Abstract
In the present study we investigate the rules governing the perception of audiovisual synchrony within spatio-temporally cluttered visual environments. Participants viewed a ring of 19 discs modulating in luminance while hearing an amplitude modulating tone. Each disc modulated with a unique temporal phase (40 ms intervals), with only one synchronized to the tone. Participants searched for the synchronised disc whose spatial location varied randomly across trials. Square-wave modulation facilitated search: the synchronized disc was frequently chosen, with tight response distributions centred near zero-phase lag. In the sinusoidal condition responses were equally distributed over the 19 discs regardless of phase. To investigate whether subjective synchrony in the square-wave condition was limited by spatial or temporal factors we repeated the experiment with either reduced spatial density (9 discs) or temporal density (80 ms phase intervals). Reduced temporal density greatly facilitated synchrony perception but left the synchrony bandwidth unchanged, while no influence of spatial density was found. We conclude that audio-visual synchrony is not strongly constrained by the spatial or temporal density of the visual display, but by a temporal window within which audio-visual events are perceived as synchronous, with a full bandwidth of ~185 ms.
Highlights
In the present study we investigate the rules governing the perception of audiovisual synchrony within spatio-temporally cluttered visual environments
Accuracy was high when a single element was synchronized, but declined dramatically when more than one element was synchronized with the sound. These results indicate that even though multiple synchronized visual matches may be present within the audio-visual synchrony window, only one visual event can integrate with the auditory signal
In Experiment 2B, the display’s spatial density was manipulated by presenting either 19 discs or 9 discs. In both spatial density conditions, the modulating discs were spaced in 40 ms phase intervals, a narrower range of phase steps was used in the nine-disc condition (2160–1160 ms: see Fig. 1F) to keep a constant temporal density within the temporal window of integration
Summary
In the present study we investigate the rules governing the perception of audiovisual synchrony within spatio-temporally cluttered visual environments. Accuracy was high when a single element was synchronized, but declined dramatically when more than one element was synchronized with the sound These results indicate that even though multiple synchronized visual matches may be present within the audio-visual synchrony window, only one visual event can integrate with the auditory signal. The first kind of error would occur if spatial proximity was prioritised, and the second kind would indicate temporal proximity is prioritised and spatial proximity is irrelevant If the latter is true, plotting distributions of target location judgments in terms of phase will reveal a tight cluster of synchrony responses located near the point of physical synchrony. If spatial proximity contributes to synchrony judgements (i.e., errors of the former kind) the distribution of perceived synchrony over temporal phase will be much broader
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