Signaled reinforcement effects on fixed-interval performance of the rat

In three experiments using fixed-interval schedules with a 500-msec delay of reinforcement, rats receiving a localized light signal during the delay leverpressed more slowly than rats trained without the signal. In Experiment 1 these groups showed no differences in temporal patterning of responding, but in the remaining two experiments the signaled rats showed better patterning than the unsignaled rats. In Experiments 2 and 3 rats receiving a diffuse tone signal during the delay instead of a light pressed more rather than less rapidly than the unsignaled group. Their patterning was better than that of the unsignaled rats in one of these experiments. Several explanations for both the attenuation and enhancing effects of signaling reward are discussed.