When seeing doesn't matter: assessing the after-effects of tactile distractor processing in the blind and the sighted.

Negative priming (NP) refers to the finding that people's responses to probe targets previously presented as prime distractors are usually slower than to unrepeated stimuli. Intriguingly, the effect sizes of tactile NP were much larger than the effect sizes for visual NP. We analyzed whether the large tactile NP effect is just a side effect of the higher difficulty when processing tactile compared to visual stimuli. Thus, we analyzed tactile NP in a sample of blind participants and in a control sample of sighted participants. Although the blind participants handled the tactile stimuli with ease, we found no evidence that the size of the tactile NP effect diminished. In two control experiments with sighted participants, we varied the processing difficulty in the visual and tactile modality and found that both modality and processing difficulty had an effect on the size of NP. Taken together, our data show that the difficulty associated with processing tactile stimuli is only partially the reason for the unusual large tactile NP effect. These results suggest that non-spatial tactile distractors are processed and selected quite differently from visual distractors.