We replicated and extended prior results by showing a dose-dependent proportional overestimation of time that was equivalent on both procedures (i.e., subjects behaved as though they expected reinforcement to be available earlier in real time). Single-trials analyses demonstrated that the reduction in peak rate that is often observed after MAP administration is due to an increase in the proportion of trials in which responding occurred at very low rates and without temporal control. However, these low-rate trials were not the source of the leftward shift in the temporal estimates. Rather, we found that the leftward shift of the PI functions was due to proportional changes in the placement of temporally controlled high-rate responding, which is consistent with a DA-mediated alteration in clock speed.