Vision seems to be a continuous process even though eye movements occupy a portion of the time spent in reading or inspecting objects in the field of view. This observation has led to the supposition that a “blanking out” of vision occurs with saccadic eye movements. Some workers attribute this effect to the rapid motion of the image on the retina. Others have suggested a central inhibition, possibly related to the physiological mechanisms of attention. The present research compared vision during saccades with vision during fixation by means of three representative psychophysical tasks. Each stimulus pattern was presented to the fovea in the form of an instantaneous flash that was delivered before, during, or after an eye movement. The flash lasted only 20 μsec, so that retinal blur due to movement was reduced to a negligible amount. The time of the stimulus flash was signaled on a continuously moving film on which the eye movements were recorded by a corneal reflection technique. Detection thresholds for dot patterns and recognition thresholds for words were found to be about 0.5 log unit higher during saccades than during steady fixation. Similar differences, though smaller and less consistent, were found in the minimum angles for the resolution of gratings. It is concluded that vision is not “blanked out” during eye movements, but that it is significantly depressed even under conditions that minimize blur due to movement of the retinal image, and that assure foveal stimulation.
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