Incongruent Audiovisual Inducer Information and Fission/Fusion Illusions

In research studies on how people perceive simultaneously presented audiovisual information, researchers have often shown that the number of visual flashes participants perceive on a computer screen can be altered by varying the number of accompanying auditory, visual, or combined audiovisual cues or inducers. In the present study, we examined the effects of number-incongruent audiovisual inducer stimuli on the participants' perceived number of target flashes. We instructed 16 participants (eight males and eight females; M = 21.56; SD = 1.93) to report their perceived number of target flashes while ignoring the visual and auditory inducers. Across 18 different experimental conditions, we presented one or two target flashes in association with varied numbers (0, 1, 2) of auditory and visual inducer stimuli. In the condition with one target flash paired with one visual and two auditory inducers, the number of visual inducers (i.e., one) had a greater influence on the number of perceived target flashes than did the number of auditory inducers (i.e., two). Under all other number incongruent audiovisual inducer conditions, the participants' perceived number of target flashes was influenced more by the number of auditory than the number of visual inducers. We discuss these findings in the context of perceptual grouping and perceptual temporal uncertainty.