chapter 5 infancy: physical development

Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. RathusChapter 5

Chapter 5Infancy: 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

What are the Sequences of Physical Development?


• 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

What Patterns of Growth Occur in Infancy?


Figure 5.2 Changes in the Proportions of the Body


• 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

What is Failure to Thrive?


• 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

What are the Nutritional Needs of Children?


• 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

Guidelines for Infant Nutrition


• 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

Why do Women Bottle-feed or Breastfeed their Children?


• 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

What are the Advantages and Disadvantages of Breast Milk?


Development of the Brain and Nervous System


• Basic unit of nervous system, receive and transmit messages• Neurons vary according to function and location, but all contain

– Cell Body– Dendrites– Axon

• Neurotransmitters

What are Neurons?


Figure 5.3 Anatomy of a Neuron


• 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

How do Neurons Develop?


• 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

What is 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

Structures of the Brain


Figure 5.5 Structures of the Brain


• 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

How Does the Brain Develop?


Figure 5.6 Increase in Neural Connections in 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

How do Nature and Nurture Affect the Development of the Brain?


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

What is 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

What are the Roles of Nature and Nurture in Motor Development?


Sensory and Perceptual Development


• 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

Development of Visual Acuity and Peripheral Vision


• 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

What Captures the Attention of Infants? How do Visual Preferences Develop?


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


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


• 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

How do Researchers Determine Whether Infants will “Go Off the Deep End”?


Figure 5.13 The Visual Cliff


A Closer Look

Strategies for Studying the Development of Shape Constancy


• 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

What are Perceptual Constancies? How do they Develop?


• 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

How Does the Sense of Hearing Develop in Infancy?


Figure 5.14 Declining Ability to Discriminate the Sounds of Foreign Languages


• 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.

What is the Evidence for the Roles of Nature and Nurture in Perceptual Development?

chapter 5 infancy: physical development

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