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Jeff Moher, Howard Egeth, Steven Yantis, Veit Stuphorn; Top-down control modulates the effect of capture based on distractor probability. Journal of Vision 2008;8(6):1119. doi: 10.1167/8.6.1119.
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There are differing views regarding whether or not top-down control can mediate the effect of an irrelevant salient distractor during search for a target (e.g., Theeuwes, 1991 and Bacon and Egeth, 1994). Recent work in our lab (Moher et. al, 2007) has shown that the cost of a distractor in a visual search task differs depending on the probability of that distractor appearing in a given block. When a highly expected distractor appears, participants make faster saccades to a target and make fewer incorrect saccades compared to when an unexpected distractor appears. However,it was possible that implicit perceptual learning was causing participants to habituate the orienting response to more common distractors since the trials were blocked (Sokolov, 1975). In order to further investigate this prospect, we created a mixed-block design where participants received a cue prior to each trial informing them of the probability that a distractor would occur on the upcoming trial. In a visual search task where participants were required to respond with a manual response to the letter inside the unique shape in a display, the cost of a color distractor (the difference in reaction time between a correct response on a distractor versus a no-distractor trial) was greater in the 10% condition (154 ms) compared to the 90% condition (54 ms, p[[lt]].05). Initial eyetracking data suggest that the difference in error rates between distractor and no-distractor trials is greater with a 10% distractor probability cue (13%) compared to a 90% distractor probability cue (4%). Overall, these data suggest participants are able to use top-down control in order to adopt an attentional set consistent with their expectation of an upcoming irrelevant distractor, and that highly expected distractors cause less interference in the search for a target.
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