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Martin Lages, Stephanie Boyle, Rob Jenkins; Illusory Expansion Improves Visual Acuity. Journal of Vision 2015;15(12):12. doi: https://doi.org/10.1167/15.12.12.
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© ARVO (1962-2015); The Authors (2016-present)
A Snellen-type chart is commonly used for routine eye examination. This test serves as a benchmark for visual acuity where observers read out Sloan letters of decreasing size at a recommended viewing distance. The smallest readable letter size is typically used as a measure of visual acuity. For example, vision of 20/20 and 10/10 describes the ability to resolve letters subtending 5 minutes of arc at a viewing distance of 20 (6m) and 10 feet (3m), respectively. Here we show that adaptation to a rotating spiral and the ensuing motion aftereffect (MAE) significantly alters visual acuity in observers with normal or corrected-to-normal vision. In a first group n=44 observers adapted to contracting motion and in a second group n=30 observers adapted to expanding motion before reading out a string of five letters. The results demonstrate that the expanding MAE significantly facilitated subsequent letter recognition whereas the contracting MAE impaired letter recognition. There also was an effect of crowding between letters but the absence of a significant interaction indicated that the adaptation effect was not qualified by crowding. We conclude that illusory expansion increases perceptual fields by recruiting additional feature detectors thereby enlarging the apparent size of letters. Illusory contraction on the other hand decreases perceptual fields and number of feature detectors thereby reducing the apparent size of letters. It is a special feat of the visual system that adaptation to motion can improve visual acuity - a measure that is typically associated with refractive error in the optics of the eyes rather than perceptual inference. We speculate that optimal integration (multiplexing) of information from motion and form processing is responsible for this surprising effect.
Meeting abstract presented at VSS 2015
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