Audiovisual "Invisible Rabbit": Auditory Suppression of Visual Flashes in Spatiotemporal Stimuli

Abstract

Background: In general, vision dominates perception in the spatial domain, and audition in the temporal. What happens with conflicting spatiotemporal stimuli? We show that, by optimizing the signal-to-noise ratio, audition can suppress vision, postdictively (i.e. retroactively). Methods: Three flashes (13 ms each, total stimulus duration 145 ms) were presented at a 10-degree eccentricity (below fixation) with apparent left-to-right horizontal motion, where the first and last flashes were paired with 7 ms beeps [3F2B]. As controls, stimuli with no beeps [3F0B] or beeps paired with each flash [3F3B] were presented. Participants reported the perceived number of flashes. A second experiment tested the illusion's postdictive aspect with two added stimulus conditions: one with two flashes, the first flash paired with a beep [2F1B], and the other with three flashes, the first two flashes paired with beeps [3F2B-r]. A final experiment asked participants to report the locations of the perceived flashes in the 3F2B condition when two flashes were perceived. Results: Expt. 1: Three flashes with no beeps [3F0B] and with three beeps [3F3B] were perceived as approximately three flashes, whereas three flashes accompanied by two beeps [3F2B] was perceived as two flashes; the number of perceived flashes in 3F2B is significantly fewer than with 3F3B (p = 10-34). Expt. 2: The number of perceived flashes was significantly greater when the beep-flash pairs preceded the lone flash [3F2B-r], rather than when flanking [3F2B] (p = 10-8). This indicates that the last flash-beep suppresses the perception of the middle lone flash postdictively in 3F2B trials. Expt. 3: The distribution of reported flash locations is consistent with suppression of the middle flash. Discussion: Our results indicate that auditory stimuli can change visual perception postdictively, thereby broadening postdictive phenomena to suppression. Together with the "illusory rabbit", results suggest that audition dominates vision under short time conditions.

Meeting abstract presented at VSS 2016