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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.

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) 2022 APA, all rights reserved).

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.

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. In the present study, we 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.

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.

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 STATEMENTThe 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.

Identifying a fixed-feature singleton that pops out from an otherwise uniform array of distractors elicits an event-related potential (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 (1994) 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-onsetting and longer-lasting singleton detection positivity (SDP) 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).

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.

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.

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.

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.

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.

The capacity of visual short-term memory (VSTM) is commonly estimated by K scores obtained with a change-detection task. Contrary to common belief, K may be influenced not only by capacity but also by the rate at which stimuli are encoded into VSTM. Experiment 1 showed that, contrary to earlier conclusions, estimates of VSTM capacity obtained with a change-detection task are constrained by temporal limitations. In Experiment 2, we used change-detection and backward-masking tasks to obtain separate within-subject estimates of K and of rate of encoding, respectively. A median split based on rate of encoding revealed significantly higher K estimates for fast encoders. Moreover, a significant correlation was found between K and the estimated rate of encoding. The present findings raise the prospect that the reported relationships between K and such cognitive concepts as fluid intelligence may be mediated not only by VSTM capacity but also by rate of encoding.

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.

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.

A recent study in humans (McDonald et al., 2013) found that peripheral, task-irrelevant sounds activated contralateral visual cortex automatically as revealed by an auditory-evoked contralateral occipital positivity (ACOP) recorded from the scalp. The present study investigated the functional significance of this cross-modal activation of visual cortex, in particular whether the sound-evoked ACOP is predictive of improved perceptual processing of a subsequent visual target. A trial-by-trial analysis showed that the ACOP amplitude was markedly larger preceding correct than incorrect pattern discriminations of visual targets that were colocalized with the preceding sound. Dipole modeling of the scalp topography of the ACOP localized its neural generators to the ventrolateral extrastriate visual cortex. These results provide direct evidence that the cross-modal activation of contralateral visual cortex by a spatially nonpredictive but salient sound facilitates the discriminative processing of a subsequent visual target event at the location of the sound. Recordings of event-related potentials to the targets support the hypothesis that the ACOP is a neural consequence of the automatic orienting of visual attention to the location of the sound.

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

The presence of a salient distractor interferes with visual search. According to the salience-driven selection hypothesis, this interference is because of an initial deployment of attention to the distractor. Three event-related potential (ERP) findings have been regarded as evidence for this hypothesis: (a) salient distractors were found to elicit an ERP component called N2pc, which reflects attentional selection; (b) with target and distractor on opposite sides, a distractor N2pc was reported to precede the target N2pc (N2pc flip); (c) the distractor N2pc on slow-response trials was reported to occur particularly early, suggesting that the fastest shifts of attention were driven by salience. This evidence is equivocal, however, because the ERPs were noisy (b, c) and were averaged across all trials, thereby making it difficult to know whether attention was deployed directly to the target on some trials (a, b). We reevaluated this evidence using a larger sample size to reduce noise and by analyzing ERPs separately for fast- and slow-response trials. On fast-response trials, the distractor elicited a contralateral positivity (PD)-an index of attentional suppression-instead of an N2pc. There was no N2pc flip or early distractor N2pc. As it stands, then, there is no ERP evidence for the salience-driven selection hypothesis.

Salient distractors delay visual search for less salient targets in additional-singleton tasks, even when the features of the stimuli are fixed across trials. According to the salience-driven selection hypothesis, this delay is due to an initial attentional deployment to the distractor. Recent event-related potential (ERP) studies found no evidence for salience-driven selection in fixed-feature search, but the methods employed were not optimized to isolate distractor ERP components such as the N2pc and distractor positivity (PD; indices of selection and suppression, respectively). Here, we isolated target and distractor ERPs in two fixed-feature search experiments. Participants searched for a shape singleton in the presence of a more-salient color singleton (Experiment 1) or for a color singleton in the presence of a less-salient shape singleton (Experiment 2). The salient distractor did not elicit an N2pc, but it did elicit a PD on fast-response trials. Furthermore, distractors had no effect on the timing of the target N2pc. These results indicate that (a) the distractor was prevented from engaging the attentional mechanism associated with N2pc, (b) the distractor did not interrupt the deployment of attention to the target, and (c) competition for attention can be resolved by suppressing locations of irrelevant items on a salience-based priority map.

