Make your own free website on

Chapter 4
Physical Development in Infancy


The Major Principles Governing Growth

The CEPHALOCAUDAL PRINCIPLE states that growth follows a pattern that begins with the head and upper body parts and then proceeds to the rest of the body.

2) The PROXIMODISTAL PRINCIPLE states that development proceeds from the center of the body outward.

3) The PRINCIPLE OF INDEPENDENCE OF SYSTEMS suggests that different body systems grow at different rates.

The Nervous System Comprises the Brain and the Nerves That Extend Throughout the Body

Infants are born with between 100 and 200 billion NEURONS ( the nerve cells of the nervous system).

As the infant's experience in the world increases, neurons that do not become interconnected become unnecessary and die off .

Neurons become coated with MYELIN, a fatty substance that helps insulate neurons and speeds transmission of nerve impulses.

PLASTICITY Is the Degree to Which a Developing Structure (E.G., The Brain) or Behavior Is Susceptible to Experience

The brain is relatively plastic.

Infants who grow up in severely restricted environments are likely to show differences in brain structure and weight.

The Infantís State

-- An infant's STATE is the degree of awareness it displays to both internal and external stimulation .

-- Includes various levels of wakeful behaviors (alertness, crying, etc.) and various levels of sleep (active, quiet).

-- Changes in state are reflected in brain waves measured by a device called an EEG.

The Major State Occupying the Infant Is Sleep

On average, newborns sleep 16-17 hours daily, ranging from 10-20 hours a day.

Sleep stages are fitful and "out of sync" during early infancy.

By the end of the first year most infants are sleeping through the night .

The Infantís Cycle of Sleep

Infants have a cycle of sleep similar to but different than REM - RAPID EYE MOVEMENT, (the period of sleep found in adults and children and is associated with dreaming)

Brain waves are different than the dreaming sleep of adults.

This active rem-like sleep takes up half an infants sleep at first.

Researchers think the function of REM sleep in infants is to provide a means for the brain to stimulate itself (autostimulation).

For a Small Number of Infants, the Rhythm of Sleep Is Interrupted by a Deadly Occurrence: SIDS

SUDDEN INFANT DEATH SYNDROME (SIDS) is a disorder in which seemingly healthy infants die in their sleep

Affects 1,000 children in U.S. Annually

Actual cause unknown

The leading cause of death in children under 1 year old

Boys, African-Americans, and low birthweight and low apgar scorers, and babies whose mothers smoked during pregnancy are at higher risk.


Gross Motor Skills
(Rolling Over, Sitting Upright, Walking)

By 6 months infants can move by themselves.

Most can sit unsupported by 6 months.

Crawling appears between 8-10 months .

Infants can walk holding on to furniture by 9 months and most can walk alone by 1 year.


Fine Motor Skills
(Coordination, Sophistication)

By 3 months infants can coordinate movements of limbs.

Infants can grasp an object by 11 months.

By age 2, infants can drink from a cup without spilling.

Nutrition in Infancy: Fueling Motor Development

Without proper nutrition, infants cannot reach their physical potential and also may suffer cognitive and social consequences.


Malnutrition & Its Effects

Malnutrition, the condition of having an improper amount and balance of nutrients produces several results :

--Slower growth

--Susceptibility to disease

--Lower IQ scores

Undernutrition is more common in developed countries (dietary deficiencies)


Development of the Senses

Infants come to understand the world around them through sensation & perception.

SENSATION is the stimulation and responsiveness of the sense organs,

PERCEPTION is the sorting out, interpretation, analysis, and integration of stimuli involving the sense organs and brain,

Visual Perception: Seeing the World

Newborn infants cannot see beyond a distance of 20 feet, but by 6 months, the average infantís vision is 20/20.

Binocular vision, the ability to combine both eyes' vision to see depth and motion is achieved at 14 weeks.

Gibson's "visual cliff" experiments showed that most infants between 6-14 months would not crawl over the apparent cliff.

The "visual cliff" experiment examines the depth perception of infants.

We do not know how early this depth perception occurs in infancy.


(Vision Continued)

Infants show clear visual preferences that are present at birth

Infants prefer to look at patterns and complex stimuli,

Infants prefer to look at faces,

Minutes after birth they show a preference for certain colors, shapes, configurations,

May support the existence of specialized brain cells (genetic influence on visual preferences)óbut environmental influences, also.

Auditory Perception:
The World of Sound

It is clear that infants hear from the time they are bornóand even before.

Infants are more sensitive than adults to high and low frequencies but not to the middle ranges.

Sound localization permits infants to discern direction from which a sound is emanating .

--This skill is poorer in infants than adults because of infants' smaller heads .

--It reaches adult level at 1 year.

--Infants can differentiate changes in melodies and sounds - a requirement for language - and their mother's voice from other voices.




Smell and Taste in Infancy

Infants react to unpleasant tastes and smells from birth.

Newborns can detect their mother's smell, but only when breastfed.

Infants have an innate sweet tooth.

Sensitivity to Pain and Touch

Infants are born with the capacity to feel pain.

Touch is one of the most highly developed sensory systems in a newborn.

The rooting reflex is strong.

Infants gain information about the world through touch.

Even the youngest infants respond to gentle touches and are calmed by them.