Learning not to attend to distractors if the task is demanding: Constraints on the attentional white bear effect.

Four experiments investigated the attentional white bear (AWB) effect, in which attention increases for an upcoming distractor, and identified two key factors that interact to determine when it occurs: learned attentional set and top-down attentional control. Participants do not show enhanced attention if they begin the experiment with trials that include distractors; the effect only appears in participants who start with a block of trials without distractors. The presence or absence of distractors induces participants to adopt an attentional set that they then maintain when the distractor condition changes. Furthermore, the enhanced attention is only eliminated in the distractor-first participants if the task has a high working memory load. With a low load, the distractor always receives enhanced attention, probably because it poses less competition for resources. The results suggest that participants normally adopt a "process-all" approach, but that top-down attentional control can overrule this approach by suppressing distractor attention if there appear to be insufficient attentional resources to process all the stimuli present. The results show that the AWB effect is subject to attentional control and that a processing strategy adopted as the task is being learned is likely to be maintained even when conditions change. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

What gaze direction can tell us about cognitive processes in invertebrates.

Most visually guided animals shift their gaze using body movements, eye movements, or both to gather information selectively from their environments. Psychological studies of eye movements have advanced our understanding of perceptual and cognitive processes that mediate visual attention in humans and other vertebrates. However, much less is known about how these processes operate in other organisms, particularly invertebrates. We here make the case that studies of invertebrate cognition can benefit by adding precise measures of gaze direction. To accomplish this, we briefly review the human visual attention literature and outline four research themes and several experimental paradigms that could be extended to invertebrates. We briefly review selected studies where the measurement of gaze direction in invertebrates has provided new insights, and we suggest future areas of exploration.

Both feature comparisons and location comparisons are subject to bias.

Four experiments explore the generalizability of two different types of bias in visual comparison. The first type is a spatial congruency bias, in which two target stimuli are more likely to be classified as matching ('same') if they appear successively at the same location. The second type is an analytic bias, which varies depending on the overall similarity of the displays and the need to select specific parts from each object. Both types of bias had previously been demonstrated in comparisons based on shape and other visual features. The current tasks move beyond feature comparisons, requiring the comparison of the local positions of visual elements (dots or letters) that appear within each pattern. Given the privileged role of location in visual representations and attentional selection, it is important to test how visual comparisons of location differ from comparisons of shape and other features. The spatial congruency bias is replicated in the comparison of local positions and, as in previous experiments, its strength diminishes when the displays being compared are less similar to one another. Also, as demonstrated previously with letter comparisons, there is an analytic bias shifting responses toward 'different' when the displays being compared are less similar to one another. Responses are also shifted more toward 'same' in location comparisons relative to feature comparisons. The general pattern of results suggests that as more attentional selection is required in a comparison task, there is a stronger overall bias to respond 'different'.

Experience with searching in displays containing depth improves search performance by training participants to search more exhaustively.

In a typical visual search task, participants search for single targets amongst displays containing non-overlapping objects that are presented on a single depth plane. Recent work has begun to examine displays containing overlapping objects that are presented on different depth planes to one another. It has been found that searching displays containing depth improves response accuracy by making participants more likely to fixate targets and to identify targets after fixating them. Here we extended this previous research by seeking first of all to replicate the previous pattern of results, and then to determine whether extensive training using depth in search transfers to two-dimensional displays. We provided participants with sixteen sessions of training with displays containing transparent overlapping objects presented in depth, and found a similar pattern of results to our previous study. We also found evidence that some performance improvements from the depth training transferred to search of two-dimensional displays that did not contain depth. Further examinations revealed that participants learn to search more exhaustively (i.e., search for longer) in displays containing depth. We conclude that depth does influence search performance but the influences depend very much on the stimuli and the degree of overlap within them.

A region complexity effect masquerading as object-based attention.

A large portion of the evidence for object-based attention comes from experiments using the two-rectangle paradigm introduced by Egly, Driver, and Rafal (1994), in which response times are longer when the two stimulus locations relevant to the task are on separate objects. In the new experiments presented here, response times are longer when the two locations are part of the same object but are separated by a concavity in the object, so that the region directly between the two locations is crossed by the object's boundaries. Response times when the two locations are separated by the concavity are not statistically different from when they are on two separate objects. The results are similar for a two-letter comparison task and for a spatial cuing task. Thus, in these experiments, the response time increase does not reflect the cost of shifting attention from object to object, because it appears when the two locations are on the same object, and it is not increased when they are on different objects. Instead, it seems to reflect the complexity of the region between the two stimulus locations. This finding raises questions about whether data from previous two-rectangle experiments should be attributed to object-based attention.

Using Eye Movements to Understand how Security Screeners Search for Threats in X-Ray Baggage.

