habituation

being abnormally tolerant to and dependent on something that is psychologically or physically habit-forming (especially alcohol or narcotic drugs)

एक कमरे में कैद संजू अंधेरे और अकेलेपन का ऐसा आदी हो जाता है कि किसी को देखते ही भयानक रूप से चीख उठता है|

Thus, habituation must be distinguished from extinction, which is an associative process.