In Psychology, BIS/BAS questionnaire assess Reward drive, fun seeking like behavior of an individual. Wherever, I have read, I have seen generalized questions in BIS/BAS. I am looking for a questionnaire that assesses affinity of individual specific for reward. For example, for substance use. Is there any questionnaire which can differentiate an individual who takes substance just for fun (fun seeking) from someone who has high reward drive for substance. Given that BIS/BAS scores of both individuals are same. Is modifying BIS/BAS questionnaire for reward is acceptable or is there any other questionnaire available that shows affinity of an individual towards specific stimulus (Reward)?