Habituation and Sensitization

Habituation

  • Definition: Habituation is a simple form of learning characterized by a decrease in response to a repeated stimulus.

    • Example: Startle response to a gunshot diminishes with repeated presentations.

  • Ubiquity: Found across species from single-celled organisms to humans.

  • Neural mechanisms: Studied extensively due to its simplicity and occurrence in simple nervous systems.

    • Eric Kandel won the Nobel Prize for his work on habituation in sea snails, which offered some of our most basic understanding of how learning occurs in the brain.

Reflexes and Innate Behaviors

  • Innate abilities: Animals are not born as blank slates; they possess complex survival-dependent abilities.

    • Examples: Breathing, blood circulation, nutrient ingestion.

  • Reflexes: Triggered by environmental events.

    • Examples: Startle response to loud noises, blinking when something moves towards the eye.

  • Characteristics of Reflexes

    • Present at birth.

    • Appear at predictable times in development.

    • Protect from injury (withdrawal from pain).

    • Aid in food consumption (sucking reflex).

  • Modification of Reflexes: Reflexes can be modified, contrary to the assumption that they are automatic and invariable.

Alterations in Response

  • Habituation: Decrease in response size with repeated stimulation.

  • Sensitization: Increase in response size and duration with repeated stimulation.

Importance of Habituation

  • Ignoring unimportant stimuli: Allows focusing on relevant environmental aspects.

    • Example: Neuroscience lab workers habituate to animal odors.

    • Relevance to various jobs: Sewage workers getting used to bad smells.

Decline in Responding: Alternative Explanations

  • Fatigue: Physical tiredness from repeated responses.

    • Example: Rat's decreased jumping response due to fatigue.

  • Sensory Adaptation: Changes in the sensory system's sensitivity.

    • Example: Pupil contraction and adaptation to bright light.

  • Distinguishing Habituation: Decline in responding due to fatigue or adaptation of the sensory system aren't examples of habituation.

Discriminating Habituation

  • Dishabituation: Evidence to discern these explanations and true habituation.

    • Stimulus specificity: Response recovery to a novel stimulus.

    • Time sensitivity: Response recovery after withholding the stimulus for a period.

    • Context change: Dishabituation due to change in context.

Habituation for Cognitive Assessment

  • Infant Studies: Habituation used to assess cognitive and perceptual abilities in infants.

    • Non-verbal assessment: Useful since infants can't verbally express their knowledge.

  • Other-Race Effect Study

    • Hayden et al. study: Investigated whether infants better discriminate faces of their own race.

    • Method: Caucasian infants shown Asian or Caucasian faces until habituated, then shown morphed faces (70% original, 30% other race).

    • Results:

      • Infants habituated to Asian faces didn't dishabituate to morphed faces.

      • Infants habituated to Caucasian faces showed a preference for the new, morphed face.

    • Conclusion: Caucasian infants show an "other-race effect" at 3.5 months, better detecting differences in Caucasian faces.