Integration of visual and tactile modalities.

Experiments have been carried out in which subjects were required to discriminate time-varying visual and tactile stimuli presented simultaneously via a 2D array of light-emitting diodes and a vibrator on the fingertip. Contrary to expectations, no problems in parallel visual and tactile perception were apparent. Similar results were obtained in a second experiment in which subjects were require to lipread from a video image and simultaneously identify speech-derived tactile stimuli. The generally poor performance of tactile aids to lipreading has been attributed to problems of parallel perception, but such problems are clearly not present in all circumstances.