Abstract
In our previous study, we found that observer's active control of the stimulus movement would reduce the illusory flash-lag effect when the upward (downward) movement of the stimulus on the front parallel display is coupled with the forward (backward) mouse movement on the desk, as in most computer operating systems (Ichikawa & Masakura, 2006 Vision Research). In this study, we examined whether the repetitive observation with the directional relationship between the stimulus and hand movements, which is opposite to the one used in most computer operating systems, and therefore unfamiliar to observers, would affect the flashlag effect. In the active condition, 28.8 arc deg of vertical movement of the stimulus (19.1 x 19.0 arc min) on the display corresponded to about 30.0 cm of the mouse movement on the desk. The upward (downward) movement of the stimulus was coupled with the backward (forward) mouse movement. In the automatic condition, the stimulus moved automatically with a constant velocity which was determined by the average of the stimulus movement in the active condition. A flash stimulus (19.1 x 19.0 arc min) was presented beside the moving stimulus. The vertical position lag between the flash and moving stimuli ranged from -76.0 to 76.0 arc min by 19.0 arc min step (negative value indicates that the position of the flash was behind of the moving stimulus). Observers judged whether the moving stimulus was below or above the flash. We measured the flash-lag effect for the active and automatic conditions before and after 360 training trials with the unfamiliar relationship between mouse and stimulus movements. We found that, after the training trials, the flash-lag effect was reduced only in the active condition. This result suggests that the learning of a specific directional relationship between hand and stimulus movements would reduce the flash-lag effect.
Grant-in-Aid for Scientific Reserach #21530760, JSPS.