Infancy: Physical Development

1. Infancy: Physical Development Chapter 4 Development Across the Life Span

2. Growth and Stability: Physical Growth • Over the first 2 years of a human’s life, growth occurs at a rapid pace!

3. Height & Weight Growth The greatest height & weight increases occur during the 1st year of life, but children continue to grow through infancy & toddlerhood.

4. --By age 5 months, the average infant's birthweight has doubled to about 15 pounds. • --By age 1, the infants' birthweight has tripled to approximately 22 pounds. • --By the end of its second year, the average child weighs four times its birthweight. • --By age 1, the average baby stands 30 inches tall. • --By the end of the second year the average child is three feet tall. • Average birthweights (progression through the 1st 2 years)

5. Decreasing Proportions… At birth, the head is ¼ of the neonate’s body. By adulthood, it is only 1/8th the size of the body.

6.  Not all parts of the body grow at the same rate.The 4 Major Principles Governing Growth 1) The CEPHALOCAUDAL PRINCIPLEstates that growth follows a pattern that begins with the head and upper body parts and then proceeds to the rest of the body. 2) The PROXIMODISTAL PRINCIPLEstates that development proceeds from the center of the body outward.

7. (Major Principles Governing Growth continued) 3) The PRINCIPLE OF HIERARCHICAL INTEGRATIONstates that simple skills typically develop separately and independently but are later integrated into more complex skills. 4) The PRINCIPLE OF INDEPENDENCE OF SYSTEMSsuggests that different body systems grow at different rates.

8. Maturation Rates Different body systems mature at different rates. For instance, the nervous system is highly developed during infancy.

9. The nervous system comprises the brain and the nerves that extend throughout the body.  Infants are born with between 100 and 200 billionNEURONS! (the nerve cells of the nervous system).  As the infant's experience in the world increases, neurons that do not become interconnected become unnecessary and die off.

10. The Neuron The basic element of the nervous system

11. More About Neurons… -- Neurons increase in size. -- Neurons become coated with MYELIN,a fatty substance that helps insulate neurons and speeds transmission of nerve impulses. -- The brain is made up of neurons, and triples its weight in the first two years of life. • The infant's brain is 3/4 its adult size by age two

13. More About Neurons… * As they grow, neurons become arranged by function. * Some move into the CEREBRAL CORTEX,the upper layer of the brain. * Others move to subcortical levels, which regulate fundamental activities such as breathing and heart rate (and are below the cerebral cortex).

14. Networks of neurons become more complex over the first few years of life. Neuron Networks

15. PLASTICITYis the degree to which a developing structure (e.g., the brain) or behavior is susceptible to experience Brain development occurs because of genetic patterns and environmental influences.  The brain is relatively plastic -- Infants who grow up in severely restricted environments are likely to show differences in brain structure and weight.

16. (brain development, continued) -- Research with non-humans reveals that a SENSITIVE PERIOD exists which is a specific but limited time span, usually early in an organism's life, during which the organism is particularly susceptible to environmental influences relating to some particular facet of development.

17. Development of Body Rhythms • Behavior (sleeping, eating, crying, attending to the world) becomes integrated through the development of various body RHYTHMS (repetitive, cyclic patterns of behavior) • Some rhythms are obvious/easy to notice • The change from being asleep to being awake/breathing patterns

18. (development of body rhythms, continued) • Some rhythms are more subtle • Jerking suddenly while sleeping *Some are apparent right after birth, others emerge over the course of the 1st year as the nervous system becomes more integrated

19. One of the major body rhythms is an infants state -- An infant's STATEis the degree of awareness it displays to both internal and external stimulation. -- Includes various levels of wakeful behaviors (alertness, crying, etc.) and various levels of sleep (active, quiet) -- Changes in state are reflected in brain waves measured by a device called anEEG, or electroencephalogram.

20. The major state occupying the infant is sleep. • On average, newborns sleep 16-17 hours daily, ranging from 10-20 hours a day. • Sleep stages are fitful and "out of sync" during early infancy. • By the end of the first year most infants are sleeping through the night.

21. The Infant’s Cycle of Sleep… • Infants have a cycle of sleep similar to but different than REM - RAPID EYE MOVEMENT, (the period of sleep found in adults and children and is associated with dreaming). • Brain waves are different than the dreaming sleep of adults. • This active REM-like sleep takes up half an infants sleep at first. • Researchers think the function of REM sleep in infants is to provide a means for the brain to stimulate itself (autostimulation).

22. REM Sleep Through the Lifespan REM sleep increases & the total amount of sleep falls as we age.

23. For a small % of infants, the rhythm of sleep is interrupted by a deadly occurrence: SIDS • SUDDEN INFANT DEATH SYNDROME (SIDS) is a disorder in which seemingly healthy infants die in their sleep. • affects 7,000 children in U.S. annually • no cause found • The leading cause of death in children under 1 year old • Boys, African-Americans, and low birthweight and low Apgar scorers, and babies whose mothers smoked during pregnancy are at higher risk.

24. Declining Rates of SIDS US rates have dropped 38% since 1992 as parents have learned to have babies sleep on their backs.

