Priors for perceived speed combine supramodally for visual-tactile motion but not for audio-visual motion.

Perception integrates sensory input with learned expectations based on past experiences. One such effect is the tendency for estimates to drift towards a prior, determined by the average of observed stimuli. However, it is unclear whether these priors are unique to each sense or shared across them. Researchers investigated this by examining how speed is perceived in visual, auditory, and tactile modalities.

By assigning distinct speed ranges to each sense, the researchers anticipated different outcomes depending on whether priors are specific to a single modality or shared across them.

When visual and tactile cues were presented separately, speed estimates for each modality converged towards a supramodal prior. The less reliable modality exhibited a greater shift, consistent with a weighted average that favors the more reliable sense. However, in the case of visual and auditory cues, the priors remained largely separate.

While audition (the less reliable modality) did show a partial shift, it did not align with the supramodal mean. This specific behavior persisted even when the visual cue's precision was reduced, suggesting that the lack of an early spatial mapping in auditory processing may be responsible.

The findings indicate that crossmodal integration of motion perception is possible between visual and tactile signals, but not between visual and auditory signals. This implies that the ability of the brain to combine information across senses may depend on the specific senses involved, which is likely due to the absence of an early spatial mapping in auditory processing.