Physical Developemnt ibn Infancy and Toddlerhood Breast reduction

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					                      Lifespan overheads, chapter 4: physical development in infancy & toddlerhood
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 Chapter 4: Physical Development in Infancy and Toddlerhood

Body Growth
   body size and muscle/fat
       o by the end of 1st year, height increases by 50%
       o by 2 years old, height increases by 75%
       o by 5 months weight has doubled
       o at 1 year weight has tripled
       o at 2 years weight has quadrupled
       o “baby fat” peaks around 9 months
       o muscle tissue develops slowly

   Individual and group differences
       o In infancy girls are slightly shorter and lighter and have a
          higher ratio of fat to muscle than boys.
       o Some children just grow more quickly than others.
       o skeletal age: X-raying the long bones of the body to see
          the extent to which cartilage has hardened into bone
       o African-American children are slightly ahead of Caucasian
          children at all ages
       o girls are considerably ahead of boys

   body proportions
      o cephalocaudal trend:
             at birth, the head is ¼ of total body length
             yy age 2 the head is 1/5 of body length
      o proximodistal trend: head, chest, and trunk  arms
         and legs  hands and feet

Brain Development
   neurons
        o 100 to 200 billion neurons (nerve cells).
        o Synapses: spaces between adjacent neurons
        o By end of 2nd trimester, production of neurons is over
        o After birth, they start to form synaptic connections
        o synaptic pruning
        o Neurons that get stimulated establish new synapses
        o glial cells create myelin sheaths; multiply rapidly from
          the 4th month of pregnancy through the 2 nd year of life.
                  Lifespan overheads, chapter 4: physical development in infancy & toddlerhood
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 the cerebral cortex
     o accounts for 85% of the brain’s weight, contains the most
        neurons.
     o last part of the brain to stop growing
     o different regions have specific functions

            Frontal Lobe: motor control, executive functions
                 One of the last regions to develop. It will not
                  finish growing until the early 20s!

            Parietal Lobe: controlling incoming sensory
             information

            Occipital Lobe: handles visual information

            Temporal Lobe: auditory information is processed

     o lateralization of the cortex:

              LEFT          spontaneous language
                             complex movement
                             memory for words, numbers
                             anxiety, positive emotions

              RIGHT  memory for music
                      memory for geometric patterns
                      face recognition
                      negative emotions

     o may be reversed in left-handed people
     o Most newborns show greater activity in the LH when
       listening to speech, whereas the RH reacts more to non-
       speech sounds and stimuli that cause a negative emotion

     o Plastic brain! still adaptable. If a part of the brain is
       damaged, other parts will take over the tasks. Once
       lateralization is complete (age 8-10), the brain is less able
       to adapt to damage
                   Lifespan overheads, chapter 4: physical development in infancy & toddlerhood
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 brain growth spurts and sensitive periods:
     o sensory deprivation research
            keep a month-old kitten in the dark for 3 or 4 days,
              visual areas of the brain degenerate. 2 months in
              the dark: damage is permanent
            severe stimulus deprivation affects overall brain
              growth.
     o intermittent growth spurts in the brain from infancy to
        early adulthood
            1st year of life:
                  3-4 months, when they begin to reach
                  8 months, when they begin to crawl
                  12 months, when they begin to walk
                  1 ½ and 2 years, when they start to use
                    language
            what “wires” a kid’s brain during these periods is
              experience
            impoverished environments threaten this
              development.
            so does overwhelming the child with expectations
              beyond their current capacities

     o states of arousal: By 2, the child is sleeping 12 to 13
       hours a day, but most of the sleep happens in one
       extended period, with maybe one or 2 naps during the
       day
           once the baby is in the middle of their first year, the
             brain secretes more melatonin at night than during
             the day
                      Lifespan overheads, chapter 4: physical development in infancy & toddlerhood
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Influences on early physical growth
    heredity
    nutrition
        o Breast versus bottle feeding:
                2/3 of North American mothers breast feed
                Breast fed babies in poverty-stricken nations are
                 less likely to be malnourished; 6 to 14 times more
                 likely to survive the first year of life
                mother is less likely to get pregnant while nursing
                breast and bottle fed youngsters in industrialized
                 nations do not differ in intelligence or emotional
                 adjustment

        o chubby babies: infants and toddlers can eat nutritious
          foods freely, without risk of becoming too fat


   malnutrition:
      o 40 to 60% of the world’s children are malnourished
      o In the US, 12% of children are malnourished
      o Globally 4 to 7% are severely affected
              Marasmus
              Kwashiorkor


