Sensitive Periods• During development there
are specific times when a biological event is more ‘sensitive’ to environmental stimuli e.g. language acquisition (age 3-7) – i.e. a SENSITIVE PERIOD
• We can still learn after the sensitive period has closed, but the learning process is less efficient.
• Note: Sensitive periods start and end gradually
Critical Periods• Refers to a finite period in which an
organism has heightened sensitivity to external stimuli that are compulsory for development of a particular skill
• e.g. certain areas of the visual cortex are only capable of synapse formation during early stages of development, once the crucial period has elapsed the individual will have some visual impairment
• E.g. Hubel & Wiesal temporarily blindfolded a kitten during a critical period (of visual development) from birth to 3 months when the blindfold was taken off, it never fully developed vision in the blindfolded eye. It actually resulted in reduced dendritic branching at the end of the neuron in comparison to the non deprived eye which had increased afferent activity as the eye developed.
Sensitive period vs Critical periods
Sensitive periods Critical periods
Starts and ends Gradually abruptly
During the period It is a period of maximal sensitivity
The organism has heightened sensitivity to external stimuli that are
compulsory for development of a
particular skillAfter the period The skill can still be learned,
but less efficientlyThe cortical areas
allocated for the particular skill will adapt and perform a different
function.Examples Language development Full development of visual
capabilities (from @ 8 months to 3 years)
Experience expectant learning• During EXPERIENCE EXPECTANT
LEARNING – the brain ‘expects’ and is primed for being exposed to the environmental ‘experience’ resulting in a rewiring of the brain (i.e. the establishment of a neural pathway resulting in learning)
• E.g the brain expects to be exposed to visual images, sounds, etc. in order for our visual, auditory, etc systems to develop.
Experience dependent learning• EXPERIENCE DEPENDENT
LEARNING – refers to additional skills developed over the lifespan (that the brain doesn’t expect
• E.g. an eskimo child learning how to build an igloo – which may be dependent on Observational learning (or Operant conditioning)
• There is no optimal period for experience dependent learning e.g. you can learn how drive when your 16, 30 or 50 (older people may struggle due to age related memory decline e.g. slowing of the Central.N.S)
Experience Expectant vs Experience Dependent Learning
Experience expectant learning Experience dependent learning
Stage of Lifespan that the genetic structural modifications occur
Early in life Over the lifespan in response to complex environmental
stimuli
During which period During the ‘Sensitive Periods’ There is no optimal period i.e. It occurs over the lifespan
Language Development of primary language (the brain expects to be exposed to
language)
Development of 2nd Language (it is dependent on exposure
to environmental stimuli)General or Specific General – e.g. We are all exposed
to visual stimuli, thus the brain expects and is highly responsive to visual stimuli during the sensitive
periods
Unique to individuals e.g. Exposure to igloo building at
a young age for eskimos