Rewards shape attentional search modes

Visual attention can be configured for specific stimulus features (feature search mode) or it can be non-specifically set for salient pop-outs (singleton detection mode). Additionally, monetary rewards have been shown to bias attention toward specific features, but it is unknown whether secondary reinforcers (images of US$) can shape global attention via search modes. In a between-group study, we trained participants to value one search mode over the other. In a testing phase, a salient distractor captured the attention of the value-singleton group; however, the value feature group was completely unaffected. This suggests that rewards automatically bias global attention mechanisms and potentially mediate the handoff between stimulus-driven and goal-directed attentional control.     

Beyond the search surface: visual search and attentional engagement.

Treisman (1991) described a series of visual search studies testing feature integration theory against an alternative (Duncan & Humphreys, 1989) in which feature and conjunction search are basically similar. Here the latter account is noted to have 2 distinct levels: (a) a summary of search findings in terms of stimulus similarities, and (b) a theory of how visual attention is brought to bear on relevant objects. Working at the 1st level, Treisman found that even when similarities were calibrated and controlled, conjunction search was much harder than feature search. The theory, however, can only really be tested at the 2nd level, because the 1st is an approximation. An account of the findings is developed at the 2nd level, based on the 2 processes of input-template matching and spreading suppression. New data show that, when both of these factors are controlled, feature and conjunction search are equally difficult. Possibilities for unification of the alternative views are considered.     

Scale of attentional focus in visual search

The effects of the spatial scale of attention on feature and conjunction search were examined in two experiments. Adult participants in three age groups—young, young-old, and old-old—were given precues of varying validity and precision in indicating the location of a target letter subsequently presented in a visual array. Systematic decreases in the size of a valid precue (toward the size of the target) progressively facilitated both feature and conjunction search, with a greater benefit accruing to conjunction search. Age-related slowing in conjunction search was mitigated by precise (small and valid) precues, presumably because they reduced the need for participants in the young-old group to focus and to shift attention. Nevertheless, this benefit was reduced in the old-old group. The effects of valid location precue size varied with cue-target stimulus onset asynchrony (SOA) in a manner that interacted with search difficulty: Effects of cue size developed more rapidly in feature search but more slowly in conjunction search. Finally, when precues were invalid for target location, search was faster with larger sized precues. Thus, in both easy feature search and hard conjunction search, the scale of visuospatial attention modulates the speed of visual search. Furthermore, when the SOA is sufficiently long for cue effects to develop, the ability to dynamically adjust the scale of visuospatial attention appears to decline in advanced age. These results go beyond current models in suggesting that visuospatial attention possesses two dynamic properties—shifting in space and varying in scale—that are deployed independently, depending on task demands.     

Top-down search strategies cannot override attentional capture

Bacon and Egeth (1994) have claimed that color singletons do not interfere with search for a shape singleton when, instead of using asingleton detection mode, participants are forced to use afeature search mode. Bacon and Egeth induced a feature search mode by adding different shape singletons to the display so that observers could not simply respond touniqueness to find the target. We did exactly the same but used larger display sizes to ensure that the target and distractor singletons remained salient. The results show that under these conditions, an irrelevant color singleton interferes with search for a shape singleton. It is argued that the notion of differential search modes may be incorrect and that the results can be explained in terms of bottom-up salience signals.     

Multisensory enhancement of attentional capture in visual search

Multisensory integration increases the salience of sensory events and, therefore, possibly also their ability to capture attention in visual search. This was investigated in two experiments where spatially uninformative color change cues preceded visual search arrays with color-defined targets. Tones were presented synchronously with these cues on half of all trials. Spatial-cuing effects indicative of cue-triggered capture of attention were larger on tone-present than on tone-absent trials, demonstrating multisensory enhancements of attentional capture. Larger capture effects for audiovisual events were found when cues were color singletons, and also when they appeared among heterogeneous color distractors. Tone-induced increases of attentional capture were independent of color-specific top-down task sets, suggesting that this multisensory effect is a stimulus-driven bottom-up phenomenon.     

