Extinction and Stimulus Generalization

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Extinction and Stimulus Generalization

• Kandise G. Viar
• Senior Seminar
• March 4, 2008

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Extinction

• When an old association no longer exists.
• A previously acquired association will be
  diminished through repeated presentation of the
  CS in the absence of the US.
• Extinction is not just unlearning but rather
  reflects a combination of unlearning and the
  learning of the new.
• Pavlov and his assistants showed that they could
  also weaken an animals trained response to the
  bell.
• The salivation to the bell gradually decreased as
  the animal learned that the bell no longer
  predicted food.

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Besides Pavlov

• Other studies have been conducted that
  demonstrate the extinction process.
• Eye-blinking studies
• Humans
• Rabbits
• Reflex is consistent across species.
• Way more ethical than earlier face-slapping
  studies done in the 1920s on human participants.

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Eye-Blinking Studies

• The CS is delivered through headphones (a
  particular tone).
• The US is a puff of air delivered through a
  rubber tube.
• The eye-blink CR is recorded by EMG
  (electromyography) detectors placed above and
  below the eye.
• At the end of extinction training the subject or
  participant is no longer responding to the CS.
  However, the learned response is not gone, it is
  just not being expressed.
• Spontaneous Recovery of the CS.
• In theory, the original learned response
  (blinking at the sound of the tone) can reappear
  if the subject is moved to another context or if
  a long time passes before the subject is retested
  with a presentation of the CS.

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Generalization

• Defined as the transfer of past learning to new
  situations and problems.
• Therefore, when you perform a skill that has been
  learned in the past, you are generalizing from a
  past experience to the present.
• Every performance of a skill involves a transfer
  of training.
• Through experiences acquire meaningful
  associations.
• In Pavlovs study the dogs responded to any kind
  of bell, not just one type of bell.

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Similarity-Based vs. Meaning-Based Generalizations

• Similarity-based generalization arises
  naturally between two stimuli that are physically
  similar.
• Ex Fruit
• Meaning-based generalization two things are
  assumed to have the same meaning even though they
  do not have any relevant similarities.
• If two things predict the same stimulus then they
  are related regardless of what they actually are.

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Pigeon Study Geoffrey Hall

• Trained pigeons to peck at a light that changed
  between six different colors.
• Then trained the animals that four color
  sequences predicted the arrival of a food reward.
• Birds acquired equivalency.
• Prior training that two stimuli were equivalent
  increased the amount of generalization between
  them even if the those stimuli were not alike.

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Review

• Extinction when an old association no longer
  exists achieved through repeated presentation of
  the CS in absence of the US.
• Generalization transfer of past learning to new
  situations and problems through experiences
  acquire meaningful associations.

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Any Questions?
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Reference

• Gluck, M. A., Mercado, E. Myers, C. E. (2008).
  Learning and memory From brain to behavior. New
  York, NY Worth Publishers.