The Impact of Response Structure on the McGurk Effect
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Date
2008-06
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The Ohio State University
Abstract
Understanding speech is a complicated process. Once thought to be a unimodal function, the perception of speech has since been demonstrated to be a multimodal process. The compensatory use of visual information during speech perception is easily evidenced by examining communication in compromised listening situations, like in a noisy restaurant. In such an environment, listeners use visual cues to help understand speech and fill in the missing pieces of auditory information. What is more interesting is that people use visual cues to process speech even when the auditory signal is perfect (McGurk and MacDonald, 1976). The combining of auditory and visual cues during speech perception is termed audio-visual integration.
The subjects in McGurk and MacDonald’s study were presented with “discrepant” auditory and visual stimuli and perceptual responses were recorded. The results showed that when a listener was presented, for example, with the audio syllable /ba/ simultaneously with the visual syllable /ga/, the most frequently reported response was /da/, a fusion of the two sounds. This phenomenon has been termed “the McGurk Effect” and has been used to explore audio-visual integration.
Although reports in the literature indicate a substantial degree of McGurk-type integration by both normal-hearing and hearing-impaired subjects (e.g., Grant and Seitz, 1998), previous studies in our laboratory have not found such a high incidence of McGurk integration. One possible explanation for this difference is the fact that previous work in our laboratory employed an open-set response task, in which respondents were not given a fixed set of response options, whereas studies such as that of Grant and Seitz employed a closed-set response task.
The present study explored how the type of response task might influence the McGurk Effect. In the present study, 20 normal-hearing participants were presented with audiovisual syllables featuring a degraded auditory component. Half of the subjects were tested with a closed-set task, and the rest were tested with an open-set task. Results indicated significantly higher incidence of McGurk-type integration for subjects tested with the closed set response task. These findings are discussed in terms of their implications for the development of aural rehabilitation programs for hearing-impaired persons.
Advisor: Janet M. Weisenberger
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Keywords
McGurk Effect, Speech Perception, Response Structure