Processing overlap-dependent distractor dilution rather than perceptual target load determines attentional selectivity

The perceptual load theory of attentional selection argues that the degree to which distractors interfere with target processing is determined by the “perceptual load” (or discrimination difficulty) of target processing: when perceptual load is low, distractors interfere to a greater extent than when it is high. A well-known exception is load-independent interference effects from face distractors during processing of name targets. This finding was reconciled with load theory by proposing distinct processing resources for faces versus names. In the present study, we revisit this effect to test (a) whether increasing the processing overlap (perceptual, lexical, conceptual) between potential targets and distractors would reinstate the classic load effect, and (b) whether this data pattern could be better explained by load theory or by a rival account that argues that distractor dilution rather than target load determines the degree of distractor interference. Over four experiments, we first replicate the original finding and then show that load effects grow with increasing processing overlap between potential targets and distractors. However, by adding dilution conditions, we also show that these processing overlap dependent modulations of distractor interference can be explained by the distractor dilution perspective but not by perceptual load theory. Thus, our findings support a processing overlap dilution account of attentional selection.     

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.     

Attentional sets influence perceptual load effects,but not dilution effects

Perceptual load theory [Lavie, N. (1995). Perceptual load as a necessary condition for selective attention. Journal of Experimental Psychology: Human Perception and Performance, 21, 451–468.; Lavie, N., & Tsal, Y. (1994) Perceptual load as a major determinant of the locus of selection in visual attention. Perception & Psychophysics, 56, 183–197.] proposes that interference from distractors can only be avoided in situations of high perceptual load. This theory has been supported by blocked design manipulations separating low load (when the target appears alone) and high load (when the target is embedded among neutral letters). Tsal and Benoni [(2010a). Diluting the burden of load: Perceptual load effects are simply dilution effects. Journal of Experimental Psychology: Human Perception and Performance, 36, 1645–1656.; Benoni, H., & Tsal, Y. (2010). Where have we gone wrong? Perceptual load does not affect selective attention. Vision Research, 50, 1292–1298.] have recently shown that these manipulations confound perceptual load with “dilution” (the mere presence of additional heterogeneous items in high-load situations). Theeuwes, Kramer, and Belopolsky [(2004). Attentional set interacts with perceptual load in visual search. Psychonomic Bulletin & Review, 11, 697–702.] independently questioned load theory by suggesting that attentional sets might also affect distractor interference. When high load and low load were intermixed, and participants could not prepare for the presentation that followed, both the low-load and high-load trials showed distractor interference. This result may also challenge the dilution account, which proposes a stimulus-driven mechanism. In the current study, we presented subjects with both fixed and mixed blocks, including a mix of dilution trials with low-load trials and with high-load trials. We thus separated the effect of dilution from load and tested the influence of attentional sets on each component. The results revealed that whereas perceptual load effects are influenced by attentional sets, the dilution component is not. This strengthens the notion that dilution is a stimulus-driven mechanism, which enables effective selectivity.     

知觉表征精度对工作记忆中抑制干扰能力的影响

工作记忆的容量十分有限,需要选择性地抑制与目标无关信息的干扰,工作记忆容量高的个体,其抑制干扰的能力也更强。本研究采用带有不同形状干扰刺激的色块颜色回忆任务考察干扰对工作记忆容量和表征精度的影响,结果发现,当负荷超出工作记忆容量范围时,干扰减少了记忆所能表征客体的个数;当负荷在工作记忆容量范围内时,干扰降低了记忆中表征客体的精度。更进一步,研究采用独立的知觉任务来测量知觉表征的精度,并探讨作为信息加工的初始阶段的知觉表征如何影响工作记忆加工过程中抑制干扰的能力。将实验中收集的48名有效被试按照知觉表征精度的高低平均分为两组,结果发现上述干扰效应主要表现在知觉表征精度较低的组中,并且该组中知觉表征精度越高的个体,其工作记忆抑制干扰的能力也越强。本研究为实践中通过知觉训练来提升工作记忆的抑制干扰能力提供了理论指导。     

