Is the Latency for Perceiving Ambiguous Motion Affected by the Timing of Modulatory Stimulus Presentation?

Abstract

Perception of one event is affected by another event (modulator) that occurs either before or after the event (prediction and postdiction). A possible account for these temporal interactions is that the processing of an event does not start immediately, but waits a constant period for potentially relevant input. This hypothesis predicts that the perceptual latency of the target event is invariant to changes in the timing of modulator presentation. We tested this prediction by measuring the reaction time to judge an ambiguous motion event either as “bounce” or “stream” while changing the modulator (sound or flash) timing. The results showed that the modulator timing had little effect on RT for “stream” perception, but significantly modulated RT for “bounce” perception—the earlier the modulator, the shorter the RT. These results reject the constant delay hypothesis, but suggest more situation-adaptive temporal processing such as accumulating perceptual evidence over time.