Age-related changes in selective attention and perceptual load during visual search.

Three visual search experiments were conducted to test the hypothesis that age differences in selective attention vary as a function of perceptual load (E. A. Maylor & N. Lavie, 1998). Under resource-limited conditions (Experiments 1 and 2), the distraction from irrelevant display items generally decreased as display size (perceptual load) increased. This perceptual load effect was similar for younger and older adults, contrary to the findings of Maylor and Lavie. Distraction at low perceptual loads appeared to reflect both general and specific inhibitory mechanisms. Under more data-limited conditions (Experiment 3), an age-related decline in selective attention was evident, but the age difference was not attributable to capacity limitations as predicted by the perceptual load theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention set for number: Expectation and perceptual load in inattentional blindness.

Inattentional blindness is the failure to detect unexpected events when attention is otherwise engaged. Previous research indicates that inattentional blindness increases as perceptual demands intensify. The authors present 6 cuing experiments that manipulated both the perceptual demands of a primary letter-naming task and the expectations of the individual. Inattentional blindness was greatest for individuals who held a numerical expectation that was consistent with the number of primary-task items presented. Expectation also affected detection differentially at various levels of perceptual load: Detection at moderate and high perceptual load was significantly affected by expectation, whereas detection at low perceptual load was not. The authors suggest that at moderate to high levels of perceptual load, individuals whose numerical expectations are fulfilled terminate processing when the primary task is complete, at the expense of the unexpected visual event. These experiments provide compelling evidence that expectations do affect detection of an unexpected stimulus, and they are the first to demonstrate that individuals set their attention for the number of items to be detected and are vulnerable to inattentional blindness whenever their primary-task numerical expectation is fulfilled. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of perceptual load in object recognition.

Predictions from perceptual load theory (Lavie, 1995, 2005) regarding object recognition across the same or different viewpoints were tested. Results showed that high perceptual load reduces distracter recognition levels despite always presenting distracter objects from the same view. They also showed that the levels of distracter recognition were unaffected by a change in the distracter object view under conditions of low perceptual load. These results were found both with repetition priming measures of distracter recognition and with performance on a surprise recognition memory test. The results support load theory proposals that distracter recognition critically depends on the level of perceptual load. The implications for the role of attention in object recognition theories are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Processing capacity under perceptual and cognitive load: A closer look at load theory.

Variations in perceptual and cognitive demands (load) play a major role in determining the efficiency of selective attention. According to load theory (Lavie, Hirst, Fockert, & Viding, 2004) these factors (a) improve or hamper selectivity by altering the way resources (e.g., processing capacity) are allocated, and (b) tap resources rather than data limitations (Norman & Bobrow, 1975). Here we provide an extensive and rigorous set of tests of these assumptions. Predictions regarding changes in processing capacity are tested using the hazard function of the response time (RT) distribution (Townsend & Ashby, 1978; Wenger & Gibson, 2004). The assumption that load taps resource rather than data limitations is examined using measures of sensitivity and bias drawn from signal detection theory (Swets, 1964). All analyses were performed at two levels: the individual and the aggregate. Hypotheses regarding changes in processing capacity were confirmed at the level of the aggregate. Hypotheses regarding resource and data limitations were not completely supported at either level of analysis. And in all of the analyses, we observed substantial individual differences. In sum, the results suggest a need to expand the theoretical vocabulary of load theory, rather than a need to discard it. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Much dilution little load in Lavie and Torralbo's (2010) response: A reply.

Lavie and Torralbo (2010) present a response to the critique of load theory put forward by Tsal and Benoni (2010). We note that this response includes long discussions that dilute the major points of the debate and deals only with the first experiment in Tsal and Benoni, and we question whether it covers the broader critique we offer. In our reply, we argue against the points made by Lavie and Torralbo and propose that the “dilution” critique of the theory is justified. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Load induced blindness.

Although the perceptual load theory of attention has stimulated a great deal of research, evidence for the role of perceptual load in determining perception has typically relied on indirect measures that infer perception from distractor effects on reaction times or neural activity (see N. Lavie, 2005, for a review). Here we varied the level of perceptual load in a letter-search task and assessed its effect on the conscious perception of a search-irrelevant shape stimulus appearing in the periphery, using a direct measure of awareness (present/absent reports). Detection sensitivity (d′) was consistently reduced with high, compared to low, perceptual load but was unaffected by the level of working memory load. Because alternative accounts in terms of expectation, memory, response bias, and goal-neglect due to the more strenuous high load task were ruled out, these experiments clearly demonstrate that high perceptual load determines conscious perception, impairing the ability to merely detect the presence of a stimulus--a phenomenon of load induced blindness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual load influences selective attention across development.

