Infancy: Physical Development

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Infancy Physical Development

• Chapter 4
• Development Across the Life Span

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Growth and Stability Physical Growth

• Over the first 2 years of a humans life, growth
  occurs at a rapid pace!

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Height Weight Growth
The greatest height weight increases occur
during the 1st year of life, but children
continue to grow through infancy toddlerhood.
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• 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.

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Decreasing Proportions
At birth, the head is ¼ of the neonates body. By
adulthood, it is only 1/8th the size of the body.
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? 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.

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(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.

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Maturation Rates
Different body systems mature at different rates.
For instance, the nervous system is highly
developed during infancy.
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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.

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The Neuron
The basic element of the nervous system
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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

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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).

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Networks of neurons become more complex over the
first few years of life.
Neuron Networks
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PLASTICITY is the degree to which a developing
structure (e.g., the brain) or behavior is
susceptible to experience
Brain development occurs because of genetic
patterns and environmental influences.

• ? The brain is relatively plastic
• -- Infants who grow up in severely restricted
  environments are likely to show differences in
  brain structure and weight.

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(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.

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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

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(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

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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.

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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.

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The Infants 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).

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REM Sleep Through the Lifespan
REM sleep increases the total amount of sleep
falls as we age.
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For a small 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 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.

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Declining Rates of SIDS
US rates have dropped 38 since 1992 as parents
have learned to have babies sleep on their backs.
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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

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More about reflexes in motor development

• 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

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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.

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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.

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Milestones of Motor Development
50 of children are able to perform each skill at
the month indicated, but the specific timing
varies widely!
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• 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)

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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.

• supplements the Apgar
• 27 categories of responses
• interactions with others
• motor behavior
• physiological control
• response to stress

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More about norms

• 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

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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.

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Underweight Children
In developing countries, the number of
underweight children under age 5 is substantial.
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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

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Malnutrition Its 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.

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(malnutrition, continued)

• 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).

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Children Living in Poverty
Single-parent and minority families are more
likely to have kids under age 3 living in
poverty.
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For the first four to six months of life there is
no better food for an infant than breast milk!
Why?
Nutrition as Fuel for Motor Development Breast
or Bottle??

• all essential nutrients
• natural immunity to childhood diseases
• more easily digested
• health advantages for mother (lower cancer)
• emotional advantages for both mother and child
• bonding?
• In spite of this, only half of mothers in U.S.
  breast-feed

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Breast Milk Advantages
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Introducing Solid Foods

• ?Most babies can begin to eat solid foods at
  about 4-6 months.
• Foods are introduced gradually.
• Weaning, the cessation of breast-feeding, occurs
  on average in the U.S. at 3-4 months.
• ?Experts recommend infants be breast-fed for 6-12
  months.

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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.

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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.

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(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.

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(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)but environmental influences too!

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Preferring Complexity
In a classic experiment, Robert Fantz found that
2- and 3-month-old infants preferred to look at
more complex stimuli.
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Auditory Perception The World of Sound

• It is clear that infants hear from the time they
  are bornand even before! (prenatally)
• Infants are more sensitive than adults to high
  and low frequencies but not to the middle ranges.
  

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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

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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.

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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

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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)
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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!

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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!)

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(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.)

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The Point

• Infants perceptual abilities are increasing
• Their physical development is advancing
• They are developing senses that will serve as
  foundations of life!

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Dont forget

• Read Chapter 5 for next time