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C. S. Barnes, W. De l'Aune, R. A. Schuchard; Characteristics Affecting Performance Variability on a Face Discrimination Test. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4727.
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A previous pilot study of a novel Face Discrimination test showed variability in response times and accuracies both in older control subjects and in individuals with low vision. The purpose of the present study was to further investigate the effects of age, visual acuity, and contrast sensitivity on test performance.
25 subjects with normal age-related vision (22-30 or 60-82 yrs old), and 16 individuals diagnosed with age-related macular degeneration (64-87 yrs) had binocular visual acuity and contrast sensitivity measured with the ETDRS and Pelli-Robson charts. In separate halves of the Faces test, colour photographs of 8 male or 8 female faces were presented continuously. On each trial, subjects matched the central test face to one of the comparison faces, as quickly but accurately as possible. Test faces differed from the comparison faces in pose and/or expression. Outcome measures were response time (RT) for face discrimination, and percent correct responses. Differences listed were statistically significant at p<0.05.
The young subjects responded quickly (subjects’ mean RTs from 2.1 to 2.7 s), with almost no errors. RTs for the older normal subjects were longer and more variable (means from 4.7 to 6.7 s), and they made more errors. However, in addition to being older, those subjects had lower visual acuities and contrast sensitivities than the young subjects. Across all 41 subjects, visual acuity and contrast sensitivity both contributed significantly to the variances in RTs and accuracy (e.g., largest R2 was 0.30 for contrast sensitivity for RT). RT Stdevs (within subject variances) were more closely related to mean RTs than to characteristics such as visual acuity.
The ceiling effect on accuracy for younger subjects suggests limitations on use of this test. Older subjects had wider-ranging scores, consistent with greater variability reported with aging in other psychophysical studies. Data across a wider range of subjects would help to clarify the variation in face discrimination performance within and between subjects.
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