Load theory of selective attention and cognitive control

A load theory of attention in which distractor rejection depends on the level and type of load involved in current processing was tested. A series of experiments demonstrates that whereas high perceptual load reduces distractor interference, working memory load or dual-task coordination load increases distractor interference. These findings suggest 2 selective attention mechanisms: a perceptual selection mechanism serving to reduce distractor perception in situations of high perceptual load that exhaust perceptual capacity in processing relevant stimuli and a cognitive control mechanism that reduces interference from perceived distractors as long as cognitive control functions are available to maintain current priorities (low cognitive load). This theory resolves the long-standing early versus late selection debate and clarifies the role of cognitive control in selective attention.     

Dilution, not load, affects distractor processing

Lavie and Tsal (1994) proposed that spare attentional capacity is allocated involuntarily to the processing of irrelevant stimuli, thereby enabling interference. Under this view, when task demands increase, spare capacity should decrease and distractor interference should decrease. In support, Lavie and Cox (1997) found that increasing perceptual load by increasing search set size decreased interference from an irrelevant distractor. In three experiments, we manipulated the cue set size (number of cued locations) independently of the display set size (number of letters presented). Increasing the display set size reduced distractor interference regardless of whether the additional letters were relevant to the task. In contrast, increasing the cue set size increased distractor interference. Both findings are inconsistent with the load explanation, but are consistent with a proposed two-stage dilution account.     

Selective target processing: perceptual load or distractor salience?

Perceptual load theory (Lavie, 1995) states that participants cannot engage in focused attention when shown displays containing a low perceptual load, because attentional resources are not exhausted, whereas in high-load displays attention is always focused, because attentional resources are exhausted. An alternative "salience" hypothesis holds that the salience of distractors and not perceptual load per se determines selective attention. Three experiments were conducted to investigate the influence that target and distractor onsets and offsets have on selective processing in a standard interference task. Perceptual load theory predicts that, regardless of target or distractor presentation (onset or offset), interference from ignored distractors should occur in low-load displays only. In contrast, the salience hypothesis predicts that interference should occur when the distractor appears as an onset and would occur for distractor offsets only when the target was also an offset. Interference may even occur in highload displays if the distractor is more salient. The results supported the salience hypothesis.     

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。     

The effects of acute stress and perceptual load on distractor interference

Selective attention can be improved under conditions in which a high perceptual load is assumed to exhaust cognitive resources, leaving scarce resources for distractor processing. The present study examined whether perceptual load and acute stress share common attentional resources by manipulating perceptual and stress loads. Participants identified a target within an array of nontargets that were flanked by compatible or incompatible distractors. Attentional selectivity was measured by longer reaction times in response to the incompatible than to the compatible distractors. Participants in the stress group participated in a speech test that increased anxiety and threatened self-esteem. The effect of perceptual load interacted with the stress manipulation in that participants in the control group demonstrated an interference effect under the low perceptual load condition, whereas such interference disappeared under the high perceptual load condition. Importantly, the stress group showed virtually no interference under the low perceptual load condition, whereas substantial interference occurred under the high perceptual load condition. These results suggest that perceptual and stress related demands consume the same attentional resources.     

The effects of acute stress and perceptual load on distractor interference

Selective attention can be improved under conditions in which a high perceptual load is assumed to exhaust cognitive resources, leaving scarce resources for distractor processing. The present study examined whether perceptual load and acute stress share common attentional resources by manipulating perceptual and stress loads. Participants identified a target within an array of nontargets that were flanked by compatible or incompatible distractors. Attentional selectivity was measured by longer reaction times in response to the incompatible than to the compatible distractors. Participants in the stress group participated in a speech test that increased anxiety and threatened self-esteem. The effect of perceptual load interacted with the stress manipulation in that participants in the control group demonstrated an interference effect under the low perceptual load condition, whereas such interference disappeared under the high perceptual load condition. Importantly, the stress group showed virtually no interference under the low perceptual load condition, whereas substantial interference occurred under the high perceptual load condition. These results suggest that perceptual and stress related demands consume the same attentional resources.     

