The size of an attentional window modulates attentional capture by color singletons

Researchers have proposed that during visual search, a color singleton cannot capture attention in a bottom-up fashion (Jonides & Yantis, 1988). In the present study, we manipulated the size of the attentional window by asking participants to detect either a global (diffuse attention) or a local (focused attention) shape before starting the search for a nonsingleton target. We demonstrate that increasing the size of attentional window causes the observers to frequently orient to an irrelevant color singleton. We conclude that although the size of attentional window might be under a top-down control, within the attentional window, an irrelevant salient singleton can capture attention in a bottom-up fashion.     

Search efficiency is not sufficient: The nature of search modulates stimulus-driven attention

It has long been debated whether or not a salient stimulus automatically attracts people’s attention in visual search. Recent findings showed that a salient stimulus is likely to capture attention especially when the search process was inefficient due to high levels of competition between the target and distractors. Expanding these studies, the present study proposes that a specific nature of visual search, as well as search efficiency, determines whether or not a salient, task-irrelevant singleton stimulus captures attention. To test this proposition, we conducted three experiments, in which participants performed two visual search tasks whose underlying mechanisms are known to be different: orientation-feature search and Landolt-C search tasks. We found that color singleton distractors captured attention when participants performed the orientation-feature search task. The magnitude of this capture effect increased as search efficiency decreased. On the contrary, the capture by singleton distractors was not observed under the Landolt-C search task. This differential pattern of capture effect was not due to differences in search efficiency across the search tasks; even when search efficiency was controlled for, stimulus-driven capture of attention by a salient distractor was found only under the feature search. Based on these results, the present study suggests that in addition to search efficiency, the nature of search strategy and the extent to which attentional control is strained play crucial roles in observing stimulus-driven attentional capture in visual search.     

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.     

Effects of search mode and intertrial priming on singleton search

There is no consensus as to what information guides search for a singleton target. Does the most salient display element capture attention, regardless of the observer's attentional set? Do observers adopt a default salience-based search mode? Does knowledge of the target's defining featural property (when available) affect search? Finally, can intertrial contingencies account for the disparate results in the literature? We investigated search for a shape singleton when (1) the target and nontarget shapes switched unpredictably from trial to trial, (2) the target feature remained fixed, and (3) the target was a singleton on only one third of the trials. We examined overall reaction times, search slopes, errors, and the magnitude of the slowing caused by a cross-dimensional singleton distractor. Our results argue against the idea that search is guided solely by stimulus-driven factors or that subjects adopt a singleton detection mode that is blind to feature information. They show also that intertrial contingencies, although potent, cannot account for the variety of results in the literature.     

The visual hemifield asymmetry in the spatial blink during singleton search and feature search

The present study examined a visual field asymmetry in the contingent capture of attention that was previously observed by Du and Abrams (2010). In our first experiment, color singleton distractors that matched the color of a to-be-detected target produced a stronger capture of attention when they appeared in the left visual hemifield than in the right visual hemifield. This replicated Du and Abrams and also revealed a difference between hemifields in the time course of this effect. Our second experiment suggested that this asymmetry is moderated by the tuning of attentional control settings: when the target was easier to detect the asymmetry was attenuated. Our third experiment showed that this asymmetry is also present during singleton detection: a color singleton distractor produced a larger capture effect in the left hemifield than in the right hemifield. Finally, our fourth experiment suggested that this asymmetry is moderated by the salience of the attention-capturing distractor: when the distractor was not salient, the asymmetry was attenuated. These results suggest that there are boundary conditions in the observed hemifield asymmetry in the contingent capture of attention and several underlying brain systems might be involved.     

Bottom-up guidance in visual search for conjunctions

Understanding the relative role of top-down and bottom-up guidance is crucial for models of visual search. Previous studies have addressed the role of top-down and bottom-up processes in search for a conjunction of features but with inconsistent results. Here, the author used an attentional capture method to address the role of top-down and bottom-up processes in conjunction search. The role of bottom-up processing was assayed by inclusion of an irrelevant-size singleton in a search for a conjunction of color and orientation. One object was uniquely larger on each trial, with chance probability of coinciding with the target; thus, the irrelevant feature of size was not predictive of the target's location. Participants searched more efficiently for the target when it was also the size singleton, and they searched less efficiently for the target when a nontarget was the size singleton. Although a conjunction target cannot be detected on the basis of bottom-up processing alone, participants used search strategies that relied significantly on bottom-up guidance in finding the target, resulting in interference from the irrelevant-size singleton.     