There has been an increasing drive to understand failures in searches for weapons and explosives in X-ray baggage screening. Tracking eye movements during the search has produced new insights into the guidance of attention during the search, and the identification of targets once they are fixated. Here, we review the eye-movement literature that has emerged on this front over the last fifteen years, including a discussion of the problems that real-world searchers face when trying to detect targets that could do serious harm to people and infrastructure.

Location-Specific Orientation Set Is Independent of the Horizontal Benefit with or Without Object Boundaries.

Chen and Cave (2019) showed that facilitation in visual comparison tasks that had previously been attributed to object-based attention could more directly be explained as facilitation in comparing two shapes that are configured horizontally rather than vertically. They also cued the orientation of the upcoming stimulus configuration without cuing its location and found an asymmetry: the orientation cue only enhanced performance for vertical configurations. The current study replicates the horizontal benefit in visual comparison and again demonstrates that it is independent of surrounding object boundaries. In these experiments, the cue is informative about the location of the target configuration as well as its orientation, and it enhances performance for both horizontal and vertical configurations; there is no asymmetry. Either a long or a short cue can enhance performance when it is valid. Thus, Chen and Cave's cuing asymmetry seems to reflect unusual aspects of an attentional set for orientation that must be established without knowing the upcoming stimulus location. Taken together, these studies show that a location-specific cue enhances comparison independently of the horizontal advantage, while a location-nonspecific cue produces a different type of attentional set that does not enhance comparison in horizontal configurations.

When is object-based attention not based on objects?

Some studies using methods introduced by Egly, Driver, and Rafal (1994) to measure object-based attention have shown surprising effects of object orientation. Rectangles oriented horizontally produce evidence for object-based attention, whereas vertical rectangles do not. We explore these differences using a two-letter comparison task. Across all the experiments, responses are faster when the targets are arranged horizontally rather than vertically. The horizontal advantage persists when the rectangles are removed, demonstrating its independence from object-based attention. Furthermore, responses are faster for vertically configured targets when they are within the same rectangle. This effect only arises when the rectangle orientation is informative about the target configuration orientation. This same-object advantage would normally be attributed to object-based attention, but the same pattern of data emerged when the rectangles were replaced with a salient orientation cue. The rectangles can apparently serve as a cue, making the cuing effect appear to be an object-based attention effect. However, the cuing effect can also be triggered by a horizontal bar in the center of the display. Thus participants can adopt an attentional set for a horizontal orientation independently of stimulus location. Results from comparison tasks that might have been attributed to object-based attention could instead be due to a combination of a horizontal advantage and an orientation set cost. Although these results lead to a diminished role for object-based attention, they also call for a better understanding of how an attentional set can be adopted without selecting either locations or objects. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The relationship between working memory and the dual-target cost in visual search guidance.

Searching for two targets produces a dual-target cost compared with single-target search, with reduced attentional guidance toward targets (Stroud, Menneer, Cave, & Donnelly, 2012). We explore the effect of holding a color in working memory (WM) on guidance in single-target search. In Experiments 1 and 2, participants searched for a T of a specific color while holding one of the following in WM: a color patch, a letter, a dot pattern, or an oriented bar. Only when holding a color in WM was guidance in single-target search affected as strongly as it is in dual-target search. In Experiment 3, the target changed color from trial to trial. A color in WM reduced guidance, but not to the extent of dual-target search. However, search and WM error rates were high, suggesting interference and incomplete engagement with the combined task. We conclude that the guidance cost in dual-target search is not solely due to attentional capture by the WM-color, because the WM-color can be effectively separated from search color, with little confusion between the two. However, WM load does cause substantial interference in guidance when both tasks involve color. These results illustrate the complex interactions between WM and attentional guidance. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

We can guide search by a set of colors, but are reluctant to do it.

For some real-world color searches, the target colors are not precisely known, and any item within a range of color values should be attended. Thus, a target representation that captures multiple similar colors would be advantageous. If such a multicolor search is possible, then search for two targets (e.g., Stroud, Menneer, Cave, and Donnelly, Journal of Experimental Psychology: Human Perception and Performance, 38(1): 113-122, 2012) might be guided by a target representation that included the target colors as well as the continuum of colors that fall between the targets within a contiguous region in color space. Results from Stroud, Menneer, Cave, and Donnelly, Journal of Experimental Psychology: Human Perception and Performance, 38(1): 113-122, (2012) suggest otherwise, however. The current set of experiments show that guidance for a set of colors that are all from a single region of color space can be reasonably effective if targets are depicted as specific discrete colors. Specifically, Experiments 1-3 demonstrate that a search can be guided by four and even eight colors given the appropriate conditions. However, Experiment 5 gives evidence that guidance is sometimes sensitive to how informative the target preview is to search. Experiments 6 and 7 show that a stimulus showing a continuous range of target colors is not translated into a search target representation. Thus, search can be guided by multiple discrete colors that are from a single region in color space, but this approach was not adopted in a search for two targets with intervening distractor colors.

