Attentional capture in singleton-detection and feature-search modes.

Six experiments were conducted to determine the circumstances under which an irrelevant singleton captures attention. Subjects searched for a target while ignoring a salient distractor that appeared at different stimulus onset asynchronies (SOAs) prior to each search display. Spatial congruency and interference effects were measured. The strategies available to find the target were controlled (only singleton-detection mode, only feature-search mode, or both search strategies available). An irrelevant abrupt onset captured attention in search for a color target, across SOAs, whatever strategies were available. In contrast, in search for a shape target, an irrelevant color singleton captured attention in the singleton-detection condition but delayed response at its location in the feature-search condition, across SOAs. When both strategies were available, capture was short lived (50- to 100-msec SOAs). The theoretical implications of these findings in relation to current views on attentional capture are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory Attentional Capture: Effects of Singleton Distractor Sounds.

The phenomenon of attentional capture by a unique yet irrelevant singleton distractor has typically been studied in visual search. In this article, the authors examine whether a similar phenomenon occurs in the auditory domain. Participants searched sequences of sounds for targets defined by frequency, intensity, or duration. The presence of a singleton distractor that was unique on an irrelevant dimension (e.g., a low-frequency singleton in search for a target of high intensity) was associated with search costs in both detection and discrimination tasks. However, if the singleton feature coincided with the target item, search was facilitated. These results establish the phenomenon of auditory attentional capture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional capture by a salient distractor in visual search: The effect of target-distractor similarity.

Models of attentional selection are based on either stimulus-driven or goal-directed processes. Support for the latter comes from a study showing that a salient singleton in a search display can be ignored when the target has a different defining feature (Kumada, 1999). We show that this finding holds only when the target and the nonsalient distractors are highly dissimilar from one another. When the target and the distractors are made more similar, whilst ensuring that the target still pops out of the display, the salient distractor can no longer be ignored. This outcome is consistent with predictions from stimulus-driven accounts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional capture by irrelevant emotional distractor faces.

We establish attentional capture by emotional distractor faces presented as a “singleton” in a search task in which the emotion is entirely irrelevant. Participants searched for a male (or female) target face among female (or male) faces and indicated whether the target face was tilted to the left or right. The presence (vs. absence) of an irrelevant emotional singleton expression (fearful, angry, or happy) in one of the distractor faces slowed search reaction times compared to the singleton absent or singleton target conditions. Facilitation for emotional singleton targets was found for the happy expression but not for the fearful or angry expressions. These effects were found irrespective of face gender and the failure of a singleton neutral face to capture attention among emotional faces rules out a visual odd-one-out account for the emotional capture. The present study thus establishes irrelevant, emotional, attentional capture. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Selectivity in distraction by irrelevant featural singletons: Evidence for two forms of attentional capture.

Four experiments addressed the degree of top-down control over attentional capture in visual search for featural singletons. In a modified spatial cuing paradigm, the spatial relationship and featural similarity of target and distractor singletons were systematically varied. Contrary to previous studies, all 4 experiments showed that when searching for a singleton target, an irrelevant featural singleton captures spatial attention only when defined by the same feature value as the target. Experiments 2, 3, and 4 provided a potential explanation for the discrepancy with previous studies by showing that irrelevant singletons can produce distraction effects that are dissociable from shifts of spatial attention. The results suggest the existence of 2 distinct forms of attentional capture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Irrelevant singletons in pop-out search: Attentional capture or filtering costs?

The aim of the present study was to investigate whether costs invoked by the presence of an irrelevant singleton distractor in a visual search task are due to attentional capture by the irrelevant singleton or spatially unrelated filtering costs. Measures of spatial effects were based on distance effects, compatibility effects, and differences between singleton and nonsingleton target trials. The results show that the distractor only regularly captures attention when it is nonpredictive of the target position and unpredictably changes its features. When the distractor is antipredictive of the target position and the irrelevant features of target and distractor remain constant throughout the experiment, spatially unrelated filtering costs prevail. Further experiments showed that filtering costs accrue from distractor inhibition or target activation processes, which in turn can be modeled as instances of priming of pop-out. The present study thus clarifies the notion of filtering costs and modifies present accounts of the distraction effect. Moreover, the results also relate to research of intertrial priming by showing that priming affects the stage of attentional selection and depends on top-down attentional control settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics of covert and overt visual orienting: Evidence from attentional and oculomotor capture.

