Effects Of Perceptual Load Research Articles

Negative affective state mimics effects of perceptual load on spatial perception.

Recent electrophysiological evidence has shown that perceptual load and negative affective state can produce very similar, early-attention gating effects in early visual areas, modulating the processing of peripheral stimuli. Here we assessed the question of whether or not these modulatory effects of perceptual load and negative affect (NA) lead to comparable changes in spatial perception abilities, which could be captured at the behavioral level. High perceptual load at fixation impaired the precise spatial localization of peripheral textures, relative to a low perceptual load condition. By contrast, the coarse spatial encoding of these peripheral stimuli was not load-dependent, under neutral affective conditions. The transient experience of NA was induced in an independent sample of participants, who showed decreased performance in the localization task, even at a low perceptual-load level. These results were observed in the absence of any systematic eye movement toward the peripheral textures. These findings suggest that spatial location perception is an attention-dependent, as well as state-dependent process, in the sense that NA, very much like load, can dynamically shape early spatial perceptual abilities. Although NA mimics load during spatial localization, we discuss the possibility that these two effects likely depend upon nonoverlapping brain networks.

Degraded stimulus visibility and the effects of perceptual load on distractor interference.

In this study we examined whether effects of perceptual load on the attentional selectivity are modulated by degradation of the visual input. According to the perceptual load theory, increasing task difficulty via degradation of stimulus visibility should not alter the typical effect of perceptual load. In previous studies only the target was degraded, resulting in increased distractor saliency. Here we combined manipulation of perceptual load with a more systematic degradation of visual information. Experiment 1 included five conditions. Three conditions involved low perceptual load + contrast reduction of: (A) only the target; (B) only the distractor; (C) both target and distractor. The other two conditions included non-degraded stimuli with low or high perceptual load. In Experiment 2 visibility degradation was established via manipulation of exposure duration. It included two exposure durations—100 and 150 ms—for each load level (low vs. high). The results of both experiments demonstrated reliable distractor interference of a similar magnitude with both degraded and non-degraded stimuli. This finding suggests that task difficulty, when manipulated via degradation of stimulus visibility, does not play a critical role in determining the efficiency of the attentional selectivity. However, contrary to the predictions of the perceptual load theory, in both experiments distractor interference emerged under the high load condition. In Experiment 2 the high-load interference was of the same magnitude as that of the low load condition. This high-load interference is not due to the presence of a mask (Experiment 3) or a mixed design (Experiment 4). These findings suggest that perceptual load may also play a lesser role in attentional selectivity than that assigned to it by the perceptual load theory.

Effect of Perceptual Load on Semantic Access by Speech in Children

To examine whether semantic access by speech requires attention in children. Children (N = 200) named pictures and ignored distractors on a cross-modal (distractors: auditory-no face) or multimodal (distractors: auditory-static face and audiovisual-dynamic face) picture word task. The cross-modal task had a low load, and the multimodal task had a high load (i.e., respectively naming pictures displayed on a blank screen vs. below the talker's face on his T-shirt). Semantic content of distractors was manipulated to be related vs. unrelated to the picture (e.g., picture "dog" with distractors "bear" vs. "cheese"). If irrelevant semantic content manipulation influences naming times on both tasks despite variations in loads, Lavie's (2005) perceptual load model proposes that semantic access is independent of capacity-limited attentional resources; if, however, irrelevant content influences naming only on the cross-modal task (low load), the perceptual load model proposes that semantic access is dependent on attentional resources exhausted by the higher load task. Irrelevant semantic content affected performance for both tasks in 6- to 9-year-olds but only on the cross-modal task in 4- to 5-year-olds. The addition of visual speech did not influence results on the multimodal task. Younger and older children differ in dependence on attentional resources for semantic access by speech.

Selection Modulated by Inter-Trial Discriminability: Robust Reversals of Perceptual Load Effects

Selection Modulated by Inter-Trial Discriminability: Robust Reversals of Perceptual Load Effects

Processing of angry voices is modulated by visual load

Visual perceptual load has been shown to modulate brain activation to emotional facial expressions. However, it is unknown whether cross-modal effects of visual perceptual load on brain activation to threat-related auditory stimuli also exist. The current fMRI study investigated brain responses to angry and neutral voices while subjects had to solve an easy or a demanding visual task. Although the easy visual condition was associated with increased activation in the right superior temporal region to angry vs. neutral prosody, this effect was absent during the demanding task. Thus, our results show that cross-modal perceptual load modulates the activation to emotional voices in the auditory cortex and that high visual load prevents the increased processing of emotional prosody.

