Definition by Carol Hevia, Psy.D., reproduced with permission from International OCD Foundation.
The process during which a person stops responding to a stimulus because it is no longer new. For example, after jumping into a cold swimming pool, one might initially feel that the water is too cold; however, after splashing around for a few minutes, the water begins to feel warmer (even though the water temperature has not changed at all) because the swimmer has gotten used to the water temperature. An example of this in OCD would be when someone who worries about germs touches a doorknob without a barrier for at least 1.5 hours. As time passes without the person ritualizing, the person can no longer maintain an anxious response.