Three experiments examined the influence of auditory stimuli on the pe
rformance of hungry rats in an instrumental discrimination task. In Ex
periment 1, presenting a response-contingent auditory stimulus on an i
ncorrect manipulandum tended to improve discrimination, relative to a
group lacking a stimulus. In contrast, presenting a visual stimulus on
the incorrect lever enhanced discrimination. In Experiment 2, the int
ensity of the auditory stimulus was varied, and the discrimination bet
ween the levers improved as the intensity of the auditory stimulus pre
sented on the incorrect lever increased. In Experiment 3, the effect o
n discrimination of presenting an auditory cue on the incorrect lever
was replicated, and it was also noted that the cue was capable of impr
oving performance if it followed responses to the reinforced lever. Th
ese results imply that, in the absence of pairing with a primary reinf
orcer, some putatively neutral auditory stimuli possess aversive prope
rties. (C) 1995 Academic Press, Inc.