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Christopher M. Fiacconi, Allison B. Sekuler, Patrick J. Bennett; The effects of aging on contrast discrimination. Journal of Vision 2009;9(8):1073. doi: 10.1167/9.8.1073.
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© ARVO (1962-2015); The Authors (2016-present)
It is well established that contrast sensitivity for sine wave gratings is reduced in older observers, but comparatively little is known about how aging affects the perception of supra-threshold contrast. The current experiments therefore examined contrast discrimination in groups of younger (n=11; mean age = 23 years) and older (n=12; mean age = 69 years) observers. In experiment one, the target — a horizontal 1.5 c/deg Gabor pattern — was added to a mask grating of the same spatial frequency, orientation, and spatial phase. Threshold-vs-contrast (TvC) curves were obtained by measuring detection thresholds for the target as a function of mask contrast, which ranged from zero to 0.32. As was reported by Beard et al. (1994), TvC curves had similar dipper shapes in both age groups. Contrast discrimination thresholds were higher in older observers, but the age differences were reduced greatly after discrimination thresholds were normalized by dividing them by detection thresholds (i.e., thresholds measured with a zero contrast mask). In a second experiment, TvC curves were measured using a vertically-oriented mask. As expected, using a mask that was orthogonal to the target significantly altered the shapes of the TvC curves, which were nearly flat and increased slightly only at the highest mask contrast. Contrast discrimination thresholds were higher in older observers, but, as was found in the first experiment, age differences were eliminated by normalizing discriminating thresholds by detection thresholds. Hence the results from both experiments suggest age differences in supra-threshold contrast discrimination can be explained by age differences in contrast sensitivity.
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