Abstract
Humans appear to make extensive use visual information during rapid upper limb reaches (e.g., Elliott et al., 2010). In an attempt to assess the visual regulation of goal-directed action from a multisensory processing perspective, we recently employed an audio-visual illusion (e.g., Shams et al., 2000) presented at different times during rapid reaching movements. These previous results demonstrated that susceptibility to the fusion illusion (i.e., perceive one flash when two flashes are presented with one beep) is reduced at high limb velocities (Tremblay & Nguyen, 2010). That is participants were more likely accurately report two flashes in the fusion illusion condition only when their limb traveled at more than 1.5 m/s. However, one missing component of that study was a resting control condition, which we added in the present study. As in the previous study, we always presented either 1 or 2 beeps with 1 or 2 flashes. Our experimental design included one control resting condition, performed at the beginning or the end of the protocol (i.e., counterbalanced across participants). As well, in the main experimental phase, one of the 4 audio-visual conditions was presented at one of 5 times relative to the onset of a rapid reaching movement (0, 50, 100, 150, and 200 ms after movement start). All experimental phase conditions were presented pseudo-randomly, 12 times each. This current study first replicated the influence of limb velocity on the fusion illusion (i.e., more likely to accurately perceive both flashes when the limb travels the fastest). Also, we observed that participants were as likely to experience the fusion illusion in the resting control condition than early in the movement (i.e., at low limb velocity). Therefore, this study suggests that visual information processing is enhanced at high limb velocities, and that is, at least compared to auditory processing.
Natural Sciences and Engineering Research Council of Canada.