Central-peripheral differences in audiovisual and visuotactile event perception.

We examined audiovisual and visuotactile integration in the central and peripheral visual field using visual fission and fusion illusions induced by sounds or taps. The fission illusion occurs when a single flash is perceived as two flashes if paired with two beeps or taps; the fusion illusion, by contrast, occurs when two flashes are perceived as a single flash if the flashes are paired with a single beep or tap. Beeps and taps induced similar patterns of illusions: the fission illusion was larger in the periphery than in the center, whereas the fusion illusion was larger in the center than in the periphery. An analysis based on signal detection theory revealed that both a decline in discriminability and a shift in criterion were associated with the more pronounced fission induced by sounds in the periphery. In contrast, only a shift in criterion was associated with the larger fission induced by taps in the periphery, and the larger fusion induced by a sound or tap in the center. To accommodate these findings, two accounts are proposed: audiovisual signals are more likely to be integrated in peripheral than in central vision, and the interpretation of visual signals favors discontinuous percepts, especially in the periphery.