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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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Proportion of fixations on relevant items for the first five fixations in each trial in experiment 2.Left: relevant items are of one color, middle: relevant items are of two colors, right: relevant items are of three colors. The same general pattern as seen in Fig 6 can be observed for each number of relevant colors in the array. The first fixation following a negative cue of one irrelevant color (leaving three relevant colors) might be guided towards this color–it is the only average that is below chance level–but this is not significant. Positive cues immediately guide participants’ gaze toward relevant items. Negative cues also provide correct guidance, but this develops more slowly than for positive cues.
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pone.0145910.g009: Proportion of fixations on relevant items for the first five fixations in each trial in experiment 2.Left: relevant items are of one color, middle: relevant items are of two colors, right: relevant items are of three colors. The same general pattern as seen in Fig 6 can be observed for each number of relevant colors in the array. The first fixation following a negative cue of one irrelevant color (leaving three relevant colors) might be guided towards this color–it is the only average that is below chance level–but this is not significant. Positive cues immediately guide participants’ gaze toward relevant items. Negative cues also provide correct guidance, but this develops more slowly than for positive cues.

Mentions: For experiment 2, we also investigated the time course of guidance by positive and negative cues (Fig 9). We performed a repeated measures ANOVA on the proportion of fixations on relevant items with the factors cue type (positive vs. negative), fixation number (1.5) and the number of relevant colors (1, 2 or 3). There is a main effect of cue type (F(1,13) = 134.9, p < .001), showing that positive cues elicit a higher proportion of fixations on relevant items. There is also a main effect of fixation number (F(4,52) = 50.71, p < .001), which shows that the proportion of fixations on relevant items increases with time. There is an interaction between cue type and fixation number (F(4,52) = 5.203, p = .001), which shows that the rate of increase of the proportion of fixation on relevant items over time, is different for the two cue types. Furthermore, there is a main effect of the number of relevant colors (F(2,16) = 13.90, p < .001), and an interaction between cue type and number of relevant colors (F(2,26) = 11.51, p < .001), but not between number of relevant colors and fixation number (F(8,104) = 1.564, p = .198). There is also a three way interaction between all three factors (F(8,104) = 3.41, p = .002), which indicates that the difference in the rate of increase between the cue types, changes with the number of relevant colors. The only average proportion of fixations that is below 50% is that for the first fixation following a negative cue for 3 relevant items (46.4%), but–unlike for experiment 1 –this fails to reach significance (t(13) = 1.676 p = .12). Aside from this, we observe the same patterns as in experiment 1: negative cues guide gaze towards relevant items, but this develops slower than guidance by positive cues.


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)

Proportion of fixations on relevant items for the first five fixations in each trial in experiment 2.Left: relevant items are of one color, middle: relevant items are of two colors, right: relevant items are of three colors. The same general pattern as seen in Fig 6 can be observed for each number of relevant colors in the array. The first fixation following a negative cue of one irrelevant color (leaving three relevant colors) might be guided towards this color–it is the only average that is below chance level–but this is not significant. Positive cues immediately guide participants’ gaze toward relevant items. Negative cues also provide correct guidance, but this develops more slowly than for positive cues.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0145910.g009: Proportion of fixations on relevant items for the first five fixations in each trial in experiment 2.Left: relevant items are of one color, middle: relevant items are of two colors, right: relevant items are of three colors. The same general pattern as seen in Fig 6 can be observed for each number of relevant colors in the array. The first fixation following a negative cue of one irrelevant color (leaving three relevant colors) might be guided towards this color–it is the only average that is below chance level–but this is not significant. Positive cues immediately guide participants’ gaze toward relevant items. Negative cues also provide correct guidance, but this develops more slowly than for positive cues.
Mentions: For experiment 2, we also investigated the time course of guidance by positive and negative cues (Fig 9). We performed a repeated measures ANOVA on the proportion of fixations on relevant items with the factors cue type (positive vs. negative), fixation number (1.5) and the number of relevant colors (1, 2 or 3). There is a main effect of cue type (F(1,13) = 134.9, p < .001), showing that positive cues elicit a higher proportion of fixations on relevant items. There is also a main effect of fixation number (F(4,52) = 50.71, p < .001), which shows that the proportion of fixations on relevant items increases with time. There is an interaction between cue type and fixation number (F(4,52) = 5.203, p = .001), which shows that the rate of increase of the proportion of fixation on relevant items over time, is different for the two cue types. Furthermore, there is a main effect of the number of relevant colors (F(2,16) = 13.90, p < .001), and an interaction between cue type and number of relevant colors (F(2,26) = 11.51, p < .001), but not between number of relevant colors and fixation number (F(8,104) = 1.564, p = .198). There is also a three way interaction between all three factors (F(8,104) = 3.41, p = .002), which indicates that the difference in the rate of increase between the cue types, changes with the number of relevant colors. The only average proportion of fixations that is below 50% is that for the first fixation following a negative cue for 3 relevant items (46.4%), but–unlike for experiment 1 –this fails to reach significance (t(13) = 1.676 p = .12). Aside from this, we observe the same patterns as in experiment 1: negative cues guide gaze towards relevant items, but this develops slower than guidance by positive cues.

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