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Benjamin Wolfe, Jonathan Dobres, Anna Kosovicheva, Ruth Rosenholtz, Bryan Reimer; Reduction in Legibility with Degradation in Older and Younger Observers. Journal of Vision 2016;16(12):1420. doi: 10.1167/16.12.1420.
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© 2017 Association for Research in Vision and Ophthalmology.
Previous work examining the impact of a set of intrinsic and extrinsic features on relative legibility of typefaces has shown that legibility losses are more pronounced in older subjects (Dobres et.al, VSS 2014). To better understand the effects of visual degradation on legibility for older and younger subjects, we performed an experiment in which two groups of subjects (20-29 and 60-69 years old) were asked to perform a lexical decision task, determining whether a briefly presented stimulus (250 ms) was a word or non-word. All stimuli were generated in the typeface Frutiger, known from our previous work to be an easily-read typeface. To simulate the loss of sensitivity to high spatial frequencies (Elliott et.al, 1990) and the increase in intrinsic noise (Bennett et.al, 2007) both of which are realities for the aging visual system, we degraded our stimuli, on separate trials, by applying either Gaussian blur, or 1/f noise at a range of levels. For each subject, we estimated 75% performance thresholds by fitting accuracy at each level to separate psychometric functions for the blur and noise conditions. We find significantly higher thresholds in the 60-69 age group compared to the 20-29 age group in both the blur and noise conditions, suggesting that our older subjects' performance was more affected by small reductions in legibility. At a more granular level, we find significant reductions in performance at low levels of distortion in older subjects, but similar maximum levels of performance in both groups without distortion. Together, these results suggest that legibility is profoundly impacted by small manipulations or degradations of the letterforms, particularly for older subjects, and that accounting for this sensitivity is essential to facilitate legibility of written material across the age span.
Meeting abstract presented at VSS 2016
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