Failures to ignore entirely irrelevant distractors: the role of load

In daily life (e.g., in the work environment) people are often distracted by stimuli that are clearly irrelevant to the current task and should be ignored. In contrast, much applied distraction research has focused on task interruptions by information that requires a response and therefore cannot be ignored. Moreover, the most commonly used laboratory measures of distractibility (e.g., in the response-competition and attentional-capture paradigms), typically involve distractors that are task relevant (e.g., through response associations or location). A series of experiments assessed interference effects from stimuli that are entirely unrelated to the current task, comparing the effects of perceptual load on task-irrelevant and task-relevant (response competing) distractors. The results showed that an entirely irrelevant distractor can interfere with task performance to the same extent as a response-competing distractor and that, as with other types of distractors, the interfering effects of the irrelevant distractors can be eliminated with high perceptual load in the relevant task. These findings establish a new laboratory measure of a form of distractibility common to everyday life and highlight load as an important determinant of such distractibility.     

Harnessing the wandering mind: The role of perceptual load

Perceptual load is a key determinant of distraction by task-irrelevant stimuli (e.g., Lavie, N. (2005). Distracted and confused?: Selective attention under load. Trends in Cognitive Sciences, 9, 75-82). Here we establish the role of perceptual load in determining an internal form of distraction by task-unrelated thoughts (TUTs or “mind-wandering”).Four experiments demonstrated reduced frequency of TUTs with high compared to low perceptual load in a visual-search task. Alternative accounts in terms of increased demands on responses, verbal working memory or motivation were ruled out and clear effects of load were found for unintentional TUTs. Individual differences in load effects on internal (TUTs) and external (response-competition) distractors were correlated. These results suggest that exhausting attentional capacity in task-relevant processing under high perceptual load can reduce processing of task-irrelevant information from external and internal sources alike.     

Perceptual load modulates the processing of distractors presented at task-irrelevant locations during the attentional blink

The distribution of attention in both space and time is critical for processing our dynamic environment. Studies of spatial attention suggest that the distribution of attention is decreased when the perceptual load of a task increases, resulting in decreased processing of task-irrelevant distractors. Studies of the attentional blink (AB) suggest that the temporal distribution of attention also influences distractor processing, such that distractor processing increases during the AB relative to outside the AB (Jiang & Chun, 2001). Two experiments are reported in which the extent to which the difficulty of the first target task (T1) modulates the processing of task-irrelevant distractors during the AB was tested. To investigate this issue, both the first and second target tasks (T1 and T2) required identifying a central stimulus that was flanked by low-load or high-load distractors. Consistent with previous studies of the AB, there was evidence of more distractor processing during the AB than outside the AB. Critically, however, the interference caused by distractors presented simultaneously with T2 during the AB was reduced when T1 perceptual load was high relative to when it was low. These results suggest that increasing T1 perceptual load decreases distractor processing during the AB and that perceptual processes influence both the temporal and spatial distribution of attention.     

The cognitive loci of the display and task-relevant set size effects on distractor interference: Evidence from a dual-task paradigm

The congruency effect of a task-irrelevant distractor has been found to be modulated by task-relevant set size and display set size. The present study used a psychological refractory period (PRP) paradigm to examine the cognitive loci of the display set size effect (dilution effect) and the task-relevant set size effect (perceptual load effect) on distractor interference. A tone discrimination task (Task 1), in which a response was made to the pitch of the target tone, was followed by a letter discrimination task (Task 2) in which different types of visual target display were used. In Experiment 1, in which display set size was manipulated to examine the nature of the display set size effect on distractor interference in Task 2, the modulation of the congruency effect by display set size was observed at both short and long stimulus-onset asynchronies (SOAs), indicating that the display set size effect occurred after the target was selected for processing in the focused attention stage. In Experiment 2, in which task-relevant set size was manipulated to examine the nature of the task-relevant set size effect on distractor interference in Task 2, the effects of task-relevant set size increased with SOA, suggesting that the target selection efficiency in the preattentive stage was impaired with increasing task-relevant set size. These results suggest that display set size and task-relevant set size modulate distractor processing in different ways.     