Research suggests that visual selective attention develops across childhood. However, there is relatively little understanding of the neurological changes that accompany this development, particularly in the context of adult theories of selective attention, such as N. Lavie's (1995) perceptual load theory of attention. This study examined visual selective attention across development from 7 years of age to adulthood. Specifically, the author examined if changes in processing as a function of selective attention are similarly influenced by perceptual load across development. Participants were asked to complete a task at either low or high perceptual load while processing of an unattended probe stimulus was examined using event related potentials. Similar to adults, children and teens showed reduced processing of the unattended stimulus as perceptual load increased at the P1 visual component. However, although there were no qualitative differences in changes in processing, there were quantitative differences, with shorter P1 latencies in teens and adults compared with children, suggesting increases in the speed of processing across development. In addition, younger children did not need as high a perceptual load to achieve the same difference in performance between low and high perceptual load as adults. Thus, this study demonstrates that although there are developmental changes in visual selective attention, the mechanisms by which visual selective attention is achieved in children may share similarities with adults. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The spatial focus of attention is controlled at perceptual and cognitive levels.

Selective attention has been hypothesized to reduce distractor interference at both perceptual and postperceptual levels (Lavie, 2005), respectively, by focusing perceptual resources on the attended location and by blocking at postperceptual levels distractors that survive perceptual selection. This study measured the impact of load on these selection mechanisms using a flanker paradigm (Eriksen & St. James, 1986) and indexing distractor interference as a function of separation. It distinguished changes in the extent of focus of the distractor-interference function of separation (reflecting perceptual selection) from changes in the amplitude of distractor interference not accompanied by changes in focus (reflecting postperceptual selection). It showed that: (1) the spatial profile of perceptual resources is shaped like a “Mexican hat” (Müller et al., 2005); (2) increasing perceptual load focuses perceptual resources (Caparos & Linnell, 2009); (3) increasing cognitive load defocuses perceptual resources; and (4) participants with reduced working-memory span show reduced postperceptual blocking of distractors. While these findings are consistent with two levels of selective attention, they show that the first perceptual level is affected not only by perceptual but also by cognitive-control mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the continuity of perceptual experience: Implications for perception and attention.

When an observer views a real-world scene, some objects in the scene are partly occluded by intervening surfaces. Similarly, as the observer moves through the environment, some objects are temporarily occluded and revealed. Yet, although the retinal image is fragmented in space and time, perceptual experience is coherent and continuous. Continuity of experience is achieved by perceptual organization mechanisms, which have their effect before attention. Several experiments are described to illustrate the close interaction between perceptual organization and attention. This interaction determines the representational basis for selection, and is therefore a crucial precursor to understanding object-based mechanisms of visual selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual and cognitive load interact to control the spatial focus of attention.

Caparos and Linnell (2009, 2010) used a variable-separation flanker paradigm to show that (a) when cognitive load is low, increasing perceptual load causes spatial attention to focus and (b) when perceptual load is high, decreasing cognitive load causes spatial attention to focus. Here, we tested whether the effects of perceptual and cognitive load on spatial focus remain when, respectively, cognitive load is high and perceptual load is low. We found that decreasing cognitive load only causes spatial attention to focus when perceptual load is high and the stimulus encourages this. Moreover, and contrary to the widely held assumption that perceptual load focuses attention automatically (Lavie, Hirst, de Fockert, & Viding, 2004), perceptual load exerts its focusing effect only with the engagement of cognitive resources when cognitive load is low. In sum, perceptual and cognitive mechanisms exert interacting effects and operate in concert to focus spatial attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

When visual marking meets the attentional blink: More evidence for top-down, limited-capacity inhibition.

An attentional blink (AB) paradigm was used to investigate the attentional resources necessary for visual marking. The results showed that distractors presented inside the AB cannot easily be ignored despite participants anticipating a future target display. This supports the hypothesis that attentional resources are required for visual marking. In addition, probe dots were better detected on blinked distractors than on successfully ignored distractors, but only when the task required new items to be prioritized. In a final experiment, a stronger negative carry-over effect on search occurred for targets identical to distractors presented outside rather than inside the AB. This suggests that at least part of the inhibitory processes involved in visual marking are nonspatial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of return: Dissociating attentional and oculomotor components.

Inhibition of return (IOR) describes a performance decrement for stimuli appearing at recently cued locations. Both attentional and motor processes have been implicated in the IOR effect. The present data reveal a double dissociation between the attentional and motor components of IOR whereby the motor-based component of IOR is present when the response is oculomotor, and the attention-based component of IOR is present when the response is manual. These 2 distinct components should be considered and studied separately, as well as in relation to each other, if a comprehensive theory of IOR is to be achieved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of selective attention: Perceptual load influences early versus late attentional selection in children and adults.

The moderating effect of perceptual load on visual selective attention was examined in 2 studies. In Study 1, children and young adults searched displays of varying set size flanked by irrelevant distractors. Children's performance was as efficient as adults' under conditions of high but not low loads, suggesting that early selection engages rapidly maturing neural systems and late selection engages later-maturing systems. In Study 2, 4 age groups were tested, and place markers were set at empty locations to examine perceptual grouping effects. Study 1's pattern was replicated in all age groups, with onset of early selection occurring at lower loads for younger children. Overall, children initiated early selection at lower loads to compensate for immature anterior-system interference control processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual marking: Selective attention to asynchronous temporal groups.

