Serial dependence generalizes across the senses
Our perception often shows systematic biases revealing how the brains internal representation diverges from the physical world. In particular, what happened in the recent past can systematically attract current percepts, making them appear more similar to previous stimuli. Does this phenomenon reflect a low-level mechanism encapsulated within each sensory modality, or instead a higher-order post-perceptual decisional mechanism? Here we investigate the existence, mechanisms, and neural signature of serial dependence across vision and audition for numerosity perception. In a series of three complementary experiments, we show that serial dependence can transfer across modalities and is modulated by cross-modal attention. Electroencephalographic recordings further reveal that both uni-modal and cross-modal effects similarly emerge during the perceptual processing of the stimuli. Our results thus challenge both current mainstream accounts of serial dependence based on low-level and high-level computations, critically pointing to a central role of a functional, mid-level multisensory network in generating this phenomenon.