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Gernot Horstmann, Arvid Herwig; Eye movements during highly inefficient visual search: What determines search efficiency differences in blank trials?. Journal of Vision 2013;13(9):527. doi: 10.1167/13.9.527.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction. Some targets in visual search are more difficult to find than others; for example, a target which is similar to the distractors is more difficult to find than a target which is dissimilar to the distractors. A remarkable result is that efficiency differences manifest themselves not only in target trials but also in blank (target absent) trials. In fact, even physically identical displays are searched through with different efficiencies depending on the searched-for target (e.g., Horstmann, Lipp, & Becker, 2012; http://www.journalofvision.org/content/12/5/7.full). Obviously, this effect is not driven by the target but by the search template. Because the focus of models of visual search is on target trials, theoretical or empirical treatments of blank trials have been presented only sporadically. Eye movements are examined to explore three hypotheses concerning the causes of differential search efficiencies in blank trials: (a) distractor skipping regulated by a variable threshold, (b) rescanning, and (c) dwell times. Methods. Participants performed a very inefficient search for two types of emotional target faces among neutral distractor faces. Target-distractor similarity (TDS) was varied between blocks: while in the high TDS blocks, the target was similar to the neutral distractors, in the low TDS blocks, the target was dissimilar to the distractors. The distractors were the same in all blocks. Results. Visual search times differed between the high and the low TDS condition, replicating earlier results. Eye movements were analyzed for skipping of distractors, rescanning of distractors, and gaze dwell times. Results showed that differences in dwell time and rescanning account for most of the search time differences between high and low TDS blocks. Conclusion. Low search efficiency in blank trials of high TDS blocks is mostly due to prolonged dwelling and more frequent rescanning of distractors, at least for a very inefficient search.
Meeting abstract presented at VSS 2013
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