Vallet, G. 1, 2, 3 & Shore, D. 1
1 Multisensory Perception Laboratory (PNB), McMaster University; Hamilton, Canada
2 Laboratoire EMC, Lyon2 University, Lyon, France
3 School of Psychology, Laval University, Quebec City, Canada
Objective. Explore how action can influence the perception and integration of multisensory stimuli.
Method. Participants initiated each trial by pressing a left or a right key of the keyboard. A visual or an auditory stimulus was presented immediately (0ms SOA) or after 500ms. The second stimulus was presented after an additional 100, 200, 300 or 400ms. The light (Experiment 1) or the sound (Experiment 2) was lateralized to the ipsilateral or contralateral side of the action. Observers judged which of the two stimuli were presented first. Results. The point of subjective simultaneity (PSS) and just noticeable difference (JND) was computed. The PSS was shifted between the two SOAs such that the auditory stimulus had to be presented sooner in the 0 SOA condition (-106ms) compared to the 500ms SOA condition (-14ms). This contrasts starkly with classical results where the light must be presented before the sound (50ms) to be perceived simultaneously. The JND was smaller for the 0ms SOA condition. There was no effect of side of presentation. Conclusion. Action seems to speed the processing of visual stimuli relative to auditory stimuli. There was no support for the application of the unity assumption with action.