Scale of attentional focus in visual search.

The effects of the spatial scale of attention on feature and conjunction search were examined in two experiments. Adult participants in three age groups--young, young-old, and old-old--were given precues of varying validity and precision in indicating the location of a target letter subsequently presented in a visual array. Systematic decreases in the size of a valid precue (toward the size of the target) progressively facilitated both feature and conjunction search, with a greater benefit accruing to conjunction search. Age-related slowing in conjunction search was mitigated by precise (small and valid) precues, presumably because they reduced the need for participants in the young-old group to focus and to shift attention. Nevertheless, this benefit was reduced in the old-old group. The effects of valid location precue size varied with cue-target stimulus onset asynchrony (SOA) in a manner that interacted with search difficulty: Effects of cue size developed more rapidly in feature search but more slowly in conjunction search. Finally, when precues were invalid for target location, search was faster with larger sized precues. Thus, in both easy feature search and hard conjunction search, the scale of visuospatial attention modulates the speed of visual search. Furthermore, when the SOA is sufficiently long for cue effects to develop, the ability to dynamically adjust the scale of visuospatial attention appears to decline in advanced age. These results go beyond current models in suggesting that visuospatial attention possesses two dynamic properties--shifting in space and varying in scale--that are deployed independently, depending on task demands.     

Top-up search and the attentional blink: A two-stage account of the preview effect in search

An inefficient visual search task can be facilitated if half the distractor items are presented as a preview prior to the presentation of the remaining distractor items and target. This benefit in search is termed the preview effect. Recent research has found that a preview effect can still occur if the previewed items disappear before reappearing again just before the search items (the “top-up” procedure). In this paper we investigate the attentional demands of processing during the preview and the top-up periods. Experiment 1 found that if attention is withdrawn from the top-up stage then no preview effect occurs. Likewise if attention is withdrawn from the initial preview period then the preview effect is reduced (Experiment 2). The data suggest that the preview effect is dependent on attention being paid both to the initial display and also to the re-presentation of the old display before the search display appears. The data counter accounts of preview search in terms of automatic attention capture by new items or by inhibition of return. We discuss alternative accounts of the results, and in particular suggest an amalgamation of a temporal grouping and a visual marking account of preview search.     

Statistical regularities modulate attentional capture independent of search strategy

An earlier study using the additional singleton task showed that statistical regularities regarding the distractor location can cause an attentional bias that affects the amount of attentional capture by distractors and the efficiency of selection of targets. The distractor singleton was systematically present more often in one location than in all other locations. The present study investigated whether this bias also occurs when observers adopt a feature search mode, i.e., when they search for a specific feature (circle) between elements with different shapes, while ignoring a colored distractor singleton. It is assumed that in feature search, observers can ignore distractors in a top-down way and as such one expects that statistical regularities about the distractor location should not play a role. Contrary to this prediction, we found that even in feature search, both attentional capture by the distractors and the efficiency of selecting the target were impacted by these statistical regularities. Moreover, statistical regularities regarding the feature value of the distractor (its color) had no effect on the amount of capture or the efficiency of selection. We claim that statistical regularities cause passive lingering biases of attention such that on the priority map, the location containing a high probability distractor competes less for attention than locations that are less likely to contain distractors.     

Amount and duration of attentional demands during visual search

Previous research has suggested that, in visual-search tasks, the comparison between target and display items does not require attentional capacity. In the present experiment we used a secondary-task paradigm to distinguish the amount and duration of the attentional demands of visual search. The subjects performed visual search (the primary task) and tone detection (the secondary task) concurrently over the course of five experimental sessions (1,440 trials). For each subject, target-response mapping was either consistent or varied for Days 1-5. The results indicate that the amount of attentional demand, as reflected in secondary-task performance, increased as a function of display size in the search task. Switching from consistent to varied mapping in a sixth experimental session increased both the amount and the duration of the attentional demands of the search. The present results support models of visual-search performance in which the comparison of target and display items requires attentional capacity.     