The Effects of Perceptual Load on Localization across Saccades

Humans make roughly three saccades per second during search or scene inspection, during which time the retinal information we receive changes dramatically. Despite this upheaval in sensory information, we are able to maintain a surprisingly accurate spatial scene representation. This study examines the effect of perceptual load on scene reconstruction across eye movements to determine whether high perceptual load causes a shift from encoding spatial location with a gaze-centered strategy to a more environment-centered strategy. In our experiment we manipulate perceptual load using a continuous vernier acuity detection task while presenting a probe and environment in a secondary localization task. We expected that subjects would be able to use both gaze coordinates and environmental coordinates under low load situations, but under high load, they would be forced to rely predominantly on environmental cues. The results show that the load manipulation disrupted localization. The presence of environment cues ...

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.

A crossmodal crossover: Opposite effects of visual and auditory perceptual load on steady-state evoked potentials to irrelevant visual stimuli

Mechanisms of attention are required to prioritise goal-relevant sensory events under conditions of stimulus competition. According to the perceptual load model of attention, the extent to which task-irrelevant inputs are processed is determined by the relative demands of discriminating the target: the more perceptually demanding the target task, the less unattended stimuli will be processed. Although much evidence supports the perceptual load model for competing stimuli within a single sensory modality, the effects of perceptual load in one modality on distractor processing in another is less clear. Here we used steady-state evoked potentials (SSEPs) to measure neural responses to irrelevant visual checkerboard stimuli while participants performed either a visual or auditory task that varied in perceptual load. Consistent with perceptual load theory, increasing visual task load suppressed SSEPs to the ignored visual checkerboards. In contrast, increasing auditory task load enhanced SSEPs to the ignored visual checkerboards. This enhanced neural response to irrelevant visual stimuli under auditory load suggests that exhausting capacity within one modality selectively compromises inhibitory processes required for filtering stimuli in another.

The effect of perceptual load on attentional blink.

The effect of perceptual load on attentional blink.

Effects of Perceptual Load on Emotional Processing: an ERP study

Effects of Perceptual Load on Emotional Processing: an ERP study

High negative valence does not protect emotional event-related potentials from spatial inattention and perceptual load

Previous research suggests that intense, emotional pictures at fixation elicit an early posterior negativity (EPN) and a late positive potential (LPP) despite manipulations of spatial inattention and perceptual load. However, if high emotional intensity protects against such manipulations, then these manipulations should reduce emotional effects on EPN and LPP more strongly for medium than for intense emotional pictures. To test this prediction, pictures that were high negative, medium negative, or neutral were shown at fixation, and a small letter string was superimposed on the picture center. When participants attended the pictures, there were clear emotional effects on EPN and LPP. When participants attended the letter string, the emotional effects on LPP decreased; this decrease was smaller for medium than for high negative pictures. Thus, opposite of predictions, spatial inattention reduced the emotional effects more strongly for high than for medium negative pictures. As a manipulation of perceptual load, participants performed the letter task with one, three, or six relevant letters. Irrespective of load, EPN and LPP were similar for high and medium negative pictures. Our findings suggest that high negative valence does not protect EPN and LPP more strongly from effects of spatial inattention and perceptual load than does medium negative valence.

Perceptual load alters visual excitability.

Increasing perceptual load reduces the processing of visual stimuli outside the focus of attention, but the mechanism underlying these effects remains unclear. Here we tested an account attributing the effects of perceptual load to modulations of visual cortex excitability. In contrast to stimulus competition accounts, which propose that load should affect simultaneous, but not sequential, stimulus presentations, the visual excitability account makes the novel prediction that load should affect detection sensitivity for both simultaneous and sequential presentations. Participants fixated a stimulus stream, responding to targets defined by either a color (low load) or color and orientation conjunctions (high load). Additionally, detection sensitivity was measured for a peripheral critical stimulus (CS) presented occasionally. Increasing load at fixation reduced sensitivity to the peripheral CSs; this effect was similar regardless of whether CSs were presented simultaneously with central stimuli or during the (otherwise empty) interval between them. Controls ruled out explanations of the results in terms of strategic task prioritization. These findings support a cortical excitability account for perceptual load, challenging stimulus competition accounts.

Does stress enhance or impair selective attention? The effects of stress and perceptual load on distractor interference

Does stress enhance or impair selective attention? The effects of stress and perceptual load on distractor interference

Visual perceptual load induces inattentional deafness

In this article, we establish a new phenomenon of “inattentional deafness” and highlight the level of load on visual attention as a critical determinant of this phenomenon. In three experiments, we modified an inattentional blindness paradigm to assess inattentional deafness. Participants made either a low- or high-load visual discrimination concerning a cross shape (respectively, a discrimination of line color or of line length with a subtle length difference). A brief pure tone was presented simultaneously with the visual task display on a final trial. Failures to notice the presence of this tone (i.e., inattentional deafness) reached a rate of 79% in the high-visual-load condition, significantly more than in the low-load condition. These findings establish the phenomenon of inattentional deafness under visual load, thereby extending the load theory of attention (e.g., Lavie, Journal of Experimental Psychology. Human Perception and Performance, 25, 596–616, 1995) to address the cross-modal effects of visual perceptual load.

