Physical Development in Infancy
Chapter 4
Robert S. Feldman

GROWTH AND STABILITY
Physical Growth
Rapid growth during first two years




Principles of Growth
Cephalocaudal principle
Proximodistal principle
Principle of hierarchical integration
Principle of independence of systems

An Interesting Head Count
Are there gender and ethnic differences in infant weight and length?
See how they grow…
Nervous System and Brain
Nervous system comprises the brain and the nerves that extend throughout the body
Neurons are the basic cells of the nervous system
Quick Check
Neurons
Dendrites
Axons
Neurotransmitters
Synapses
Major Systems of the Brain
Brain stem
Limbic system
Cerebral cortex
How great brains grow!
Birth:
100-200 billion neurons
Relatively few neurons-neuron connections
During first two years:
Billions of new connections established and become more complex
Use it or lose it!
Synaptic pruning
Unused neurons are eliminated
Allows established neurons to build more elaborate communication networks with other neurons
Development of nervous system proceeds most effectively through loss of cells
Myelin
Form and Function: Brain Growth
Neurons reposition themselves with growth, becoming arranged by function
Cerebral cortex
Subcortical levels
Don’t shake the baby!
Shaken Baby Syndrome
Brain sensitive to form forms of injury
Shaking can lead to brain rotation within skull
Blood vessels tearsevere medical problems, long-term disabilities, and sometimes death
Environmental Influences on Brain Development
Plasticity: degree to which developing structure or behavior is modifiable due to experience

Sensitive period: specific but limited time, usually early in life, during which organism is particularly susceptible to environmental influences relating to a facet of development

Do Baby Einstein programs really work?
What do babies do all day?
Life Cycles of Infancy
Wake
Sleep
Eat
Defecate


Rhythms and States
State
One of major body rhythms
Degree of awareness infant displays to both internal and external stimulation
Change in state alters amount of stimulation required to get infant’s attention

Sleep: Perchance to Dream
Major state
16-17 hours daily (average); wide variations
Different than adult sleep
2 hour spurts; periods of wakefulness
Cyclic pattern
By 16 weeks sleep about 6 continuous hours; by 1 year sleep through night
(See table 4-2)
Everybody Sleeps
REM Sleep
Period of active sleep
Closed eyes begin to move in a back-and-forth pattern
Takes up around one-half of infant sleep
May provide means for brain to stimulate itself through autostimulation



Do babies dream?
SIDS
Sudden infant death syndrome
Leading cause of death in children under 1 year of age
Back-to-sleep guidelines (AAP)
Differential risk
Boys
African American infants
Low birthweight
Low APGAR scores
Mother’s smoking
Some brain defects
Child abuse


Declining Rates of SIDS
SIDS is found in children of every race and socioeconomic group and in children who have had no apparent health problems

Back-to-sleep is important!
MOTOR DEVELOPMENT
Reflexes: Inborn Physical Skills
Reflexes: learned, organized involuntary responses that occur automatically in presence of certain stimuli
A Closer Look at Reflexes
Ethnic and Cultural Differences and Similarities in Reflexes
Reflexes
Genetically determined
Universal
Cultural variations in ways displayed
Moro reflex
Serves
Diagnostic tool
Social function
Survival function


Motor Development in Infancy
Milestones of Normal Motor Development


Motor Development in Infancy
Fine Motor Skills
Dynamic Systems
Dynamic systems theory describes how motor behaviors are assembled
Motor skills do not develop in vacuum
Each skill advances in context of other motor abilities
As motor skills develop, so do non-motoric skills
Theory places emphasis on child’s own motivation (a cognitive state) in advancing important aspects of motor development
Developmental Norms
Comparing Individual to Group Norms:
Represent the average performance of a large sample of children of a given age.
Permit comparisons between a particular child’s performance on a particular behavior and the average performance of the children in the norm sample.
Must be interpreted with caution.
Brazelton Neonatal Behavior Assessment Scale (NBAS)
Nutrition in Infancy
Fueling Motor Development
Without proper nutrition, infants cannot reach physical potential and may suffer cognitive and social consequences
Infants differ in growth rates, body composition, metabolism, and activity levels

So what is a healthy caloric allotment for infants?
About 50 calories per day for each pound of weight
Most infants regulate their caloric intake quite effectively on their own
If are allowed consume as much they seem to want, and not pressured to eat more, they will be healthy
Malnutrition
Children living in many developing countries
Slower growth rate
Chronically malnourished during infancy = later lower IQ score
Are problems of malnourishment restricted to developing countries?
Undernutrition: Dietary Deficiencies
Undernutrition also has long-term costs, including mild to moderate cognitive delays
Up to 25% of 1- to 5-year-old US children have diets that fall below minimum caloric intake recommended by nutritional experts

Nonorganic Failure to Thrive
Sufficient nutrition
Symptoms
Reversal
“A fat baby is a healthy baby”?
From Research to Practice
Fast-Food Babies
Develop taste for certain foods at an early age and then tend to stick with those foods as they get older
Like food mother likes
Often consume convenience foods that are high in sugar and fat and low in nutrients

Is Breast-Feeding Best?
Social Patterns in Breast-Feeding
Introducing Solid Foods: When and What?
Solids can be started at 6 months but are not needed until 9 to 12 months (AAFP)
Introduced gradually, one at a time
Cerealstrained fruits
Learning the World
Sensation
Perception

Visual Perception: Seeing the World
Newborn’s distance vision ranges from 20/200 to 20/600
By 6 months, average infant’s vision is already 20/20
Other visual abilities grow rapidly
Binocular vision
Depth perception
When Going Off the Deep End is a Good Thing!
Infant Visual Preference
Preferences that are present from birth
Genetically preprogrammed to prefer particular kinds of stimuli
Prefer to look at patterned over simpler stimuli

Auditory Perception: The World of Sound
Infants
Hear before birth and have good auditory perception after they are born
Are more sensitive to certain frequencies
Reach adult accuracy in sound localization by age 1
Can discriminate groups of different sounds
React to changes in musical key and rhythm
Can discriminate many language related sounds



Smell and Taste in a Small World
Smell
Well developed at birth
Helps in recognition of mother early in life
Taste
Have innate sweet tooth
Show facial disgust at bitter taste
Develop preferences based on what mother ate during pregnancy
Ouch!
Contemporary Views on Infant Pain
Developmental progression in reaction to pain
Infants born with capacity to experience pain; produces distress
Exposure to pain in infancy may lead to permanent rewiring of nervous system resulting in greater sensitivity to pain during adulthood
The Power of Touch
Touch is one of most highly developed sensory systems in a newborn
Even youngest infants respond to gentle touches
Several of the basic reflexes present at birth require touch sensitivity to operate

Does massage work?