Perception of continuous flicker: phantom array versus moving stimuli

During saccadic eye movements, an image is displaced on the retina, and the visual system must recalculate its position to maintain perceptual space constancy. However, when the flickering light is presented during the saccade, a phenomenon of the phantom array of lights is perceived. A similar array of lights can be perceived when a moving and flickering stimulus is presented during visual fixation. Here, we investigated differences in spatial and temporal aspects of the perception of flickering light during saccade versus flickering light movement during visual fixation. In the first experiment, the subjects made a saccade across a point light source flashing from 50 Hz to 4 kHz. In the second experiment, a moving and flickering stimulus was presented on the screen while the subjects maintained steady visual fixation. The speed of the stimulus was set to the same as the saccade speed for each subject. Subjects were asked to indicate the beginning and end of the array of lights, to evaluate the length of one dash, and to count the number of dashes. We found that the perceived length and localization of the moving lights array approximately corresponded to the physical representation of the stimulus on the retina, but during the saccade, a shorter length of the phantom array was perceived, and localization greatly varied between subjects. The phantom array was always perceived as composed of a smaller number of dashes compared to the moving lights array. However, the size of one dash was perceived to be of similar length as projected on the retina during both conditions. Therefore, we can state that the visual space is not compressed in size, but is compressed in time during saccades. The visual system reduces information flow by quantization mechanism and removes some repeatable representations of the same object from perceptual space.