Difficulty suppressing visual distraction while dual tasking.

Human beings must often perform multiple tasks concurrently or in rapid succession. Laboratory research has revealed striking limitations in the ability to dual task by asking participants to identify two target objects that are inserted into a rapid stream of irrelevant items. Under a variety of conditions, identification of the second target (T2) is impaired for a short period of time following presentation of the first target (T1). Several theories have been developed to account for this "attentional blink" (AB), but none makes a specific prediction about how processing of T1 might impact an observer's ability to ignore a salient distractor that accompanies T2. Using event-related potentials (ERPs) to track target and distractor processing, we show that healthy young adults are capable of suppressing a salient visual-search distractor (D2) while dual tasking (as measured by the PD component, which has been associated with suppression) but struggle to do so shortly after the appearance of T1. In fact, the impairment was more severe for distractor processing than it was for target processing (as measured by the N2pc component). Whereas, the T2-elicited N2pc was merely delayed during the AB, the distractor PD was reduced in magnitude and was found to be statistically absent. We conclude that the inhibitory control processes that are typically engaged to prevent distraction are unavailable while an observer is busy processing a target that appeared earlier.

Revisiting the automaticity of reading: Electrophysiological recordings show that stroop words capture spatial attention.

Interference in the Stroop task is reduced when the word and color patch are placed at different locations and is diluted further by the presence of another distractor that is response neutral. Such dilution indicates that reading is not independent of an observer's attentional focus and thus is not a fully automatic process. So where does reading fall on the automaticity continuum? To address this question, we sought to determine whether an irrelevant word that appears abruptly in the field of view invariably draws attention to its location or whether observers can successfully ignore it while identifying a centrally presented target. In two experiments, electrical brain activity was recorded while healthy young adults participated in nonintegrated Stroop tasks. Irrelevant color words appearing randomly to the left or right of a target shape elicited an event-related potential component that reflects the spatial focusing of attention (posterior contralateral N2; N2pc). This N2pc was observed when participants discriminated the color of the target and when they discriminated the shape of the target. These findings demonstrate that color words reflexively capture spatial attention even when their meaning is unrelated to the task at hand. We conclude that although reading is not fully automatic, skilled readers cannot ignore words that appear abruptly in their field of view. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Attentional enhancement predicts individual differences in visual working memory under go/no-go search conditions.

Attention-control processes transfer relevant information to visual working memory (WM) and prevent irrelevant information from consuming WM resources. Although event-related potentials (ERPs) have revealed attention-control processes associated with enhancement of relevant stimuli (targets) and suppression of irrelevant stimuli (distractors), only the suppressive processes have been found to predict WM capacity. We hypothesised a link between target-enhancement processes and WM capacity would be revealed in a task that requires more control than the conventional visual search paradigms used to study target selection. Here, participants searched for a pop-out target on Go trials and withheld responses on an equal number of randomly intermixed No-Go trials, depending on the colour of the stimulus array. Magnitudes of ERP indices associated with target enhancement (the singleton detection positivity, SDP, and N2pc) were positively correlated with individual differences in WM capacity. These relationships vanished when participants searched for the pop-out target on every trial, regardless of stimulus-array colour. Inhibitory processes associated with suppressing distractors (PD) and withholding responses (no-go P3) on No-Go trials did not predict WM capacity. These findings indicate that target-enhancement mechanisms control access to WM in search tasks that require dynamic control and disconfirm the view that the gateway to WM is entirely inhibitory by nature.

Searching for Visual Singletons Without A Feature to Guide Attention.

RT studies have provided evidence for a singleton-detection strategy that is used to search for salient targets when there is no additional featural knowledge that would help guide attention. Despite this behavioral evidence, there have been few ERP studies of singleton detection mode because it was reported early on that the ERP signature of attentional selection (the N2pc) is absent without feature guidance. Recently, however, it was discovered that a small and relatively late N2pc occurs in singleton detection mode along with a previously unreported component called the singleton detection positivity (SDP). Here, we show that both components are influenced by the number of items in the display, as one might expect in a salience-based search mode. Specifically, the N2pc and SDP were larger when the set size was increased to make the singleton "pop out" more easily, when participants responded more quickly regardless of set size, and when RT search slopes were negative (Experiment 1). The latency of the SDP also depended on set size. In Experiment 2, EEG was recorded with a higher density electrode array to better characterize the scalp topography of the components and to estimate their neural sources. Regional sources near the ventral surface of extrastriate cortex in the occipital lobe explained over 96% of N2pc and SDP activities. These results indicate that searching in singleton detection mode selectively modulates processing within perceptual regions of visual cortex.