Age-related preservation of top-down attentional guidance during visual search

Younger (19-27 years of age) and older (60-82 years of age) adults performed a letter search task in which a color singleton was either noninformative (baseline condition) or highly informative (guided condition) regarding target location. In the guided condition, both age groups exhibited a substantial decrease in response time (RT) to singleton targets, relative to the baseline condition, as well as an increase in RT to nonsingleton targets. The authors conclude that under conditions that equate the physical structure of individual displays, top-down attentional guidance can be at least as effective for older adults as for younger adults.     

Absence of attentional capture in parallel search is possible: A failure to replicate attentional capture in a non-singleton target search task

The notion of a singleton versus a feature search mode (Bacon & Egeth, 1994) in visual search is generally widely accepted. Yet Theeuwes (2004) claimed a different, potentially more parsimonious position. He suggested that the size of an attentional window is under top-down control and that salient distractors within this window capture attention. We report on four experiments. The first two experiments represent our various initial attempts to replicate the crucial Experiment 1 in the Theeuwes (2004) study, all of which were not successful. In Experiment 3, we showed that our distractor was able to yield attentional capture in a situation promoting the use of the singleton search mode (Bacon & Egeth, 1994). Experiment 4 was similar to Experiment 1 but incorporated further details that may account for the discrepant findings. Still, no attentional capture was found. In sum, it was not possible to replicate a crucial piece of evidence for the attentional window hypothesis, and our results are more consistent with the assumption of two different search modes.     

Memory search for the first target modulates the magnitude of the attentional blink

The resolution of temporal attention is limited in a manner that makes it difficult to identify two targets in short succession. This limitation produces the phenomenon known as the attentional blink (AB), in which processing of a first target (T1) impairs identification of a second target (T2). In the AB literature, there is broad agreement that increasing the time it takes to process T1 leads to a larger AB. One might, therefore, predict that increasing the number of possible T1 identities, or target set, from 1 to 16 would lead to a larger AB. We were surprised to find that this manipulation of T1 difficulty had no influence on AB magnitude. In subsequent experiments, we found that AB magnitude interacts with T1 processing time only under certain circumstances. Specifically, when the T1 task was either well masked or had to be completed online, we found a reliable interaction between AB magnitude and the target set size. When neither of these conditions was fulfilled, there was no interaction between target set size and the AB. Previous research found that when the target set changes from trial to trial, trials with more possible targets elicited a larger AB. In the present study, the target set is held constant, reducing the demands on working memory. Nevertheless, AB magnitude still interacts with target set size, as long as the T1 task cannot be processed offline. Thus, the act of searching memory delays subsequent processing, even when the role of working memory has been minimized.     

自我相关信息对视觉搜索主动抑制的易化作用

工作记忆表征会以自上而下的方式调控注意选择过程, 其中一种表现就是能够对储存的干扰物表征产生注意的主动抑制, 进而提高对目标的搜索效率。另一方面, 凸显性刺激也会以自下而上的方式优先捕获注意。那么, 当保持在工作记忆中的干扰物为更具社会凸显性特征的刺激(如与自己有关的信息)时, 会对视觉搜索过程中的注意抑制产生怎样的影响, 目前尚不清楚。本研究采用短暂联结任务和工作记忆引导的视觉搜索任务范式, 探讨了自我凸显性对注意主动抑制的影响。结果发现, 相比他人和中性条件, 当工作记忆表征为自我联结刺激时, 目标搜索反应更快。本研究从行为层面为自我相关信息能够易化主动抑制过程提供了证据。     

Spatial probability as an attentional cue in visual search

We investigated the role of spatial probabilities in target location during participants' performance of a visual search task. Experiments 1 and 2 demonstrated that spatial probabilities could serve as a powerful attentional bias that produced faster detection of targets in high-probability locations than of those in low- or random-probability locations. The effect could not be explained by repetition priming alone. Moreover, responses to targets in low-probability locations were slowed only when a distractor was present in the high-probability location. In Experiments 3-5, we compared the effects of spatial probability with an explicit endogenous cue and a salient exogenous cue. Facilitation due to spatial probability was independent of any benefit afforded by the explicit endogenous cue but interacted with the salient exogenous cue, such that the exogenous cue validity effect was compressed for targets in the high-probability location. Together, these results suggest that the spatial probabilities governing target location constitute a potent bias of visual processing and, as such, can be considered an attentional cue that differs from both typical explicit endogenous and salient exogenous cues.     

