1. Infancy: Physical Development
CHAPTER 4
Infancy: Physical Development

2. Physical Growth and Development

3. Patterns in Height and Weight
Most dramatic gains in height and weight occur during prenatal development
Weight gains
5 months Double birth weight
1st year Triple weight
2nd year Gain 4 to 7 pounds
Height gains
Infants grow in spurts and do not follow smooth growth chart
1st year Height increases by 50%
2nd year Grow 4 to 6 inches:

4. Figure 4.1: Growth Curves for Weight and Height (Length) from Birth to Age 2 Years.
The curves indicate the percentiles for weight and length at different ages. Lines labeled 97th show the height and weight of children who are taller and heavier than 97% of children of a particular age. Lines marked 50th indicate the height and weight of the average child of a given age.
Fig. 4-1, p. 73

5. Changes in Body Proportions
Head
Neonate head is about one-fourth the length of body
Gradually diminishes in proportion to the body
Doubles in size by adulthood
Arms and legs
Equal in length in the neonate
Arms grow more rapidly than the legs at first
Arms grow longer than legs by 2nd birthday
Legs will soon catch up and surpass the arms
Neck lengthens by first birthday

6. Failure to Thrive (FTT)
Organic FTT (OFTT)
A biological underlying health problem accounts for infant’s failure to obtain or make use of adequate nutrition.
Does not make normal gains in weight
Nonorganic FTT (NOFTT)
A nonbiologically based underlying health problem accounts for the infant’s failure to obtain or make use of adequate nutrition.
Has psychological roots, social roots, or both

7. Failure to Thrive Problems
FTT infants typically have feeding problems.
Variable eaters
Less hungry
Slow physical growth
Cognitive, behavioral, and emotional problems
Children at age 8 ½ diagnosed with FTT during infancy :
remained smaller
were less cognitively advanced
were more emotionally and behaviorally disturbed than normal children

8. Catch-Up Growth Organic factors If problem is addressed,
Illness and diet can slow child’s genetically determined growth pattern
If problem is addressed,
child’s rate of growth frequently accelerates to approximate its normal curve
Referred to as canalization

9. Nutrition: Fueling Development
Infant nutrition guidelines
From birth, should be fed breast milk or iron-fortified infant formula (first year or longer) AAP
Solids generally introduced 4-6 months of age
Cow’s milk should be delayed until 9-12 months of age
Avoid overfeeding or underfeeding
Provide some fat and cholesterol
Do not overdo high-fiber foods
Avoid added sugar and salt
Encourage eating of high-iron foods
Infants from poor families more likely to display signs of poor nutrition such as anemia and FTT

10. Breast Feeding versus Bottle Feeding
Past to present
Breast feeding has become more popular
70% of American mothers now breast feed for some time
Pros of breast milk
Considered to be the best nourishment for infants
Does not upset the infant’s stomach
Is adequate nourishment for first 6 months after birth
Conforms to human digestion processes & changes to help meet infant’s changing needs.
Only 2 in 5 women continue to breast-feed after 6 months
Only 1 in 5 is still breastfeeding after 1 year.

11. Breast Feeding versus Bottle Feeding (cont’d)
Benefits for infant
Improved immune system functioning
Protects against childhood lymphoma
Decreased likelihood of
developing allergic responses and constipation
developing obesity later in life
developing serious cases of diarrhea
Better neural and behavioral organization
Benefits for mother
Reduces the risk of early breast and ovarian cancer
Stronger bones and reduced likelihood of hip fractures that result from osteoporosis following menopause
Helps shrink uterus after delivery

12. Pros of Bottle Feeding Allows for others to feed the infant
Breasts are not sore and tender
Mother is not sole provider for nourishment
Whether to breast feed or to bottle feed is a personal decision
Many mothers opt to combine breast feeding with bottle feeding

13. Development of the Brain and Nervous System

14. Development of the Brain and Nervous System
People are born with 100 billion neurons.
Each neuron has a cell body, dendrites, and an axon
Dendrites
Short fibers that extend from cell body and receive incoming information
Axon
Extends trunk-like from the cell body and accounts for much of the difference in length in neurons
Neurotransmitters
Message-carrying chemicals released from axon terminals

15. Figure 4.2: Anatomy of a Neuron.
“Messages” enter neurons through dendrites, are transmitted along the axon, and are sent through axon terminals to muscles, glands, and other neurons. Neurons develop by proliferation of dendrites and axon terminals and through myelination.
Fig. 4-2, p. 76

16. Myelin Myelin sheath Myelination Multiple sclerosis
Fatty, whitish substance that encases and insulates axons
Myelination
Process by which axons are coated with myelin
Not completed at birth
Myelination of brain’s prefrontal matter continues into the 2nd decade of life
Multiple sclerosis
Myelin is replaced by hard, fibrous tissue that disrupts the timing of neural transmission, interfering with muscle control
PKU and congenital infection with HIV affect the myelination process

