Contributions of semantic and facial information to perception of nonsibilant fricatives.

Most studies have been unable to identify reliable acoustic cues for the recognition of the English nonsibilant fricatives [see text]. The present study was designed to test the extent to which the perception of these fricatives by normal-hearing adults is based on other sources of information, namely, linguistic context and visual information. In Experiment 1, target words beginning with /f/, /theta/, /s/, or [see text] were preceded by either a semantically congruous or incongruous precursor sentence. Results showed an effect of linguistic context on the perception of the distinction between /f/ and /theta/ and on the acoustically more robust distinction between /s/ and [see text]. In Experiment 2, participants identified syllables consisting of the fricatives [see text] paired with the vowels /i, a, u/. Three conditions were contrasted: Stimuli were presented with (a) both auditory and visual information, (b) auditory information alone, or (c) visual information alone. When errors in terms of voicing were ignored in all 3 conditions, results indicated that perception of these fricatives is as good with visual information alone as with both auditory and visual information combined, and better than for auditory information alone. These findings suggest that accurate perception of nonsibilant fricatives derives from a combination of acoustic, linguistic, and visual information.