Infancy: Physical
Development
Chapter 4
Development Across
the Life Span
Growth and Stability: Physical Growth
Over the first 2 years
of a human’s life, growth
occurs at a rapid pace!

Height & Weight Growth
The greatest
height & weight
increases occur
during the 1st
year of life, but
children
continue to
grow through
infancy &
toddlerhood.

Average birthweights
(progression through the 1st 2 years)
--By age 5 months, the average infant's
birthweight has doubled to about 15 pounds.
--By age 1, the infants' birthweight has tripled to
approximately 22 pounds.
--By the end of its second year, the average child
weighs four times its birthweight.
--By age 1, the average baby stands 30 inches tall.
--By the end of the second year the average child
is three feet tall.
Decreasing Proportions…
At birth, the head is ¼ of the neonate’s body. By
adulthood, it is only 1/8th the size of the body.
 Not all parts of the body grow at the same rate.
The 4 Major Principles Governing Growth
1) 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.
(Major Principles Governing Growth continued)
3) The PRINCIPLE OF HIERARCHICAL
INTEGRATION states that simple skills
typically develop separately and
independently but are later integrated into
more complex skills.
4) The PRINCIPLE OF INDEPENDENCE OF
SYSTEMS suggests that different body
systems grow at different rates.
Maturation Rates
Different body systems mature at different rates.
For instance, the nervous system is highly
developed during infancy.
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.
The Neuron
The basic
element of
the nervous
system
More About Neurons…
-- Neurons increase in size.
-- Neurons become coated with MYELIN, a
fatty substance that helps insulate
neurons and speeds transmission of
nerve impulses.
-- The brain is made up of neurons, and
triples its weight in the first two years of
life.

The infant's brain is 3/4 its adult size by
age two
More About Neurons…
* As they grow, neurons become arranged by
function.
* Some move into the CEREBRAL CORTEX, the
upper layer of the brain.
* Others move to subcortical levels, which regulate
fundamental activities such as breathing and
heart rate (and are below the cerebral cortex).
Networks of neurons become more
complex over the first few years of
life.
Neuron Networks
Brain development occurs because of genetic
patterns and environmental influences.
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.
(brain development, continued)
-- Research with non-humans reveals
that a SENSITIVE PERIOD exists
which is a specific but limited time
span, usually early in an organism's
life, during which the organism is
particularly susceptible to
environmental influences relating to
some particular facet of
development.
Development of Body Rhythms

Behavior (sleeping, eating, crying, attending
to the world) becomes integrated through the
development of various body RHYTHMS
(repetitive, cyclic patterns of behavior)
 Some rhythms are obvious/easy to notice
• The change from being asleep to being
awake/breathing patterns
(development of body rhythms, continued)
 Some
rhythms are more subtle
• Jerking suddenly while
sleeping
*Some are apparent right after
birth, others emerge over the
course of the 1st year as the
nervous system becomes more
integrated
One of the major body rhythms is an infants
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, or
electroencephalogram.
The major state occupying the infant is sleep.


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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 Infant’s 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).
REM Sleep Through the Lifespan
REM sleep increases & the total amount of sleep falls as we age.
For a small % of infants, the rhythm of
sleep is interrupted by a deadly
occurrence: SIDS

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SUDDEN INFANT DEATH SYNDROME (SIDS) is a
disorder in which seemingly healthy infants die in their
sleep.
affects 7,000 children in U.S. annually
no cause found
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.
Declining Rates of SIDS
US rates have
dropped 38%
since 1992 as
parents have
learned to have
babies sleep on
their backs.
Motor Development
 Basic REFLEXES, unlearned, organized,
involuntary responses that occur automatically in
the presence of certain stimuli, represent
behavior that has survival value for the infant.
 swimming reflex
 eye blink reflex
More about reflexes in motor
development…

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Some reflexes stay throughout life; others
disappear over time.
Some researchers believe reflexes stimulate the
brain toward development.
Reflexes are genetically determined and
universal and may be remnants from the past.
Reflexes can serve as helpful diagnostic tools
for pediatricians because they appear and
disappear on a regular timetable
Gross Motor Skills
(rolling over, sitting upright, walking)

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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)

