Sensory mediation of stimulus-driven attentional capture in multiple-cue displays

Three location-cuing experiments were conducted in order to examine the stimulus-driven control of attentional capture in multiple-cue displays. These displays consisted of one to four simultaneously presented direct location cues. The results indicated that direct location cuing can produce cue effects that are mediated, in part, by nonattentional processing that occurs simultaneously at multiple locations. When single cues were presented in isolation, however, the resulting cue effect appeared to be due to a combination of sensory processing and attentional capture by the cue. This suggests that the faster responses produced by direct cues may be associated with two different components: an attention-related component that can be modulated by goal-driven factors and a nonattentional component that occurs in parallel at multiple direct-cue locations and is minimally affected by goal-driven factors.     

Interaction between stimulus-driven orienting and top-down modulation in attentional capture

The present study investigated whether visual and kinesthetic stimuli are stored as multisensory or modality-specific representations in unimodal and crossmodal working memory tasks. To this end, angle-shaped movement trajectories were presented to 16 subjects in delayed matching-to-sample tasks either visually or kinesthetically during encoding and recognition. During the retention interval, a secondary visual or kinesthetic interference task was inserted either immediately or with a delay after encoding. The modality of the interference task interacted significantly with the encoding modality. After visual encoding, memory was more impaired by a visual than by a kinesthetic secondary task, while after kinesthetic encoding the pattern was reversed. The time when the secondary task had to be performed interacted with the encoding modality as well. For visual encoding, memory was more impaired, when the secondary task had to be performed at the beginning of the retention interval. In contrast, memory after kinesthetic encoding was more affected, when the secondary task was introduced later in the retention interval. The findings suggest that working memory traces are maintained in a modality-specific format characterized by distinct consolidation processes that take longer after kinesthetic than after visual encoding.     

Overriding stimulus-driven attentional capture

Theeuwes (1992) found a distracting effect of irrelevant-dimension singletons in a task involving search for a known target. He argued from this that selectivity is determined solely by stimulus salience; the parallel stage of visual processing cannot provide top-down guidance to the attentive stage sufficient to permit completely selective use of task-relevant information. We argue that in the task used by Theeuwes, subjects may have adopted the strategy of searching for an odd form even though the specific target form was known. In Experiment 1, we replicated Theeuwes’s findings. Search for a circle target among diamond nontargets was disrupted by the presence of a diamond nontarget that was uniquely colored. In two subsequent experiments, we discouraged the singleton detection strategy, forcing subjects to search for the target feature. There was no distracting effect of a color singleton in these experiments, even with displays physically identical to those of Experiment 1, demonstrating that top-down selectivity is indeed possible during visual search. We conclude that goal-directed selection of a specific known featural identity may override stimulus-driven capture by salient featural singletons.     

Goal-driven modulation of oculomotor capture

In a recent study, Ludwig and Gilchrist (2002) showed that stimulus-driven oculomotor capture by abrupt onset distractors was modulated by distractor-target similarity: Participants were more likely to fixate an irrelevant onset when it shared the target color. Here we test whether this pattern of performance is the result of (1) inhibition of all items in the distractor color, (2) a response bias to local color discontinuities, or (3) the integration of stimulus-driven abrupt onset signals with goal-driven information about the target features. The results of two experiments clearly support the third explanation. We conclude that oculomotor capture is modulated by, but not contingent upon, top-down control, and our findings argue for an integrative view of the saccadic system.     

Automatic,stimulus-driven attentional capture by objecthood

In three experiments, we investigated whether the mere organization of some elements in the visual field by Gestalt factors into a coherent unit (an object), with no abrupt onset or any other unique transient, could attract attention automatically. Participants viewed a display of nine red and green elements, one of which was the target, and had to identify the target’s color. On some trials, a subset of the elements was grouped by Gestalt factors (collinearity, closure, and symmetry) into an object. The object was task-irrelevant and unpredictive of the target. Performance on trials with an object present in the display was faster than performance on trials with no object for targets in the object area (a benefit) but slower for targets in a nonobject area (a cost). These findings demonstrate that an object by itself can capture attention automatically in a stimulus-driven manner, much as exogenous cues can.     

