Part II

1. Part II Chapter Five The First Two Years: Infant and Toddlers Body Changes Brain Development Senses and Motor Skills Public Health Measures Prepared by Madeleine Lacefield Tattoon, M.A.

2. “Adults don’t change much in a year or two. Their hair might grow longer, grayer, or thinner; they might be a little fatter; or they might learn something new. But if you saw friends you hadn’t seem for two years, you’d recognize them immediately.”

3. “By contrast, if you cared for newborn 24 hours a day for a month, went away for two years, and then came back,you might not recognized him or her, because the baby would have quadrupled in weight, grown taller by more than a foot, and sprouted a new head of hair. • Behavior would have changed, too. Not much crying, but some laughter and fear—including of you.”

4. “A year or two is not much compared with the 75 or so years of the average life span. However, in two years newborns reach half their adult height, talk in sentences, and express almost every emotion—not just joy and fear but also love, jealousy, and shame.”

5. Biosocial Development

6. Body Changes • In infancy • growth is fast • neglect can be severe • gain needs to be monitored • health check-up need to include • height, weight and head circumference

7. Body Size • rapid growth • infants typically double their birth weight by the 4th month and triple by the 1st birthday • physical growth slows in the 2nd year • by 24 months weight is about 30 lbs, height about 32”-36” • these numbers are “norms”

8. Body Size • “norms” • an average or standard for a particular population • “particular population” • a representative sample of North American infants • “percentiles” • a number that is midway between 0 and 100, with ½ the children above it and ½ below it

9. Body Size • Weight increase in the early months is fat, providing insulation for warmth and nourishment • Nourishment keeps the brain growing, if teething or illness interfere with eating • When nutrition is temporarily inadequate, the body stops growing but not the brain • this is known as a phenomenon called “head-sparing”

10. Sleep • Infants sleep about 17 hours or more a day • Regular and ample sleep correlates with normal brain maturation, learning, emotional regulation, and psychological adjustment in school and within the family

11. Sleep • Over the first month the amount of time spent in each type or stage of sleep changes • Newborns dream a lot, or at least they have a high proportion of “REM sleep” • REM sleep • rapid eye movement sleep is a stage of sleep characterized by flickering eyes behind closed lids, dreaming, and rapid brain waves

12. Sleep • Sleep Patterns can be… • affected by birth order • first born typically receive more attention • diet • parents might respond to predawn cries with food, and/or play (babies learn to wake up night after night) • child-rearing practices • “Where should infants sleep?” • co-sleeping or bed-sharing • brain maturation

13. “Who Sleeps Where?”

14. Brain Development • the newborn’s skull is disproportionately large • large enough to hold the brain, which at birth is 25% of the adult brain • the neonate’s body is typically 5% of the adult weight • by age 2 the brain is almost 75% of the adult brain weight • the child’s total body weight is only about 20% of its adult weight

15. Connection in the Brain • Head circumference provides a rough idea of how the brain is growing, and that is why medical checkups include measurement of the skull. • Head typically increases about 35% within the 1st year

16. Basic Brain Structures • The brain’s communication system begins with nerve cells, called neurons. • Neurons are one of the billions of nerve cells in the central nervous system, especially the brain. • Infants have billions of neutrons • Located in the brain or in the brain stem • the region that controls automatic responses, I.e., heartbeat, breathing, temperature, and arousal • 70% of the neurons are in the cortex

17. Basic Brain Structures • The cortex is crucial for humans… • 80% of the human brain materials in the cortex • in other mammals the cortex is proportionally smaller, and non-mammals have no cortex • most thinking, feeling, and sensing take place in the cortex, although other parts of the brain join in.

18. Basic Brain Structures • Areas of the cortex specialize in particular functions: • visual • auditory • an area dedicated to the sense of touch for each body part • regional specialization within the cortex occurs not only for motor skills and senses but also for aspects of cognition

19. Basic Brain Structures • Between brain areas, neurons are connected to other neurons by intricate networks of nerve fibers called axons and dendrites • a neuron has a single axon and numerous dendrites, which spread out like the branches of a tree • axons and neurons meet the dendrites of other neurons at intersections called synapses which are critical communication links within the brain

20. Basic Brain Structures

21. Basic Brain Structures • Transient Exuberance and Pruning • The fivefold increase in dendrites in the cortex occurs in the 24 months after birth, with about 100 trillion synapses being present at age 2 • The expanded growth is followed by pruning in which unused neurons and misconnected dendrites atrophy and die • Synapses, dendrites, and even neurons continue to form and die throughout life, though more rapidly in infancy than at any other time

22. Basic Brain Structures • Experience Shapes the Brain • brain structure and growth depends on genes and experiences • experiences produce “postnatal rise and fall” • some dendrites wither away because they are underused; no experiences have caused them to send a message to the axons of other neurons. • increasing cognitive complexity of childhood is related to a loss of synapses

23. Basic Brain Structures • Stress and the Brain • example of the role of experience in brain development begins when the brain produces cortisol and other hormones in response to stress, which happen throughout life

24. Basic Brain Structures • Necessary and Possible Experiences • Scientist William Greenough identified two experience-related aspects of brain development • The development of experience-expectant referring to brain functions that require certain basic common experiences, which an infant can be expected to have in order to develop normally • The development of experience-dependent referring to brain functions that depend on particular, variable experience and that therefore may or may not develop in a particular infant

25. Basic Brain Structures • Necessary and Possible Experiences • Basic, common experiences must happen for normal brain maturation to occur, and they almost always do happen • The brain is designed to expect them and use them for growth • in contrast, dependent experiences might happen. Because of them, one brain differs from another • experience varies; language babies hear or how their mothers reacts to frustration • all people are similar, but each person is unique, because of early experiences

