The effects of d-amphetamine on the automaintained key pecking of pigeons.

Three food-deprived pigeons were initially exposed to an automaintenance procedure in which 8-s response key illuminations were followed by food delivery without regard to the subject's behavior. The percentage of occasions on which key illumination was followed by food delivery was then successively reduced from 100 to 50, 25, 10, and 2.5%. Despite the lack of a programmed contingency between key pecking and food delivery or key illumination, key pecking occurred under all automaintenance conditions. Mean responses per 8-s key illumination during non-drug sessions varied from over 15 to less than one, with the 100 and 50% pairing conditions engendering the highest rates and the 2.5% pairing condition the lowest. Under all automaintenance conditions, d-amphetamine in does of 0.5, 1, and 2 mg/kg decreased responding in a dose-dependent fashion. Rate-dependent effects were not evident despite the appreciable differences in mean response rates engendered by the various conditions.