Five visual search experiments found oculomotor and attentional capture consistent with predictions of contingent orienting, contrary to claims that oculomotor capture is purely stimulus driven. Separate saccade and attend-only conditions contained a color target appearing either singly, with an onset or color distractor, or both. In singleton mode, onsets produced oculomotor and attentional capture. In feature mode, capture was absent or greatly reduced, providing evidence for top-down modulation of both types of capture. Although attentional capture by color abstractors was present throughout, oculomotor capture by color occurred only when accompanied by transient change, providing evidence for a dissociation between oculomotor and attentional capture. Oculomotor and attentional capture appear to be mediated by top-down attentional control settings, but transient change may be necessary for oculomotor capture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional control within 3-D space

Four experiments investigated whether directing attention to a particular plane in depth enables observers to filter out information from another depth plane. Observers viewed stereoscopic displays and searched for a red line segment among green line segments. The results showed that directing attention to a particular depth plane cannot prevent attentional capture from another depth plane when the colors of the target and distractor are identical. However, it can prevent attentional capture by a singleton from another depth plane when the colors of the target and distractor are different. These results indicate that only when both color and depth information are selective in guiding attention to the target singleton can attentional capture by irrelevant singletons be prevented. The results also suggest that retinal disparity does not have the same special status as location information in two dimensions and should be considered as just another feature along which selection may occur.     

Attentional capture and aging: Implications for visual search performance and oculomotor control.

Two studies examined potential age-related differences in attentional capture. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside it. On half the trials, a new stimulus (i.e., a sudden onset) appeared simultaneously with the presentation of the color singleton target. The onset was always a task-irrelevant distractor. Response times were lengthened, for both young and old adults, whenever an onset distractor appeared, despite the fact that Ss reported being unaware of the appearance of the abrupt onset. Eye scan strategies were also disrupted by the appearance of the onset distractors. On about 40% of the trials on which an onset appeared, Ss made an eye movement to the task-irrelevant onset before moving their eyes to the target. Fixations close to the onset were brief, suggesting parallel programming of a reflexive eye movement to the onset and goal-directed eye movement to the target. Results are discussed in terms of age-related sparing of the attentional and oculomotor processes that underlie attentional capture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional capture by irrelevant color singletons.

Four experiments investigated attentional capture by a color singleton in visual search for a nonsingleton target. B. S. Gibson and E. M. Kelsey (1998) found that a color singleton in a precuing array facilitated target discrimination at that location if the same color also signaled the target array onset. The authors found similar cuing effects regardless of whether the singleton color matched the target array and regardless of whether subjects could anticipate the singleton or target-array color. In Experiment 4, a color singleton captured attention when it appeared in the precuing array but not when it appeared in the target array. The results indicate that attentional control settings for displaywide attributes are imprecise: Although subjects may anticipate a specific color, they cannot avoid attentional capture by other irrelevant colors. In addition, the effect of irrelevant singletons depends on whether a target is simultaneously present in the array. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dilution: A theoretical burden or just load? A reply to Tsal and Benoni (2010).

Load theory of attention proposes that distractor processing is reduced in tasks with high perceptual load that exhaust attentional capacity within task-relevant processing. In contrast, tasks of low perceptual load leave spare capacity that spills over, resulting in the perception of task-irrelevant, potentially distracting stimuli. Tsal and Benoni (2010) find that distractor response competition effects can be reduced under conditions with a high search set size but low perceptual load (due to a singleton color target). They claim that the usual effect of search set size on distractor processing is not due to attentional load but instead attribute this to lower level visual interference. Here, we propose an account for their findings within load theory. We argue that in tasks of low perceptual load but high set size, an irrelevant distractor competes with the search nontargets for remaining capacity. Thus, distractor processing is reduced under conditions in which the search nontargets receive the spillover of capacity instead of the irrelevant distractor. We report a new experiment testing this prediction. Our new results demonstrate that, when peripheral distractor processing is reduced, it is the search nontargets nearest to the target that are perceived instead. Our findings provide new evidence for the spare capacity spillover hypothesis made by load theory and rule out accounts in terms of lower level visual interference (or mere “dilution”) for cases of reduced distractor processing under low load in displays of high set size. We also discuss additional evidence that discounts the viability of Tsal and Benoni's dilution account as an alternative to perceptual load. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When does visual attention select all features of a distractor?

What happens after visual attention is allocated to an object? Although many theories of attention assume that all of its features are selected and processed, there has been little direct evidence that an irrelevant feature dimension of an attended nontarget is processed. In 5 experiments presented here, the authors used a singleton paradigm to investigate the effect of attention on nontarget objects. Participants made a speeded feature discrimination of a target for which the response was either compatible or incompatible with an irrelevant feature dimension of a distractor. The results show that the irrelevant distractor features were processed to the point that they interfered with the response to the target. The response compatibility effect was observed even when the location of the target or the distractor was invariant, although it was much weaker when both locations were invariant. These results demonstrate that in many circumstances, an attended distractor is completely selected and fully processed, and the complete processing of distractors depends on a number of factors, many of which are related to the strength of attention to the distractor. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional capture by salient color singleton distractors is modulated by top-down dimensional set.

