Physical Development in Infancy

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Physical Development in Infancy

• Chapter 4

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Growth and Stability Physical Growth

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

• Cephalocaudal Principal
• Head to Tail
• Proximodistal Principal
• Near to Far
• Principal of Hierarchical Integration
• Simple skills -- complex skills
• Principal of the Independence of Systems
• Different systems grow at different rates

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The Nervous System and the Brain

• A neuron is the basic cell nerve cell of the
  brain and CNS
• Communicate with each other by passing chemicals
  between to the synapses
• Born with 100-200 Billion neurons
• Synaptic Pruning

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More About Neurons

• Neurons increase in size.
• 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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The Neuron
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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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Nature and Nurture

• Plasticity The degree to which a developing
  structure or behavior is modifiable due to
  experience
• Animal research
• Without enriched environment and warm social
  contact a babys brain will literally shrink

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Sensitive Periods

• A specific, but limited time during which an
  organism is particularly susceptible to
  environmental factors that will affect
  development
• Has been shown through animal research and
  observed in humans
• Early years (0-3) may be the most important

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Development of Body Rhythms

• Body Rhythms
• Helps behavior (sleeping, eating, crying,
  attending to the world) become integrated
• Some rhythms are easy to notice
• Awake vs. asleep
• Some rhythms are more subtle
• Jerking suddenly while sleeping
• Changes in state of awareness can be seen on an
  EEG
• Rhythms and states become more organized as CNS
  grows

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Sleep is Infants Job

• On average, newborns sleep 16-17 hours daily,
  ranging from 10-20 hours a day.
• Sleep like a baby?
• 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 RAPID EYE MOVEMENT, (the period of
  sleep found in adults and children that is
  associated with dreaming).
• Brain waves are different than the dreaming sleep
  of adults
• REM-like sleep takes up half an infants sleep at
  first.
• Autostimulation

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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 Reflexes

• Unlearned, organized, involuntary responses that
  occur automatically in the presence of certain
  stimuli
• Genetically determined
• Universal
• Cultural Differences

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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
These ages are Averages ONLY! 50 of infants
have obtained these skills by the given times.
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Normal Development

• 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

• Nutrition during infancy is extremely important!
• Malnutrition
• Slower growth rate
• Smaller body proportions
• Susceptibility to disease
• Lower IQ

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Malnutrition Its Effects

• MARASMUS A disease characterized by the
  cessation of growth in infants.
• KWASHIORKOR A disease in which a child's
  stomach, limbs, and face swell with water.
• Risks greater in underdeveloped countries and in
  areas with high poverty rates.
• Undernutrition more common in developed
  countries - SES
• Failure to Thrive Different from malnutrition

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Single-parent and minority families are more
likely to have kids under age 3 living in
poverty.
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Other side Obesity

• Weight greater than 20 above the average for a
  given height
• No clear correlation between obesity in infancy
  and obesity at age 16 years, it is suggested that
  it may lead to creation of excess fat cells
• Obesity in babies may be associated with adult
  weight problems

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Breast IS Best

• All essential nutrients
• Natural immunity to childhood diseases
• More easily digested
• Health advantages for mother (lower cancer)
• Emotional advantages for both mother and child
• In spite of this, only half of mothers in U.S.
  breast-feed
• Inadequate milk production
• Economic constraints

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Solid Food Time

• Can begin as early as 6 months, but is not needed
  until 9-12 months
• Start introducing food while still breast or
  bottle feeding
• Timing of weaning is personal, cultural decision
• If possible, breast-feeding should continue for
  first 12 months of life

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Development of the SensesVisual Perception

• Newborn infants have distance vision that ranges
  from 20/200 to 20/600
• By 6 months, the average infant's vision is 20/20
• Binocular Vision
• achieved at 14 weeks.
• Gibson's "visual cliff"
• We do not know how early depth perception occurs
  in infancy

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Vision Continued

• Infants do show clear visual preferences at birth
• Prefer more complex patterns and designs
• Curved over straight lines
• Human faces
• Moms face is favorite
• Evidence for specialized cells in brain

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Auditory Perception

• Most infants can hear prior to birth
• More low and high freq but not middle
• Sound Localization
• Reaches adult levels by age 1
• Can differentiate two similar sounds by 1 month
  (i.e. pa and ba)
• Mom vs. Dad

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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 breastfed infants
• Infants have an innate sweet tooththey smile
  when sweet tasting liquid is placed on their
  tongue

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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
• Plays a role in the future development
• 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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Circumcision Dont Snip It!

• Customary for some faiths/cultures
• Risks outweigh benefits
• Risks Infection, irritation, bleeding, reduced
  sexual pleasure, decreased pain tolerance
• May have other
• Minor Benefits slightly lower risk of urinary
  track infections

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Multimodal Perception

• Initially sensory systems work alone
• Similar to Principal of Independence of Systems
• As the brain grows, infants use multimodal
  perception
• Information collected by various individual
  sensory systems is integrated and coordinated
• Infants are remarkably sophisticated at this

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Multimodal Perception Contd

• The infants growing perceptual ability is aided
  by the development of affordances (action
  possibilities connected to a situation or
  stimulus)
• Example Jessica learns that her toy truck has
  several affordances It can be grabbed and
  squeezed, chewed, thrown across the room at the
  cat, etc.