We studied brain activity during retention and retrieval phases of two visual short-term memory (VSTM) experiments. Experiment 1 used a balanced memory array, with one color stimulus in each hemifield, followed by a retention interval and a central probe, at the fixation point that designated the target stimulus in memory about which to make a determination of orientation. Retrieval of information from VSTM was associated with an event-related lateralization (ERL) with a contralateral negativity relative to the visual field from which the probed stimulus was originally encoded, suggesting a lateralized organization of VSTM. The scalp distribution of the retrieval ERL was more anterior than what is usually associated with simple maintenance activity, which is consistent with the involvement of different brain structures for these distinct visual memory mechanisms. Experiment 2 was like Experiment 1, but used an unbalanced memory array consisting of one lateral color stimulus in a hemifield and one color stimulus on the vertical mid-line. This design enabled us to separate lateralized activity related to target retrieval from distractor processing. Target retrieval was found to generate a negative-going ERL at electrode sites found in Experiment 1, and suggested representations were retrieved from anterior cortical structures. Distractor processing elicited a positive-going ERL at posterior electrodes sites, which could be indicative of a return to baseline of retention activity for the discarded memory of the now-irrelevant stimulus, or an active inhibition mechanism mediating distractor suppression.

Synchronization of gamma oscillations among brain regions is relevant for dynamically organizing communication among neurons to support cognitive and perceptual processing, including attention orienting. Recent research has demonstrated that inter-regional synchronization in the gamma-band is modulated by theta rhythms during cortical processing. It has been proposed that such cross-frequency dynamics underlie the integration of local processes into large-scale functional networks. To investigate the potential role of theta-gamma mechanisms during auditory attention control, we localized activated regions using EEG beamformer analysis, and calculated inter-regional gamma-band synchronization between activated regions as well as modulation of inter-regional gamma-band synchronization by the phase of cortical theta rhythms. Abundant synchronization of gamma-band oscillations among regions comprising the auditory attention control network was observed. This inter-regional gamma synchronization was modulated by theta phase. These results provide further evidence implicating inter-regional gamma-band synchronization, and theta-gamma interactions, in task-dependent communication among cortical regions, and provide the first evidence that such mechanisms are relevant for auditory attention control.

A lateralized event-related potential (ERP) component elicited by attention-directing cues (ADAN) has been linked to frontal-lobe control but is often absent when spatial attention is deployed in the auditory modality. Here, we tested the hypothesis that ERP activity associated with frontal-lobe control of auditory spatial attention is distributed bilaterally by comparing ERPs elicited by attention-directing cues and neutral cues in a unimodal auditory task. This revealed an initial ERP positivity over the anterior scalp and a later ERP negativity over the parietal scalp. Distributed source analysis indicated that the anterior positivity was generated primarily in bilateral prefrontal cortices, whereas the more posterior negativity was generated in parietal and temporal cortices. The anterior ERP positivity likely reflects frontal-lobe attentional control, whereas the subsequent ERP negativity likely reflects anticipatory biasing of activity in auditory cortex.

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A substantial literature examining the neural correlates of working memory using functional magnetic resonance imaging (fMRI) has revealed the involvement of a predominantly fronto–parietal network in the maintenance and manipulation of information in working memory. However, the temporal dynamics of activity in this system cannot be revealed by fMRI at the sub-second level. We employed magnetoencephalography (n = 12) to investigate the temporal dynamics of spatial working memory in a well-studied task, the n-back. Dynamic imaging of coherent sources (beamforming) was employed to determine the sources of effects evident in temporal spectral evolution analyses. Results indicated the involvement of brain regions traditionally identified in fMRI, predominantly in the beta frequency range 500–1500 ms post-stimulus.

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.

The neural systems that mediate voluntary shifts of attention to visual and auditory stimuli were investigated by examining the patterns of human brain electricity elicited by attention-directing cues in auditory and visual tasks. Several lateralized event-related potential (ERP) components were observed when participants shifted attention in expectation of visual targets (experiment 1). One component was focused over frontal cortex and a second was focused primarily over the occipital-temporal cortex but also spread to parietal regions of the scalp. Previous work has indicated that the frontal component reflects supramodal processes involved in the executive control of attention and that the posterior component reflects either spatial attentional control processes in the posterior parietal lobe or modulation of processes in visual cortex. Here, the posterior component was observed when participants shifted attention in expectation of auditory targets (experiments 2-4), but the frontal component was found only in the visual task. The posterior component seemed to be generated in parietal and occipital areas even when there was no visual information about the to-be-attended locations. These results are consistent with the view that voluntary shifts of attention are mediated by supramodal processes in the parietal lobe and that the spatial coordinates of the to-be-attended location are based on visual representations of space.