Isolating the Neural Substrates of Visually Guided Attention Orienting in Humans.

The neural processes that enable healthy humans to orient attention to sudden visual events are poorly understood because they are tightly intertwined with purely sensory processes. Here we isolated visually guided orienting activity from sensory activity using event-related potentials (ERPs). By recording ERPs to a lateral stimulus and comparing waveforms obtained under conditions of attention and inattention, we identified an early positive deflection over the ipsilateral visual cortex that was associated with the covert orienting of visual attention to the stimulus. Across five experiments with male and female adult participants, this ipsilateral visual orienting activity (VOA) could be distinguished from purely sensory-evoked activity and from other top-down spatial attention effects. The VOA was linked with behavioral measures of orienting, being significantly larger when the stimulus was detected rapidly than when it was detected more slowly, and its presence was independent of saccadic eye movements toward the targets. The VOA appears to be a specific neural index of the visually guided orienting of attention to a stimulus that appears abruptly in an otherwise uncluttered visual field.SIGNIFICANCE STATEMENT The study of visual attention orienting has been an important impetus for the field of cognitive neuroscience. Seminal reaction-time studies demonstrated that a suddenly appearing visual stimulus attracts attention involuntarily, but the neural processes associated with visually guided attention orienting have been difficult to isolate because they are intertwined with sensory processes that trigger the orienting. Here, we disentangled orienting activity from sensory activity using scalp recordings of event-related electrical activity in the human brain. A specific neural index of visually guided attention orienting was identified. Surprisingly, whereas peripheral sensory stimulation is processed initially and predominantly by the contralateral visual cortex, this electrophysiological index of visual orienting was recorded over the cerebral hemisphere that was ipsilateral to the attention-capturing stimulus.

Dynamic inhibitory control prevents salience-driven capture of visual attention.

The salience-driven selection theory is comprised of three main tenets: (a) the most salient stimulus within a monitored region of the visual field captures attention, (b) the only way to prevent salience-driven distraction is by narrowly focusing attention elsewhere, and (c) all other goal-driven processes are possible only after the most salient item has been attended. Evidence for and against this theory has been provided from two experimental paradigms. Here, event-related potentials (ERPs) recorded in a novel Go/No-Go paradigm disconfirmed all three of tenets of the theory. Participants were instructed to search cyan-item displays for a salient orientation singleton (Go trials) and to ignore randomly intermixed yellow-item displays that could also contain an orientation singleton (No-Go trials). ERP components associated with attentional orienting (posterior contralateral N2; N2pc), distractor suppression (distractor positivity; PD), and stimulus relevance (P2a) were isolated to test predictions stemming from the salience-driven selection theory. On No-Go trials, the salient oddball elicited a PD rather than an N2pc, indicating that it was suppressed, not attended. Moreover, a P2a emerged before the N2pc on Go trials, demonstrating that observers first evaluated the global color of each display and then decided to search for the oddball (Go trials) or to ignore it (No-Go trials). We conclude that goal-driven processes can lead to the prevention of salience-driven attention capture by salient visual objects within the attentional window. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Diversion of Attention Leads to Conflict between Concurrently Attended Stimuli, Not Delayed Orienting to the Object of Interest.

The control processes that guide attention to a visual-search target can result in the selection of an irrelevant object with similar features (a distractor). Once attention is captured by such a distractor, search for a subsequent target is momentarily impaired if the two stimuli appear at different locations. The textbook explanation for this impairment is based on the notion of an indivisible focus of attention that moves to the distractor, illuminates a nontarget that subsequently appears at that location, and then moves to the target once the nontarget is rejected. Here, we show that such delayed orienting to the target does not underlie the behavioral cost of distraction. Observers identified a color-defined target appearing within the second of two stimulus arrays. The first array contained irrelevant items, including one that shared the target's color. ERPs were examined to test two predictions stemming from the textbook serial-orienting hypothesis. Namely, when the target and distractor appear at different locations, (1) the target should elicit delayed selection activity relative to same-location trials, and (2) the nontarget search item appearing at the distractor location should elicit selection activity that precedes selection activity tied to the target. Here, the posterior contralateral N2 component was used to track selection of each of these search-array items and the previous distractor. The results supported neither prediction above, thereby disconfirming the serial-orienting hypothesis. Overall, the results show that the behavioral costs of distraction are caused by perceptual and postperceptual competition between concurrently attended target and nontarget stimuli.

