1. Infancy: Physical Development
Chapter Four

2. Sequences of Physical Development Cephalocaudal and Proximodistal
Cephalocaudal: development proceeds from the upper part of the head to the lower parts of the body due to the importance of brain regulation such as breathing; head develops more rapidly than the rest of the body during embryonic stage
Proximodistal: development proceeds from the trunk outward, from body’s central axis toward the periphery; brain and spinal cord follow a central axis down through body due to necessity for nerves to be in place before infant can control arms and legs

3. Differentiation
Physical reactions become less global and more specific as children mature
Neonate’s response to stimuli such as a burn may include thrashing about, crying, withdrawing the burned finger, whereas toddlers may cry as well and withdraw finger, but thrashing about as a response to the pain is gone

4. Growth Patterns in Height and Weight
Most dramatic gains in height and weight occur during prenatal development
Infants double birth weight in about 5 months and triple weight by the first birthday
Height increases by 50% during first year
Infants grow in spurts and do not follow smooth growth chart
Infants grow 4 to 6 inches during 2nd year
Infants gain 4 to 7 pounds during 2nd year

6. Changes in Body Proportions
Length of the head of an adult varies from 1/8th to 1/10th of the entire body
Children’s head proportionally larger
Adult’s arms are nearly 3 times the length of the head; legs four times as long
Neonates arms and legs are equal in length
Neck lengthens by first birthday
Arms grow more rapidly than the legs at first
Arms longer by 2nd birthday
These proportions illustrate typical growth patterns

7. Failure to Thrive
Organic failure to thrive (FTT): 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: a nonbiologically based underlying health problem accounting for the infant’s failure to obtain or make use of adequate nutrition; has psychological roots, social roots, or both; does not make normal gains in weight

8. Failure to Thrive Continued
Infants described as variable eaters
Less hungry
Slow physical growth
Related to cognitive, behavioral and emotional problems
Children at age 8 ½ diagnosed with FTT during infancy remained smaller, were less cognitively advanced and were more emotionally and behaviorally disturbed than normal children

9. Catch-up Growth
Organic factors such as 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

10. Nutrition: Fueling Development
Infants from poor families more likely to display signs of poor nutrition such as anemia and FTT
Infants need to be fed breast milk or iron-fortified infant formula
Solids generally introduced 4–6 months of age
American Academy of Pediatrics recommends infants be fed breast milk for at least the first year or longer if possible
Cow’s milk delayed until 9–12 months of age

11. Breast Feeding versus Bottle Feeding
Breast milk considered to be the best nourishment for infants
Use of breast milk declined due to introduction of bottle feeding as more “scientific”
70% of American mothers now breast feed for some time
Breast milk does not upset the infant’s stomach
Breast milk alone is adequate nourishment for first 6 months after birth

12. Breast Feeding versus Bottle Feeding Continued
Breast milk changes as infant matures to meet their needs
Breast milk contains mother’s antibodies which helps to ward off disease
Breast milk helps protect against childhood lymphoma
Breast milk decreases lingering cases of diarrhea
Breast-fed infants less likely to develop allergic responses and constipation

13. Breast Feeding versus Bottle Feeding Continued
Breast-fed infants less likely to develop obesity later in life
Breast feeding associated with better neural and behavioral organization in the infant
Women who breast fed have lower likelihood of early breast and ovarian cancer
Breast feeding builds strength of bones in breast feeding/fed mothers
Breast feeding helps shrink uterus after delivery

14. Breast Feeding versus Bottle Feeding
Bottle feeding allows for others to feed the infant
Breasts are not sore and tender if bottle feeding
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

15. Development of the Brain and Nervous System
People are born with 100 billion neuron; 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

16. VIDEO: Brain Organization, Structure and Function

19. Myelin
Myelin sheaths – high, fatty substance insulating the neuron from electrically charged atoms in the fluids the encase the nervous system
Myelination – process by which axons are coated with myelin; not completed at birth; myelination of brain’s prefrontal matter continues into the 2nd year 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

20. Structures of the Brain
Medulla – nerves that connect spinal cord to higher levels of the brain pass through here; vital in the control of basic functions such as heartbeat and respiration; part of brain stem
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

23. Growth Spurts of the Brain
Formation of neurons completed at birth
Brain growth spurt during 4th and 5th month of prenatal development
2nd growth spurt between 25th week of prenatal development and the end of the 2nd year of life after birth
2nd growth spurt due to proliferation of dendrites and axon terminals

