Isolating perceptual biases caused by trial history during auditory categorization

Just as most experiences have their origin in our perceptions, our perceptions can also be fundamentally shaped by our experiences. However, isolating which events in the recent past can impact perceptual judgments remains a difficult question, partly because post-perceptual processes can also introduce strong history dependencies. Two mechanisms have been hypothesized to specifically modulate perception: 1) the repulsive influence caused by previous stimuli and generally labeled as aftereffects, and 2) the modulation caused by stimulus predictions based on learned temporal regularities of the sensory environment, a key assumption in the predictive coding framework. Here, we ask whether these two mechanisms do indeed bias perception by training rats in an auditory task featuring serial correlations along the sequence of stimuli. We develop a detailed behavioral model that isolates the repulsive aftereffect generated by previous stimuli and shows that this repulsion cannot be explained from an interaction between past and current stimuli, and that it is still present in catch trials lacking the current stimulus. Moreover, the model describes that the bias caused by the animals' expectation, as they leverage the predictability of the stimulus sequence, is present in a foraging task without the sensory component but with the same serial correlations in the sequence of rewards. These results indicate that the aftereffect and the prediction biases observed during an auditory task can all be revealed in the absence of a sensory stimulus, putting into question their perceptual nature. ### Competing Interest Statement The authors have declared no competing interest.