The Stimulus type (T, [VT + nostim – V]) × Group (deaf, hearing) ANOVA on P100 amplitudes revealed a marginally significant main effect of Stimulus type, F (1, 18) = 3.50, p = 0.078, with larger amplitudes for [VT + nostim – V] than for unisensory tactile responses T ( M = 4.0 vs. 3.2 μV), indicating a tendency for multisensory interactions about 100 ms after stimulus presentation in both deaf and hearing participants.
The response time difference between the visual and tactile condition in deaf individuals, however, did not reach statistical significance and is therefore rather unlikely to be the reason for the reduced redundancy gain observed in the deaf.
This group difference was significant for tactile and approached significance for visual targets.
We found tactile P300 amplitudes to be significantly larger in deaf than in hearing participants whereas the group difference for visual P300 amplitudes pointed into the same direction approaching significance.