Yeeun Kang¹, Chai-Youn Kim¹; ¹Korea University

Prolonged exposure to audiovisual temporal asynchrony induces recalibration, where the point of subjective simultaneity shifts toward the adapted lag (Fujisaki et al., 2004; Vroomen et al., 2004). Previous studies primarily used explicit temporal judgment tasks, leaving unclear whether recalibration extends to implicit audiovisual integration. We investigated whether audiovisual lag adaptation modulates the temporal binding window (TBW) measured through the sound-induced flash illusion (SIFI; Shams et al., 2000), where a single flash paired with multiple beeps can be perceived as multiple flashes. Eleven participants completed SIFI trials before and after lag adaptation, judging whether they perceived one or two flashes. Each trial presented a white circle under fixation with auditory beeps in congruent (one-flash one-beep [1F1B], two-flashes two-beeps [2F2B]) and illusory (one-flash two-beeps [1F2B]) conditions. In 1F2B and 2F2B trials, stimulus onset asynchronies (SOAs) between a flash-beep pair and additional component (a beep or another flash-beep pair, respectively) varied within ±300ms. Adaptation sessions exposed participants to either auditory-leading (-235ms) or visual-leading (+235ms) asynchrony using identical audiovisual stimuli as SIFI. Participants performed an oddball detection task during three-minute initial adaptation, with post-adaptation SIFI blocks interleaved with top-up adaptation. We analyzed illusion rates in 1F2B trials to derive perceptual sensitivity (d') and TBW (Foss-Feig et al., 2010). While not significant, post-adaptation TBWs shifted approximately 50ms toward each adapted lag (Baseline: -150 to 100ms; Visual-first: -50 to 150ms; Auditory-first: -100 to 100ms). Visual-first adaptation yielded significantly higher d' at -300 and -100ms SOAs than auditory-first (ps=0.040, 0.032). The magnitude of sensitivity changed from baseline (Δd') was significantly greater after visual-first than auditory-first adaptation at these SOAs (ps=0.041, 0.033). These findings reveal that audiovisual temporal recalibration can be detected via SIFI through changes in perceptual sensitivity. Notably, auditory-leading exposure induced stronger recalibration than visual-leading exposure, indicating asymmetric plasticity in temporal processing.

Acknowledgements: Supported by NRF-2023R1A2C2007289