Interstimulus interval function of the nictitating membrane response of the rabbit under delay versus trace conditioning.

Abstract

Each of 144 Ss [subjects, rabbits] received 2 adaptation, 10 acquisition, and 2 extinction sessions in a 3 x 4 factorial design with fixed CS [conditioned stimulus] delay, simultaneous offset of CS and US [unconditional stimulus] delay, and fixed CS trace procedures as one dimension and interstimulus intervals (ISI) of .25, .50, 1.00, and 2.00 sec. comprising the other. ISI functions differed in shape and slope for different delay and trace procedures. Rate and level of conditioning were inverse functions of ISI, except under fixed CS delay. Median latency decreased as training progressed; means and SDs of response latency increased with ISI. Latency data appeared to be consistent with time discrimination and stimulus trace hypotheses of learning.