25. 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 of motor area of the cerebral cortex begins at the 4th month of prenatal development
Development of intentional physical activity in alignment with myelination as the disorganized movements of the neonate come under increasing control

26. Brain Development in Infancy Continued
Myelination of the nerves to muscles largely developed by age 2
Touch and hearing (myelinated 6th month of pregnancy) well developed prenatally, areas of cortex involved in vision (myelination process complete 5 to 6 months after birth), hearing and skin are less well developed at birth
As myelination progresses and interconnections between different areas of cortex thicken, children are more capable of complex and integrated sensorimotor activities

27. 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

28. Motor Development
Motor development follows cephalocaudal and proximodistal patterns and differentiation
Neonates can lift head up aiding in avoiding suffocation; first they lift head and 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

30. Control of the Hands: Getting a Grip
At 3 months infants make clumsy, swiped movements toward objects (ulnar grasp)
Infants 4 to 6 months are more successful at grasping objects; good age for giving rattles, large plastic spoons, mobiles and other brightly colored hanging toys that are kept out of reach

31. Control of Hands con’t
Pincer grasp gives infants ability to pick up tiny objects between 9 and 12 months of age
Children can stack 2 blocks at 15 months; 3 at 18 months; 5 at 24 months; at 24 months children can copy horizontal and vertical lines

32. Locomotion
Locomotion – movement from one place to another; variation in age of ability
Infants roll over, turn from back to stomach by 6 months; can also sit if supported
By 7 months infants usually sit on their own
At 8 to 9 months infants begin to crawl or creep
Creep – infants move themselves along up on their hands and knees

33. Locomotion con’t
Standing overlaps with crawling and creeping; most infants stand at age of 8 or 9 months; may walk with support of adult; can pull self up at 11 months
Walking on own happens between 12 and 15 months earning the name of toddler
They run in bowlegged manner

34. Locomotion Con’t
Because they are top heavy they fall easily; 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
At age 2, children can climb one step at a time
Myelination and differentiation of the motor areas of the cortex has to mature to master skills

35. Locomotion Continued
Neonate’s stepping and swimming reflexes disappear when cortical development inhibits some functions of the lower brain; when they reappear they differ in quality
Neural readiness most important the development of motor skills; early introduction to extensive motor skills training levels off (Arnold Gesell study, 1929)
Iranian infants (unlike Hopi children) in orphanage were exposed to extreme social and physical deprivation; they did not overcome motoric retardation (Dennis study, 1960)

36. Visual Acuity, Peripheral Vision and Preference
Most dramatic gains in visual acuity made between birth and 6 months of age; acuity reaches about 20/50
Neonates have poor peripheral vision; expands to 45 degrees by the age of 7 weeks
Neonates prefer stripes and curved lines
Neonates can prefer and identify mother’s face after 8 hours of contact over 4 days
Neonates prefer edges of face such as chin; may be due to attention to movement and contrast

39. Visual Cliff
Gibson and Walk (1960) known for visual cliff study; identified age at which infants have depth perception; ability to crawl indicated in ability to perceive depth
Campos et al (1970) study indicated 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)

41. 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
At 4 to 5 months old infants grasp the shape constancy under certain conditions

42. Development of Hearing
At 18 months of age hearing is similar to adults’
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
At 1 month infants perceive differences between speech sounds that are similar
Can discriminate parent’s voices at 3 ½ months of age
Exposure to native language causes loss of ability to discriminate sounds not in their native language

44. Development of Coordination of the Senses
Five-month-old infants look at novel stimulation longer than familiar sources of stimulation
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; infants looked at unfamiliar objects longer than objects they had held in their hands

45. 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 replaces “capture” – automatic responses to stimulation, 2) systematic search replaces unsystematic search, and 3) attention becomes selective, and 4) irrelevant information becomes ignored

46. The Role of Nature and Nurture
Neonates born with sensory skills and perceptual skills e.g. they can see nearby objects, hearing is fine, able to track moving objects, prefer certain kinds of stimuli - nature
Sensory and motor changes linked to maturation of nervous system - nature
Children have critical periods in their perceptual development; failure to receive adequate sensory stimulation can result in permanent sensory deficits - nurture
Health problems with vision in child’s eye where patch is needed extensively can result in permanent visual impairment - nurture