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Christian Poth, Arvid Herwig, Werner Schneider; Perturbing object stability across saccadic eye movements facilitates displacement detection but hinders object recognition. Journal of Vision 2015;15(12):883. doi: https://doi.org/10.1167/15.12.883.
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© ARVO (1962-2015); The Authors (2016-present)
By making saccadic eye movements, we can bring interesting peripheral objects into the fovea for high-acuity examination. Every saccade abruptly displaces and alters the retinal image of objects. Nevertheless, we perceive objects as stable in their locations. The visual system seems to deal with the retinal image displacement by actively assuming object stability across saccades. This assumption seems to be responsible for concealing actual object displacements across the saccade, rendering them hard to detect (cf. Bridgeman et al., 1975, Vis Res). Pre-saccadic object representations are updated with post-saccadic information, leaving only the latter one accessible and impairing displacement detection. In contrast, briefly showing a post-saccadic blank screen prior to the shifted object improves displacement detection (Deubel & Schneider, 1994, BBS). Such blanking may violate the assumption of object stability. Pre-saccadic object representations should then be maintained separately from post-saccadic ones. Here, we investigated whether perturbing object stability during saccadic eye movements affects the recognition of post-saccadic objects. Observers saccaded to an abruptly appearing peripheral ellipse. The ellipse was displaced during the saccade to the left or right. After the saccade, the ellipse was either blanked for 100 ms (blank condition) or immediately shown (no-blank condition). Then a letter appeared within the ellipse (80 ms), followed by a pattern mask (300 ms). In two different blocks of trials, observers either reported displacement direction or letter identity. Reports of displacement direction were more accurate in the blank compared to the no-blank condition. Strikingly, this was reversed for reports of the post-saccadic letter, for which accuracy was lower in the blank than in the no-blank condition. Blanking may improve displacement detection by preventing updating of pre-saccadic object representations so that these are separately maintained (Schneider, 2013, Phil Trans B). This extra pre-saccadic and non-updated object representation interferes with competitive post-saccadic object recognition.
Meeting abstract presented at VSS 2015
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