Distortions of visual time induced by motor adaptation

As perception of time is fundamental for action planning and execution, we investigated how action distorts the perception of visual duration. Participants adapted to tapping in mid-air for a few seconds, either slowly or quickly, then judged the relative duration of two drifting gratings, one spatially coincident with the tapped region and the other in the opposite field. Fast tapping decreased apparent duration in the tapping region while slow tapping increased it. The effect was spatially specific in external (not body-centered) coordinates, occurring within a 10° region centered on the tapping hand. Within this space, motor adaptation similarly distorts visual numerosity, suggesting common mechanisms for number and time. However, motor adaptation did not affect the perception of speed, a lower level visual properties, suggesting that the interactions were at a high level of processing. These results reinforce studies suggesting that visual time perception is coupled with action, and suggest the existence of multiple local visuo-motor clocks.