The CS-US interval function in rabbit nictitating membrane response conditioning: Single vs multiple trials per conditioning session

The effect of varying trials per day conditions on the CS-US interval or interstimulus interval (ISI) function in rabbit nictitating membrane response conditioning was studied in two experiments. Experiment 1 showed that a 1250-msec ISI was more effective than a 250-msec ISI when there was 1 trial/day. Experiment 2 showed that as the number of trials per day decreased from 20 to 1, the superiority of the 250-msec ISI group over the 1250-msec ISI group declined, with a reversal at 1 trial/day. Results are interpreted in terms of the role of a hypothesized CS-elicited short-duration orienting response in CR performance.