Los, S. A. & Van der Burg, E.
VU University, Amsterdam, Netherlands
A well known finding in the human reaction time (RT) literature is that an irrelevant auditory stimulus (S1) reduces RT for a simultaneous visual target stimulus (S2). Two explanations have been offered for this finding: (1) the information of the visual and auditory senses merge to yield a stronger percept than when the visual stimulus is presented alone (i.e., multisensory integration); (2) the auditory S1 arrives earlier at a central level than the visual S2 and initiates a preparation process that reduces RT (i.e., temporal preparation). Starting from the temporal preparation explanation, we devised a procedure that allowed us to estimate the effective preparation period (EPP) - the interval between S1 and S2 corrected for differences in their central arrival times. In addition, we manipulated the stimulus onset asynchrony (SOA) between S1 and S2 (0 - 400 ms) in conjunction with the modality of S1. When expressed as a function of SOA, we observed a substantial effect of S1 modality on RT. However, this effect disappeared completely after re-expressing RT as a function of EPP. This finding strongly supports the temporal preparation explanation.