On the distinction between visual salience and stimulus-driven attentional capture.

It is often assumed that the efficient detection of salient visual objects in search reflects stimulus-driven attentional capture. Evidence for this assumption, however, comes from tasks in which the salient object is task relevant and therefore may elicit a deliberate deployment of attention. In 9 experiments, participants searched for a nonsalient target (vertical among tilted bars). In each display, 1 bar was highly salient in a different dimension (e.g., color or motion). When the target and salient elements coincided only rarely, reducing the incentive to attend deliberately to the salient stimuli, response times depended little on whether the target was salient, although some interesting exceptions were observed. It is concluded that efficient selection of an element in visual search does not constitute evidence that the element captures attention in a purely stimulus-driven fashion.     

Goal-driven attentional capture by invisible colors: Evidence from event-related potentials

We combined event-related brain potentials (ERPs) and behavioral measures to test whether subliminal visual stimuli can capture attention in a goal-dependent manner. Participants searched for visual targets defined by a specific color. Search displays served as metacontrast masks for preceding cue displays that contained one cue in the target color. Although this target-color cue was spatially uninformative, it produced behavioral spatial cuing effects and triggered an ERP correlate of attentional selection (i.e., the N2pc component). These results demonstrate that target-color cues captured attention, in spite of the fact that cue localization performance assessed in separate blocks was at chance level. We conclude that task-set contingent attentional capture is not restricted to supraliminal stimuli, but is also elicited by visual events that are not consciously perceived.     

Exploring the modulation of attentional capture by attentional control settings using performance and illusory line motion

Modulation of attentional capture by attentional control settings was explored using performance and phenomenology. Trials began with four figure-8s presented above, below, left, and right of fixation. Any figure-8 (or none) brightened uninformatively (cue) before presentation of either a digit target (2 or 5 made from a figure-8 by deletion) calling for a speeded identification, or a line connecting adjacent figure-8s calling for a motion judgement. Such lines are seen drawn away from an adjacent cue. Digit targets appeared only on the horizontal or vertical axes, encouraging voluntary attention to two (target-relevant) of the four figure-8s. Whereas voluntary attention reduced attentional capture from cues at taskirrelevant locations (when lines were unlikely to be presented near the task-irrelevant locations), it had no effect on motion judgements, suggesting that cue-elicited exogenous attention affects perceptual arrival times while voluntary attention prioritizes locations for further processing without affecting arrival times.     

Coordination of voluntary and stimulus-driven attentional control in human cortex

Visual attention may be voluntarily directed to particular locations or features (voluntary control), or it may be captured by salient stimuli, such as the abrupt appearance of a new perceptual object (stimulus-driven control). Most often, however, the deployment of attention is the result of a dynamic interplay between voluntary attentional control settings (e.g., based on prior knowledge about a target's location or color) and the degree to which stimuli in the visual scene match these voluntary control settings. Consequently, nontarget items in the scene that share a defining feature with the target of visual search can capture attention, a phenomenon termed contingent attentional capture. We used functional magnetic resonance imaging to show that attentional capture by target-colored distractors is accompanied by increased cortical activity in corresponding regions of retinotopically organized visual cortex. Concurrent activation in the temporoparietal junction and ventral frontal cortex suggests that these regions coordinate voluntary and stimulus-driven attentional control settings to determine which stimuli effectively compete for attention.     

