Abstract
Recent research showed improvement on a motor synchronization task when tapping along to a bouncing ball stimulus in comparison to flashes (Iversen et al., 2015). However, it was unclear whether the bouncing ball was benefitting the motor system or the visual system while participants performed the task. In experiment 1 we implemented similar bouncing ball and flash stimuli to test whether the ball gave a perceptual timing advantage compared to the flash on a temporal interval discrimination task. Participants were asked to judge which pair of events contained the longer temporal interval. We found a three-fold decrease in threshold when participants performed the task with the bouncing ball stimulus compared to the flash. However, the speed of the ball confounded the temporal interval such that a fast ball indicated a short temporal interval. Participants may have used speed to perform the task. In experiment 2 we controlled for speed by selecting a constant bounce trajectory that defined the events that specified the temporal intervals. If speed were the cue used to respond in experiment 1, then we hypothesized performance would be poor across all conditions in experiment 2. Another cue that participants might’ve used to perform well with the ball in experiment 1 was its continuity of motion. We created five bouncing ball conditions that varied by how many samples of motion were shown. If continuity of the ball’s motion were important in experiment 1, then we hypothesized that performance in experiment 2 would be a function of the number of samples shown in each condition. The data supported the hypothesis that speed information was being used in experiment 1, as performance on all conditions in experiment 2 was poor. Thus, it seems speed was useful and continuous motion was irrelevant for these temporal interval discrimination experiments.