1,720,988 research outputs found
Roles of salience and strategy in conjunction search.
No full textIn some cases, the search for a conjunction target proceeds through the smaller group of elements in a display, whereas in others, search is limited to those elements that share a particular feature with the target. In 6 experiments, participants searched for a conjunction target among displays consisting of various proportions of 2 distractor types. Smaller-group search was more prevalent than target-feature search with denser displays and with features that were highly discriminable. Explicit instructions to limit search to a specific feature affected performance only when the discriminability of the guiding feature was much greater than the other target feature. Together, these experiments show that bottom-up factors have more influence in guiding conjunction searches than previously thought
Grouping effects on spatial attention in visual search.
No full textIn visual search tasks, spatial attention selects the locations containing a target or a distractor with one of the target's features, implying that spatial attention is driven by target features (M.-S. Kim & K. R. Cave, 1995). The authors measured the effects of location-based grouping processes in visual search. In searches for a color-shape combination (conjunction search), spatial probes indicated that a cluster of same-color or same-shape elements surrounding the target were grouped and selected together. However, in searches for a shape target (feature search), evidence for grouping by an irrelevant feature dimension was weaker or nonexistent. Grouping processes aided search for a visual target by selecting groups of locations that shared a common feature, although there was little or no grouping by an irrelevant feature when the target was defined by a unique salient feature
Top-down and Bottom-up Attentional Control: On the Nature of Interference from a Salient Distractor
No full textIn two experiments using spatial probes, we measured the temporal and spatial interactions between top-down control of attention and bottom-up interference from a salient distractor in visual search. The subjects searched for a square among circles, ignoring color. Probe response times showed that a color singleton distractor could draw attention to its location in the early stage of visual processing (before a 100-msec stimulus onset asynchrony [SOA]), but only when the color singleton distractor was located far from the target. Apparently the bottom-up activation of the singleton distractor's location is affected early on by local interactions with nearby stimulus locations. Moreover, probe results showed that a singleton distractor did not receive attention after extended practice. These results suggest that top-down control of attention is possible at an early stage of visual processing. In the long-SOA condition (150-msec SOA), spatial attention selected the target location over distractor locations, and this tendency occurred with or without extended practice.<br/
The prevalence effect is imbalanced: it is stronger for high target presentation rates, than for low
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Perceptual failures in the selection and identification of low-prevalence targets in relative prevalence visual search
No full textPrevious research has shown that during visual search tasks target prevalence (the proportion of trials in which a target appears) influences both the probability that a target will be detected, and the speed at which participants will quit searching and provide an ‘absent’ response. When prevalence is low (e.g., target presented on 2 % of trials), participants are less likely to detect the target than when prevalence is higher (e.g., 50 % of trials). In the present set of experiments, we examined perceptual failures to detect low prevalence targets in visual search. We used a relative prevalence search task in order to be able to present an overall 50 % target prevalence and thereby prevent the results being accounted for by early quitting behavior. Participants searched for two targets, one of which appeared on 45 % of trials and another that appeared on 5 % of trials, leaving overall target prevalence at 50 %. In the first experiment, participants searched for two dissimilar targets; in the second experiment, participants searched for two similar targets. Overall, the results supported the notion that a reduction in prevalence primarily influenced perceptual failures of identification, rather than of selection. Together, these experiments add to a growing body of research exploring how and why observers fail to detect low prevalence targets, especially in real-world tasks in which some targets are more likely to appear than others
The effects of increasing target prevalence on information-processing during visual search
No full textThe proportion of trials on which a target is presented (referred to as the target prevalence) during visual search influences the probability that the target will be detected. As prevalence increases, participants become biased toward reporting that the target is present. This bias results in an increase in detection rates for the target, coupled with an increased likelihood of making a false alarm. Previous work has demonstrated that, as prevalence increases, participants spend an increasing period of time searching on target-absent trials. The goal of the present study was to determine the information processing during the additional time spent searching on target-absent trials as prevalence increased. We recorded participants’ eye movement behavior as they were engaged in low-prevalence (25% target-present trials), medium-prevalence (50%), or high-prevalence (75%) search. Increased prevalence primarily influenced search by increasing the time spent examining objects in the display, rather than by increasing the proportion of objects examined in each display. In addition, the additional time spent examining objects in high-prevalence target-absent trials was the result of revisiting objects. We discuss the implications of these results in relation to current models of search as well as ongoing efforts to alleviate the prevalence effect
Visual Saliency as an aid to updating digital maps
No full textVisual attention is considered in the context of a professional computer-based task, using aerial photography for updating topographic mapping data (photogrammetry). There is potential for using visual attention models to help develop various semi-automated ‘attention-aware’ support systems for this task, and these are discussed. An experimental study is described which examined the potential influence of expertise, image type and exposure duration on the role of visual saliency or salience (as calculated by Itti, L., & Koch, C. (2000). A saliency-based search mechanism for overt and covert shifts of visual attention. Vision Research, 40, 1389–1506 saliency maps) in the distribution of visual attention with such imagery. Using a non-intrusive, low-resolution and low-cost method to determine the approximate distribution of visual attention, effects of expertise and landscape type were found. Unexpectedly, saliency appeared to be more relevant to visual attention among expert users than novices, and potential reasons for this are explored. Implications and further research plans are discussed
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