Multisensory integration enhances phonemic restoration

Abstract

Phonemic restoration occurs when speech is perceived to be continuous through noisy interruptions, even when the speech signal is artificially removed from the interrupted epochs. This temporal filling-in illusion helps maintain robust comprehension in adverse environments and illustrates how contextual knowledge through the auditory modality (e.g., lexical) can improve perception. This study investigated how one important form of context, visual speech, affects phonemic restoration. The hypothesis was that audio-visual integration of speech should improve phonemic restoration, allowing the perceived continuity to span longer temporal gaps. Subjects listened to tri-syllabic words with a portion of each word replaced by white noise while watching lip-movement that was either congruent, temporally reversed (incongruent), or static. For each word, subjects judged whether the utterance sounded continuous or interrupted, where a "continuous" response indicated an illusory percept. Results showed that illusory filling-in of longer white noise durations (longer missing segments) occurred when the mouth movement was congruent with the spoken word compared to the other conditions, with no differences occurring between the static and incongruent conditions. Thus, phonemic restoration is enhanced when applying contextual knowledge through multisensory integration.