Visual determinants of a cross-modal illusion

Contrary to the predictions of established theory, Schutz and Lipscomb (2007) have shown that visual information can influence the perceived duration of concurrent sounds. In the present study, we deconstruct the visual component of their illusion, showing that (1) cross-modal influence depends on visible cues signaling an impact event (namely, a sudden change of direction concurrent with tone onset) and (2) the illusion is controlled primarily by the duration of post-impact motion. Other aspects of the post-impact motion--distance traveled, velocity, acceleration, and the rate of its change (i.e., its derivative, jerk)--play a minor role, if any. Together, these results demonstrate that visual event duration can influence the perception of auditory event duration, but only when stimulus cues are sufficient to give rise to the perception of a causal cross-modal relationship. This refined understanding of the illusion's visual aspects is helpful in comprehending why it contrasts so markedly with previous research on cross-modal integration, demonstrating that vision does not appreciably influence auditory judgments of event duration (Walker & Scott, 1981).