Three experiments examined whether salient color singleton distractors automatically interfere with the detection singleton form targets in visual search (e.g., J. Theeuwes, 1992), or whether the degree of interference is top-down modulable. In Experiments 1 and 2, observers started with a pure block of trials, which contained either never a distractor or always a distractor (0% or 100% distractors)--varying the opportunity to learn distractor suppression. In the subsequent trial blocks, the proportion of distractors was systematically varied (within-subjects factor in Experiment 1, between-subjects factor in Experiment 2)--varying the incentive to use distractor suppression. In Experiment 3, observers started with 100% distractors in the first block and were presented with "rare" color or luminance distractors, in addition to "frequent" color distractors, in the second block. The results revealed distractor interference to vary as a function of both the initial experience with distractors and the incentive to suppress them: the interference was larger without relevant practice and with a lesser incentive to apply suppression (Experiments 1-3). This set of findings suggests that distractor interference is top-down modulable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is Posner's "beam" the same as Treisman's "glue?" On the relation between visual orienting and feature integration theory.

In the present study we investigated whether the visually allocated "beam" studied by Posner and others is the same visual attentional resource that performs the role of feature integration in Treisman's model. Subjects were cued to attend to a certain spatial location by a visual cue, and performance at expected and unexpected stimulus locations was compared. Subjects searched for a target letter (R) with distractor letters that either could give rise to illusory conjunctions (PQ) or could not (PB). Results from three separate experiments showed that orienting attention in response to central cues (endogenous orienting) showed similar effects for both conjunction and feature search. However, when attention was oriented with peripheral visual cues (exogenous orienting), conjunction search showed larger effects of attention than did feature search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Capturing Attention When Attention "Blinks".

Four experiments addressed the question of whether attention may be captured when the visual system is in the midst of an attentional blink (AB). Participants identified 2 target letters embedded among distractor letters in a rapid serial visual presentation sequence. In some trials, a square frame was inserted between the targets; as the only geometric object in the sequence, it constituted a singleton. Capture effects obtained when the AB was most severe and when it was over were compared. There were 3 main results. First, capture occurred even when the AB was crippling, suggesting that a singleton exogenously engaged attention even when processing of a previous target was continuing apace. Second, when the singleton contained the key target feature, capture effects were clearly manifest. Third, even when the singleton did not possess the key target feature, it still succeeded in capturing attention, although the effects were both feeble and fleeting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Top-down controlled, delayed selection in the attentional blink.

In a previous study, it was shown that the attentional blink (AB)--the failure to recall the 2nd of 2 visual targets (T1 and T2) presented within 500 ms in rapid serial visual presentation--is reduced when T2 is preceded by a distractor that shares a feature with T2 (e.g., color; Nieuwenstein, Chun, van der Lubbe & Hooge, 2005). Here, this cuing effect is shown to be contingent on attentional set. For example, a red distractor letter preceding a green digit T2 is an effective cue when the task is to look for red and green digits, but the same red cue is relatively ineffective when the task is to look for only green digits or when the color of T2 is not specified. It is also shown that cuing is not interrupted by a distractor intervening between the cue and T2. These findings provide evidence for a contingent, delayed selection account of the AB. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Aging and involuntary attention capture: Electrophysiological evidence for preserved attentional control with advanced age.

The present study examined whether people become more susceptible to capture by salient objects as they age. Participants searched a target display for a letter in a specific color and indicated its identity. In Experiment 1, this target display was preceded by a non-informative cue display containing one target-color box, one ignored-color box, and two white boxes. On half of the trials, this cue display also contained a salient-but-irrelevant abrupt onset. To assess capture by the target-color cue, we used the N2pc component of the event-related potential, thought to reflect attentional allocation to the left or right visual field. The target-color box in the cue display produced a substantial N2pc effect for younger adults and, most importantly, this effect was not diminished by the presence of an abrupt onset. Therefore, the abrupt onset was unable to capture attention away from the target-color cue. Critically, older adults demonstrated the same resistance to capture by the abrupt onset. Experiment 2 extended these findings to irrelevant color singleton cues. Thus, we argue that the ability to attend to relevant stimuli and resist capture by salient-but-irrelevant stimuli is preserved with advancing age. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Perceiving spatially inseparable objects: Evidence for feature-based object selection not mediated by location.

In 4 experiments, stimulus elements were arranged into an LED-like array, and letters were defined within the array by feature similarity between the elements with respect to color and form. These stimuli allowed the display of a target and a distractor letter simultaneously at the same location. They were spatially inseparable but could be separated in feature space. Participants had to identify the letter on a prespecified feature dimension (color or form). As a result, the distractors produced specific compatibility effects. This showed that nontarget features could not be ignored at an early stage (i.e., that color and form were processed automatically and in parallel up to a high stage). The target was selected from the resulting objects according to the prespecified feature dimension. Results demonstrate that object selection is possible without selecting absolute spatial arrays. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)