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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.
Milestones of
Motor
Development
50% of
children are
able to
perform each
skill at the
month
indicated, but
the specific
timing varies
widely!
It is important to keep in mind that
developmental NORMS are the
average performance of a large
sample of individuals of a certain
age and mask substantial individual
differences!
(Norms are based on scales
developed by developmental
psychologists & pediatricians)
A common technique to determine
infants’ normative standing:
BRAZELTON NEONATAL BEHAVIORAL ASSESSMENT
SCALE (NBAS)

NBAS is a measure used to determine infants'
neurological and behavioral responses to their
environment. a. supplements the Apgar
b. 27 categories of responses
c. interactions with others
d. motor behavior
e. physiological control
f. response to stress
More about norms…
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Norms should be based on large,
heterogeneous samples.
The time at which specific motor
skills appear is in part determined
by cultural factors.
There are certain genetic
constraints on how early a skill can
emerge
Nutrition in Infancy Fuels Motor
Development
Nutrition during infancy is
extremely important!
Without proper nutrition,
infants cannot reach their
physical potential and also
may suffer cognitive and
social consequences.
Underweight Children
In developing countries, the number of underweight
children under age 5 is substantial.
Malnutrition & It’s Effects
Malnutrition, the condition of having an
improper amount and balance of
nutrients produces several results.
--slower growth
--susceptibility to disease
--lower IQ scores
Malnutrition & It’s Effects, continued
--Malnutrition can also cause
MARASMUS, a disease
characterized by the cessation of
growth in infants.
--Older children are susceptible to
KWASHIORKOR, a disease in which a
child's stomach, limbs, and face swell
with water.
(malnutrition, continued)

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Risks of malnutrition are greater
in underdeveloped countries and
in areas with high poverty rates.
Undernutrition is more common
in developed countries
(deficiency in the diet).
Children Living in Poverty
Single-parent
and minority
families are
more likely to
have kids under
age 3 living in
poverty.
Nutrition as Fuel for Motor Development: Breast or Bottle??
For the first four to six months of life there is no better
food for an infant than breast milk! Why?
a.
all essential nutrients
b.
natural immunity to childhood diseases
c.
more easily digested
d.
health advantages for mother (lower cancer)
e.
emotional advantages for both mother and
child
f.
bonding?
In spite of this, only half of mothers in U.S. breastfeed
Breast Milk Advantages
Introducing Solid Foods
Most babies can begin to eat solid
foods at about 4-6 months.

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Foods are introduced gradually.
Weaning, the cessation of breastfeeding, occurs on average in the U.S.
at 3-4 months.
Experts recommend infants be
breast-fed for 6-12 months.
Development of the Senses
Infants come to understand the world around them
through sensation & perception

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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.

By 6 months, the average infant's
vision is 20/20.
(vision continued)
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
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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)—but
environmental influences too!
Preferring Complexity
In a classic
experiment, Robert
Fantz found that 2- and
3-month-old infants
preferred to look at
more complex stimuli.
Auditory Perception:
The World of Sound

It is clear that infants hear from
the time they are born—and
even before! (prenatally)

Infants are more sensitive than
adults to high and low frequencies
but not to the middle ranges.
Auditory Perception continued…

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
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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

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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
Effects of Massage Touch on Weight Gain
The weight gain
of premature
infants who were
systematically
massaged is
greater than those
who did not
receive the
massage!
(Field, 1988)
~From research to practice
Knowing what we know about pain & touch…

Should Male Infants be Circumcised?
 Jewish & Islamic faiths: this is a custom
 American Academy of Pediatrics (2000): NO! Minor
health benefits outweighed by risks.
-Risks: infection, irritation, bleeding, reduced sexual
pleasure
-Minor benefits: slightly lower risk of urinary track
infections
~Cultural & psychological issues involved in
decision!
Initially, information is collected and interpreted by
individual sensory systems, but…
Eventually infants use the
MULTIMODAL APPROACH TO
PERCEPTION in which information
collected by various individual
sensory systems is integrated and
coordinated.
This approach is evidence of the
sophisticated perceptual abilities of
infants (combining sensory inputs!)
(MULTIMODAL APPROACH TO PERCEPTION, continued)

The infants growing perceptual
ability is aided by the development
of affordances (action possibilities
connected to a situation or
stimulus).

Example: Julissa learns that her toy
truck has several affordances: It can be
grabbed and squeezed, chewed, thrown
across the room at the cat, etc.)
The Point:
• Infants’ perceptual abilities
are increasing
• Their physical development is
advancing
• They are developing senses
that will serve as foundations of
life!
Don’t forget…
 Read
Chapter 5 for next
time…