The amount of exposure determines generalization in animal perceptual learning using short inter-stimulus intervals.

While human and animal perceptual learning (PL) had sometimes yielded similar results, there is evidence of some striking discrepancies. It has been proposed that such differences reflect the existence of multiple species-specific mechanisms, especially regarding to humans. However, it is also possible that those discrepancies are caused by procedural differences. One of the most important differences between PL experiments in humans and laboratory animals is the inter-stimulus interval (ISI) used. In the former, short ISI reliably produces PL, while in the latter reducing the ISI leads to paradoxical results. We report two experiments with rodents to prove that the length of exposure is a key element under such conditions. In the first experiment we replicated the paradoxical results already present in the literature using a short exposure. In a follow up experiment, we increased the exposure trials and obtained normal PL in animals using short ISI. Our results support current associative theories of PL and highlight the impact of procedural differences on this phenomenon.