Resistance to positional noise in human vision

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Abstract
HUMAN eyes are in constant and rapid motion even when observers try to maintain steady fixation1,2. Also, the visual system has a sluggish temporal response3. In combination, these two factors would be expected to blur stimuli and reduce spatial sensitivity4,5. But observers are able to detect a difference in separation of a few seconds of arc between two closely spaced parallel lines6. Here we report that even very large amounts of positional jitter of the line pair has minimal impact on this ability. This result is in marked contrast to the deterioration observed when targets are swept linearly across the retina5, but is consistent with a system that must ignore oculomotor jitter. To explain these results will require a re-evaluation of current models of position coding in human vision5,7,8.