro-nutrient malnutrition
Macronutrient malnutrition
Diet containing too few calories
Leading worldwide cause of death in children under five
Marasmus
Severe calorie deficit
Extremely small
Can cause permanent brain damage
Kwashiorkor
Diet too low in protein
Micronutrient malnutrition
Deficiency of certain vitamins and/or minerals
Marasmus and Kwashiorkor are found in many developing countries.
Industrial societies suffer more from micronutrient malnutrition—a deficiency of certain vitamins or minerals. Iron deficiency leads to anemia, which may impede both social and language development.

27. HEALTH AND WELLNESS Health Care and Immunization
Health Care and Immunizations
Routine health professional visits are important.
Overall health and motor skills are assessed during visits.
Vaccinations are given to prevent diseases.
Vaccinations: three for hepatitis, four for diphtheria/tetanus/pertussis, three for influenza, one for measles
U.S. vaccination rates are high, but declining.
Continued education efforts and government support are needed.
Daycare babies have twice as many respiratory illnesses as stay-at-home babies do.

28. HEALTH AND WELLNESS Health Care and Illness
Illnesses in the First Two Years
Respiratory illnesses common
Higher in children participating in childcare programs
Chronic ear infections
Daycare babies have twice as many respiratory illnesses as stay-at-home babies do.

29. HEALTH AND WELLNESS Infant Mortality
Death within the First Year of Life
7 babies per 1000 in the U.S.
Related to prenatal care
Varies widely among U.S. ethnic groups
Racial differences occur in infant mortality (Figure 4.3 [p. 94]): lowest among Asian-American infants; highest among African-American infants.
7 babies per 1000 in the U.S.
Has declined steadily for several decades
Higher in U.S. than in other industrialized countries
Poverty is still a leading cause of infant mortality regardless of race.

30. GROUP DIFFERENCES IN INFANT MORTALITY
Figure 4.3 (p. 94): As you can see, infant mortality rates vary widely across U.S. ethnic groups. (Source: MacDorman & Atkinson, 1999; Mathews& MacDorman, 2010.)

31. WHEN AN INFANT DIES
Guidelines for use to support parents who have lost an infant
Don’t attempt to force talking about grief.
Refer to their deceased infant by his or her name.
Express sincere feelings of loss.
Follow the parents’ lead in reminiscences about the baby.
Assure the parents of the normalcy of their grief.
Don’t pressure parents to replace the lost child with another pregnancy.
Don’t offer rationalizations.
Understand that grief is likely to affect all family members.

32. Reflections
If you were one of Morgan’s co-workers or relatives, how do you think you would behave toward her in everyday situations?
What sort of “mental script” could you develop from the recommendations above that would be helpful to friends and relatives of a person who has lost a child?

33. NEXT, LET’S LOOK AT EARLY PRENATAL CARE AND ETHNICITY
See if you can identify disparities across ethnic groups with regard to access to prenatal care.
Do you see any correspondence between these disparities and infant mortality?

34. EARLY PRENATAL CARE AND ETHNICITY
Figure 4.4 (p. 94): Early Prenatal Care and Ethnicity
Wide disparities exist across ethnic groups with regard to access to prenatal care. (Source: National Center for Health Statistics (NCHS) (2006, 2010).)

35. HEALTH AND WELLNESS Sudden Infant Death Syndrome (SIDS)
Incidence: SIDS is the leading cause of death in the U.S. in infants one to twelve months old.
Links:
Apnea
Sleeping on stomach
Maternal smoking
More common in babies with apnea (brief cessations in breathing)
Racial differences occur in infant mortality (Figure 4.3): lowest among Asian-American infants; highest among African-American infants.
Poverty is still a leading cause of infant mortality regardless of race.