Recoiling from Threat: Anxiety is Related to Heightened Suppression of Threat, Not Increased Attention to Threat.

Increased attention to threat is considered a core feature of anxiety. However, there are multiple mechanisms of attention and multiple types of threat, and the relationships among attention, threat, and anxiety are poorly understood. The present study used event-related potentials (ERPs) to separately isolate attentional selection (N2pc) and suppression (PD) of pictorial threats (photos of weapons, snakes, etc.) and conditioned threats (colored shapes paired with electric shock). In a sample of 48 young adults, both threat types were initially selected for increased attention (an N2pc), but only conditioned threats elicited subsequent suppression (a PD) and a reaction time (RT) bias. Levels of trait anxiety were unrelated to N2pc amplitude, but increased anxiety was associated with larger PDs (i.e., greater suppression) and reduced RT bias to conditioned threats. These results suggest that anxious individuals do not pay more attention to threats, but rather engage more attentional suppression to overcome threats.

Circadian misalignment impairs ability to suppress visual distractions.

Evening-type individuals often perform poorly in the morning because of a mismatch between internal circadian time and external social time, a condition recognized as social jet lag. Performance impairments near the morning circadian (~24 hr) trough have been attributed to deficits in attention, but the nature of the impairment is unknown. Using electrophysiological indices of attentional selection (N2pc) and suppression (PD ), we show that evening-type individuals have a specific disability in suppressing irrelevant visual distractions. More specifically, evening-type individuals managed to suppress a salient distractor in an afternoon testing session, as evidenced by a PD , but were less able to suppress the distractor in a morning testing session, as evidenced by an attenuated PD and a concomitant distractor-elicited N2pc. Morning chronotypes, who would be well past their circadian trough at the time of testing, did not show this deficit at either test time. These results indicate that failure to filter out irrelevant stimuli at an early stage of perceptual processing contributes to impaired cognitive functioning at nonoptimal times of day and may underlie real-world performance impairments, such as distracted driving, that have been associated with circadian mismatch.

From alternation to repetition: Spatial attention biases contribute to sequential effects in a choice reaction-time task.

Observers often take longer to respond to a visual target when it appears at a recently stimulated location than when it appears at a new location in the visual field. This behavioral impairment - known as inhibition of return (IOR) - is mirrored by a reduction of an event-related potential (ERP) component called the N2pc that has been associated with attentional selection. Together, these findings indicate that the mechanism underlying IOR operates to bias covert attention against re-visiting the most recently attended location. The goal of the present study was to determine how this inhibitory attention bias evolves across successive trials of a two-item search task. Initially, targets appearing at previously attended locations were associated with behavioral IOR and a concomitant reduction of the N2pc. After several successive trials, this initial inhibitory bias was superseded by expectancy-based biases associated with "predictable" inter-trial patterns of location repeats or location changes, in some cases leading to faster responses and a larger N2pc when the target location repeated (facilitation of return).  These results provide evidence that biases in the covert deployment of attention are updated dynamically according to the recent selection history and contribute to well-known sequential effects in serial choice reaction-time tasks.

Involuntary orienting of attention to sight or sound relies on similar neural biasing mechanisms in early visual processing.

A sudden visual or acoustic change in the environment can capture attention involuntarily and facilitate perceptual processing of a subsequent visual target at the same location. The behavioral consequences of this involuntary (exogenous) cueing of attention have been well documented, but the underlying neural mechanisms and how they may differ depending on the modality of the cue remain unknown. We here report the effects of a spatially uninformative visual cue on the processing of a subsequent visual target and neural activity elicited by the cue itself and compare these results to the effects of an auditory cue. The results reveal that both visual and auditory cues enhanced the perceived brightness contrast of the subsequent co-localized target and boosted early cortical processing of the target beginning at about 100 ms post-target onset. Furthermore, both visual and auditory cues elicited a slow positive deflection (visible on target-absent trials) that was larger over contralateral relative to ipsilateral occipital scalp regions and was hypothesized to reflect the biasing of visual sensitivity for potential targets at that location. Overall, the data suggest that sudden events in the environment - regardless of sensory modality - initiate involuntary shifts of attention to the event's location and that the visual-perceptual consequences and neural mechanisms of these involuntary shifts are qualitatively similar for auditory and visual events.

Electrophysiological correlates of visual singleton detection.

