Perception of causality and synchrony dissociate in the audiovisual bounce-inducing effect (ABE)

A sound can cause 2 visual streaming objects appear to bounce (the audiovisual bounce-inducing effect, ABE). Here we examined whether the stream/bounce percept affects perception of audiovisual synchrony. Participants saw 2 disks that either clearly streamed, clearly bounced, or were ambiguous, and heard a sound around the point of contact (POC). They reported, on each trial, whether they perceived the disks to ‘stream’ or ‘bounce’, and whether the sound was ‘synchronous’ or ‘asynchronous’ with the POC. Results showed that the optimal time of the sound to induce a bounce was before the POC (−59 msec), whereas audiovisual synchrony was maximal when the sound came after the POC (+16 msec). The range of temporal asynchronies perceived as ‘synchronous’, the temporal binding window (TBW), was wider when disks were perceived as bouncing than streaming, with no difference between ambiguous and non-ambiguous visual displays. These results demonstrate 1) that causality differs from synchrony, 2) that causality widens the TBW, and 3) that the ABE is perceptually real.