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Shinsuke Shimojo, Noelle Stiles, Monica Li, Carmel Levitan, Yukiyasu Kamitani; Audiovisual "Illusory Rabbit": The Role of Postdiction in Crossmodal Spatiotemporal Dynamics. Journal of Vision 2016;16(12):869. doi: 10.1167/16.12.869.
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© 2017 Association for Research in Vision and Ophthalmology.
Background: The temporal paradox of stimuli following an event affecting that event's perception (postdiction), provides a unique window into brain processing (Shimojo, fpsyg 2014). This study revisits the audiovisual rabbit illusion (Kamitani & Shimojo, VSS 2001) and examines whether audition can modify visual perception postdictively. Methods: A sequence of flashes (13 ms each, total stimulus duration 145(?) ms) was presented on a computer monitor moving left-to-right, while accompanying beeps (7 ms each) were communicated on a single left-hand-side speaker. Stimuli included: two lone flashes (2F0B), two flash-beep pairs (2F2B) and two flashes and three beeps, with the two flashes accompanying the first and the third beeps, respectively (2F3B). Subjects reported the number of flashes perceived (Expt. 1), or both the number of flashes and the location of the flashes (Expt. 2). Results: Expt 1: Participants (N = 8) perceived significantly more flashes with 2F3B than 2F2B (p < 10-33), indicating the perception of an illusory flash in the 2F3B condition. Expt 2: The second flash (of three reported flashes) location in the 2F3B condition was midway between the first and third flash, indicating the illusory flash's location is postdictively determined. Discussion: The illusory flash following the first flash was perceived to be moved laterally in space toward the final flash location. This mid-location of the illusory flash must be determined after its perception, as no spatial movement is conveyed before or during its presentation. It indicates that the location of the illusory flash can be postdictively modified, and further that postdictive processing extends to crossmodal interactions.
Meeting abstract presented at VSS 2016
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