adaptation, selective

n. Alteration of a sensory or learning system to a particular stimulus so that the stimulus produces less and less reaction but a new stimulus will produce a reaction at the original level of the first stimulus. For example, a person who hears traffic going by will soon show little reaction to it as long as it does not change intensity but will react to the sound of a voice equal in loudness to the traffic at the same level as if he/she had not been accustomed to the traffic noise.