Dual Target Search is Neither Purely Simultaneous nor Purely Successive.

Previous research shows that visual search for two different targets is less efficient than search for a single target. Stroud, Menneer, Cave and Donnelly (2012) concluded that two target colours are represented separately based on modeling the fixation patterns. Although those analyses provide evidence for two separate target representations, they do not show whether participants search simultaneously for both targets, or first search for one target and then the other. Some studies suggest that multiple target representations are simultaneously active, while others indicate that search can be voluntarily simultaneous, or switching, or a mixture of both. Stroud et al.'s participants were not explicitly instructed to use any particular strategy. These data were revisited to determine which strategy was employed. Each fixated item was categorised according to whether its colour was more similar to one target or the other. Once an item similar to one target is fixated, the next fixated item is more likely to be similar to that target than the other, showing that at a given moment during search, one target is generally favoured. However, the search for one target is not completed before search for the other begins. Instead, there are often short runs of one or two fixations to distractors similar to one target, with each run followed by a switch to the other target. Thus, the results suggest that one target is more highly weighted than the other at any given time, but not to the extent that search is purely successive.

Two kinds of bias in visual comparison illustrate the role of location and holistic/analytic processing differences.

A number of studies have shown that two stimuli appearing successively at the same spatial location are more likely to be perceived as the same, even though location is irrelevant to the task. This bias to respond "same" when stimuli are at the same location is termed spatial congruency bias. The experiments reported here demonstrate that the spatial congruency bias extends to letter strings: Participants tend to respond "same" when comparing two strings appearing successively at the same location. This bias may arise because successive stimuli at the same location are more likely to be perceived as a single object. Bias is also affected by the nature of the comparison task. We show that if letters must be compared individually (analytical comparison), there is a bias to respond "different," but if letter strings are compared as unified wholes (holistic comparison), there is no bias or a bias to respond "same." This analytical bias is apparently separate from the spatial congruency bias. It appears whether the task requires localization of differences between strings, or counting the number of differences, or ignoring differences in some parts of the stimuli while attending to others. All of these analytical comparison tasks require that letters be selected individually, and the analytical bias may reflect difficulty in preventing interference from neighboring letters in this selection process. Each type of bias reflects a different aspect of visual processing, and both can be measured to probe how processing changes across different tasks.

Dual-target cost in visual search for multiple unfamiliar faces.

The efficiency of visual search for one (single-target) and either of two (dual-target) unfamiliar faces was explored to understand the manifestations of capacity and guidance limitations in face search. The visual similarity of distractor faces to target faces was manipulated using morphing (Experiments 1 and 2) and multidimensional scaling (Experiment 3). A dual-target cost was found in all experiments, evidenced by slower and less accurate search in dual- than single-target conditions. The dual-target cost was unequal across the targets, with performance being maintained on one target and reduced on the other, which we label "preferred" and "non-preferred" respectively. We calculated the capacity for each target face and show reduced capacity for representing the non-preferred target face. However, results show that the capacity for the non-preferred target can be increased when the dual-target condition is conducted after participants complete the single-target conditions. Analyses of eye movements revealed evidence for weak guidance of fixations in single-target search, and when searching for the preferred target in dual-target search. Overall, the experiments show dual-target search for faces is capacity- and guidance-limited, leading to superior search for 1 face over the other in dual-target search. However, learning faces individually may improve capacity with the second face. (PsycINFO Database Record

Adding depth to overlapping displays can improve visual search performance.

Standard models of visual search have focused upon asking participants to search for a single target in displays where the objects do not overlap one another, and where the objects are presented on a single depth plane. This stands in contrast to many everyday visual searches wherein variations in overlap and depth are the norm, rather than the exception. Here, we addressed whether presenting overlapping objects on different depths planes to one another can improve search performance. Across 4 different experiments using different stimulus types (opaque polygons, transparent polygons, opaque real-world objects, and transparent X-ray images), we found that depth was primarily beneficial when the displays were transparent, and this benefit arose in terms of an increase in response accuracy. Although the benefit to search performance only appeared in some cases, across all stimulus types, we found evidence of marked shifts in eye-movement behavior. Our results have important implications for current models and theories of visual search, which have not yet provided detailed accounts of the effects that overlap and depth have on guidance and object identification processes. Moreover, our results show that the presence of depth information could aid real-world searches of complex, overlapping displays. (PsycINFO Database Record

Eye movements are an important part of the story, but not the whole story.