26. Basic Brain Structures • Necessary and Possible Experiences • The last part of the brain to mature is the prefrontal cortex • The area for anticipation, planning, and impulse control • Virtually inactive in early infancy • telling an infant to stop crying is pointless • shaking a baby to stop crying, “shaken baby syndrome,” is useless • Gradually becomes more efficient over the years of childhood and adolescence

27. Basic Brain Structures • Implications for Caregivers • Early brain growth is rapid and reflects experience… • caressing a newborn, • talking to a preverbal infant • showing affection toward a small person • …are essential to develop that person’s full potential

28. Basic Brain Structures • Implications for Caregivers • Each part of the brain has sequence of… • growing • connecting • pruning • Stimulations are meaningless before the brain is ready • advisable to follow the baby’s lead • infants respond most strongly and positively to their brain’s need • Self-righting is the inborn drive to remedy a developmental deficit

29. Basic Brain Structures • Implications for Caregivers • the human brain is designed to grow and adapt • some plasticity is retained throughout life • the brain protects itself from overstimulation • ex., overstimulated babies cry or sleep • babies adjust to understimulation • by developing new connections lifelong

30. Basic Brain Structures • Implications for Caregivers • Neuroscientist once thought that brains were influenced by • Genes and prenatal influences • By contrast, social scientist by • Childhood environment was crucial… • Cultures • Societies • Parents • …credited or blamed for child’s emotions and/or actions

31. Basic Brain Structures • THINK LIKE A SCIENTIST • Plasticity and Orphans

32. Senses and Motor Skills • Piaget called the first period of intelligence the • Sensorimotor stage • cognition develops from the senses and motor skills • infant brain development depends on sensory experiences and early movement • within hours of birth vital organs are functioning, assessing basic senses and motor responses (Brazelton Neonatal Assessment Scale; measures 26 items of newborn behavior)

33. Sensation and Perception • All the senses function at birth • open eyes, sensitive ears, and responsive noses, tongues, and skin • Very young babies attend to everything • Infants don’t focus on anything in particular • To about age one taste in the primary way humans learn about objects

34. Sensation and Perception • Sensation is the response of a sensory system… • eyes, ears, skin, tongue, nose • …when it detects a stimulus • when the inner ear reverberates with sound • The retina and pupil of the eye intercept light

35. Sensation and Perception • Perception is the mental processing of sensory information… • the brain notices and processes a sensation… • when the brain interprets a sensation… • Infant’s brains are attuned to experiences that are repeated, striving to make sense of them

36. Senses and Motor Skills • Hearing • Hearing is acute at birth • Certain sounds trigger reflexes • Sudden noises startle newborns • Rhythmic sounds soothe them and put them to sleep • The first days of life infants turn their heads towards sound • They soon connect sight and sound with accuracy

37. Senses and Motor Skills • Seeing • At birth vision is the least mature • The infant eyes are sensitive to bright light even though the eyes open in mid-pregnancy • Newborns are “legally blind” they can only see objects 4” – 30” away

38. Senses and Motor Skills • Seeing • At two months infants look more intensely at faces and often smile • At three months infants look more closely at the eyes and mouth • The ability to focus the two eyes in a coordinated manner in order to see one image is known as binocular vision

39. Senses and Motor Skills • Tasting, Smelling and Touching

40. Senses and Motor Skills • Tasting, Smelling and Touching • At birth the senses of taste, smell and touch function and rapidly adapt to the social world • As infants learn their caregiver’s smell and touch (handling) they relax and cuddle • Over time infants become responsive to whose touch it is and what it communicates

41. Senses and Motor Skills • Early sensation seems to have two goals: • Social interaction • To respond to familiar caregivers • Comfort • To be soothed amid the disturbances of infant life

42. Senses and Motor Skills • Motor Skill is the learned ability to move some part of the body, from a large leap to a flicker of the eyelid. (motor refers to movement of muscles; the abilities needed to move and control the body)

43. Senses and Motor Skills • Reflexes are a responsive movement that seems automatic because it almost always occurs in reaction to a particular stimulus. Newborns have many reflexes, some of which disappear with maturation (a reflex is an involuntary response to a particular stimulus

44. Senses and Motor Skills • Reflexes • Infants have dozen of reflexes • three sets are critical for survival • that maintain oxygen supply • that maintain constant body temperature • that manage feeding

45. Senses and Motor Skills • Gross Motor Skills are physical abilities involving large body movements (gross meaning “big”) • walking • jumping • Walking progress • from reflexive, • to hesitant • to adult-supported stepping • to a smooth coordinated gait

46. Senses and Motor Skills • Gross Motor Skills • Three factors combine to allow toddlers to walk • muscle strength • brain maturation within the motor cortex • practices

47. Senses and Motor Skills • Fine Motor Skills are physical abilities involving small body movements, especially of the hands and fingers (fine in this text means “small”) • drawing • picking up a coin

48. Senses and Motor Skills • Ethnic Variation • healthy infants develop skills in the same sequence • they vary in the age at which they acquire them (the table on the next slide show some “norms”) • Walking, when grouped by ethnicity: • Generally African American are ahead of Hispanic Americans • Hispanic American are ahead of European American • Internationally the earliest walkers are in Uganda • The latest walkers are in France

49. Senses and Motor Skills

50. Senses and Motor Skills • Genes are only a small part of most ethnic differences • Cultural patterns of child rearing can affect sensation, perception, and motor skills