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Patrick Cavanagh, Alex O. Holcombe; Non-retinotopic crowding. Journal of Vision 2007;7(9):338. doi: 10.1167/7.9.338.
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Sixteen radial arms are presented, each with a test letter at the third location from the center, flanked by 2 distractors on each side. The display counterphases targets and distractors in the following way: in one frame, every even arm (2nd, 4th, ..) shows only the target without distractors, while the odd arms (1st, 3rd, ..) show only the distractors without the targets; in the other frame, odd arms show distractors while even arms show the targets. When attending to any one location, a flickering test is seen, surrounded by flickering distractors. However, when a guide (a faint radial sector) moves from arm to arm in phase with the alternation, it contains only the test letter and no flankers. Targets are presented either in normal or mirror reversed orientation. Subjects fixate the center of the array and report the orientation of the test. When attention is directed to one fixed location, there is substantial interference from the flanking letters. However, when following the guide, crowding is much reduced, suggesting that crowding is specific to the flankers, if any, that move with the target and not to the letters that surround each target locally in retinotopic coordinates.
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