EFFECTS OF SIGNALED REINFORCER MAGNITUDE ON DELAYED MATCHING-TO-SAMPLE PERFORMANCE

Pigeons were trained in delayed matching-to-sample with red and green key lights. A random half of the trials was accompanied by an auditory signal correlated with a large (4.5 s) reinforcer, and the other half by a different signal correlated with a small (1.5 s) reinforcer, for correct matches. Delays varied from trial to trial so that delay gradients could be determined within sessions and separately for large and small reinforcer trials. For all birds, accuracy was higher on large-reinforcer trials, but the average delay gradients were similar in slope. When performance was disrupted-either by the houselight during the delay interval, by injections of sodium pentobarbital, or by reduced sample duration-accuracy decrements on large-reinforcer trials were equal to or greater than those on small-reinforcer trials. Although these results accord with incentive effects on human memory, they are inconsistent with many findings on resistance to change of free-operant behavior.