Chapter 5 Infancy: Physical Development

1. Chapter 5Infancy: Physical Development

2. What are the Sequences of Physical Development? • Cephalocaudal Development • Upper part of the head to the lower parts of the body • Proximodistal Development • Trunk outward – from body’s central axis toward periphery • Differentiation • Tendency of behavior to become more specific and distinct

3. What Patterns of Growth Occur in Infancy? • Weight doubles at about 5 months; triples by first birthday • Height increase by 50% in first year • Infants grow 4 to 6 inches in second year; and gain 4 to 7 pounds • Growth appears continuous but actually occurs in spurts

4. Figure 5.2 Changes in the Proportions of the Body

5. What is Failure to Thrive? • Growth impairment during infancy and early childhood • Causes may be organic or non-organic • Biologically based or non-biologically based • Links to physical, cognitive, behavioral and emotional problems • Deficiencies in caregiver-child interaction may play a role • Canalization – catch up growth once FTT is resolved

6. What are the Nutritional Needs of Children? • Infants require breast milk or iron fortified formula • Solid foods may be introduced about 4 to 6 months • Iron-enriched cereal, strained fruits, vegetables and meats • Whole cow’s milk delayed until 9 to 12 months • Teething biscuits in later part of first year

7. Guidelines for Infant Nutrition • Build up variety of foods • Avoid overfeeding or underfeeding • Don’t restrict fat and cholesterol • Don’t overdo high-fiber foods • Avoid items with added sugar and salt • Encourage high-iron foods U.S. Dept of Agriculture, 2000

8. Why do Women Bottle-feed or Breastfeed their Children? • Choice to breastfeed is influenced by • Attitudes regarding benefits for bonding and infant health • Fear of pain, unease with breastfeeding and public breastfeeding • Domestic and occupational arrangements • Community and familial support • Level of education

9. What are the Advantages and Disadvantages of Breast Milk? • Advantages of breast milk • Conforms to digestion process • Possesses needed nutrients • Contains mother’s antibodies • Helps protect against infant diarrhea • Is less likely, than formula, to cause allergies • Disadvantages of breast milk • HIV, alcohol, drugs and environmental hazards may be transmitted through breast milk • Physical demands on mother

10. Development of the Brain and Nervous System

11. What are Neurons? • Basic unit of nervous system, receive and transmit messages • Neurons vary according to function and location, but all contain • Cell Body • Dendrites • Axon • Neurotransmitters

12. Figure 5.3 Anatomy of a Neuron

13. How do Neurons Develop? • As child matures • Axons grow in length • Dendrites and axon terminals proliferate • Connection networks become more complex • Myelin Sheaths • Makes messages more efficient • Myelination occurs with maturation • Inhibition of myelination results in disease

14. What is the Brain? • Command center of organism • Brain of neonate weighs less than one pound • By first birthday, the brain triples in weight, reaching nearly 70% of adult weight

15. Structures of the Brain • Medulla • Controls basic body functions - heartbeat, respiration • Cerebellum • Maintains balance, control motor behavior, coordinate eye movements with body sensations • Cerebrum • Allows human learning, thought, memory and language

16. Figure 5.5 Structures of the Brain

17. How Does the Brain Develop? • Growth Spurts in Brain Development • Prenatal – fourth and fifth months • Proliferation of neurons • Prenatal – 25th week through 2 years old • Proliferation of dendrites and axon terminals

18. Figure 5.6 Increase in Neural Connections in the Brain

19. How do Nature and Nurture Affect the Development of the Brain? • Brain development is affected by maturation (nature) and sensory stimulation and motor activity (nurture) • Rats in enriched environment • More dendrites and axon terminals • Human infants have more neural connections than adults • If activated by experience, connection survives • If not activated, connection does not survive

20. Motor Development

21. What is Motor Development? • Developments in the activity of muscles, and is connected with changes in posture, movement, and coordination • Follows cephalocaudal and proximodistal patterns • Lifting and holding head before torso • Voluntary reaching • Locomotion • Sequence: rolling over, sitting up, crawling, creeping, walking, running

22. What are the Roles of Nature and Nurture in Motor Development? • Maturation (nature) • Myelination and differentiation is needed for certain voluntary motor activities • Experience (nurture) • Experimentation to achieve milestones • Slight effect in training to accelerate motor skills

23. Sensory and Perceptual Development

24. Development of Visual Acuity and Peripheral Vision • Neonates are nearsighted • Greatest gains in visual acuity between birth and 6 months • By about 3 to 5 years of age, approximate adult levels • Neonates have poor peripheral vision • Perceive stimuli within 30 degree angle • By 7 weeks increases to 45 degrees • By 6 months of age, equal to adult

25. What Captures the Attention of Infants? How do Visual Preferences Develop? • Neonates attend longer to stripes than blobs • By 8 to 12 weeks, prefer curved lines over straight • Infants prefer faces • Discriminate maternal and stranger faces • Prefer attractive faces • Pay most attention to edges

26. Figure 5.11 Preferences in Visual Stimuli in 2-Month-Olds

27. Figure 5.12 Eye Movements of 1- and 2-Month Olds

28. How do Researchers Determine Whether Infants will “Go Off the Deep End”? • Depth Perception • Develops around 6 months (onset of crawling) • Research using the Visual Cliff • Gibson and Walk (1960) • Relationship between crawling and fear of heights

29. Figure 5.13 The Visual Cliff

30. A Closer Look Strategies for Studying the Development of Shape Constancy

31. What are Perceptual Constancies? How do they Develop? • Perceptual constancy – perception of object remains stable although sensations may differ under various conditions • Size constancy – perception of object’s size remains stable although retinal size may differ • Appears by 2 1/2 to 3 months • Shape constancy – perception of object‘s shape remains stable although shape on retina may change • Appears by 4 to 5 months

32. How Does the Sense of Hearing Develop in Infancy? • Neonates can orient toward direction of a sound • 18 months locate sounds as well as adults • By 3 1/2 months discriminate caregivers’ voices • Infants perceive most speech sounds present in world languages • By 10 to 12 months, lose capacity to discriminate sounds not found in native language

33. Figure 5.14 Declining Ability to Discriminate the Sounds of Foreign Languages

34. What is the Evidence for the Roles of Nature and Nurture in Perceptual Development? • Sensory changes are linked to maturation of nervous system (Nature) • Experience also plays a role (Nurture) • Critical periods • Newborn kittens with patched eye – become blind in that eye • Nature and nurture interact to shape perceptual development.