Relative time and delay of reinforcement

Rats were trained on a conditional discrimination in which either a light or a noise cued whether the left or right lever was the correct choice. Faster learning occurred when shorter delays were imposed between presentation of the stimuli and the choice opportunity, and the effect of delay variation was dependent on the value of the intertrial interval Cm): the effects of the retention interval were smaller with longer ITI's. When the delays were inserted between the choice response and its consequence, main effects of delay and ITI occurred, but there was no interaction between them. The occurrence of relative time effects with delayed stimulus control, but not with delay-of-reinforcement procedures, suggests that different types of delay intervals depend upon different psychological processes. (C) 1998 Academic Press.