In 5 experiments, we assessed the effects of preexposure to simple auditory stimuli on subsequent conditioning and discrimination learning. Experiment 1 showed that preexposure to a single stimulus retarded acquisition of conditioned responding to that stimulus. The same preexposure regimen facilitated the subsequent acquisition of a discrimination between 2 stimuli that flanked the preexposed stimulus along the frequency dimension. Experiment 2 replicated this midpoint preexposure effect on discrimination learning but also found that alternating preexposure to the discriminative stimuli retarded discrimination learning. Experiments 3 to 5 explored the causes of these effects. These experiments are the first to examine perceptual learning in animals using simple auditory stimuli, and their results suggest that in at least some circumstances alternating preexposure to auditory stimuli results in an increase in generalization between them. (PsycInfo Database Record (c) 2021 APA, all rights reserved).