Perceptual grouping operates independently of attentional selection: Evidence from hemispatial neglect

To what extent can human observers process visual information that is not currently the focus of attention? We evaluated the extent to which unattended visual information (i.e., that which appears on the neglected side of space in individuals with hemispatial neglect) is perceptually organized and influences the perceptual processing of information on the attended side. To examine this, patients (and matched controls) judged whether successive, complex checkerboard stimuli (targets), presented entirely to their intact side of space, were the same or different. Concurrent with this demanding task, irrelevant distractor elements appeared on the unattended side and either changed or retained their perceptual grouping on successive displays, independently of changes in the ipsilesional task-relevant target. Changes in the grouping of the unattended task-irrelevant distractor elements produced congruency effects on the attended target-change judgment to the same extent in the neglect patients as in the control participants, and this was true even in those patients with severe attentional deficits. These results suggest that some perceptual processes, such as grouping, can operate in the absence of attention.     

Working memory load and distraction: dissociable effects of visual maintenance and cognitive control

We establish a new dissociation between the roles of working memory (WM) cognitive control and visual maintenance in selective attention as measured by the efficiency of distractor rejection. The extent to which focused selective attention can prevent distraction has been shown to critically depend on the level and type of load involved in the task. High perceptual load that consumes perceptual capacity leads to reduced distractor processing, whereas high WM load that reduces WM ability to exert priority-based executive cognitive control over the task results in increased distractor processing (e.g., Lavie, Trends in Cognitive Sciences, 9(2), 75–82, 2005). WM also serves to maintain task-relevant visual representations, and such visual maintenance is known to recruit the same sensory cortices as those involved in perception (e.g., Pasternak & Greenlee, Nature Reviews Neuroscience, 6(2), 97–107, 2005). These findings led us to hypothesize that loading WM with visual maintenance would reduce visual capacity involved in perception, thus resulting in reduced distractor processing—similar to perceptual load and opposite to WM cognitive control load. Distractor processing was assessed in a response competition task, presented during the memory interval (or during encoding; Experiment 1a) of a WM task. Loading visual maintenance or encoding by increased set size for a memory sample of shapes, colors, and locations led to reduced distractor response competition effects. In contrast, loading WM cognitive control with verbal rehearsal of a random letter set led to increased distractor effects. These findings confirm load theory predictions and provide a novel functional distinction between the roles of WM maintenance and cognitive control in selective attention.     

知觉负载对负性分心面孔的知觉加工和记忆的影响

本研究采用视觉搜索和意外再认记忆任务,结合事件相关电位技术,考察知觉负载对负性分心面孔的知觉加工和记忆的影响。在视觉搜索任务中,行为上恐惧分心面孔在高负载下干扰任务。ERP结果上,恐惧比中性分心面孔诱发更大的N170和N250;在低负载下恐惧比中性分心面孔诱发更大的N700,在高负载下没有差异。在意外再认记忆中,个体对低负载下的恐惧分心面孔表现出记忆。这些结果说明负性分心物在早期是自动化加工;晚期加工受知觉负载的调节,负载越低对负性分心物的过滤越少,存在对负性分心物的记忆偏向。     

Absorbed in thought: the effect of mind wandering on the processing of relevant and irrelevant events

This study used event-related potentials to explore whether mind wandering (task-unrelated thought, or TUT) emerges through general problems in distraction, deficits of task-relevant processing (the executive-function view), or a general reduction in attention to external events regardless of their relevance (the decoupling hypothesis). Twenty-five participants performed a visual oddball task, in which they were required to differentiate between a rare target stimulus (to measure task-relevant processes), a rare novel stimulus (to measure distractor processing), and a frequent nontarget stimulus. TUT was measured immediately following task performance using a validated retrospective measure. High levels of TUT were associated with a reduction in cortical processing of task-relevant events and distractor stimuli. These data contradict the suggestion that mind wandering is associated with distraction problems or specific deficits in task-relevant processes. Instead, the data are consistent with the decoupling hypothesis: that TUT dampens the processing of sensory information irrespective of that information's task relevance.     