Surprise-induced blindness: a stimulus-driven attentional limit to conscious perception

The cost of attending to a visual event can be the failure to consciously detect other events. This processing limitation is well illustrated by the attentional blink paradigm, in which searching for and attending to a target presented in a rapid serial visual presentation stream of distractors can impair one's ability to detect a second target presented soon thereafter. The attentional blink critically depends on 'top-down' attentional settings, for it does not occur if participants are asked to ignore the first target. Here we show that 'bottom-up' attention can also lead to a profound but ephemeral deficit in conscious perception: Presentation of a novel, unexpected, and task-irrelevant stimulus virtually abolishes conscious detection of a target presented within half a second after the 'Surprise' stimulus, but only for its earliest occurrences (generally 1 to 2 presentations). This powerful but short-lived deficit contrasts with a milder but more enduring form of attentional capture that accompanies singleton presentations in rapid serial visual presentations. We conclude that the capture of stimulus-driven attention alone can limit explicit perception.     

Goal-driven modulation as a function of time in saccadic target selection

Four experiments were performed to investigate the contribution of goal-driven modulation in saccadic target selection as a function of time. Observers were required to make an eye movement to a prespecified target that was concurrently presented with multiple nontargets and possibly one distractor. Target and distractor were defined in different dimensions (orientation dimension and colour dimension in Experiment 1), or were both defined in the same dimension (i.e., both defined in the orientation dimension in Experiment 2, or both defined in the colour dimension in Experiments 3 and 4). The identities of target and distractor were switched over conditions. Speed-accuracy functions were computed to examine the full time course of selection in each condition. There were three major results. First, the ability to exert goal-driven control increased as a function of response latency. Second, this ability depended on the specific target-distractor combination, yet was not a function of whether target and distractor were defined within or across dimensions. Third, goal-driven control was available earlier when target and distractor were dissimilar than when they were similar. It was concluded that the influence of goal-driven control in visual selection is not all or none, but is of a continuous nature.     

Actions modulate attentional capture

The purpose of the present study was to determine whether the action system plays a role in determining which stimulus characteristics capture attention by assessing the interference effects caused by dynamic discontinuities that have similar attention-capturing properties, but different action affordances. Results revealed that offset distractors caused significant interference when onset targets were presented in a keypress task, but did not increase reaction times when the same onset targets were presented in a goal-directed aiming task In contrast, onset distractors caused interference when offset targets were presented in both keypress and aiming tasks. This pattern of results suggests that the attentional set, and thus the properties of stimuli that capture attention, is modulated by the interaction between stimulus and response expectations.     

Attentional capture in driving displays

Drivers face frequent distraction on the roadways, but little is known about situations placing them at risk of misallocating visual attention. To investigate this issue, we asked participants to search for a red target embedded within simulated driving scenes (photographs taken from inside a car) in three experiments. Distraction was induced by presenting, via a GPS unit, red or green distractors positioned in an irrelevant location at which the target never appeared. If the salient distractor captures attention, visual search should be slower on distractor‐present trials than distractor‐absent trials. In Experiment 1, salient distractors yielded no such capture effect. In Experiment 2, we decreased the frequency of the salient distractor from 50% of trials to only 10% or 20% of trials. Capture effects were almost five times larger for the 10% occurrence group than for the 20% occurrence group. In Experiment 3, the amount of available central resources was manipulated by asking participants to either simultaneously monitor or ignore a stream of spoken digits. Capture effects were much larger for the dual‐task group than for the single‐task group. In summary, these findings identify risk factors for attentional capture in real‐world driving scenes: distractor rarity and diversion of attention.     

Actions modulate attentional capture

The purpose of the present study was to determine whether the action system plays a role in determining which stimulus characteristics capture attention by assessing the interference effects caused by dynamic discontinuities that have similar attention-capturing properties, but different action affordances. Results revealed that offset distractors caused significant interference when onset targets were presented in a keypress task, but did not increase reaction times when the same onset targets were presented in a goal-directed aiming task. In contrast, onset distractors caused interference when offset targets were presented in both keypress and aiming tasks. This pattern of results suggests that the attentional set, and thus the properties of stimuli that capture attention, is modulated by the interaction between stimulus and response expectations.     

