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Hauke S. Meyerhoff, Nina A. Gehrer, Simon Merz, Christian Frings; The Beep-Speed Illusion: Non-Spatial Tones Increase the Perceived Speed of Visual Objects. Journal of Vision 2021;21(9):1874. doi: https://doi.org/10.1167/jov.21.9.1874.
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© ARVO (1962-2015); The Authors (2016-present)
Coinciding auditory information alters early processing of visual scenes, however, the interplay between audio-visual integration and selective visual attention is far from being understood. Here, we introduce the beep-speed illusion revealing both the impact of audio-visual integration on attentional guidance as well as perceptual consequences following the selective allocation of visual attention toward audio-visually synchronized objects. We observed the illusion with displays involving two simultaneously moving objects that change their motion trajectories occasionally, but only the direction changes of one object are accompanied by spatially uninformative tones. Whereas this object always moved with 4.5 deg/s, we varied the speed of the other, purely visual object across trials. The task of the participants was to indicate which of the two discs moved faster. From these answers, we calculated the point of subjective equality (i.e. the speed of the visual object at which both objects appeared to move at the same speed). We observed a selective increase in perceived object speed (4-8%) of the audio-visually synchronized object (Exp. 1a) which persists when preventing eye movements (Exp. 1b). When the coinciding tones were replaced with temporally matched color changes of the synchronized object, we observed a comparable illusory increase in perceived speed, whereas presenting color changes of a surrounding frame instead of tones had no effect (Exp. 2). Finally, the illusion even emerged with spatially incongruent tones (Exp. 3). Taken together, our pattern of results suggests that audio-visual synchrony attracts visual attention towards the coinciding visual object, leading to an increase in speed-perception. Although future research is necessary to explore the boundary conditions of the beep-speed illusion, the striking phenomenology as well as quantifiability of the illusory increase in perceived object speed render this illusion a promising road for a better understanding of the interplay between audio-visual integration and attentional selection.
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