In visual search, when a subset of distractors is previewed 1 s before the target and the remaining distractors, search speed is independent of the number of previewed items. This is visual marking. What allows old items to be marked? Four experiments show that marking is disrupted if the onset of the new items is accompanied by synchronous changes to the old items, but it is not disrupted by changes restricted to the background or by asynchronous changes to the old items. Further, behaviorally relevant old items can be prioritized over new items. Visual marking is based on temporal asynchrony between new and old items, which allows segregation of these items into 2 temporal groups. Attention is then selectively applied to 1 group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual marking and change blindness: Moving occluders and transient masks neutralize shape changes to ignored objects.

Visual search efficiency improves by presenting (previewing) one set of distractors before the target and remaining distractor items (D. G. Watson & G. W. Humphreys, 1997). Previous work has shown that this preview benefit is abolished if the old items change their shape when the new items are added (e.g., D. G. Watson & G. W. Humphreys, 2002). Here we present 5 experiments that examined whether such object changes are still effective in recapturing attention if the changes occur while the previewed objects are occluded or masked. Overall, the findings suggest that masking transients are effective in preventing both object changes and the presentation of new objects from capturing attention in time-based visual search conditions. The findings are discussed in relation to theories of change blindness, new object capture, and the ecological properties of time-based visual selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Central perceptual load does not reduce ipsilesional flanker interference in parietal extinction.

In healthy individuals, filtering of distractors improves when the perceptual difficulty, or load, of a central task increases. Following an earlier study by Lavie and Robertson (2001), this study examined whether increasing the perceptual load of a visual discrimination task attenuates the influence of ipsilesional and contralesional distractors in patients with spatial extinction. The authors used a flanker task in which participants identified a central target letter flanked by congruent, incongruent, or neutral distractors in the left and right hemifields. Perceptual load was manipulated by positioning the central target letter above or below a hash mark (#) in the low-load condition, or a letter ("R") in the high-load condition. Target identification was significantly more difficult under high load than low load. Despite this difference in task difficulty, the interference from incongruent flankers was equivalent across the two load conditions, for both contralesional and ipsilesional flankers. Our results suggest that perceptual load does not attenuate the distracting influence of ipsilesional stimuli. Rather, selectivity is strongly influenced by the strength of representations in brain areas that code salience across the visual field. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual selective attention in parkinson's disease: Dissociation of exogenous and endogenous inhibition.

Impairment in the inhibitory mechanism of visual selective attention in patients with Parkinson's disease (PD) is controversial. The present study sought to understand disparate findings in a manner analogous to the relative preservation of exogenously evoked movement and impairment of endogenously evoked movement. The authors examined inhibition of return (i.e., exogenously evoked inhibition; IOR) and negative priming (i.e., endogenously evoked inhibition; NP) in a group of 14 patients with PD and 14 healthy controls (HC). Unlike the HC, who demonstrated significant inhibition in both tasks, the group with PD demonstrated intact inhibition only in the IOR task. Dopamine replacement therapy did not affect performance. The findings are discussed within the context of a model that differentiates the essential involvement of the basal ganglia for endogenously evoked spatial inhibition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of fear and anger on selective attention.

This experiment examined the effects of two discrete negative emotions, fear and anger, on selective attention. A within-subjects design was used, and all participants (N = 98) experienced the control, anger, and fear conditions. During each condition, participants viewed a film clip eliciting the target emotion and subsequently completed a flanker task and emotion report. Selective attention costs were assessed by comparing reaction times (RTs) on congruent (baseline) trials with RTs on incongruent trials. There was a significant interaction between emotion condition (control, anger, fear) and flanker type (congruent, incongruent). Contrasts further revealed a significant interaction between emotion and flanker type when comparing RTs in the control and fear conditions, and a marginally significant interaction when comparing RTs in the control and anger conditions. This indicates that selective attention costs were significantly lower in the fear compared to the control condition and were marginally lower in the anger compared with the control condition. Further analysis of participants reporting heightened anger in the anger condition revealed significantly lower selective attention costs during anger compared to a control state. These findings support the general prediction that high arousal negative emotional states inhibit processing of nontarget information and enhance selective attention. This study is the first to show an enhancing effect of anger on selective attention. It also offers convergent evidence to studies that have previously shown an influence of fear on attentional focus using the global-local paradigm. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fast color grouping and slow color inhibition: Evidence for distinct temporal windows for separate processes in preview search.

The authors report 4 experiments that examined color grouping and negative carryover effects in preview search via a probe detection task (J. J. Braithwaite, G. W. Humphreys, & J. Hodsoll, 2003). In Experiment 1, there was evidence of a negative color carryover from the preview to new items, using both search and probe detection measures. There was also a negative bias against probes on old items that carried the majority color in the preview. With a short preview duration (150 ms) carryover effects to new items were greatly reduced, but probe detection remained biased against the majority color in the old items. Experiments 2 and 4 showed that the color bias effects on old items could be reduced when these items had to be prioritized relative to being ignored. Experiment 3 tested and rejected the idea that variations in the probability of whether minority or majority colors were probed were crucial. These results show that the time course of color carryover effects can be separated from effects of early color grouping in the preview display: Color grouping is fast, and inhibitory color carryover effects are slow. (PsycINFO Database Record (c) 2010 APA, all rights reserved)