36. SENSORY SKILLS Vision Rapid Development of Visual Acuity
20/200 at birth; 20/20 at 2 years of age
Color Vision
Red, blue, and green at one month of age
Tracking
Tracking slow-moving object before two months of age; skilled tracking at six to ten weeks of age
Infants younger than two months show some tracking ability for brief periods; by six to ten weeks, babies have become skillful at tracking.
20/200 at birth
20/20 by 2 years
Color vision
Red, green, and blue present by one month
Color sense almost identical to an adult’s
Tracking
Process of following moving object
Initially inefficient but improves rapidly
Track for short period of time when younger than two months (slow-moving target)
By ten weeks, skillful

37. SENSORY SKILLS Hearing
Adult voices heard well and some directional loud-sound location
Smelling and Tasting
Newborns react differently to each basic taste as early as birth.
Touch and Motion
Best developed of all the senses
Hearing
Adult voices are heard well.
High-pitched noises must be loud to be heard.
Some directional sound location
Smelling and tasting are intricately related.
Four basic tastes: sweet, sour, bitter, and salty
Sensitive to touches on the mouth, hands, soles of feet, and abdomen

38. STOP AND THINK!
In what ways do babies’ sensory skills contribute to the development of the parent–infant relationship?

39. PERCEPTUAL SKILLS Studying Perceptual Development
Preference Technique
Study how long the baby attends to a particular stimulus.
Habituation/Dishabituation
Study loss of interest in a particular stimulus after repeated exposures.
Operant conditioning
Vary the stimulus and study the learned responses.
How does a baby interpret or combine sensory experience? The process is called perception.
Preference technique: the baby is shown two pictures; researchers keep track of how long the baby looks at each one.
Habituation: show a baby something over and over until the baby stops looking at it.
Dishabituation: renewed interest in something that is slightly different than the original stimulus

40. LOOKING SKILLS Depth Perception
Depth perception can be judged by:
Binocular cues
Monocular cues
Kinetic cues
Do you know the differences among these cues?
Binocular cues
Involve both eyes
The closer an object, the more the views from the two eyes differ.
Information from eye muscles tells the brain about distance.
Monocular cues
Input from one eye
Interposition
Linear perspective
Kinetic cues
Motion from objects or the eyes

41. DEPTH PERCEPTION A Walk on the Wild Side—Almost
Visual Cliff: Gibson and Walk (1960)
Initial findings: six-month-old babies would not cross the visual cliff.
Recent findings: three-month-olds have some depth perception.
Recent findings:
Babies use kinetic information as early as three months.
Binocular cues are used at four months.
Linear perspective cues are used by babies as young as five to seven months old.

42. PERCEPTUAL SKILLS What Babies Look at: Scanning
Initially scan for sharp, light/dark contrasts and then scan edges
2 months: scan entire object and look for patterns
2-3 months: shift from where to what object
3-4 months: attention to patterns, not just specific stimuli
Visual attention: guided by the search for a meaningful pattern
Babies demonstrate a preference for light/dark contrasts.
Albert Caron and Rose Caron used habituation (Figure 4.5): small over big.

43. LISTENING What Babies Hear: Discriminating Speech Sounds
At one month old: discriminate between “pa” and “ba”
At three months old: respond to male, female, and children’s voices similarly
At six months old: discriminate between two-syllable words
At six months old: distinguish sound contrasts in any language; fades by one year
Babies prefer their mother’s voice above all others.
Very young infants make fine discriminations among individual sounds and pay attention to patterns.

44. LANGLOIS’S STUDIES OF BABIES’ PREFERENCES FOR ATTRACTIVE FACES
Langlois and her colleagues (1987) showed two- to three-month-olds and six- to eight-month-olds color slides of adult-judged attractive and unattractive women.
Babies consistently looked longer at attractive faces of individuals of different races.
Similar findings resulted when slides of attractive infants and animals were used.

45. Critical Analysis
If there is an inborn template against which faces are compared, how might such a template affect adults’ interactions with others?
How would researchers determine the degree to which attractiveness affects adults’ perceptions of infants’ faces? Why would such research be unable to tell us whether the concept of attractiveness is inborn?

46. PERCEPTUAL SYSTEMS Combining Information from Several Senses
Intermodal perception: formation of the single perception of stimulus that is based on information from two or more senses
Possible by one month
Common by six months
Important in infant learning
Gibson and Gibson argue that cross-modal transfer is an inborn set of skills.
Learn in one sense modality; transfer information to another modality.
Intersensory integration is essential to infant learning.

47. PERCEPTUAL SYSTEMS Explaining Perceptual Development
Nativists
Empiricists
Most perceptual abilities inborn Many of these abilities present at birth
Most perceptual abilities learned Experience needed to develop perceptual systems
Gibson and Gibson argue that cross-modal transfer is an inborn set of skills.
Intersensory integration is essential to infant learning.
A compromise position: perceptual skill development is the result of interaction between inborn and experiential factors.