Identifying a fixed-feature singleton that pops out from an otherwise uniform array of distractors elicits an ERP component called the N2pc over the posterior scalp. The N2pc has been used to track attention with millisecond accuracy, inform theories of visual selection, and test for specific attention deficits in clinical populations, yet it is still unclear what neuro-cognitive process gives rise to the component. One hypothesis is that the N2pc reflects a spatial filtering process that suppresses irrelevant distractors. In support of this hypothesis, Luck and Hillyard (1994a) showed that the N2pc is eliminated when the features of the target and distractors switch unpredictably across trials (so that participants cannot prepare to filter out irrelevant items). The present study aimed to replicate Luck and Hillyard's singleton detection experiment but with modifications to enhance the N2pc signal and to gain statistical power. We show that orientation singletons do, in fact, elicit the N2pc as well as an earlier-onset and longer-lasting singleton detection positivity over the occipital scalp when the target and distractor orientations swap randomly across trials. We conclude that spatial filtering might not play a major role in the generation of the N2pc and that the selection processes required to search for fixed-feature targets (in feature-search mode) are also engaged in the detection of variable-feature singletons (in singleton detection mode).

High Level of Trait Anxiety Leads to Salience-Driven Distraction and Compensation.

Individuals with high levels of anxiety are hypothesized to have impaired executive control functions that would otherwise enable efficient filtering of irrelevant information. Pinpointing specific deficits is difficult, however, because anxious individuals may compensate for deficient control functions by allocating greater effort. Here, we used event-related-potential indices of attentional selection (the N2pc) and suppression (the PD) to determine whether high trait anxiety is associated with a deficit in preventing the misallocation of attention to salient, but irrelevant, visual search distractors. Like their low-anxiety counterparts ( n = 19), highly anxious individuals ( n = 19) were able to suppress the distractor, as evidenced by the presence of a PD. Critically, however, the distractor was found to trigger an earlier N2pc in the high-anxiety group but not in the low-anxiety group. These findings indicate that, whereas individuals with low anxiety can prevent distraction in a proactive fashion, anxious individuals deal with distractors only after they have diverted attention.

Salience drives overt selection of two equally relevant visual targets.

In the present study, we investigated whether salience determines the sequence of selection when participants search for two equally relevant visual targets. To do this, attentional selection was tracked overtly as observers inspected two items of differing physical salience: one a highly salient color singleton, and the other a less salient shape singleton. Participants were instructed to make natural eye movements in order to determine whether two line segments contained within the two singletons were oriented in the same or in different directions. Because both singleton items were task-relevant, participants had no reason to inspect one item before the other. As expected, observers fixated both targets on the majority of trials. Critically, saccades to the color singleton preceded saccades to the less salient shape singleton on the majority of trials. This demonstrates that the order of attentional object selection is largely determined by stimulus salience when task relevance is equated.

Electrophysiological evidence of an attentional bias in crossmodal inhibition of return.

Inhibition of return (IOR) refers to a delay in responding to targets when they appear at recently attended locations, relative to unattended locations. Within the visual modality, this attentional bias has been associated with a reduction in the N2pc event-related potential (ERP) component at previously attended locations. The present study examined whether a similar attentional bias was observed in crossmodal audio-visual IOR. Our results demonstrate that for visual targets, the attentional component of IOR behaves similarly for both unimodal and crossmodal target pairs, as indexed by a reduction in the N2pc component for targets appearing at previously attended locations. Further, similar IOR-related modulations on the auditory-evoked N2ac indicated that an attentional bias can be observed for auditory targets as well. Finally, we identified two additional ERP components - the ACOP and VCAN - that appear to reflect biasing of attention in the currently unattended sensory modality. These results suggest that the inhibitory attentional bias that underlies the IOR effect may be supramodal and bias attention away from previously attended locations regardless of sensory modality.

Learning what matters: A neural explanation for the sparsity bias.

The visual environment is filled with complex, multi-dimensional objects that vary in their value to an observer's current goals. When faced with multi-dimensional stimuli, humans may rely on biases to learn to select those objects that are most valuable to the task at hand. Here, we show that decision making in a complex task is guided by the sparsity bias: the focusing of attention on a subset of available features. Participants completed a gambling task in which they selected complex stimuli that varied randomly along three dimensions: shape, color, and texture. Each dimension comprised three features (e.g., color: red, green, yellow). Only one dimension was relevant in each block (e.g., color), and a randomly-chosen value ranking determined outcome probabilities (e.g., green > yellow > red). Participants were faster to respond to infrequent probe stimuli that appeared unexpectedly within stimuli that possessed a more valuable feature than to probes appearing within stimuli possessing a less valuable feature. Event-related brain potentials recorded during the task provided a neurophysiological explanation for sparsity as a learning-dependent increase in optimal attentional performance (as measured by the N2pc component of the human event-related potential) and a concomitant learning-dependent decrease in prediction errors (as measured by the feedback-elicited reward positivity). Together, our results suggest that the sparsity bias guides human reinforcement learning in complex environments.

