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Susana T. L. Chung, Dennis M. Levi, Roger W. Li; Learning to identify contrast-defined letters in peripheral vision. Journal of Vision 2005;5(8):861. doi: 10.1167/5.8.861.
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© ARVO (1962-2015); The Authors (2016-present)
Performance for identifying luminance-defined letters in peripheral vision improves with training. The purpose of the present study was to examine whether performance for identifying contrast-defined letters also improves with training in peripheral vision, and whether any improvement transfers to luminance-defined letters. Eight observers were trained to identify contrast-defined letters presented singly at 10° eccentricity in the inferior visual field. Before and after training, we measured observers' contrast thresholds for identifying luminance-defined and contrast-defined letters, embedded within a field of white luminance noise (RMS contrast = 0, 0.25 and 0.5), at the same eccentric location. Training consisted of 10 blocks of identifying contrast-defined letters at a background noise contrast of 0.5. Letters (x-height = 4.2°) were the 26 lowercase letters of the Times-Roman alphabet. Luminance-defined letters were generated by introducing a luminance difference between the stimulus letter and its mid-gray background. The background noise covered both the letter and its background. Contrast-defined letters were generated by introducing a differential noise contrast between the group of pixels that made up the stimulus letter and the group of pixels that made up the background. Following training, observers showed a reduction in contrast threshold for identifying contrast-defined letters. Averaged across observers and background noise contrasts, the reduction was 29%, with the greatest reduction (36%) occurring at the trained background noise contrast (0.5). There was little transfer of improvement to luminance-defined letters (average threshold reduction = 9%). Our results extend previous findings (Dosher & Lu, VSS 2004) in showing that training also improves performance for identifying contrast-defined letters in peripheral vision. This learning effect seems to be stimulus-specific, as it shows little transfer to the identification of luminance-defined letters.
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