Attended objects are perceived to occur before unattended objects even when the two objects are presented simultaneously. This finding has led to the widespread view that attention modulates the speed of neural transmission in the various perceptual pathways. We recorded event-related potentials during a time-order judgment task to determine whether a reflexive shift of attention to a sudden sound modulates the speed of sensory processing in the human visual system. Attentional cueing influenced the perceived order of lateralized visual events but not the timing of event-related potentials in visual cortex. Attentional cueing did, however, enhance the amplitude of neural activity in visual cortex, which shows that attention-induced shifts in visual time-order perception can arise from modulations of signal strength rather than processing speed in the early visual-cortical pathways.

The time required to find an object of interest in the visual field often increases as a function of the number of items present. This increase or inefficiency was originally interpreted as evidence for the serial allocation of attention to potential target items, but controversy has ensued for decades. We investigated this issue by recording ERPs from humans searching for a target in displays containing several differently colored items. Search inefficiency was ascribed not to serial search but to the time required to selectively process the target once found. Additionally, less time was required for the target to “pop out” from the rest of the display when the color of the target repeated across trials. These findings indicate that task relevance can cause otherwise inconspicuous items to pop out and highlight the need for direct neurophysiological measures when investigating the causes of search inefficiency.

To find objects of interest in a cluttered and continually changing visual environment, humans must often ignore salient stimuli that are not currently relevant to the task at hand. Recent neuroimaging results indicate that the ability to prevent salience-driven distraction depends on the current level of attentional control activity in frontal cortex, but the specific mechanism by which this control activity prevents salience-driven distraction is still poorly understood. Here, we asked whether salience-driven distraction is prevented by suppressing salient distractors or by preferentially up-weighting the relevant visual dimension. We found that salient distractors were suppressed even when they resided in the same feature dimension as the target (that is, when dimensional weighting was not a viable selection strategy). Our neurophysiological measure of suppression—the PDcomponent of the event-related potential—was associated with variations in the amount of time it took to perform the search task: distractors triggered the PDon fast-response trials, but on slow-response trials they triggered activity associated with working memory representation instead. These results demonstrate that during search salience-driven distraction is mitigated by a suppressive mechanism that reduces the salience of potentially distracting visual objects.

We recorded ERPs to pairs of externally presented tones, T, and T 2 . in the absence of attentional cues to determine whether attention is momentarily sustained at the location of a behaviourally relevant sound, and what effect this focusing of attention might have on the neural response to target stimuli. ERPs to T 2 were more negative when the preceding T 1 was presented on the same side of fixation than when T 1 was presented on the opposite side of fixation. This negative difference consisted of an early, parietal phase and a later, frontocentral phase. These results confirm and extend previously reported effects of transient spatial attention on auditory ERPs, and they demonstrate that transient spatial attention has a distinct and robust effect on the early stages of stimulus processing in the auditory system.