The effects of perceptual load in central and peripheral regions of the visual field

The perceptual load model claims that attentional selectively depends on perceptual load. Selectivity is high with high load, but low with low load. Previous studies only manipulated load levels at task-relevant regions. In this study, perceptual load was orthogonally manipulated in both relevant (central) and nonrelevant (peripheral) regions, by varying the similarity between the target and nontarget letters and the nontarget letters' heterogeneity. The participants had to identify a target-letter appearing in a central circle of letters. A distractor-letter, appearing in a peripheral circle, was compatible, neutral, or incompatible with the target. As expected, increasing peripheral load deteriorated performance, but only with low levels of central load. The pattern of distractor interference did not follow the model's predictions because distractor interference under high load levels was occasionally found. The expected pattern of results emerged only when the spatial uncertainty regarding the distractor position was low, implying that spatial uncertainty plays an important role in attentional selectivity.     

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.     

Trait anxiety and perceptual load as determinants of emotion processing in a fear conditioning paradigm

The impact of trait anxiety and perceptual load on selective attention was examined in a fear conditioning paradigm. A fear-conditioned angry face (CS+), an unconditioned angry face (CS-), or an unconditioned face with a neutral or happy expression were used in distractor interference and attentional probe tasks. In Experiments 1 and 2, participants classified centrally presented letters under two conditions of perceptual load. When perceptual load was high, distractors had no effect on selective attention, even with aversive conditioning. However, when perceptual load was low, strong response interference effects for CS+ face distractors were found for low trait-anxious participants. Across both experiments, this enhanced distractor interference reversed to strong facilitation effects for those reporting high trait anxiety. Thus, high trait-anxious participants were faster, rather than slower, when ignoring CS+ distractors. Using an attentional probe task in Experiment 3, it was found that fear conditioning resulted in strong attentional avoidance in a high trait-anxious group, which contrasted with enhanced vigilance in a low trait-anxious group. These results demonstrate that the impact of fear conditioning on attention is modulated by individual variation in trait anxiety when perceptual load is low. Fear conditioning elicits an avoidance of threat-relevant stimuli in high trait-anxious participants.     

Interference from familiar natural distractors is not eliminated by high perceptual load

A crucial prediction of perceptual load theory is that high perceptual load can eliminate interference from distractors. However, Lavie et al. (Psychol Sci 14:510–515, 2003) found that high perceptual load did not eliminate interference when the distractor was a face. The current experiments examined the interaction between familiarity and perceptual load in modulating interference in a name search task. The data reveal that high perceptual load eliminated the interference effect for unfamiliar distractors that were faces or objects, but did not eliminate the interference for familiar distractors that were faces or objects. Based on these results, we proposed that the processing of familiar and natural stimuli may be immune to the effect of perceptual load.     

Selective Attention and Perceptual Load in Autism Spectrum Disorder

ABSTRACT— It has been suggested that the locus of selective attention (early vs. late in processing) is dependent on the perceptual load of the task. When perceptual load is low, irrelevant distractors are processed (late selection), whereas when perceptual load is high, distractor interference disappears (early selection). Attentional abnormalities have long been reported within autism spectrum disorder (ASD), and this study is the first to examine the effect of perceptual load on selective attention in this population. Fourteen adults with ASD and 23 adults without ASD performed a selective attention task with varying perceptual loads. Compared with the non-ASD group, the ASD group required higher levels of perceptual load to successfully ignore irrelevant distractors; moreover, the ASD group did not show any general reduction in performance speed or accuracy. These results suggest enhanced perceptual capacity in the ASD group and are consistent with previous observations regarding superior visual search abilities among individuals with ASD.     

