This study investigated the effects of presumably non-neurotoxic regimens of psychostimulants on acquisition of reward-related behavior. Prior to conditioning, rats received saline, cocaine, d-amphetamine or (2 5 mg/kg) S-(+)-MDMA via intra-peritoneal injection for 5 days. Seven days after treatment, water-deprived rats learned to get a water reward, but with punishment for attempts to obtain it too early (before end of interval). A tone and a light were associated with the reward. Duration and number of head entries for water during appropriate period and inappropriate head entries were counted, and learning the reward-cue analyzed across days. Pre-treatment with either amphetamine or cocaine increased head entries during appropriate time and increased acquisition of Pavlovian approach behavior (approaching reward-associated cue). Pre-treatment with S-(+)-MDMA did not enhance Pavlovian approach behavior, but did increase inappropriate head entries, which the authors considered a measurement of "impulsiveness." These results suggest that a presumably non-neurotoxic regimen of S-(+)-MDMA could alter behavior so as to produce impulsive behavior or ineffective regulation of reward-related behavior. It is important to note that the researchers administered only the more active enantiomer of MDMArather than the racemic mixture of both enantiomers that has been employed in psychotherapy and non-medical human use. In other words, they administered the amount of S-(+)-MDMA that would be found in 5.0 mg/kg (±)-MDMA. It is also not clear how long the MDMA-induced increase in inappropriate head entries ("impulsiveness") lasts, as animals were tested only for ten days beginning seven days after the last MDMA administration. On the final day of testing, MDMA-treated animals appear similar to placebo-treated animals and it is possible that the difference detected is transient. Finally, it is worth noting that this paper can be seen as further evidence that MDMA is fundamentally different from classic psychostimulants.