17. Structures of the Brain
Medulla
Vital in the control of basic functions such as heartbeat and respiration
Part of brain stem
Nerves that connect spinal cord to higher levels of the brain pass through here
Cerebellum
Helps child maintain balance, control motor behavior, and coordinate eye movements with bodily sensations
Cerebrum
Two hemispheres that become more wrinkled as child develops, coming to show ridges and valleys called fissures
Contributes to human learning, thought, memory, and language

18. Growth Spurts of the Brain
Formation of neurons completed at birth
First growth spurt
During 4th and 5th month of prenatal development
Due to formation of neurons
Second growth spurt
Between 25th week of prenatal development and the end of the 2nd year of life after birth
Due to proliferation of dendrites and axon terminals

19. Figure 4.3: Growth of Body Systems as a Percentage of Total Postnatal Growth.
The brain will triple in weight by the infant’s first birthday, reaching nearly 70% of its adult weight.
Fig. 4-3, p. 78

20. Brain Development in Infancy
Myelination contributes to what infants are able to do.
Reflexive functions such as breathing due to myelination
Myelination of motor pathways allows neonates to show stereotyped reflexes.
Myelination will allow the disorganized movements of the neonate to come under increasing control.
Myelination of motor area of the cerebral cortex begins at the 4th month of prenatal development.
Myelination of the nerves to muscles is largely developed by the age of 2 years.
Some myelination continues to some degree into adolescence.

21. Changes in Neurons
The infant’s brain is literally waiting for experiences to determine how connections are made
Experience enhances brain development
Experience-expectant brain growth
Examples: Maturation, eating, sensory
Experience-dependent brain growth
Examples: Language, siblings, parent interaction

22. Brain Development in Infancy (cont’d)
Sensory development
Vision, hearing, and skin senses are less well myelinated at birth.
Myelination progresses and allows for increasingly complex and integrated sensorimotor activities.
Hearing
Myelination begins at 6th month
Continues through age 4
Vision
Myelination begins only shortly before full term
Completes process by 5th or 6th month
As myelination progresses and interconnections between different areas of cortex thicken, children are more capable of complex and integrated sensorimotor activities

23. Nature and Nurture in Brain Development
Sensory stimulation and physical activity during early infancy sparks growth of the cortex.
Infants have more connections among neurons than adults.
Connections activated by experience survive
Others are pruned
Lack of stimulation
Can impair motor development and adaptability
Inadequate fetal nutrition
especially during prenatal growth spurt of the brain
results in small brain size, formation of fewer neurons, and less myelination

24. Motor Development

25. Motor Development
Motor development follows cephalocaudal and proximodistal patterns and differentiation.
Neonates can lift head up aiding in avoiding suffocation.
First they lift head
Then they lift chest
Heads must be supported when held
Can hold up head between 3 to 6 months old
Infants handled carelessly can develop neck injuries

26. Figure 4.6: Motor Development in Infancy.
Motor development proceeds in an orderly sequence, but there is considerable variation in the timing of marker events.
Fig. 4-6, p. 81

27. Control of the Hands: Getting a Grip
3 months
Infants make clumsy, swiped movements toward objects
Ulnar grasp
4 to 6 months
Infants are more successful at grasping objects
Can transfer objects back and forth between hands.
Good age for giving rattles, large plastic spoons, mobiles, and other brightly colored hanging toys that are kept out of reach
9 to 12 months
Pincer grasp gives infants ability to pick up tiny objects
Oppositional thumb comes into play
15 to 24 months
Children show progression in stacking ability
Stacking progressions:
2 blocks at 15 months
3 blocks at 18 months
5 at 24 months

28. Locomotion 6 months 7 months 8 to 9 months 11 months
Infants roll over, turn from back to stomach
Infants can sit if supported
7 months
Infants usually sit on their own
8 to 9 months
Infants begin to crawl or creep
Standing overlaps with crawling and creeping
May walk with support of adult
11 months
Infants can pull themselves up
Locomotion – movement from one place to another; variation in age of ability
Creep – infants move themselves along up on their hands and knees

29. Locomotion (cont’d) 12 to 15 months
Walk on their own, earning the name of toddler
Run in bowlegged manner
Fall easily because they are top heavy
Some toddlers fall without notice and get back up
Others cry
Toddlers differentiate between shallow slopes and steep ones, choosing to slide or crawl down steep ones
Age 2
Child can climb one step at a time, run well, walk backward, kick a large ball, and jump several inches

30. Locomotion (cont’d)
Myelination and differentiation of the motor areas of the cortex must occur to master skills
Neonate’s stepping and swimming reflexes
disappear when cortical development inhibits some functions of the lower brain
reappear later, yet differ in quality
Effects of training
Early introduction to extensive motor skills training levels off (Arnold Gesell study, 1929)
Iranian infants in orphanage were exposed to extreme social and physical deprivation
They did not overcome motoric retardation (Dennis study, 1960)

31. Sensory and Perceptual Development

32. Sensory and Perceptual Development
Sensation occurs when information interacts with sensory receptors -- the eyes, ears, tongue, nostrils, and skin
Example: Everything…
Perception is the interpretation of what is sensed
Example: Mommy, foods, HOT!

