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Derek Arnold, Ryan Schindel; Visual sensitivity can scale with illusory size changes. Journal of Vision 2010;10(7):1391. doi: https://doi.org/10.1167/10.7.1391.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal image size is fundamental to human vision. It can place a necessary limit on sensitivity, as the retina is the instrument that transforms physical input into neural signals. However, retinal image size does not predict the apparent size of associated objects. Rather, images of the same physical dimensions can appear to represent different sized objects, as viewing distance is taken into account when determining apparent size. Here we take advantage of this to examine the relationship between visual sensitivity and the scaling processes involved in determining apparent size. We assess the impact of illusory size changes, induced by apparent viewing distance changes, on judgments concerning clearly visible stimuli and on the ability to detect low contrast inputs. We find that sensitivity to slight orientation changes, between successive and clearly visible stimuli, can scale with illusory size changes. However, illusory size changes do not impact on the ability to detect low contrast inputs. When considered in conjunction with recent brain imaging, our data suggest that visual sensitivity is linked to the spread of activity across primary visual cortex which, for clearly visible stimuli, is shaped by the scaling processes involved in the determination of apparent size.
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