Abstract
Observers would fail to detect the sudden image change when multiple distracters are presented in the scene (change blindness as a result of mudsplashes). We found that a single small flash may induce the blindness for the shape change of a moving stimulus (19.1 × 19.0 arc min). The moving stimulus went upward or downward with a constant velocity (9.8 arc deg/s) along a linear course at 2.6 arc deg right or left of the fixation point. A flash stimulus (1.6 × 0.3 arc deg) was presented at 5.5, 11.6, or 17.6 arc deg from the fixation point in the same visual field with the moving stimulus. In the half of 120 trials, the moving stimulus changed its horizontal length to 57.3 arc min at the moment of the flash. Observer's task was to detect the shape change of the moving stimulus. In 37% of the trials for the nearest flash to the fixation point, observers could not detect the shape change. Such a frequent fail in change detection was not obtained for the stationary stimulus. In the other experiment, we examined how the ipsilateral and contralateral presentation of the flash and moving stimulus affect the blindness by the use of nine time lag conditions between the shape change and flash, which ranged from −133.3 to 133.3 ms (negative and positive values indicate that the flash preceded or followed the shape change, respectively). Only when the flash and moving stimulus were presented in the ipsilateral visual field, observers missed the shape change in at least 30% of the trials with the time lag conditions from −66.7 to 33.3 ms. These results indicate that the visual system has limitation to notice events within a specific period, in particular for the moving object in the same visual field with the flash.