K.G. Munhall, P. Gribble, L. Sacco, M. Ward
Temporal constraints on the perception of the McGurk effect
Abstract:Three experiments are reported on the influence of different timing relations on the perception of the McGurk effect. In the first experiment it is shown that strict temporal synchrony between auditory and visual speech stimuli is not required for the McGurk effect. Subjects were strongly influenced by the visual stimuli when the acoustic stimuli lagged the visual stimuli by as much as 180 ms. In addition, a stronger McGurk effect was found when the visual and acoustic vowels matched. In the second experiment we paired auditory and visual speech stimuli produced under different speaking conditions (fast, normal, clear). The results showed that both the visual and auditory speaking-condition manipulations independently influenced perception. In addition, the conditions in which the auditory and visual stimuli were spoken at the same rate showed a stronger McGurk effect. In the third experiment we combined auditory and visual stimuli produced at different speaking rates and delayed the acoustics with respect to the visual stimuli. The subjects showed the same pattern of results as in the second experiment. Finally, the delay did not cause different patterns of results for the different audiovisual speaking rate combinations. The results indicate that perceivers are sensitive to concordance of the time-varying aspects of speech but they do not require temporal coincidence of that information.