The effect of a visual stimulus on the auditory continuity illusion was examined. Observers judged whether a tone that was repeatedly alternated with a band-pass noise was continuous or discontinuous. In most observers, a transient visual stimulus that was synchronized with the onset of the noise increased the limit of illusory continuity in terms of maximum noise duration and maximum tone level. The smaller the asynchrony between the noise onset and the visual stimulus onset, the larger the visual effect on this illusion. On the other hand, detection of a tone added to the noise was not enhanced by the visual stimulus. These results cannot be fully explained by the conventional theory that illusory continuity is created by the decomposition of peripheral excitation produced by the occluding sound.
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