Nonassociative Learning

A type of learning in which the organism changes it responsiveness to a stimulus that is presented repeatedly. There are two subtypes of nonassociative learning:

• Sensitization occurs when a stimulus that, although initially eliciting either a weak response or no response, begins to elicit stronger responses after:
  (a) it is presented repeatedly, or
  (b) it is presented after the presentation of a different stimulus that elicited a strong response.
  An example of the first type of sensitization is the increasing sensitivity you might begin to feel when someone lightly tickles a small spot on the bottom of your foot. At first, you may not be bothered by the tickle; but, if it continues, the tickling may begin to bother you and, perhaps, even make you laugh (that is, you become ticklish at that spot).
  An example of the second type of sensitization is the increase in your startle response to small noises, such as a screen door closing, after you have experienced an unexpected loud noise, such as a gunshot.
• Habituation occurs when a stimulus that, although initially eliciting a strong reflexive response, elicits increasingly weaker reflexive responses when it is presented repeatedly. For example, unexpected loud noise reflexively elicit a startle response. If the loud noise is presented repeatedly, however, the startle response will decrease in most people and perhaps even disappear. Habituation differs from extinction of a conditioned response in that the latter involves a decrease of a classically conditioned response (a learned automatic response), whereas the former involves a decrease of a reflexive response which one either was born with (for example, the startle response) or that developed through maturation of the nervous system (for example, ???).