habituation

Reduction of an animal's behavioral response to a stimulus, as a result of a lack of reinforcement during continual exposure to the stimulus. Habituation is usually considered a form of learning in which behaviours not needed are eliminated. It may be separated from most other forms of decreased response on the basis of permanence; the habituated animal either does not resume its earlier reaction to the stimulus after a period of no stimulus, or, if the normal reaction is resumed on reexposure to the stimulus, it wanes more quickly than before. Vital responses (e.g., flight from a predator) cannot be truly habituated.