Auditory clicks distort perceived velocity but only when the system has to rely on extra-retinal signals.
Makin, A. D. J., Lawson, R., Bertamini, M., & Pickering, J.
Previous work has found that repetitive auditory stimulation (click trains) increase the subjective velocity of subsequently presented moving stimuli. We ask whether the effect of click trains is stronger for retinal velocity signals (produced when the target moves across the retina) or for extra-retinal velocity signals (produced during smooth pursuit eye movements, when target motion across the retina is limited). In Experiment 1, participants viewed leftward or rightward moving single dot targets, travelling at speeds from 7.5 to 17.5 deg/s. They estimated velocity at the end of each trial. Prior presentation of auditory click trains increased estimated velocity, but only in the pursuit condition, where estimates were based on extra-retinal velocity signals. Experiment 2 generalised this result to vertical motion. Experiment 3 found that the effect of clicks during pursuit disappeared when participants tracked across a visually textured background that provided strong local motion cues. Together these results suggest that auditory click trains selectively affect extra-retinal velocity signals. This novel finding suggests that the cross-modal integration required for auditory click trains to influence subjective velocity operates at later stages of processing.
Quarterly Journal of Experimental Psychology (2013), 67, 455-473.