Abstract
Many studies have shown that relative visual localizations of briefly flashed stimuli are systematically modified in the presence of motion signals. These studies imply that perceived visual space may be distorted due to motion signals. To explicitly test this space-distortion hypothesis, the detailed 2-dimensional spatial mapping of mislocalization was performed.
A moving black disk was presented while observers fixating a stationary cross. A white disk was briefly presented ahead of or behind the moving disk with a vertical offset. The observer adjusted the position of the flash to indicate where the flash had been perceived relative to the moving stimulus. A flash ahead of a moving disk was perceived to lag more than a flash behind the moving disk. Moreover, the pattern of positional shifts indicated that perceived positions were distorted toward a point behind a moving stimulus. The convergent point was not influenced by the variation in the velocity of a moving stimulus. These results support the space-distortion hypothesis.
To clarify the process of the asymmetric mislocalization, the shape perception of a flash stimulus was evaluated by presenting two disks simultaneously and connecting them with a line. It was found that mislocalization was similar to that with single flash. However, the shape of connected flashes was not changed, except for space around the moving stimulus. These results suggest that the asymmetric mislocalization originates from the shift of the positional information of represented visual object, not from the distortion of space itself (i.e., medium of positional representation.)