Testing symmetry of temporal window of integration between vibrotactile and auditory speech information in voiced phoneme perception

The temporal window for enhancement in cross-modal integration is asymmetrical, and does not require synchrony of stimuli for integration; this temporal offset has been linked to differences in relative signal speed as can be seen in audio-visual integration [Munhall et al. 1996. Perc. Psychophys. 58: 351] and audio-aerotactile integration [Gick et al. 2010. Journ. Acoust. Soc. Am. 128: EL342] of speech. However, as vibrotactile cues normally accompany acoustic cues, no difference in signal speed—and no concomitant perceptual asymmetry—is experienced between these two modalities. Contrary to previous research, we predict a symmetrical window for integration. A portable voice-coil transducer is used to produce vibrotactile stimuli, similar to the laryngeal vibrations normally felt in voiced speech. Results of an experiment will be presented in which participants are asked to discriminate between minimal pairs in noise with the device between their thumb and index finger, and in which audio and vibrotactile...