25. Motor Development  Basic REFLEXES,unlearned, organized, involuntary responses that occur automatically in the presence of certain stimuli, represent behavior that has survival value for the infant. • swimming reflex • eye blink reflex

26. More about reflexes in motor development… • Some reflexes stay throughout life; others disappear over time. • Some researchers believe reflexes stimulate the brain toward development. • Reflexes are genetically determined and universal and may be remnants from the past. • Reflexes can serve as helpful diagnostic tools for pediatricians because they appear and disappear on a regular timetable

27. Gross Motor Skills (rolling over, sitting upright, walking) • By 6 months infants can move by themselves. • Most can sit unsupported by 6 months • Crawling appears between 8-10 months. • Infants can walk holding on to furniture by 9 months and most can walk alone by 1 year.

29. Fine Motor Skills(coordination, sophistication) • By 3 months infants can coordinate movements of limbs. • Infants can grasp an object by 11 months. • By age 2, infants can drink from a cup without spilling.

30. Milestones of Motor Development 50% of children are able to perform each skill at the month indicated, but the specific timing varies widely!

32. It is important to keep in mind that developmental NORMSare the average performance of a large sample of individuals of a certain age and mask substantial individual differences! (Norms are based on scales developed by developmental psychologists & pediatricians)

33. A common technique to determine infants’ normative standing: BRAZELTON NEONATAL BEHAVIORAL ASSESSMENT SCALE (NBAS) • NBAS is a measure used to determine infants' neurological and behavioral responses to their environment. • supplements the Apgar • 27 categories of responses • interactions with others • motor behavior • physiological control • response to stress

34. More about norms… • Norms should be based on large, heterogeneous samples. • The time at which specific motor skills appear is in part determined by cultural factors. • There are certain genetic constraints on how early a skill can emerge

35. Nutrition in Infancy Fuels Motor Development Nutrition during infancy is extremely important! Without proper nutrition, infants cannot reach their physical potential and also may suffer cognitive and social consequences.

36. Underweight Children In developing countries, the number of underweight children under age 5 is substantial.

37. Malnutrition & It’s Effects Malnutrition, the condition of having an improper amount and balance of nutrients produces several results. --slower growth --susceptibility to disease --lower IQ scores

38. Malnutrition & It’s Effects, continued --Malnutrition can also cause MARASMUS,a disease characterized by the cessation of growth in infants. --Older children are susceptible to KWASHIORKOR,a disease in which a child's stomach, limbs, and face swell with water.

39. (malnutrition, continued) • Risks of malnutrition are greater in underdeveloped countries and in areas with high poverty rates. • Undernutrition is more common in developed countries (deficiency in the diet).

40. Children Living in Poverty Single-parent and minority families are more likely to have kids under age 3 living in poverty.

41. For the first four to six months of life there is no better food for an infant than breast milk! Why? Nutrition as Fuel for Motor Development: Breast or Bottle?? • all essential nutrients • natural immunity to childhood diseases • more easily digested • health advantages for mother (lower cancer) • emotional advantages for both mother and child • bonding? In spite of this, only half of mothers in U.S. breast-feed

42. Breast Milk Advantages

43. Introducing Solid Foods Most babies can begin to eat solid foods at about 4-6 months. • Foods are introduced gradually. • Weaning, the cessation of breast-feeding, occurs on average in the U.S. at 3-4 months. Experts recommend infants be breast-fed for 6-12 months.

44. Development of the Senses Infants come to understand the world around them through sensation & perception • SENSATION is the stimulation and responsiveness of the sense organs. • PERCEPTION is the sorting out, interpretation, analysis, and integration of stimuli involving the sense organs and brain.

45. Visual Perception: Seeing the World • Newborn infants cannot see beyond a distance of 20 feet. • By 6 months, the average infant's vision is 20/20.

46. (vision continued) Binocular vision, the ability to combine both eyes' vision to see depth and motion is achieved at 14 weeks. • Gibson's "visual cliff" experiments showed that most infants between 6-14 months would not crawl over the apparent cliff . • The “visual cliff” experiment examines the depth perception of infants • We do not know how early this depth perception occurs in infancy.

47. (vision continued) • Infants show clear visual preferences that are present at birth • Infants prefer to look at patterns and complex stimuli. • Infants prefer to look at faces. • Minutes after birth they show a preference for certain colors, shapes, configurations May support the existence of specialized brain cells (genetic influence on visual preferences)—but environmental influences too!

48. Preferring Complexity In a classic experiment, Robert Fantz found that 2- and 3-month-old infants preferred to look at more complex stimuli.

49. Auditory Perception: The World of Sound • It is clear that infants hear from the time they are born—and even before! (prenatally) • Infants are more sensitive than adults to high and low frequencies but not to the middle ranges.

50. Auditory Perception continued… • Sound localization permits infants to discern direction from which a sound is emanating. --This skill is poorer in infants than adults because of infants' smaller heads. --It reaches adult level at 1 year. --Infants can differentiate changes in melodies and sounds - a requirement for language - and their mother's voice from other voices