Attention to faces: Effects of face inversion

Attention may be biased towards faces but a face advantage may be linked to the upright orientation of a face. Three experiments, employing a flanker and a cuing paradigm, investigated effects of face orientation, perceptual load and allocation of attention. Experiment 1 demonstrated that, irrespective of load, attention is biased towards upright face distractors while inverted face distractors are easy to ignore. Experiment 2 verified that inverted face distractors can interfere provided that they are attended to volitionally, likely because the volitional allocation of attention promotes face processing and gender classification (Experiment 3).

Anxiety overrides the blocking effects of high perceptual load on amygdala reactivity to threat-related distractors

Amygdala reactivity to threat-related distractor stimuli can be abolished in perceptually demanding contexts. Premised on the biological imperative to respond swiftly to threat, we demonstrate, however, that when participants are threatened by shock, greater amygdala responses to fearful compared to neutral distractor faces is preserved under conditions of high attentional demand. Lateral prefrontal cortices also showed selective responding to fearful distractor faces under these conditions, suggesting that threat-related distractor stimuli engaged attentional control mechanisms. We conclude that anxiety elicited by looming threat promotes neurocognitive processes that broaden attention and enhance sensitivity to potential danger cues, even when perceptual systems are taxed.

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.

Reduced visual processing capacity in sleep deprived persons

Multiple experiments have found sleep deprivation to lower task-related parietal and extrastriate visual activation, suggesting a reduction of visual processing capacity in this state. The perceptual load theory of attention (Lavie, 1995) predicts that our capacity to process unattended distractors will be reduced by increasing perceptual difficulty of task-relevant stimuli. Here, we evaluated the effects of sleep deprivation and perceptual load on visual processing capacity by measuring neural repetition-suppression to unattended scenes while healthy volunteers attended to faces embedded in face–scene pictures. Perceptual load did not affect repetition suppression after a normal night of sleep. Sleep deprivation reduced repetition suppression in the parahippocampal place area (PPA) in the high but not low perceptual load condition. Additionally, the extent to which task-related fusiform face area (FFA) activation was reduced after sleep deprivation correlated with behavioral performance and lowered repetition suppression in the PPA. The findings concerning correct responses indicate that a portion of stimulus related activation following a normal night of sleep contributes to potentially useful visual processing capacity that is attenuated following sleep deprivation. Finally, when unattended stimuli are not highly intrusive, sleep deprivation does not appear to increase distractibility.

Attentional resources in social anxiety and the effects of perceptual load

According to the attentional control theory, anxious people should process task-irrelevant distractors more than non-anxious people. This could be due to them having more attentional resources to allocate to the processing of task-irrelevant distractors. The current study was designed to assess the processing of task-irrelevant stimuli in low- and high-socially-anxious people. We conducted four experiments using perceptual load tasks. In the high-perceptual-load condition, interference effects from task-irrelevant distractors were not observed in low-socially-anxious people. This finding is consistent with the view of exhausting attentional resources to process task-relevant stimuli. However, interference effects were observed in high-socially-anxious people in the case of high perceptual load (Experiment 1). These effects were observed when presenting the distractor at a fixation (Experiment 2) or attracting attention involuntarily to the target location by spatial cueing (Experiment 3). However, when distractors were masked to decrease their visibility, distractor processing was not observed (Experiment 4). These results suggested that people with high social anxiety may have more attentional resources than people with low social anxiety, and this might partially derive from enhanced stimulus-driven attention.

Failing to Ignore: Paradoxical Neural Effects of Perceptual Load on Early Attentional Selection in Normal Aging

We examined visual selective attention under perceptual load--simultaneous presentation of task-relevant and -irrelevant information--in healthy young and older adult human participants to determine whether age differences are observable at early stages of selection in the visual cortices. Participants viewed 50/50 superimposed face/place images and judged whether the faces were male or female, rendering places perceptible but task-irrelevant. Each stimulus was repeated, allowing us to index dynamic stimulus-driven competition from places. Consistent with intact early selection in young adults, we observed no adaptation to unattended places in parahippocampal place area (PPA) and significant adaptation to attended faces in fusiform face area (FFA). Older adults, however, exhibited both PPA adaptation to places and weak FFA adaptation to faces. We also probed participants' associative recognition for face-place pairs post-task. Older adults with better place recognition memory scores were found to exhibit both the largest magnitudes of PPA adaptation and the smallest magnitudes of FFA adaptation on the attention task. In a control study, we removed the competing perceptual information to decrease perceptual load. These data revealed that the initial age-related impairments in selective attention were not due to a general decline in visual cortical selectivity; both young and older adults exhibited robust FFA adaptation and neither group exhibited PPA adaptation to repeated faces. Accordingly, distracting information does not merely interfere with attended input in older adults, but is co-encoded along with the contents of attended input, to the extent that this information can subsequently be recovered from recognition memory.