Perception of synthetic visual consonant-vowel articulations

Synthetic speech-like articulations were presented to adult subjects via the visual modality, following the classic categorical perception experimental paradigm (Liberman, Harris, Hoffman, & Griffith, 1957). Animations were generated on a computer-based graphics system. Stimuli consisted of representations of the syllables /ba/, /va/, and /wa/; as well as 6 linearly interpolated intermediate stimuli between each of the possible exemplar pairs, resulting in three 8-item continua. Three sets of observations were obtained for these stimuli. First, for each continuum, labeling data were obtained in which the subject assigned one or the other exemplar label to each of the stimuli. Next, ABX discrimination data were obtained for each continuum. In the final task, subjects assigned a rating of one through nine to each animation indicating the extent to which it was like the exemplar syllables. Although the labeling functions showed rather abrupt transitions from one response category to the other, the peaks in the discrimination functions did not coincide with the category boundaries. Further, the mean rating functions were relatively linear, and the distribution of rating responses revealed unimodal distributions whose peak locations differed depending on the stimulus.