SOME PARAMETERS OF LATENT INHIBITION

In three experiments using the conditioned suppression procedure in rats, we sought to determine the effects of preexposing the conditioned stimulus (CS) for a total of 14,400 s. For different groups, the duration of each CS trial in preexposure was 12, 120, or 720 s. Thus, Groups 12, 120, and 720 received 1200, 120, or 20 CS-preexposure trials, respectively. The duration of the CS during conditioning was 120 s in Experiment 1, 720 s in Experiment 2A, and 12 s in Experiment 2B. In each experiment there was a control group, Group 0, that received no preexposure. The pattern of retarded conditioning in the preexposed groups supported the conclusion that the most important parameter of latent inhibition is the total CS-preexposure time. Similarity in duration of the preexposed and training CS ranked a distant second. The number of preexposure trials appeared to be of little importance when total exposure time was held constant. Thus the importance usually attributed to that number may reflect only its typical confound with total exposure time. © 1992.