Thesis

A behavioral interpretation of the McGurk effect

The McGurk effect is a perceptual phenomenon in which the combination of discrepant visual and auditory speech stimuli (e.g. hear-ba/see-ga) produces reports of hearing a completely novel response form (e.g. “da”). The present study attempted to explain the McGurk effect and related phenomena in terms of principles of behavior. Skinner (1953) proposed that perception itself is behavior, and interpreting experimental results within the framework of experimentally validated behavioral principles may help to guide future research on perceptual phenomena. Additionally, the study contributed to the analysis of the McGurk effect by comparing the auditory and visually discrepant isolated syllable conditions (e.g. hear-BA/see- GA) with a second procedure, in which the same stimulus conditions were presented as the initial syllables of rhyming word pairs taken from the average educated adult English speaking repertoire (e.g. hear-BUST/see-GUST). Since the McGurk illusion is produced by auditory and visual stimuli that are discrepant in their corresponding labial or non-labial lip movements, the authors analyzed the effect by selecting two labial speech sounds “ba” and “ma,” and two non-labial speech sounds “ga” and “la.” The results support the authors’ hypothesis that the McGurk effect would be stronger when syllables were presented in isolation than when they were presented in the context of whole words. The second hypothesis, which proposed that the tendency to report hearing the word “dust” in the hear-BUST/See-NonLabial conditions would be stronger than the tendency to report hearing “nust” in the hear- MUST/See-NonLabial conditions was not supported by the present study.

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