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Eric D. Richards, Lilly Demiglio, Allison B. Sekuler, Patrick J. Bennett; Age-related differences in shape perception. Journal of Vision 2004;4(8):517. doi: 10.1167/4.8.517.
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Object perception is a critical component of vision, but we know almost nothing about how it is affected by age. Indeed, in contrast to older observers' self reports, one recent study suggests that a pre-cursor to object perception, global shape discrimination, is relatively spared as a function of age (Wang, 2001). Notably, although Wang's primary study used unlimited viewing time, his preliminary work with variable stimulus duration suggests that older observers may be impaired at durations under 1s. Such a result would fit well with the idea that the true extent of age-related deficits are more likely to be seen under conditions that challenge the visual system (e.g., in the presence of noise, with increased task complexity, at shorter stimulus durations). Here, we re-examine the issue of whether aging affects global shape perception in the context of a visual completion task, in which stimulus duration is manipulated as a within-subject variable. Such a task has the advantage that we can compare the relative effects of age and duration under conditions in which all the sensory information is provided (complete), only partial information is provided (fragmented), and when partial information leads to integration processes (occluded). Following Murray et al. (2001), observers viewed complete rectangles or line fragments of rectangles (with or without occluders), and judged whether the overall shape was “tall” or “fat”. We used a staircase procedure to estimate the aspect ratio that led to 71% correct performance in each condition for young and old observers with stimulus durations of 75, 150 and 500 ms. Overall, older observers required larger aspect ratios to perform the task. However, young and old observers showed the same pattern of performance across stimulus conditions and durations. Our results suggest that aging can have a negative impact on object perception, although older observers are not differentially impaired by partial contour information.
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