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Alissa R. Cantone, Katharine A. Tillman, Denis G. Pelli; Eccentric features integrate slowly. Journal of Vision 2008;8(6):653. doi: 10.1167/8.6.653.
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We read more slowly in the periphery, even though speed of information processing is faster there (Carrasco et al., 2003, Nature Neuroscience). At an eccentricity of 15 degrees, we read more slowly by a factor of 3.5. We get slower as eccentricity increases, even when the stimuli are presented at optimal print size and spacing at each eccentricity. Why is peripheral reading slower? In this study, we minimize the need for eye movements by using Rapid Serial Visual Presentation (RSVP). We measure “reading” rates for stimuli of various complexities — words (in context), 26 letters, two letters, and gratings (of two different orientations) — presented at eccentricities of 0 and 15 degrees. A stream of six items is presented at a variable rate and the reader names the items at leisure. The QUEST staircase procedure homes in on the threshold presentation rate for 80% accuracy. We find that the eccentricity effect (the ratio of “reading” rates at 0 and 15 degrees) is 3.5 for words (in context), 3 for 26 letters, 1.5 for two letters, and 1 (no eccentricity effect) for gratings. The eccentricity effect decreases with decreasing complexity (fewer features required), and it disappears when reading becomes a one-feature task. No integration is needed when a single feature suffices to distinguish the two items. Slower feature integration impairs peripheral reading.
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