Effects Of Perceptual Load Research Articles

Perceptual load modifies processing of unattended stimuli both in the presence and absence of attended stimuli

This study explored effects of perceptual load on stimulus processing in the presence and absence of an attended stimulus. Participants were presented with a bilateral or unilateral display and asked to perform a discrimination task at either low or high perceptual load. Electrophysiological responses to stimuli were then compared at the P100 and N100. As in previous studies, perceptual load modified processing of attended and unattended stimuli seen at occipital scalp sites. Moreover, perceptual load modulated attention effects when the attended stimulus was presented at high perceptual load for unilateral displays. However, this was not true when the attended and unattended stimulus appeared simultaneously in bilateral displays. Instead, only a main effect of perceptual load was found. Reductions in processing contralateral to the unattended stimulus at the N100 provide support for Lavie's (1995) theory of selective attention.

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).

Effect of perceptual load on response control

Effect of perceptual load on response control

Diluting the burden of load: Perceptual load effects are simply dilution effects

Diluting the burden of load: Perceptual load effects are simply dilution effects

Behavioral "baseline shift" effects of perceptual load

Behavioral "baseline shift" effects of perceptual load

Effects of perceptual load and response interference on target selection in macaque frontal eye field

Effects of perceptual load and response interference on target selection in macaque frontal eye field

The Effects of Perceptual Load and Category-Specific Dilution on Visual Search

The Effects of Perceptual Load and Category-Specific Dilution on Visual Search

Diluting the burden of load: Perceptual load effects are simply dilution effects.

The substantial distractor interference obtained for small displays when the target appears alone is reduced in large displays when the target is embedded among neutral letters. This finding has been interpreted as reflecting low-load and high-load processing, respectively, thereby supporting the theory of perceptual load (Lavie & Tsal, 1994). However, a possible alternative interpretation of this effect is that the distractor is similarly processed in both displays, yet its interference in the large ones is diluted by the presence of the neutral letters. We separated the effects of load and dilution by introducing dilution displays. They contained as many letters as the high-load displays but were clearly distinguished from the target, thus allowing for a low-load processing mode. Distractor interference obtained under both the low-load and high-load conditions disappeared under the dilution condition. Hence, the display size effect traditionally misattributed to perceptual load is fully accounted for by dilution. Furthermore, when dilution is controlled for, it is high load not low load producing greater interference.

Does emotion processing require attention? The effects of fear conditioning and perceptual load.

This study examined the impact of perceptual load on the processing of unattended threat-relevant faces. Participants performed a central letter-classification task while ignoring irrelevant face distractors, which appeared above or below the central task. The face distractors were graded for affective salience by means of aversive fear conditioning, with a conditioned angry face (CS+), an unconditioned angry face (CS-), and a neutral control face. The letter-classification task was presented under conditions of both low and high perceptual load. Results showed that fear conditioned (i.e., CS+) angry face distractors interfered with task performance more than CS- angry or neutral face distractors but that this interference was completely eliminated by high perceptual load. These findings demonstrate that aversively conditioned face distractors capture attention only under conditions of low perceptual load.

The fate of task-irrelevant visual motion: Perceptual load versus feature-based attention

We tested contrasting predictions derived from perceptual load theory and from recent feature-based selection accounts. Observers viewed moving, colored stimuli and performed low or high load tasks associated with one stimulus feature, either color or motion. The resultant motion aftereffect (MAE) was used to evaluate attentional allocation. We found that task-irrelevant visual features received less attention than co-localized task-relevant features of the same objects. Moreover, when color and motion features were co-localized yet perceived to belong to two distinct surfaces, feature-based selection was further increased at the expense of object-based co-selection. Load theory predicts that the MAE for task-irrelevant motion would be reduced with a higher load color task. However, this was not seen for co-localized features; perceptual load only modulated the MAE for task-irrelevant motion when this was spatially separated from the attended color location. Our results suggest that perceptual load effects are mediated by spatial selection and do not generalize to the feature domain. Feature-based selection operates to suppress processing of task-irrelevant, co-localized features, irrespective of perceptual load.

Selective Attention and Perceptual Load in Autism Spectrum Disorder

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.

The effects of perceptual load on semantic processing under inattention

Inattentional blindness refers to a failure to consciously detect an irrelevant object that appears without any expectation when attention is engaged with another task. The perceptual load theory predicts that task-irrelevant stimuli will reach awareness only when the primary task is of low load, which allows processing resources to spill over to processing task-irrelevant stimuli as well. We studied whether perceptual load has an effect on inattentional blindness for a task-irrelevant stimulus whose meaning is or is not relevant to the attentional goals of the observer. In the critical trial, a word appeared without any expectation in the center of a display of attended pictures. The results showed that, under both high and low load, unexpected words belonging to the attended semantic category were detected more often than semantically unrelated words. These results imply that task-irrelevant stimuli, whose meanings are relevant to the observer's task, enter awareness irrespective of perceptual load.

