Runway performance of amygdalectomized rats: Magnitude of reinforcement and delay of food reward

Abstract

In an alleyway, running speeds for amygdalectomized rats given large (12 pellets) or small (2 pellets) magnitude of reinforcement were initially faster for the large-magnitude group, but the small-magnitude group caught up (termed the collapse effect) in 20 trials. This is in contrast to intact animals, which typically exhibit the collapse effect anywhere between 50 and 100 trials. As such, control animals administered 20 trials showed the familiar form of responding—the speeds of the large-magnitude animals were reliably faster than those of the small-magnitude animals. With periodic increases in delay of food reward, from 0 to 45 sec in 15-sec increments, lesioned animals ran reliably faster than control animals, more so for the 30- and 45-sec delays. These results were viewed as supporting Richardson’s (1973) theory.