Orienting attention involuntarily to the location of a sensory event influences responses to subsequent stimuli that appear in different modalities with one possible exception: orienting attention involuntarily to a sudden light sometimes fails to affect responses to subsequent sounds (e.g., Spence & Driver, 1997). Here we investigated the effects of involuntary attention to a brief flash on the processing of subsequent sounds in a design that eliminates stimulus-response compatibility effects and criterion shifts as confounding factors. In addition, the neural processes mediating crossmodal attention were studied by recording eventrelated brain potentials. Our data show that orienting attention to the location of a spatially nonpredictive visual cue modulates behavioural and neural responses to subsequent auditory targets when the stimulus onset asynchrony is short (between 100 and 300 ms). These findings are consistent with the hypothesis that involuntary shifts of attention are controlled by supramodal brain mechanisms rather than by modality-specific ones. Resume L'orientation involontaire de l'attention vers l'endroit ou se produit un evenememt sensoriel influe les reponses aux stimuli qui sont subsequemment presenter selon des modalites differentes mais A une exception pres : l'orientation involontaire de l'attention provoquee par l'apparition soudaine d'une lumiere ne modifie pas toujours les reponses aux sons ulterieurs (p. ex., Spence et Driver, 1997). Dans la presente etude, nous examinons les effets de l'attention involontaire provoquee par un bref eclair lumineux sur le traitement de sons subsequents selon un plan experimental qui elimine les variables contaminantes qui sont les effets de compatibilite stimulus-reponse et les variations de crit(ere. En outre, les processus neuronaux qui permettent l'attention intermodale sont observes grace A l'enregistrement des potentiels evoques cerebraux. Nos donnees revelent que l'orientation de l'attention vers l'endroit ou est present& un indice visuel non spatialement previsible modifie les reponses comportementales et neuronales a des cibles auditives subsequentes lorsque le delai separant l'apparition de l'amorce et celle de la cible est court Centre 100 et 300 ms). Ces conclusions appuient l'hypothese selon laquelle les deplacements involontaires de l'attention sont sons le controle de mecanismes cerebraux supermodaux plutot que sous celui de mecanismes specifiques aux modalites particulieres. One of the most vigorously debated topics in the field of multisensory research is whether orienting attention to the location of an object involves modality-specific brain mechanisms or supramodal ones. A good deal of research has demonstrated that the neural processes that underlie involuntary shifts of attention in vision, audition, and touch are not completely independent (Farah, Wong, Monheit, & Morrow, 1989; McDonald & Ward, 2000; Spence & Driver, 1997; Ward, 1994; Ward, McDonald, & Lin, 2000). However, the degree to which these processes are integrated across the senses is unclear. One hypothesis is that the same supramodal processes mediate shifts of attention to stimuli appearing in different modalities (Farah et al., 1989; McDonald & Ward, 2001). An alternative hypothesis is that separate but conjoined processes mediate shifts of attention to stimuli appearing in different modalities (Spence & Driver, 1997). According to this latter hypothesis, a shift of attention in one modality elicits a corresponding shift of attention in another modality when a "link" between two different attention mechanisms exists. To determine the degree to which attention-orienting processes are integrated across the senses, researchers have examined the effects of attending to stimuli in one modality on the processing of stimuli in other modalities. In prototypical studies of involuntary, crossmodal attention, a sudden stimulus such as a light flash or noise burst is presented to the left or right side of an observer's point of eye fixation in order to capture attention at that location. …

In a previous study, Ward (1994) reported that spatially uninformative visual cues orient auditory attention but that spatially uninformative auditory cues fail to orient visual attention. This cross-modal asymmetry is consistent with other intersensory perceptual phenomena that are dominated by the visual modality (e.g., ventriloquism). However, Spence and Driver (1997) found exactly the opposite asymmetry under different experimental conditions and with a different task. In spite of the several differences between the two studies, Spence and Driver (see also Driver & Spence, 1998) argued that Ward’s findings might have arisen from response-priming effects, and that the cross-modal asymmetry they themselves reported, in which auditory cues affect responses to visual targets but not vice versa, is in fact the correct result. The present study investigated cross-modal interactions in stimulus-driven spatial attention orienting under Ward’s complex cue environment conditions using an experimental procedure that eliminates response-priming artifacts. The results demonstrate that the cross-modal asymmetry reported by Ward (1994) does occur when the cue environment is complex. We argue that strategic effects in cross-modal stimulus-driven orienting of attention are responsible for the opposite asymmetries found by Ward and by Spence and Driver (1997).

We tested the hypothesis that psychopathy is associated with abnormal processing of semantic and affective verbal information. In Task 1, a lexical decision task, and in Task 2, a word identification task, participants responded faster to concrete than to abstract words. In Task 2, psychopaths made more errors identifying abstract words than concrete words. In Task 3, a word identification task, participants responded faster to positive than to negative words. In all three tasks, nonpsychopaths showed the expected event-related potential (ERP) differentiation between word stimuli, whereas psychopaths did not. In each task, the ERPs of the psychopaths included a large centrofrontal negative-going wave (N350); this wave was absent or very small in the nonpsychopaths. The interpretation and significance of these differences are discussed.