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Matthew S. Cain, Stephen H. Adamo, Stephen R. Mitroff; What eye-tracking can tell us about multiple-target visual search. Journal of Vision 2012;12(9):1010. doi: 10.1167/12.9.1010.
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Many real-world visual searches contain multiple targets (e.g., a medical X-ray may have multiple tumors visible), and multiple-target searches present additional challenges beyond those of single-target searches. Specifically, finding one target can reduce the likelihood of finding a second target in the same array (a phenomenon dubbed ‘satisfaction of search’; Tuddenham, 1962), and this likelihood can be modulated by external factors such as anxiety (e.g., Cain, Dunsmoor, LaBar, & Mitroff, 2011). Multiple-target search effects have been examined in radiology (see Berbaum, et al., 2010) and in cognitive psychology (e.g., Fleck, Samei, & Mitroff, 2010), yet key questions remain about the underlying mechanisms. To address these questions, we utilized eye-tracking to provide insights into why targets are missed in multiple-target searches. Participants searched for perfect-T targets among pseudo-L distractors, with displays containing either 1 or 2 targets. Finding a first target in a multiple-target trial did not influence overall search performance (e.g., no change in average fixation time on distractors). However, analyses of the trials where the second target was missed revealed that: (1) second targets were not fixated on more than half of the multiple-target trials, and (2) when they were fixated, the average fixation length fell below the median fixation length for distractors. Collectively, this suggests that satisfaction of search is due, in part, to searchers not finding and fixating second targets long enough to determine their identity. These results present a different picture than previous radiological findings (Berbaum et al., 1998; Samuel et al., 1995), which found that missed targets were fixated the same amount of time regardless of whether or not another target had been detected. Satisfaction of search remains a very real problem, and these data suggest that the type of search and the searcher’s level of expertise may both play an important role.
Meeting abstract presented at VSS 2012
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