Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 5 Chapter 5 Infancy: Physical Development.

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

Chapter 5Infancy: Physical Development


The head of the newborn child doubles in length by adulthood, but the legs increase in length about five times.

Infants triple their birth weight within a year.

Infancy: Physical Development: Truth or Fiction?


Breastfeeding helps prevent obesity later in life.

A child’s brain reaches half of its adult weight by the age of 1 year.



The cerebral cortex – the outer layer of the brain that is vital to human thought and reason – is only one-eighth of an inch thick.

Native American Hopi infants spend the first year of life strapped to a board, yet they begin to walk at about the same time as children who are reared in other cultures.



Infants need to have experience crawling before they develop fear of heights.



Infancy: Physical Development

Physical Growth and 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 5.1 Growth Curves for Weight and Height (Length) From Birth to Age 2 Years


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


Developing in a World of Diversity

Alleviating Protein-Energy Malnutrition (PEM)


• 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?


Figure 5.4 Growth of Body Systems as a Percentage of Total Postnatal Growth


• 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


• Myelination– At birth brain areas well myelinated include

• Heartbeat and respiration

• Sleeping and arousal

• Reflex activity

– Myelination of sensory areas• Hearing – begins about 6th month of pregnancy and continues to age 4

• Vision – begins shortly before full term but develop rapidly

Brain Development in Infancy


• 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?


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


• Process of integrating disjointed sensations into meaningful patterns through perception

• Focus on vision and hearing– Most research is one these areas

How do Sensation and Perception Develop in the Infant?


• 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


• 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?


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


A Closer Look

Effects of Early Exposure to Garlic, Alcohol, and – Gulp - Veggies


• Neonates perception is largely passive

• Later, intentional action replaces capture– Systematic search replaces unsystematic

– Attention becomes selective

– Irrelevant information gets ignored

Do Children Play an Active or Passive Role 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.

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


• What does research tell us about the sensory capacities of newborns, such as Carter and Aiden?Cite evidence from the video that supports this research in regard to vision and hearing.

Lessons in Observation Sensation and Perception in Infancy




• Discuss how the newborn’s capacities for vision and hearing are adaptive in the context of Carter’s initial interaction with mom.

• Infants have clear visual preferences. Discuss the visual preferences of infants in the context of the response of 2-month-old Giuseppina to the stimuli presented by Dr. Basow.What method is Dr. Basow using as a test of Giuseppina’s visual preferences?What other methods are commonly used to study infant sensory and perceptual capacities?



• Does the newborn’s preference for looking at faces more than at other objects indicate that form perception is innate? Why or why not?


Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 5 Chapter 5 Infancy: Physical Development.

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