Components of Stroop-like interference in picture naming

The semantic interference effect observed in Stroop tasks and picture-word interference tasks might be due to the previous confounding of semantic similarity with task relevance (in the Stroop task) and with perceptual similarity (in the picture-word interference task). A picture-word variant of the Stroop task was devised in which the factors of task relevance and perceptual similarity were controlled. The distractor conditions allowed for the examination of four types of context effects. The results show that the overall Stroop-like interference effect can be decomposed into interference effects due to (1) a semantic relation between distractor and target, (2) the semantic relevance of the distractor word in the task at hand, (3) the presence of the distractor word in the response set, and (4) the mere presence of a word. Implications of these findings for the locus or loci of Stroop and picture-word interference effects are discussed. It is concluded that distractor words in Stroop-like naming tasks interfere mainly in the process of name retrieval.     

Attentional spread in deaf and hearing participants: Face and object distractor processing under perceptual load

The case of human deafness constitutes a unique opportunity to examine possible consequences for perceptual processing due to altered sensory experiences. We tested whether deaf??in contrast to hearing??individuals are more susceptible to visual distraction from peripheral than from central face versus object stimuli. The participants were required to classify the gender of a target male or female symbol presented either alone (low perceptual load) or together with three filler symbols (high perceptual load), while ignoring gender-congruent or -incongruent face versus object distractors presented at central or peripheral positions. The gender classifications were affected by distractor gender under low, but not under high, perceptual load in hearing participants. In contrast, the responses of deaf participants were similarly influenced by distractor gender under both levels of perceptual load. There was no evidence for generally enhanced attention to the visual periphery in deaf individuals. Our results indicate that auditory deprivation may result in enhanced attentional capacities under high perceptual load.     

Perceptual load in sport and the heuristic value of the perceptual load paradigm in examining expertise-related perceptual-cognitive adaptations

In two experiments, we transferred perceptual load theory to the dynamic field of team sports and tested the predictions derived from the theory using a novel task and stimuli. We tested a group of college students (N = 33) and a group of expert team sport players (N = 32) on a general perceptual load task and a complex, soccer-specific perceptual load task in order to extend the understanding of the applicability of perceptual load theory and further investigate whether distractor interference may differ between the groups, as the sport-specific processing task may not exhaust the processing capacity of the expert participants. In both, the general and the specific task, the pattern of results supported perceptual load theory and demonstrates that the predictions of the theory also transfer to more complex, unstructured situations. Further, perceptual load was the only determinant of distractor processing, as we neither found expertise effects in the general perceptual load task nor the sport-specific task. We discuss the heuristic utility of using response-competition paradigms for studying both general and domain-specific perceptual-cognitive adaptations.     

High perceptual load makes everybody equal: eliminating individual differences in distractibility with load

Perceptual load has been found to be a powerful determinant of distractibility in laboratory tasks. The present study assessed how the effects of perceptual load on distractibility in the laboratory relate to individual differences in the likelihood of distractibility in daily life. Sixty-one subjects performed a response-competition task in which perceptual load was varied. As expected, individuals reporting high levels of distractibility (on the Cognitive Failures Questionnaire, an established measure of distractibility in daily life) experienced greater distractor interference than did individuals reporting low levels. The critical finding, however, was that this relationship was confined to task conditions of low perceptual load: High perceptual load reduced distractor interference for all subjects, eliminating any individual differences. These findings suggest that the level of perceptual load in a task can predict whether individual differences in distractibility will be found and that high-load modifications of daily tasks may prove useful in preventing unwanted consequences of high distractibility.     

Practice in visual search produces decreased capacity demands but increased distraction

Lavie (1995) proposed a load account of selective attention, which holds that spare capacity is involuntarily allocated to the processing of irrelevant stimuli. In support of this account, Lavie and Cox (1997) combined a letter search task with a flanker task and found that increasing load (search set size) resulted in decreased interference from an irrelevant distractor letter. In three experiments using a very similar procedure, we varied distractor location and distractor distinctiveness and observed that as load increased (from set size 2 to set size 6), there was a consistent reduction in interference. Critically, we addressed a fundamental hypothesis derived from the load account-that practice reduces capacity demands. This hypothesis leads to the rather counterintuitive prediction that as performance improves with practice, distractor processing should actually increase. Indeed, we found that interference in a high-load condition (set size 6), but not in a low-load condition (set size 2), did increase with practice. We describe a two-stage dilution account of attention that accommodates these results.