The present study examined in 8-hour sessions the effects of d-amphetamine (1.0, 5.6, and 10 mg/kg) on the acquisition of lever-press responding by rats exposed to procedures in which water delivery was delayed by 0, 8, or 16 seconds relative to the response that produced it. Although neither shaping nor autoshaping occurred, substantial levels of operative-lever responding developed whenever responses produced water. Rats that did not receive water and yoked-control rats that received response-independent water emitted relatively few responses.; The lowest dose (1.0 mg/kg) of d-amphetamine either had no effect on or enhanced rates of operative-lever pressing, whereas higher doses typically produced an initial reduction in lever pressing. Nonetheless, overall rates of operative-lever pressing at these doses were as high as, or higher than, those observed with vehicle. Thus, response acquisition was observed under all reinforcement procedures at all drug doses. In the absence of drug, stimulus control of responding by the operative lever developed rapidly when reinforcement was immediate. Stimulus control also developed under both 8-s nonresetting- and resetting-delay procedures, albeit less rapidly under the resetting delay. In contrast, stimulus control did not develop with a 16-second delay under either nonresetting- or resetting-delay procedures. d-Amphetamine did not affect the development of stimulus control under any procedure. Thus, consistent with d-amphetamine's effects under repeated acquisition procedures, the drug had no detrimental effect on learning until doses that produced general behavioral disruption were achieved.
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