33. Visual Acuity, Peripheral Vision, and Preference
Neonates
Extremely nearsighted at about 20/600
Have poor peripheral vision
Expands to 45 degrees by the age of 7 weeks
Prefer stripes and curved lines
Prefer and identify mother’s face
After 8 hours of contact over 4 days
Prefer edges of face such as chin
May be due to attention to movement and contrast
Most dramatic gains in visual acuity made between birth and 6 months of age
Acuity reaches about 20/50
By 3 to 5 years,
visual acuity generally approximates adult levels about 20/20

34. Figure 4.7: Preferences for Visual Stimuli in 2-Month-Olds.
Infants appear to prefer complex to simple visual stimuli. By the time they are 2 months old, they also tend to show preference for the human face.
Fig. 4-7, p. 83

35. Depth Perception
Infants generally respond to depth cues by 6 to 8 months
Visual cliff study, Gibson and Walk (1960)
Identified age at which infants have depth perception
Ability to crawl indicated in ability to perceive depth
Campos et al. (1970) study
Heart rate increased when infants placed on edge of cliff at 9 months of age
Newly walking infants more afraid of falling off
Different postures involve the brain in different ways and influence infants’ avoidance (Adolph, 2000)

36. Figure 4.9: The Visual Cliff.
This young explorer has the good sense not to crawl out onto an apparently unsupported surface, even when mother beckons from the other side.
Fig. 4-9, p. 85

37. Development of Perceptual Constancies
Perceptual constancy
Tendency to perceive an object to be the same even though the sensations produced by the object may differ under various conditions
Size constancy
Tendency to perceive the same objects as being the same size even though their retinal sizes vary as a function of their distance
Present in early infancy (Bower, 1974)
Shape constancy
Tendency to perceive that the shape of objects remains the same regardless of the retinal image being received
At 4 to 5 months old, infants grasp shape constancy under certain conditions.
Bower (1974) conditioned 2 ½ to 3 month old infants to turn their heads to the left when shown a 12-inch cube from a distance of 3 feet. His study found that size constancy is present at birth.

38. Development of Hearing
1 month
Infants perceive differences between speech sounds that are similar.
Infants exposed to normal backdrop of moderate noise levels become habituated to them and not likely to awaken unless there is a sharp, sudden noise.
3 ½ months
Can discriminate parent’s voices
18 months
Hearing is similar to adults’
Exposure to native language causes gradual loss of capacity to discriminate sounds that are not in their native language

39. Development of Coordination of the Senses
Young infants recognize that objects experienced by one sense are the same as those experienced through another sense.
Five-month-old infants look at novel stimulation longer than familiar sources of stimulation.
Infants looked at unfamiliar objects longer than objects they had held in their hands.
This shows a transfer of information from the sense of touch to the sense of vision
Habituation -- decreased responsiveness to a stimulus after repeated presentations of the stimulus
Examples: Pacifier, holding hands, football game?
Dishabituation -- is the recovery of a habituated response after a change in stimulation
Example: sleeping in the car…
Transfer of information from the sense of touch to sense of vision at this age occurred when five-month-old infants shown pictures of objects that they had not held in their hands

40. The Active-Passive Controversy in Perceptual Development
Changes in perceptual processes of children develop from passive, mechanical reactors to the world into active, purposeful seekers and organizers of sensory information.
These changes include
1) intentional action replacing “capture”
automatic responses to stimulation
2) systematic search replacing unsystematic search
3) attention becoming selective
4) irrelevant information becoming ignored

41. The Role of Nature and Nurture
Evidence for the role of nature
Neonates born with sensory skills and perceptual skills
can see nearby objects, hearing is fine, able to track moving objects, prefer certain kinds of stimuli
Sensory and motor changes linked to maturation of nervous system
Evidence for the role of nurture
Children have critical periods in their perceptual development.
Failure to receive adequate sensory stimulation can result in permanent sensory deficits
Health problems with vision in child’s eye where patch is needed extensively can result in permanent visual impairment
Today, most developmentalists agree on the nature nurture interaction to shape perceptual development.