Are critical periods critical for early childhood education?

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Are critical periods critical for early childhood
education?

• The notion of a window of opportunity opening in
  early childhood, and then closing, never to open
  again, evoked a powerful visual image in the
  mid-1990s.
• It galvanized scientific and popular media to
  attend to the problems of early childhood
  education.
• lectures notes for developmental psychology,
  ps241, 2004, prof catherine l harris, boston
  university

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Newsweek cover story in 1996

• But they imply, too, that if you miss the window
  you're playing with a handicap. They offer an
  explanation of why the gains a toddler makes in
  Head Start are often so evanescent this intensive
  instruction begins too late to fundamentally
  rewire the brain.
• -- Newsweek, February 19, 1996

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From animal research

• Hubel and Wiesel (1970), suturing shut the eye of
  a kitten
• The ducklings raised by Konrad Lorenz imprinted
  on first moving object (recent film, Fly Away
  Home)

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Understanding the programmatic nature of early
brain development

• Born with all (cortical) neurons you will have,
  neurons die at furious pace in first years of
  life (apoptosis programmed cell death)
• Neurons that fire together, wire together
• Identifiable waves of synaptogenesis, followed by
  pruning of connections

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Neurons that don't connect, die
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What happens to animals raised in complex
environments?

• Greenough's research rats reared in enriched
  environments had more dendritic branching
• "Revelation" for Caregivers that they could
  engage in activities that would influence their
  child's brain development
• Are the effects of complex environments critical
  period effects?
• Do we think that same kind of neural processes
  underlie both kinds of effects?

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Synaptic Density Infancy to Adulthood
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More factors that raised awareness

• Deleterious effects of prenatal teratogens
  (alcohol, cocaine), and early childhood exposure
  to lead
• Early childhood risk factors poverty,
  nutritional deprivation, social neglect, maternal
  depression, childhood abuse, multiple risk
  factors neglect (Romanian orphanages)

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Summary of Ideas from Neuroscience

• Synaptogenesis -- in infancy the brain forms
  synapses in excess of adult levels.
• Critical periods -- normal development of neural
  systems requires specific experiential input at
  specific times.
• Pruning at Puberty -- at sexual maturity synapses
  are pruned back to adult levels.
• Enriched environments increase synaptic
  connections.

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Two Categories of Human Abilities

• Our brain underwent evolved under the pressure of
  natural selection to have some abilities. basic
  vision, first language learning, categorization,
  number sense, time sense, deception, social
  relations
• Our brains didn't evolve to manifest writing,
  algebra, astronomical understanding, breeding of
  animals, etc.

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• Environmental input necessary for these abilities
  are those that the brain could expect to
  encounter. If they are not present, brain
  development proceeds abnormally, and critical
  period effects can occur.
• .

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No special areas of the brain evolved to support
writing, algebra, etc.

• When these abilities develop, they generally
  recruit specific areas of the brain.
• BUT Brain development depends on the exposure to
  the relevant concepts.
• If this experience doesn't occur, brain
  development is not abnormal. Brain development
  is normal, because the brain doesn't expect
  these inputs. The hypothesis here is that
  critical period effects will not occur for these
  "experience-dependent" activities.
• All of education is about experience-dependent
  behavior.

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Side note Controversial whether these evolved

• second language acquisition
• art, music, dance, religion, story telling
• abstract "patterning" (cf. Gardner)
• warfare, infanticide, genocide,

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Critical Period for Music?

• In the brains of nine string players examined
  with magnetic resonance imaging, the amount of
  somatosensory cortex dedicated to the thumb and
  fifth finger of the left hand -- the fingering
  digits -- was significantly larger than in
  nonplayers. How long the players practiced each
  day did not affect the cortical map. But the
  younger the child when she took up an instrument,
  the more cortex she devoted to playing it.
  -- Newsweek, February 19, 1966

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Did not control for duration or practice effect
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John Bruer, Myth of the First Three Years ,1999
and other authors

• Critical periods are the exception rather than
  the rule
• Adults can learn to read or can learn a new
  language
• Do critical periods exist for providing an
  organism with a higher-quality experience?
• Recent neurobiological work life-long
  plasticity neural reorganization after brain
  injury
• Wide variability in human performance for
  non-evolutionary, "higher cognition"

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Rationale for early childhood initiatives

• What are Sensitive periods?
• Windows for learning open at birth
• The first years are foundational
• Early childhood enrichment can compensate for
  social deprivation
• Shift attention away from critical periods to
  critical experiences
• Teachable moments transitions, crises