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.     

Cognitive load modulates attentional capture by color singletons during effortful visual search

Color singletons that are irrelevant to locating a visual target do not typically capture attention if visual search is effortful. In contrast, when search is efficient color singletons are often found to capture attention. Such distraction by a color singleton can be modulated by single-task vs. dual-task manipulations when visual search is efficient. This is due, presumably, to the increased cognitive load in the dual-task condition, which interferes with top-down attentional control. This study investigated whether capture by a color singleton is also modulated by single-task vs. dual-task manipulations when visual search was effortful. The results of three experiments revealed that attentional capture effects were absent in a single-task condition and were present in a dual-task condition, but only when the identity of the color singleton is not associated with the target response-set. When the identity of the color singleton was relevant to the response-set it captured attention in both the single-task and in dual-task conditions.     

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.     

A salient distractor does not disrupt conjunction search

Leading theories of attention posit that bottom-up and top-down factors simultaneously affect attentional priority in visual search. Recent evidence, however, suggests that subjects may rely exclusively on top-down guidance when searching for a target defined by a specific known feature (Bacon & Egeth, 1994). In the present experiment, we addressed this issue in a conjunction search task. We investigated how searching for a green O among green Ts and red Os is affected by the presence of a distractor with a unique shape (green X), color (blue O), or both (blue X). We showed that the salient distractor does not disrupt performance on target-present trials, but produces a large interference on target-absent trials. We conclude that salience-based and top-down processes are alternative modes of guidance, rather than joint contributors in the allocation of attentional priority.     

Trial-by-trial adjustments of top-down set modulate oculomotor capture

The role of top-down control in visual search has been a subject of much debate. Recent research has focused on whether attentional and oculomotor capture by irrelevant salient distractors can be modulated through top-down control, and if so, whether top-down control can be rapidly initiated based on current task goals. In the present study, participants searched for a unique shape in an array containing otherwise homogeneous shapes. A cue prior to each trial indicated the probability that an irrelevant color singleton distractor would appear on that trial. Initial saccades were less likely to land on the target and participants took longer to initiate a saccade to the target when a color distractor was present than when it was absent; this cost was greatly reduced on trials in which the probability that a distractor would appear was high, as compared to when the probability was low. These results suggest that top-down control can modulate oculomotor capture in visual search, even in a singleton search task in which distractors are known to readily capture both attention and the eyes. Furthermore, the results show that top-down distractor suppression mechanisms can be initiated quickly in anticipation of irrelevant salient distractors and can be adjusted on a trial-by-trial basis.     

Attentional and oculomotor capture with static singletons

Previous research has shown that in visual search static singletons have the ability to capture attention (Theeuwes, 1991a, 1992). The present study investigated whether these singletons also have the ability to capture the eyes. Participants had to make an eye movement and respond manually to a shape singleton while a color singleton was present. When participants searched for a unique shape while a unique color singleton was present there was strong attentional and oculomotor capture (Experiment 1). However, when participants searched for a specific-shape singleton (a green circle) when a specific-color singleton (a red element) had to be ignored, there was attentional capture but no oculomotor capture (Experiment 2). The results suggest that an attentional set for a specific feature value defining both the target and the distractor (as in Experiment 2) allows such a fast disengagement of attention from the location of the distractor that a saccade execution to that location is prevented.     

