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Peter M. Vishton, Jordan Coulston; Abrupt stimulus motion eliminates task-specific immunity to pictorial illusions. Journal of Vision 2002;2(7):61. doi: https://doi.org/10.1167/2.7.61.
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Several studies have suggested that the grip-scaling component of manual prehension is largely immune to many salient pictorial illusions. More recent work has suggested that it is the focus of attention that accompanies reaching—not the choice of reaching vs. judgment behavior per se—that is primarily responsible for this immunity. Thus, if one judges the size of a single element of a display that serves as a reaching target, then the effects of pictorial illusions on judgment and reaching appear quite similar (small effects for the horizontal-vertical and Ebbinghaus illusions, large effects for the Mueller-Lyer illusion). If this account is correct, then if stimuli are generated so that it is difficult to focus attention on a single element, the effects of these pictorial illusions should return. This hypothesis was tested by presenting participants with the horizontal-vertical, Ebbinghaus, and Mueller-Lyer illusions. Some participants made comparative judgments about the key elements of these displays; others made metric judgments about the sizes of single elements in millimeter units. Half of the stimuli were stationary; the other half abruptly shifted position on the computer screen at a rate of 5 Hz. The stimulus movement did not affect comparative judgments or judgments of non-illusion inducing stimuli. However, the effects of the horizontal-vertical and Ebbinghaus illusions were significantly increased. These findings provide further evidence that perception and action control are mediated by similar information processing systems. This work was supported in part by Northwestern University start-up funds and NIH grant 1-R01-HD40827-01.
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