Blinded by fear? Prior exposure to fearful faces enhances attentional processing of task-irrelevant stimuli

Threatening information has been shown to both capture attention and enhance sensory processing. Recent evidence has also suggested that exposure to fearful stimuli may enhance perceptual processing of subsequently presented information, as well as increase attentional capacity. However, these results are inconsistent with other findings that fearful stimuli reduce task-irrelevant distraction and improve selective attention. Here, we investigated the effect of prior exposure to fearful faces on performance in the Eriksen flanker task. Across experiments, fearful cues led to increased task-irrelevant distraction for items positioned across visual space, in contrast to other emotional expressions and inverted face items, and under conditions of attentional load. Findings support the view that fearful images enhance attentional capacity, allowing one to attend to as much visual information as possible when danger is implied. Conflicting findings on the effect of fear and selective attention are discussed.     

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

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

从知觉负载理论来理解选择性注意

知觉负载理论被认为解决了选择性注意研究的早选择和晚选择观点之争。当前任务对注意资源的耗用程度决定了与任务无关的干扰刺激得到多少加工,从而导致在低知觉负载下,注意资源自动溢出去加工干扰刺激（晚选择）,而在高知觉负载下,注意资源被当前任务耗尽而无法加工干扰刺激（早选择）。知觉负载理论提出后,研究者进行了一系列研究。一部分工作专注于知觉负载对选择性注意的调节作用;另外一些工作则关注其他认知过程如何影响注意资源的分配,其中知觉负载与工作记忆负载的关系是当前关注重点。     

The inability to ignore auditory distractors as a function of visual task perceptual load

Using a response competition paradigm, we investigated the ability to ignore target response-compatible, target response-incompatible, and neutral visual and auditory distractors presented during a visual search task. The perceptual load model of attention (e.g., Lavie & Tsal, 1994) states that task-relevant processing load determines irrelevant distractor processing in such a way that increasing processing load prevents distractor processing. In three experiments, participants searched sets of one (easy search) or six (hard search) similar items. In Experiment 1, visual distractors influenced reaction time (RT) and accuracy only for easy searches, following the perceptual load model. Surprisingly, auditory distractors yielded larger distractor compatibility effects (median RT for incompatible trials minus median RT for compatible trials) for hard searches than for easy searches. In Experiments 2 and 3, during hard searches, consistent RT benefits with response-compatible and RT costs with response-incompatible auditory distractors occurred only for hard searches. We suggest that auditory distractors are processed regardless of visual perceptual load but that the ability to inhibit cross-modal influence from auditory distractors is reduced under high visual load.     

Asymmetrical perceptual load in lateralised word processing

We applied the Load Theory of attention (Lavie, 1995, 2005) to the case of distraction during processing of lateralised words presented in either the right or the left visual fields. Previous research (Brand-D'Abrescia & Lavie, 2007) showed that lexicality affects selective attention such that the number of letters in a search task only increases perceptual load and reduces irrelevant distractor effects for searches in nonwords but not in words. The present study examined the hypothesis that the effect of lexicality on distractor processing would be stronger for words presented to the left compared to the right hemisphere. The results supported this hypothesis and their implications for attention to words in the two cerebral hemispheres are discussed. We suggest that the efficiency of attentional selection differed because perceptual load in the visual fields taxed processing depending on hemispheric language expertise.     

Distractor effects during processing of words under load

The perceptual load model of attention (Lavie, 1995) suggests that processing of irrelevant distractors depends on the extent to which a relevant task engages full perceptual capacity. Word recognition models suggest that letter perception is facilitated in words relative to nonwords. These models led us to hypothesize that increasing the number of letters would increase perceptual load more for nonwords than for words, and thus would be more likely to exhaust capacity and eliminate distractor processing for nonwords than for words. In support of this hypothesis, we found that increasing the number of search letters increases RTs more for nonwords than for words and only reduces distractor interference for nonwords. Thus, although readers process words more efficiently than nonwords, they also become more prone to distraction when processing words.     

