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Gaze in Visual Search Is Guided More Efficiently by Positive Cues than by Negative Cues.

Kugler G, 't Hart BM, Kohlbecher S, Einhäuser W, Schneider E - PLoS ONE (2015)

Bottom Line: Participants exhibited longer response times when provided with negative cues compared to positive cues.Negative cues resulted in smaller proportions of fixations on relevant items, longer duration of fixations and in higher rates of fixations per item as compared to positive cues.The effectiveness of both cue types, as measured by fixations on relevant items, increased over the course of each search.

View Article: PubMed Central - PubMed

Affiliation: Institute of Clinical Neurosciences, University of Munich, Munich, Germany.

ABSTRACT
Visual search can be accelerated when properties of the target are known. Such knowledge allows the searcher to direct attention to items sharing these properties. Recent work indicates that information about properties of non-targets (i.e., negative cues) can also guide search. In the present study, we examine whether negative cues lead to different search behavior compared to positive cues. We asked observers to search for a target defined by a certain shape singleton (broken line among solid lines). Each line was embedded in a colored disk. In "positive cue" blocks, participants were informed about possible colors of the target item. In "negative cue" blocks, the participants were informed about colors that could not contain the target. Search displays were designed such that with both the positive and negative cues, the same number of items could potentially contain the broken line ("relevant items"). Thus, both cues were equally informative. We measured response times and eye movements. Participants exhibited longer response times when provided with negative cues compared to positive cues. Although negative cues did guide the eyes to relevant items, there were marked differences in eye movements. Negative cues resulted in smaller proportions of fixations on relevant items, longer duration of fixations and in higher rates of fixations per item as compared to positive cues. The effectiveness of both cue types, as measured by fixations on relevant items, increased over the course of each search. In sum, a negative color cue can guide attention to relevant items, but it is less efficient than a positive cue of the same informational value.

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Search array examples.A: Array in positive cue type: “target will be blue”. B: Array in negative cue type: “target will not be blue”. Both arrays have the same spatial configuration of items and the target. The colors of the items were switched. The target is at the same location in the lower left corner. Search arrays are not to scale.
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pone.0145910.g001: Search array examples.A: Array in positive cue type: “target will be blue”. B: Array in negative cue type: “target will not be blue”. Both arrays have the same spatial configuration of items and the target. The colors of the items were switched. The target is at the same location in the lower left corner. Search arrays are not to scale.

Mentions: In two experiments, observers were asked to perform a search task among a set of items. All items consisted of a colored disk, in which a vertical black line (0.37 degrees of visual angle) was embedded. In half of the trials, one line had a gap (0.06 degrees) in its center (Fig 1). The item that contained the broken line will be referred to as “target”, the remaining (i.e., non-target) items as “foils”. Identifying the gap required foveation of the target, as verified by pilot measurements, thus encouraging serial inspection of items. Observers were asked to report in each trial whether such a broken line was present or absent as quickly and accurately as possible, by pressing a corresponding button on a modified keypad with two buttons. The display was on until the participant responded. Times from onset of the search array until button activations were recorded (“response time”).


Gaze in Visual Search Is Guided More Efficiently by Positive Cues than by Negative Cues.

Kugler G, 't Hart BM, Kohlbecher S, Einhäuser W, Schneider E - PLoS ONE (2015)

Search array examples.A: Array in positive cue type: “target will be blue”. B: Array in negative cue type: “target will not be blue”. Both arrays have the same spatial configuration of items and the target. The colors of the items were switched. The target is at the same location in the lower left corner. Search arrays are not to scale.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4696836&req=5

pone.0145910.g001: Search array examples.A: Array in positive cue type: “target will be blue”. B: Array in negative cue type: “target will not be blue”. Both arrays have the same spatial configuration of items and the target. The colors of the items were switched. The target is at the same location in the lower left corner. Search arrays are not to scale.
Mentions: In two experiments, observers were asked to perform a search task among a set of items. All items consisted of a colored disk, in which a vertical black line (0.37 degrees of visual angle) was embedded. In half of the trials, one line had a gap (0.06 degrees) in its center (Fig 1). The item that contained the broken line will be referred to as “target”, the remaining (i.e., non-target) items as “foils”. Identifying the gap required foveation of the target, as verified by pilot measurements, thus encouraging serial inspection of items. Observers were asked to report in each trial whether such a broken line was present or absent as quickly and accurately as possible, by pressing a corresponding button on a modified keypad with two buttons. The display was on until the participant responded. Times from onset of the search array until button activations were recorded (“response time”).

Bottom Line: Participants exhibited longer response times when provided with negative cues compared to positive cues.Negative cues resulted in smaller proportions of fixations on relevant items, longer duration of fixations and in higher rates of fixations per item as compared to positive cues.The effectiveness of both cue types, as measured by fixations on relevant items, increased over the course of each search.

View Article: PubMed Central - PubMed

Affiliation: Institute of Clinical Neurosciences, University of Munich, Munich, Germany.

ABSTRACT
Visual search can be accelerated when properties of the target are known. Such knowledge allows the searcher to direct attention to items sharing these properties. Recent work indicates that information about properties of non-targets (i.e., negative cues) can also guide search. In the present study, we examine whether negative cues lead to different search behavior compared to positive cues. We asked observers to search for a target defined by a certain shape singleton (broken line among solid lines). Each line was embedded in a colored disk. In "positive cue" blocks, participants were informed about possible colors of the target item. In "negative cue" blocks, the participants were informed about colors that could not contain the target. Search displays were designed such that with both the positive and negative cues, the same number of items could potentially contain the broken line ("relevant items"). Thus, both cues were equally informative. We measured response times and eye movements. Participants exhibited longer response times when provided with negative cues compared to positive cues. Although negative cues did guide the eyes to relevant items, there were marked differences in eye movements. Negative cues resulted in smaller proportions of fixations on relevant items, longer duration of fixations and in higher rates of fixations per item as compared to positive cues. The effectiveness of both cue types, as measured by fixations on relevant items, increased over the course of each search. In sum, a negative color cue can guide attention to relevant items, but it is less efficient than a positive cue of the same informational value.

Show MeSH