Recent studies have shown that auditory signals can induce motion perception of a static visual stimulus, or ‘‘Sound-Induced-Visual-Motion” [SIVM; 1, 2]. Here we explore in two experiments whether motor movements can also change perceived visual motion. In Experiment 1, participants judged the direction of two flashing horizontal bars that either moved upward or downward (with 0.1; 0.4; 0.7 or 1.0 deg vertical bar displacement). For testing the effect of co-occurring motor movements of the hand, participants were instructed to make two button-presses, either upward (right thumb on lower button followed by right index on upper button) or downward (up-down), and the visual bars were presented at the timing of the button-presses. The results demonstrate overall more upward responses when the motor movement was upward and more down-ward responses when moving downward confirming a “Motor-Induced-Visual-Motion” (MIVM). In Experiment 2, the role of response bias was excluded in a d’prime paradigm in which each trial consisted of 6 flashing vertical bars that were either moving (left-right-left etc.) or static. Participants judged whether the bar was moving or static. Participants performed a moving motor-movement (left hand index button press followed by right hand index button press), a static motor movement (pressing twice with left or right index) or no motor movement (visual condition). Results showed more illusory motion (lower d’prime) when participants performed a moving motor movement as compared to the static or no motor movement conditions. Together these two experiments demonstrate Motor-Induced-Visual-Motion, showing that motor movements can affect ambiguous visual motion perception.

Motor-movements; visual motion perception