Emotional Well-Being
   Nonorganic failure to thrive

Learning capacities
Learning: changes in behaviour as a result of experience.

   classical conditioning:
       o Helps babies recognize which events usually occur
         together in the everyday world, so they can anticipate
         what is about to happen next.
             Nursing + stroking  sucking
             Stroking  sucking
                      Lifespan overheads, chapter 4: physical development in infancy & toddlerhood
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    operant conditioning:
       o In the early weeks of life, infants’ behaviours like sucking
          and head turning can be conditioned in this way.
       o E.g. using special pacifiers to study preferences
       o E.g. the mobile study

    Habituation and dishabituation:
       o habituation is the gradual reduction in the strength of a
          response due to repetitive stimulation
       o dishabituation: responsiveness returns to a high level
          when the stimulus is changed

    imitation: newborns have a primitive ability to learn through
     imitation. Infants as young as 2 days old can imitate a variety of
     facial expressions.
        o primitive reflex?
        o newborns imitate many facial expressions even after
            short delays; suggests that the behavior is voluntary

Motor Development
Gross motor development: control over actions that help infants get
around in the environment (crawling, standing, walking).

Fine motor development: smaller movements, like reaching, grasping.

 cephalocaudal trend: motor control of the head comes before
control of arms and trunk, which come before control of legs.

 proximodistal trend: head, trunk, and arm control happen before
coordination of hands and fingers.

Each new skill is a joint product of:
     1) the CNS
     2) movement possibilities for the body
     3) environmental supports for the skill
     4) the goal the child has, like getting a toy or crossing the room
                      Lifespan overheads, chapter 4: physical development in infancy & toddlerhood
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   Fine motor development: reaching opens up a whole new way
    to explore the environment
       o Newborns make poorly coordinated swipes at objects,
          called prereaching; drops away at around 7 weeks.
       o At 3 months, voluntary reaching appears and improves
       o Once babies can reach, they start to modify their grasp.
              A newborn’s grasp reflex is replaced by the ulnar
                grasp: fingers closing against the palm.
              By end of 1st year, use the thumb and forefinger in
                the pincer grasp.

Perceptual Development
Perception: the ability to organize and interpret incoming sensations.

   hearing:
      o 3 days old: turn eyes and head in direction of a sound.
      o can detect almost all sounds in human languages at birth
      o by 6 months old they screen out sounds that are not
          useful in their own language.
      o second half of the 1st year, recognize familiar words in
          spoken language
      o 7 to 10 month olds preferred speech with natural breaks
          to speech with pauses in unnatural places.

   vision: By 2 months, babies can focus on objects and
    discriminate colours as well as adults can.
       o Visual acuity improves steadily (20/600 at birth; to 20/100
          by 6 months; 20/20 at 11 months)

        o Depth perception: ability to judge the distance of objects
          from one another and from ourselves.
              visual cliff (Gibson & Walk, 1960):crawling babies
                cross the shallow side but react with fear to the
                deep side
              precrawlers’ abilities to use other cues to depth:
                    Motion
                    Binocular cues
                    Pictorial cues
                      Lifespan overheads, chapter 4: physical development in infancy & toddlerhood
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               independent movement and depth perception: the
                more experience a baby has crawling, the better
                their depth perception, memory for object locations

        o pattern and face perception: newborns prefer to look at
          patterned rather than plain stimuli
              3-week old infants look longest at black and white
                checkerboards with few squares, whereas 8 and 14
                week olds prefer those with many squares
              When shown a picture of a human face, 1-month
                olds limit their visual exploration to the border of the
                stimulus. By 2 months, they thoroughly explore the
                internal features of a pattern
              By 4 months, they even see subjective boundaries
                that aren’t there!
              By 2-3 months, they prefer faces to other similar
                configurations
              by 3 months, they can make fine distinctions among
                the features of different faces.
              By 7 to 10 months they consistently treat positive
                faces as different from negative ones

        o Intermodal perception:
              Newborns turn in the general direction of a sound
              Pacifier study
              3-4 month old babies can relate a child’s or adult’s
               moving lips to the corresponding sounds in speech
              by 7 months, can link a happy or angry voice with
               the appropriate face of a speaking person

Understanding perceptual development
   Eleanor & James Gibson’s differentiation theory: a built-in
    tendency to search for order and consistency, a capacity that
    gets more fine-tuned with age. We learn to get better at
    differentiating the features of various objects and patterns.

   An alternative view: babies impose meaning on what they
    perceive, constructing categories of objects and events in the
    surrounding environment.

				
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