Discussion
The aim of the present two randomized studies was to investigate the effect of d-amphetamine (0.45 mg/kg, PO) and caffeine (200 mg, PO) on SWM and VWM performance in healthy subjects following delays in recall. The results showed that there are no main effects of d-amphetamine on the SST or the DST, relative to placebo. Likewise, caffeine did not affect performance on the SST or the DST, relative to placebo, which is consistent with previous reports on WM tests [Although there are some studies that did not find effects of amphetamine on SWM, other studies did detect effects of amphetamine SWM ([