Conditioned suppression and the information hypothesis.

Abstract

To assess relevance of the information hypothesis to conditioned suppression, a compound CS [conditioned stimulus] (S1 [first stimulus] overlapping S2) was paired with shock for 2 groups of rats and suppression in bar-press rates produced by S1 and S2 individually was measured. During CS-US [unconditioned stimulus] pairings S1 occasionally occurred alone for 1 group and thus predicted shock unreliably; for the other group, S1 predicted shock reliably, making S2 redundant. Contrary to the information hypothesis, both redundant and unreliable stimuli produced as much suppression as their more informative counterparts. A pseudoconditioning control group did not suppress to either stimulus, and 2 differentially conditioned groups showed that subjects could discriminate between S1 and S2 by suppressing only to the stimulus paired with shock.