Discrimination of consonant articulation location by tactile stimulation of the forearm

In this paper, we evaluate the ability of four able-bodied participants to discriminate the articulation location for spoken consonants, using tactile cues presented on the dorsal side of their forearm. Additionally, we determine the processing capability of the dorsal forearm´s skin with a tactile sleeve worn by ten participants using two psychophysical studies. Our first study shows that 2-3 tactors arranged along the length of the forearm can be reliably identified by human users, when only the location of vibration is varied. Our second study indicates that the physical placement of localized vibrations map linearly to the perceived physical arrangement. Based on these findings, the subsequent speech experiment uses six tactors placed equidistant from each other and maps location of the constriction inside the mouth as directional cues on the forearm. Results of the speech study show that participants are able to indicate which of two randomly presented tactile cues (derived from consonant-vowel-consonant (CVC) non-sense syllables) has the preceding consonant closer to the lips. The discrimination performance is better (i) with fricatives than plosives, (ii) when the consonants are produced further apart inside the mouth, and (iii) when both place and manner of articulation feature is varied. The study also shows that discrimination performance with cues applied to the forearm is inferior to that with the fingerpads utilized in a previous study.