视觉注意捕获的快速脱离假说与信号抑制假说

快速脱离假说和信号抑制假说都是将传统的自下而上捕获和自上而下控制结合起来的混合模式假说。快速脱离假说认为突显干扰物总能在第一时间自下而上地捕获注意, 当突显干扰物与任务要求不符时, 注意会迅速脱离该位置。信号抑制假说认为突显干扰物都会产生“注意我”的信号, 当突显干扰物与任务要求不符时, 该信号会被自上而下地抑制以阻止注意捕获发生。前者相关的研究多采用空间线索提示范式和眼动脱离范式, 实验中被试采取独子探测策略, 而后者相关的研究多采用额外单例范式的变式, 实验中被试采取特征探测策略。未来研究应采用不同的刺激类型和实验方法进一步为两个假说提供证据支持, 同时要关注奖赏、训练等因素对“捕获-脱离”和“信号-抑制”的影响。     

Contingent orienting or contingent capture: A size singleton matching the target–distractor size relation cannot capture attention

In the present study, we examined whether a peripheral size-singleton distractor that matches the target–distractor size relation can capture attention and disrupt central target identification. Three experiments consistently showed that a size singleton that matches the target–distractor size relation cannot capture attention when it appears outside of the attentional window, even though the same size singleton produces a cuing effect. In addition, a color singleton that matches the target color, instead of a size singleton that matches the target–distractor size relation, captures attention when it is outside of the attentional window. Thus, a size-relation-matched distractor is much weaker than a color-matched distractor in capturing attention and cannot capture attention when the distractor appears outside of the attentional window.     

Top-down and bottom-up attentional control: On the nature of interference from a salient distractor

In 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.     

Top-down and bottom-up attentional control: on the nature of interference from a salient distractor.

In 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.     

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.     

不同搜索情境下老化对自上而下注意加工的影响

在视觉搜索过程中,老年人是否可以在不同情境下调节自上而下和自下而上的加工水平尚不明确。为了探讨老化对认知灵活性的影响,研究采用空间线索范式,通过比较有效线索和无效线索来考察对线索的注意加工水平（注意捕获、注意抑制）,通过比较目标相关和目标无关线索的注意加工水平来考察自上而下和自下而上的作用,通过改变分心物一致性来调控不同的目标凸显情境。结果发现,年轻组在目标非凸显时的空间线索效应高于目标凸显时,表明年轻人会依据目标凸显性调整自上而下的加工水平;但老年组却没有产生这种差异,其更依赖自上而下的加工,注意系统会对目标相关的线索进行注意捕获,对目标无关的线索进行注意抑制。结果表明,随着年龄的增长,认知控制的灵活性下降,表现出对自上而下加工较多的依赖;此外,老年人依然保留着注意捕获和注意抑制的能力,这对认知老化中抑制能力受损的观点提出了挑战。     

Evidence for attentional capture by a surprising color singleton in visual search

Three experiments were conducted to investigate whether surprising color singletons capture attention. Participants performed a visual search task in which a target letter had to be detected among distractor letters. Experiments 1 and 2 assessed accuracy as the dependent variable. In Experiment 1, the unannounced presentation of a color singleton 500 ms prior to the letters (and in the same position as the target letter) resulted in better performance than in the preceding conjunction search segment, in which no singleton was presented, and performance was as good in this surprise–singleton trial as in the following feature search segment, in which the singleton always coincided with the target. In contrast, no improvement was observed when the color singleton was presented simultaneously with the letters in Experiment 2, indicating that attentional capture occurred later in the surprise trial than in the feature search segment. In Experiment 3, set size was varied, and reaction time was the dependent variable. Reaction time depended on set size in the conjunction search segment, but not in the surprise trial nor in the feature search segment. The results of the three experiments support the view that surprising color singletons capture attention independently of a corresponding attentional set.     

When does feature search fail to protect against attentional capture?

ABSTRACT

When participants search for a shape (e.g., a circle) among a set of homogenous shapes (e.g., triangles) they are subject to distraction by colour singletons that are more salient than the target. However, when participants search for a shape among heterogeneous shapes, the presence of a non-target colour singleton does not slow responses to the target. Attempts have been made to explain these results from both bottom-up and top-down perspectives. What both accounts have in common is that they do not predict the occurrence of attentional capture on typical feature search displays. Here, we present a case where manipulating selection history, rather than the displays themselves, leads to attentional capture on feature search trials. The ability to map specific colours to the target and distractor appears to be what enables resistance to capture during feature search.