Abstract
Observer's active control of the stimulus movement by the use of computer mouse reduces the flash-lag effect (Ichikawa & Masakura, 2006 Vision Research, 2010 AP&P). Results of these previous studies suggested that the reduction of the flash-lag effect for the moving stimulus depends upon the learning of the directional consistency between the hand movement and stimulus movement in everyday-computer use. In order to examine the effects of directional consistency between hand movement and visual stimulus change, we measured the flash-lag effect for the luminance change in which there was no intrinsic directional relationship between hand movement and luminance change in computer use. In the active condition, the luminance of the visual stimulus was controlled by the use of computer-mouse while, in the automatic condition, the luminance changed automatically. In the active condition, there were two conditions which concerned with the directional relationship between hand movement and luminance change in visual stimulus. In the consistent direction condition, the luminance increment and decrement were always coupled with backward and forward hand movement, respectively. In the inconsistent direction condition, the luminance increment and decrement were respectively coupled with backward and forward hand movement in half of the trials while they were respectively coupled with forward and backward hand movement in the remaining trials. We found that the reduction of the flash-lag effect in the active condition was restricted to the consistent direction condition. The observers who had participated in sessions with the inconsistent direction condition showed no significant reduction of the flash-lag effect in additional observation with the consistent direction condition. These results suggest that the proprioceptive signal to control the visual stimulus would be effective in reducing the flash-lag effect in terms of motor-visual cooperation only when the directional relationship between hand movement and stimulus change is always consistent.
MI is supported by JSPS grant (#21530760).