The role of perceptual load in inattentional blindness

Perceptual load theory offers a resolution to the long-standing early vs. late selection debate over whether task-irrelevant stimuli are perceived, suggesting that irrelevant perception depends upon the perceptual load of task-relevant processing. However, previous evidence for this theory has relied on RTs and neuroimaging. Here we tested the effects of load on conscious perception using the "inattentional blindness" paradigm. As predicted by load theory, awareness of a task-irrelevant stimulus was significantly reduced by higher perceptual load (with increased numbers of search items, or a harder discrimination vs. detection task). These results demonstrate that conscious perception of task-irrelevant stimuli critically depends upon the level of task-relevant perceptual load rather than intentions or expectations, thus enhancing the resolution to the early vs. late selection debate offered by the perceptual load theory.     

Task-relevance modulates the effects of peripheral distractors

The current study investigated whether task-relevant information affects performance differently from how information that is not relevant for the task does when presented peripherally and centrally. In three experiments a target appeared inside the focus of attention, whereas a to-be-ignored distractor appeared either in the periphery (Experiments 1 and 2) or at the centre (Experiment 3) of attention. In each trial the distractor carried both task-relevant and irrelevant information. The results confirmed the “task relevance” hypothesis: Task-irrelevant information affected performance only when it appeared at the centre of attention, whereas task-relevant information affected performance when it appeared inside as well as outside the main focus of attention. The current results do not support suggestions that spatial stimuli (e.g., arrows) draw attention automatically regardless of task relevance.     

Task-relevance modulates the effects of peripheral distractors

The current study investigated whether task-relevant information affects performance differently from how information that is not relevant for the task does when presented peripherally and centrally. In three experiments a target appeared inside the focus of attention, whereas a to-be-ignored distractor appeared either in the periphery (Experiments 1 and 2) or at the centre (Experiment 3) of attention. In each trial the distractor carried both task-relevant and irrelevant information. The results confirmed the “task relevance” hypothesis: Task-irrelevant information affected performance only when it appeared at the centre of attention, whereas task-relevant information affected performance when it appeared inside as well as outside the main focus of attention. The current results do not support suggestions that spatial stimuli (e.g., arrows) draw attention automatically regardless of task relevance.     

The role of consciousness in attentional control differences in trait anxiety

Trait anxiety has long been associated with impaired selective attention to task-irrelevant threat stimuli, both when threat is presented consciously and outside of awareness. However recent research has suggested broader deficits in selective attention, with poorer ability to ignore supraliminal non-emotional information in anxiety. Here, we investigated whether anxiety could equally be associated with poorer selective attention for non-emotional stimuli in a subliminal context. Participants performed a simple arrow discrimination task, where prior incompatible or compatible response primes were presented before targets either unmasked (supraliminal) or masked (subliminal). While distractor interference was evident in both conditions, trait anxiety was associated with increased task-irrelevant processing only in the supraliminal condition; group effects were eliminated when primes were masked. Our findings are in line with traditional accounts suggesting that differences in selective attention and cognitive control solely modulate conscious distractor processing.     

Contrasting effects of sensory limits and capacity limits in visual selective attention

The effects of perceptual load and those of target-stimulus degradation on distractor processing were contrasted. Targets either had to be found among several nontargets (high perceptual load) or were presented alone and were intact (low perceptual load), had reduced size and contrast (Experiment 1), had reduced duration and were followed by a mask (Experiment 2), or had reduced visual acuity owing to position eccentricity (Experiment 3) in the degraded low-load condition. The results showed that both high perceptual load and target degradation increased general task difficulty, as is reflected by overall reaction times and accuracy. However, whereas high perceptual load reduced response-competition effects of irrelevant distractors, target degradation increased distractor effects. These results support the hypothesis that distractor processing depends on the extent to which high perceptual load exhausts attention in relevant processing and provide a dissociation between perceptual load and general task difficulty and processing speed.     

What causes auditory distraction?

The role of separating task-relevant from task-irrelevant aspects of the environment is typically assigned to the executive functioning of working memory. However, pervasive aspects of auditory distraction have been shown to be unrelated to working memory capacity in a range of studies of individual differences. We measured individual differences in global pattern matching and deliberate recoding of auditory sequences, and showed that, although deliberate processing was related to short-term memory performance, it did not predict the extent to which that performance was disrupted by task-irrelevant sound. Individual differences in global sequence processing were, however, positively related to the degree to which auditory distraction occurred. We argue that much auditory distraction, rather than being a negative function of working memory capacity, is in fact a positive function of the acuity of obligatory auditory processing.