Rats’ preferences in the suboptimal-choice procedure are affected by the perceptual salience of the stimuli

Studies examining rats' performance in the suboptimal choice procedure have shown that rats behave suboptimally when the signal predicting reinforcement (S+) is more salient than the signal predicting the absence of reinforcement (S-). The purpose of this work is to complement that research by evaluating the effect of the perceptual salience of stimuli when used both as predictor of the reinforcer and of its absence. We trained twelve rats in an ABA design in which the discriminative alternative was composed of two stimuli, one of them assumed to be more salient than the other, with the particular function of each being reversed across conditions. We found that when a salient stimulus composed of sequences of tones and lights was used as S+ and a blackout as S-, animals showed a greater proportion of choice for the discriminative alternative. On the other hand, when the function of stimuli was reversed, that is, when the more salient stimulus was used as S- the animals strongly rejected the discriminative alternative. While these results demonstrate that stimulus salience modulates animal choice, the underlying mechanisms remain to be elucidated in future studies.