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Christine Gamble, Joo-Hyun Song; Impact of conscious versus unconscious distractors in pop-out visual search. Journal of Vision 2016;16(12):1319. doi: 10.1167/16.12.1319.
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It has consistently been demonstrated that in singleton pop-out search, increasing the number of homogenous distractors reduces reaction time (RT) for target discrimination. This is thought to be due to larger overall set sizes facilitating the grouping of visual stimuli. However, it is currently unknown how unconscious visual stimuli compare to conscious stimuli in visual search, and the degree to which conscious awareness is necessary for grouping and singleton pop-out. In the present study, we directly compared the influence of conscious versus unconscious distractor number on singleton pop-out in visual search. In order to establish the facilitation of pop-out via conscious distractor grouping, we presented participants with a target of either red or green, and between 3 and 20 distractors of the alternate color. To determine the influence of unconscious distractors on pop-out, we replicated these conditions using a continuous flash suppression (CFS) paradigm designed to suppress awareness of all but 2 of the distractors. We measured participants' RT to correctly identify the shape of the singleton target via button-press, and compared these RTs across distractor number and conscious versus unconscious distractor presentation. Consistent with past visual search studies, we found that increasing the number of conscious distractors caused a linear decrease in RT, consistent with search facilitation via grouping. However, unconscious distractor presentation had the opposite effect, with increasing numbers leading to an overall increase in RT. This indicates that participants still processed unconscious distractors despite a lack of conscious visual awareness. However, rather than facilitating visual search as conscious distractors do, unconscious distractors interfered with visual search, likely due to a failure of grouping. This suggests that in visual search unconscious stimuli are processed inherently differently from conscious stimuli, and that stimulus grouping may be a primarily conscious process.
Meeting abstract presented at VSS 2016
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