Abstract
Purpose. Most studies on auditory-visual interactions report that what we hear is influenced by what we see [i.e., McGurk and ventriloquism effects]. There are a few reports of reverse influences [i.e., Sekuler, Sekuler & Lau, Nature 1997; Shams, Kamitani & Shimojo, Nature 2000]. We investigated whether hearing can affect vision in cases where only influences of vision on hearing have been observed [Kitagawa & Ichihara, Nature 2002]. Methods. We used ambiguous approaching/retreating visual stimuli by displaying oscillating locally-paired expanding/contracting dots [Qian, Andersen & Adelson, J. Neurosc. 1994], simultaneously with either ascending- or descending-amplitude pink auditory noise (0.2 — 8 kHz) . We used trials without sound, or with a fixed-amplitude white noise as controls. We biased the visual stimulus by moving the center of a variable percentage of dot pairs radially outward or inward. In a sequence of 1.2-s trials, participants reported whether they perceived an expanding or contracting visual stimulus. We used a constant-stimulus design, where the parameter was the percentage of dot pairs that moved either outward or inward. The sound stimulus was randomized across trials. Results. Participants' percept of an approaching or retreating visual stimulus was significantly affected by the simultaneous presence of the auditory stimulus. They showed a tendency to judge the same visual stimulus more often as expanding when it was accompanied by the ascending- than by the descending-amplitude sound, and vice versa. Conclusion. These results indicate that auditory stimuli can influence the processing of simultaneously present visual stimuli, when the visual stimuli are dynamic and ambiguous, but not when they are static and stable, as in Kitagawa & Ichihara [2002]. The results complement recent findings of similar intermodal interactions [Meyer & Wuerger, Neuroreport 2001; Masuda, Wada, Kitagawa & Noguchi, 2002], in which audition affects vision.
This work was supported by NIH/NEI grant R01 EY 013758-01.