Abstract
Space and time are strictly linked, and a multisensory experience is crucial for developing a merged representation of spatial and temporal domains, with vision scaffolding spatial representations and audition temporal representations. However, it is still unclear how temporal and spatial domains interact in the lack, for example, of the visual experience. Investigating speed perception provides a unique opportunity to study this interaction. Thus, we explored the role of vision in the use of spatio-temporal cues to discriminate the speed of moving sounds. In a two-alternative forced-choice task, ten early blind and ten sighted (blindfolded) individuals determined the speed of a target sound, by saying whether it was moving faster or slower than a reference sound. The target speed was manipulated by changing the distance traveled by the moving sound and/or its duration, based on the experimental conditions. To identify the target speed, participants could rely on spatial, temporal, or both cues. Using a discrimination contours technique (Freeman et al., 2014), we revealed that both sighted and early blind participants preferentially used temporal cues to determine the target sound's speed. Specifically, both groups followed a temporal prior that identifies as faster stimuli those that last less than the reference sound, even if that leads to a misperception of the stimulus speed in some conditions. Interestingly, early blind participants appeared to be significantly more affected by this potentially misleading temporal prior, showing impairment in speed discrimination, compared to sighted controls. To conclude, the present study adds new insights on the role of vision on human perception by showing that auditory speed discrimination is preferentially based on temporal cues and that the absence of visual experience early in life affects this ability by increasing the preference for the temporal domain.