Some previous accounts of visual search have emphasized covert attention at the expense of eye movements, and others have focused on eye movements while ignoring covert attention. Both selection mechanisms are likely to contribute to many searches, and a full account of search will probably need to explain how the two interact to find visual targets.

Identifying visual targets amongst interfering distractors: Sorting out the roles of perceptual load, dilution, and attentional zoom.

Visual selection is imperfect; whenever a complex array of objects is processed, representations of multiple objects are likely to be active simultaneously. A full account of attentional processing must explain how these representations affect one another and how they interact to produce a response. Evidence on these interactions comes from measures of distractor interference and from dilution of distractor effects by other nontargets. Based on these data, different principles have been proposed to help understand target-distractor interactions, including accounts based on perceptual load and on dilution among nontargets. We review evidence from a number of experiments, including some using Yantis and Jonides's (Journal of Experimental Psychology: Human Perception and Performance, 10, 601-621, 1984, Journal of Experimental Psychology: Human Perception and Performance, 16, 121-134, 1990) methods for preventing abrupt onsets, which can disrupt spatial attention. The results underscore spatial constraints on the allocation of attention to include targets and exclude distractors. Selection is most effective when a single region can be selected that includes all possible target locations and excludes possible distractor locations. This region can be expanded or contracted as needed for the task, as suggested by C. W. Eriksen and St. James's (Perception & Psychophysics, 40, 225-240, 1986) zoom lens model. This attentional zoom setting is probably affected by a number of factors, including the number of nontargets, the similarity among stimulus elements, the discriminability of the possible targets, and the discrimination difficulty of a concurrent task. A narrower attentional zoom setting that excludes a distractor will prevent interference from that distractor. Interference from a distractor will be diluted by nontargets, but only if they are within the attentional zoom region.

Zooming in on the cause of the perceptual load effect in the go/no-go paradigm.

Perceptual load theory (Lavie, 2005) claims that attentional capacity that is not used for the current task is allocated to irrelevant distractors. It predicts that if the attentional demands of the current task are high, distractor interference will be low. One particularly powerful demonstration of perceptual load effects on distractor processing relies on a go/no-go cue that is interpreted by either simple feature detection or feature conjunction (Lavie, 1995). However, a possible alternative interpretation of these effects is that the differential degree of distractor processing is caused by how broadly attention is allocated (attentional zoom) rather than to perceptual load. In 4 experiments, we show that when stimuli are arranged to equalize the extent of spatial attention across conditions, distractor interference varies little whether cues are defined by a simple feature or a conjunction, and that the typical perceptual load effect emerges only when attentional zoom can covary with perceptual load. These results suggest that attentional zoom can account for the differential degree of distractor processing traditionally attributed to perceptual load in the go/no-go paradigm. They also provide new insight into how different factors interact to control distractor interference. (PsycINFO Database Record

Understanding the contribution of target repetition and target expectation to the emergence of the prevalence effect in visual search.

Behavior in visual search tasks is influenced by the proportion of trials on which a target is presented (the target prevalence). Previous research has shown that when target prevalence is low (2 % prevalence), participants tend to miss targets, as compared with higher prevalence levels (e.g., 50 % prevalence). There is an ongoing debate regarding the relative contributions of target repetition and the expectation that a target will occur in the emergence of prevalence effects. In order to disentangle these two factors, we went beyond previous studies by directly manipulating participants' expectations regarding how likely a target was to appear on a given trial. This we achieved without using cues or feedback. Our results indicated that both target repetition and target expectation contribute to the emergence of the prevalence effect.

Singleton search is guided by knowledge of the target, but maybe it shouldn't be.

Among studies of visual search for a singleton, some studies show evidence of top-down attentional guidance driven by goals, while others do not, leading to uncertainty as to how goal-driven guidance should be included in attentional theories. Six experiments tested this guidance when a target shape is found by locating a singleton feature (color or shape) and an orientation within the target is then reported. Experiments 1 and 2 use the dimensional priming paradigm underlying the most effective arguments against goal-driven guidance, and show evidence for guidance in many circumstances. Experiment 3 extends the results to feature priming, and demonstrates a complex interaction between attentional goals and memory for previous targets. In Experiment 4, symbolic (word) cues were just as effective as image cues, further strengthening the case for goal-driven guidance. In Experiments 5 and 6, as in the previous experiments, valid cues again produced faster responses than invalid cues, showing the advantage of goal-driven guidance. Surprisingly, however, responses were even faster when the cues were uninformative. Furthermore, participants who began the experiment with neutral cues seemed to ignore informative cues later in the experiment. The results show that attention can be guided by goals even in easy searches, but that searchers have much flexibility in the use of this guidance, and may choose not to use it. Furthermore, their decisions about using this guidance are not always well informed, because they are not aware of the relative costs and benefits.