Impulsive behavior is the hallmark of many psychopathologies. Uncovering the neurobiological mechanisms driving impulsivity is paramount in the development of through the delay discounting (DD) task in both human and animal models. The present study is an examination of the predictive validity of the two primary types of DD procedures in animals, the Adjusting Amounts (AA) and within session Increasing Delays (ID) tasks. Methods:Subjects were administered either1.25 mg/kg d-amphetamine (AMP), 1.5 g/kg ethanol (EtOH) or saline and tested in either the AA or ID method for 15 days to evaluate drug effects on impulsive behavior. Results: Stimulant administration resulted in a reduction of impulsivity in the AA group, but had no effect in the ID group. There was no effect on impulsivity of EtOH administration in AA or ID groups. Conclusion: Given the ability of stimulant administration to reduce impulsivity in clinical studies, the AA version of DD provides the best predictive validity for the animal mode
