Abstract
Previous studies on perception have yet to establish that psychophysical adaptation effects transfer from one sense to another. To test for this phenomenon, the current study examines the possible crossmodal transfer of temporal rate adaptation from vision to audition (VA) and from audition to vision (AV). Participants were trained, using feedback, to discriminate the perceived rapidity of either auditory or visual stimuli presented at a range of randomly-ordered frequencies (3.25–4.75 Hz) as compared to that of stimuli (of the same modality) at a familiar average frequency (4 Hz). Afterwards, subjects were repeatedly exposed to stimuli (of the other modality) at a specific rate (3 Hz or 5 Hz). To test whether adaptation resulted from this exposure, subjects again completed the task previously used for training, but now without feedback. After the initial training and adaptation phases, these test and adaptation tasks were presented in 20 alternating blocks. A comparison of the pre- and post-adaptation responses showed crossmodal changes in subjects' perception of temporal rate, such that adaptation to 5 Hz led to the subsequent stimuli seeming slower than they had before adaptation. On the other hand, after exposure to 3 Hz stimuli, the opposite effect was seen. This shift occurred in both VA and AV conditions. As audition and vision were never simultaneously presented, this is suggestive of a strong linkage between the two modalities in perceiving rate. We propose that this is due to the presence of early, distributed, within-modal clocks, that can vigorously modulate each other cross-modally.