Motor commands induce time compression for tactile stimuli

Abstract

Saccades cause compression of visual space towards the saccadic target, and also a compression of time, both phenomena thought to be related to the problem of maintaining saccadic stability. Interestingly, similar phenomena occur around the time of hand movements, when brief tactile stimuli are systematically mislocalized in the direction of the movement. In this study we measured whether hand movements also cause an alteration of the perceived timing of the touch signals. Participants compared the temporal separation between two pairs of tactile taps delivered to either the right moving or left stationary hand. An auditory tone cued participants to move their right hand as fast as possible along a track. At variable delays from sound presentation the first pair of tactile taps (test) was presented with a fixed onset asynchrony of 150 ms. After 2 s from test presentation the second pair of taps was delivered (probe) with a variable temporal separation. When the tactile stimuli were presented on the motor effector, their perceived temporal separation was reduced. The time compression began approximately 150 ms before movement onset, it increased until just before the hand started moving and continued during the movement. The time compression was effector-specific, as perceived time was veridical for the left stationary hand, ruling out high-level attentional modulation. The results indicate that tactile time intervals are compressed around the time of hand movements. As for vision the mislocalizations of time and space of touch stimuli may be consequences of a mechanism attempting to achieve perceptual stability.