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.

Musical expertise modulates the effects of visual perceptual load

Several studies have demonstrated that faces are processed differently from other types of objects, implicating a special role that faces have within the human visual system. However, other studies have suggested that faces may be special only in that they constitute a highly familiar category of visual objects with which most humans have expertise. In this study, we tested a group of expert musicians with a musical instrument classification task during which irrelevant images of musical instruments were presented as visual distractors under varying conditions of perceptual load. Unlike nonmusicians (who had been tested in Lavie, Ro, & Russell, 2003, using the same paradigm as in the present study), the musicians processed these irrelevant images of musical instruments even under conditions of high perceptual load. These results suggest that musical instruments are processed automatically and without capacity limits in subjects with musical expertise and implicate a specialized processing mechanism for objects of high familiarity.

Perceptual load modulates attentional capture by abrupt onsets

The abrupt appearance of a new object captures attention, even when the object is task irrelevant. These findings suggest that abrupt onsets capture attention in a stimulus-driven manner and are not susceptible to top-down influences on attentional control. However, previous studies examining the ability of abrupt onsets to capture attention have used search displays that lacked significant complexity. Because attention is a limited capacity mechanism, it is possible that increasing the complexity, or perceptual load, of the search arrays may modulate capture by abrupt onsets. We used a flanker task to examine the effect of perceptual load on attentional capture by abruptly appearing objects. Subjects searched for a target letter through low-load (set size = 1) and high-load (set size = 6) displays. On each trial, irrelevant flankers also appeared, one as an onset and the other as an offset. Onset flankers affected search in low-load but not high-load displays. This modulation of attentional capture was not caused by generalized slowing when subjects searched through high-load displays; search for a single perceptually degraded target slowed response times but did not affect attentional capture. These findings demonstrate that attentional capture by an abrupt onset is attenuated when people search through high-load scenes.

Perceptual load modulates object-based attention.

Two experimental series are reported using both reaction time (RT) and a data-limited perceptual report to examine the effects of perceptual load on object-based attention. Perceptual load was manipulated across 3 levels by increasing the complexity of perceptual judgments. Data from the RT-based experiments showed object-based effects when the target was near the cued location. Results from the data-limited procedure showed that, with low perceptual load, attention spread along the cued object, supporting an object-based attention account. As load increased, attention was constrained to object locations near the cue, but attention still favored the cued object, inconsistent with a scanning prioritization account of object-based attention effects. Furthermore, findings showed that perceptual load modulates object selection in a manner similar to spatial attention, suggesting that there might be a common process underlying object-based and spatial attention.

Perceptual Load Modulates Visual Cortex Excitability to Magnetic Stimulation

Much recent research has shown that the level of perceptual load in a task determines the perception of task-irrelevant stimuli and associated neural activity, but the mediating neural mechanisms remain unclear. Here we show that increasing the level of perceptual load in a static letter search task results in an increase in the intensity of transcranial magnetic stimulation over V5/MT required to elicit the perception of a moving phosphene. These findings suggest that the neural mechanisms mediating the effects of perceptual load involve reduced visual cortex excitability in task-unrelated areas.

Unconscious orientation processing depends on perceptual load

The effects of perceptual load on the level of adaptation to task-irrelevant and invisible oriented gratings were examined. Participants performed a task at fixation under conditions of low (detecting color targets) or high (detecting conjunctions of color and shape) perceptual load. Simultaneously, a task-irrelevant-oriented grating was presented monocularly in a more peripheral location but was suppressed from awareness by flashing a dynamic mask stimulus at the same retinal location in the other eye. Orientation-specific adaptation to the invisible irrelevant grating was found at low perceptual load but was eliminated with high perceptual load. These results demonstrate that early unconscious processing of orientation depends on the allocation of limited attentional capacity, and conversely that the allocation of attentional capacity under low (versus high) load is insufficient to bring orientation representations to awareness.

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.

知覚的負荷並びに左右両視野への分割呈示が選択的注意に及ぼす影響

Based on the load theory and the assumption that each hemisphere has independent resources, we examined the effects of perceptual load in each hemisphere on the compatibility effect. In Experiments 1, and 2ab, two letter-strings were presented to the left and right visual-fields with a distracter, which was presented on the center of the screen. Two conditions were prepared by pairing a letter-string which contained a target with one which did not. Right-handed participants were asked to identify the target in the letter-strings while ignoring the distracter. The results showed that the compatibility effect was larger when the perceptual load of the letter-string which did not contain a target was low. This suggests that the residual resources of the hemisphere where the target was not projected facilitated the processing of the distracter. In Experiment 3, two letter-strings were presented to both hemispheres. The results showed that the compatibility effect was constant, irrespective of the perceptual load of the letter-string. Our findings suggested that selective attention is modulated by the resources of each hemisphere.