视觉搜索中注意模板促进搜索的内在机制

生物的视觉搜索能力对适应外部复杂环境具有非常重要的生存意义。注意模板可以在搜索任务的过程中增强相关信息和抑制无关信息,从而快速找到目标。总结近期研究结果主要有以下发现：在建立注意模板的过程中并不能明确是基于语义信息还是视觉特征信息;注意模板不仅可以存储在工作记忆中,也可以存储在长时记忆中;不同类型注意模板的神经机制存在差异。未来的研究应关注注意模板在建立过程中内部信息如何传递,并关注不同人群注意模板的神经机制,以及解决拒绝模板抑制机制的理论争议。     

Top-down search strategies determine attentional capture in visual search: Behavioral and electrophysiological evidence

To investigate how attentional capture in visual search is affected by generalized top-down search strategies, ERPs and behavioral performance were measured in two experiments where spatially nonpredictive color singleton cues preceded visual search arrays that contained one of two equally likely color singletons. When both singletons served as targets, irrelevant-color singleton cues produced behavioral attentional capture effects and elicited an N2pc component, indicative of a singleton search mode. When responses were required to only one of the two color singletons, the same cues no longer elicited behavioral spatial cuing effects, and the N2pc to these cues was attenuated and delayed, in line with the hypothesis that search was now guided by a feature-specific search strategy. Results demonstrate that the ability of visual singleton stimuli to capture attention is not simply determined by their bottom-up salience, but strongly modulated by top-down task sets.     

Visual search proceeds concurrently during the attentional blink and response selection bottleneck

It is well known that human information processing comprises several distinct subprocesses—namely, the perceptual, central, and motor stage. In each stage, attention plays an important role. Specifically, a type of attention—perceptual attention—operates to detect and identify a sensory input. Following this, another class of attention—central attention—is involved in working memory encoding and response selection at the central stage. While perceptual attention and central attention are known to be separate, distinct processes, some researchers reported findings that loading central attention postponed the deployment of perceptual attention needed to perform a spatial configuration search. We tested whether a similar pattern of results would emerge when a different kind of search task is used. To do so, we had participants perform a visual-search task of searching for a feature conjunction target, taxing perceptual attention while they are engaged in central processes, such as working memory encoding and response selection. The results showed that perceptual processing of conjunction search stimuli could be carried out concurrently with central processes. These results suggest that the nature of the concurrent visual search process is a determinant responsible for the dynamic relationship between perceptual attention deployed for visual search and central attention needed for working memory encoding and response selection.

     

Reward history but not search history explains value-driven attentional capture

In past years, an extensive amount of research has focused on how past experiences guide future attention. Humans automatically attend to stimuli previously associated with reward and stimuli that have been experienced during visual search, even when it is disadvantageous in present situations. Recently, the relationship between “reward history” and “search history” has been discussed critically. We review results from research on value-driven attentional capture (VDAC) with a focus on these two experience-based attentional selection processes and their distinction. To clarify inconsistencies, we examined VDAC within a design that allows a direct comparison with other mechanisms of attentional selection. Eighty-four healthy adults were trained to incidentally associate colors with reward (10 cents, 2 cents) or with no reward. In a subsequent visual search task, distraction by reward-associated and unrewarded stimuli was contrasted. In the training phase, reward signals facilitated performance. When these value-signaling stimuli appeared as distractors in the test phase, they continuously shaped attentional selection, despite their task irrelevance. Our findings clearly cannot be attributed to a history of target search. We conclude that once an association is established, value signals guide attention automatically in new situations, which can be beneficial or not, depending on the congruency with current goals.