Feeling voices

Abstract

Two experiments investigated deaf individuals' ability to discriminate between same-sex talkers based on vibrotactile stimulation alone. Nineteen participants made same/different judgments on pairs of utterances presented to the lower back through voice coils embedded in a conforming chair. Discrimination of stimuli matched for F0, duration, and perceived magnitude was successful for pairs of spoken sentences in Experiment 1 (median percent correct = 83%) and pairs of vowel utterances in Experiment 2 (median percent correct = 75%). Greater difference in spectral tilt between "different" pairs strongly predicted their discriminability in both experiments. The current findings support the hypothesis that discrimination of complex vibrotactile stimuli involves the cortical integration of spectral information filtered through frequency-tuned skin receptors.

Figure 1. Boxplots of percent correct by participant across two conditions.

Median is shown as a bolded line. Lower and upper edges of the boxes indicate lower and upper quartiles, respectively, and whiskers indicate sample minima and maxima.

Figure 2. Boxplots of percent correct by participant across four conditions.

Outliers are shown as circles.

Figure 3. Spectral slices (50 msec in length, starting from 1 s) of 220 Hz vowel utterances.

F0 and its harmonics are sharp peaks at 220 Hz and integer multiples. Formants (F1, F2, F3) can be seen as shallower peaks each containing multiple harmonics. (left panel) Where spectral tilt (H1-A3) was nearly identical between Female-A and Female-B, responses were at chance (40% correct); (right panel) difference in spectral tilt between Male-B and Male-C was large and elicited 87% correct responses.

Figure 4. Correlation between the absolute difference in global spectral tilt and percent correct.