Nonspatial interdimensional attentional capture

Accuracy in identifying a target is impaired by a task-irrelevant singleton distractor even when the target and distractor appear in the same location. However, whether this impairment, known as a nonspatial interdimensional attentional capture, is contingent on a top-down attentional set or determined by stimulus-driven signals from distractors is unclear. To examine whether interdimensional attentional capture is affected by a top-down attentional set, the present study explicitly manipulated observers’ search strategies (the singleton detection or feature search modes) and the number of objects consisting of the search items. The results indicated that interdimensional attentional capture occurred even under the feature search mode but that the capture effect decreased under this search mode irrespective of the number of distractors, suggesting that top-down knowledge was effective in modulating nonspatial interdimensional capture.     

Overriding auditory attentional capture

Attentional capture by color singletons during shape search can be eliminated when the target is not a feature singleton (Bacon & Egeth, 1994). This suggests that a "singleton detection" search strategy must be adopted for attentional capture to occur. Here we find similar effects on auditory attentional capture. Irrelevant high-intensity singletons interfered with an auditory search task when the target itself was also a feature singleton. However, singleton interference was eliminated when the target was not a singleton (i.e., when nontargets were made heterogeneous, or when more than one target sound was presented). These results suggest that auditory attentional capture depends on the observer's attentional set, as does visual attentional capture. The suggestion that hearing might act as an early warning system that would always be tuned to unexpected unique stimuli must therefore be modified to accommodate these strategy-dependent capture effects.     

No commonality between attentional capture and attentional blink

Visual search for a unique target is impaired when a salient distractor is presented (attentional capture). This phenomenon is said to occur because attention is diverted to a distractor before it reaches the target. Similarly, perception of the second of two targets embedded in a rapid stream of nontargets is impaired, suggesting attentional deprivation due to the processing of the first target (attentional blink). We examined whether these phenomena emerge from a common underlying attentional mechanism by using correlation studies. If these phenomena share a common foundation, the magnitude of these deficits should show within-subject correlations. Participants (N = 135) revealed significant attentional deficits during spatial and temporal capture and the attentional blink tasks. However, no significant correlation was found among these tasks. Experiment 2 (N = 95) replicated this finding using the same procedure as that used in Experiment 1 but included another attentional blink task that required spatial switching between the two targets. Strong correlations emerged only between the two attentional blink tasks (with/without spatial switching). The present results suggest that attentional deficits during spatial and temporal capture and the attentional blink tasks reflect different aspects of attention.     

No commonality between attentional capture and attentional blink

Visual search for a unique target is impaired when a salient distractor is presented (attentional capture). This phenomenon is said to occur because attention is diverted to a distractor before it reaches the target. Similarly, perception of the second of two targets embedded in a rapid stream of nontargets is impaired, suggesting attentional deprivation due to the processing of the first target (attentional blink). We examined whether these phenomena emerge from a common underlying attentional mechanism by using correlation studies. If these phenomena share a common foundation, the magnitude of these deficits should show within-subject correlations. Participants (N?=?135) revealed significant attentional deficits during spatial and temporal capture and the attentional blink tasks. However, no significant correlation was found among these tasks. Experiment 2 (N?=?95) replicated this finding using the same procedure as that used in Experiment 1 but included another attentional blink task that required spatial switching between the two targets. Strong correlations emerged only between the two attentional blink tasks (with/without spatial switching). The present results suggest that attentional deficits during spatial and temporal capture and the attentional blink tasks reflect different aspects of attention.     

Enhanced attentional capture in trait anxiety

Attentional Control Theory (ACT) proposes that anxiety is specifically associated with more attentional distraction by salient stimuli. Moreover, there is some suggestion that worry is one mechanism whereby anxiety impairs attentional control. However, direct evidence for these hypotheses is lacking. In the current study we addressed limitations of previous work by examining the relationships between trait anxiety and worry and attentional distraction by a salient, task-irrelevant color singleton in a visual search task. Results revealed that trait anxiety, but not worry, was related to increased attentional distraction (i.e., capture) by the color singleton. The current results suggest that anxiety is associated with a general enhancement of bottom-up processes involved in motivational significance detection. (PsycINFO Database Record (c) 2012 APA, all rights reserved).