Heimler, B. 1 & Pavani, F. 1, 2
1 Center for Mind/Brain Sciences, University of Trento, Italy
2 Department of Cognitive Science and Education, University of Trento, Italy
Reactivity enhancement has been repeatedly observed in deaf compared to hearing individuals through visual simple detection tasks, but it remains unknown whether these effects extend to other intact sensory modalities. Deaf also proved worse than hearing individuals on tactile temporal discrimination, but this ability has never been investigated in vision. It is thus unclear whether these differences are modality specific or amodal. Eight early deaf (loss > 70dB) and twelve hearing participants performed a simple detection or a temporal discrimination task. Stimuli were either tactile or visual, and they occurred at central or peripheral locations (vision: 1° and 32°; touch: forefinger, forearm, neck). Simple detection revealed a clear modality specific effect in deaf individuals: reactivity enhancement emerged selectively for vision, with no anticipation responses and regardless of stimulus eccentricity. By contrast, temporal discrimination revealed an amodal effect in deaf individuals, with poor sensitivity for both modalities and a clear speed-accuracy trade-off. The modality specific effect excludes a role for motivational and motor preparation factors in enhanced reactivity to visual events, suggesting instead a role of perceptual and attentional processes. The amodal finding reveals, however, that impulsiveness may indeed characterise deaf performance, particularly when a difficult perceptual discrimination is required.