Involuntary orienting of attention to a sound desynchronizes the occipital alpha rhythm and improves visual perception.

Directing attention voluntarily to the location of a visual target results in an amplitude reduction (desynchronization) of the occipital alpha rhythm (8-14Hz), which is predictive of improved perceptual processing of the target. Here we investigated whether modulations of the occipital alpha rhythm triggered by the involuntary orienting of attention to a salient but spatially non-predictive sound would similarly influence perception of a subsequent visual target. Target discrimination was more accurate when a sound preceded the target at the same location (validly cued trials) than when the sound was on the side opposite to the target (invalidly cued trials). This behavioral effect was accompanied by a sound-induced desynchronization of the alpha rhythm over the lateral occipital scalp. The magnitude of alpha desynchronization over the hemisphere contralateral to the sound predicted correct discriminations of validly cued targets but not of invalidly cued targets. These results support the conclusion that cue-induced alpha desynchronization over the occipital cortex is a manifestation of a general priming mechanism that improves visual processing and that this mechanism can be activated either by the voluntary or involuntary orienting of attention. Further, the observed pattern of alpha modulations preceding correct and incorrect discriminations of valid and invalid targets suggests that involuntary orienting to the non-predictive sound has a rapid and purely facilitatory influence on processing targets on the cued side, with no inhibitory influence on targets on the opposite side.

Signal enhancement, not active suppression, follows the contingent capture of visual attention.

Irrelevant visual cues capture attention when they possess a task-relevant feature. Electrophysiologically, this contingent capture of attention is evidenced by the N2pc component of the visual event-related potential (ERP) and an enlarged ERP positivity over the occipital hemisphere contralateral to the cued location. The N2pc reflects an early stage of attentional selection, but presently it is unclear what the contralateral ERP positivity reflects. One hypothesis is that it reflects the perceptual enhancement of the cued search-array item; another hypothesis is that it is time-locked to the preceding cue display and reflects active suppression of the cue itself. Here, we varied the time interval between a cue display and a subsequent target display to evaluate these competing hypotheses. The results demonstrated that the contralateral ERP positivity is tightly time-locked to the appearance of the search display rather than the cue display, thereby supporting the perceptual enhancement hypothesis and disconfirming the cue-suppression hypothesis. (PsycINFO Database Record

Inability to suppress salient distractors predicts low visual working memory capacity.

According to contemporary accounts of visual working memory (vWM), the ability to efficiently filter relevant from irrelevant information contributes to an individual's overall vWM capacity. Although there is mounting evidence for this hypothesis, very little is known about the precise filtering mechanism responsible for controlling access to vWM and for differentiating low- and high-capacity individuals. Theoretically, the inefficient filtering observed in low-capacity individuals might be specifically linked to problems enhancing relevant items, suppressing irrelevant items, or both. To find out, we recorded neurophysiological activity associated with attentional selection and active suppression during a competitive visual search task. We show that high-capacity individuals actively suppress salient distractors, whereas low-capacity individuals are unable to suppress salient distractors in time to prevent those items from capturing attention. These results demonstrate that individual differences in vWM capacity are associated with the timing of a specific attentional control operation that suppresses processing of salient but irrelevant visual objects and restricts their access to higher stages of visual processing.

Cross-modal orienting of visual attention.

This article reviews a series of experiments that combined behavioral and electrophysiological recording techniques to explore the hypothesis that salient sounds attract attention automatically and facilitate the processing of visual stimuli at the sound's location. This cross-modal capture of visual attention was found to occur even when the attracting sound was irrelevant to the ongoing task and was non-predictive of subsequent events. A slow positive component in the event-related potential (ERP) that was localized to the visual cortex was found to be closely coupled with the orienting of visual attention to a sound's location. This neural sign of visual cortex activation was predictive of enhanced perceptual processing and was paralleled by a desynchronization (blocking) of the ongoing occipital alpha rhythm. Further research is needed to determine the nature of the relationship between the slow positive ERP evoked by the sound and the alpha desynchronization and to understand how these electrophysiological processes contribute to improved visual-perceptual processing.