Distractor Dwelling, Skipping, and Revisiting Determine Target Absent Performance in Difficult Visual Search

Refixation behavior in naturalistic viewing: Methods, mechanisms, and neural correlates

When freely viewing a scene, the eyes often return to previously visited locations. By tracking eye movements and coregistering eye movements and EEG, such refixations are shown to have multiple roles: repairing insufficient encoding from precursor fixations, supporting ongoing viewing by resampling relevant locations prioritized by precursor fixations, and aiding the construction of memory representations. All these functions of refixation behavior are understood to be underpinned by three oculomotor and cognitive systems and their associated brain structures. First, immediate saccade planning prior to refixations involves attentional selection of candidate locations to revisit. This process is likely supported by the dorsal attentional network. Second, visual working memory, involved in maintaining task-related information, is likely supported by the visual cortex. Third, higher-order relevance of scene locations, which depends on general knowledge and understanding of scene meaning, is likely supported by the hippocampal memory system. Working together, these structures bring about viewing behavior that balances exploring previously unvisited areas of a scene with exploiting visited areas through refixations.

Establishing gaze markers of perceptual load during multi-target visual search

Highly-automated technologies are increasingly incorporated into existing systems, for instance in advanced car models. Although highly automated modes permit non-driving activities (e.g. internet browsing), drivers are expected to reassume control upon a 'take over' signal from the automation. To assess a person's readiness for takeover, non-invasive eye tracking can indicate their attentive state based on properties of their gaze. Perceptual load is a well-established determinant of attention and perception, however, the effects of perceptual load on a person's ability to respond to a takeover signal and the related gaze indicators are not yet known. Here we examined how load-induced attentional state affects detection of a takeover-signal proxy, as well as the gaze properties that change with attentional state, in an ongoing task with no overt behaviour beyond eye movements (responding by lingering the gaze). Participants performed a multi-target visual search of either low perceptual load (shape targets) or high perceptual load (targets were two separate conjunctions of colour and shape), while also detecting occasional auditory tones (the proxy takeover signal). Across two experiments, we found that high perceptual load was associated with poorer search performance, slower detection of cross-modal stimuli, and longer fixation durations, while saccade amplitude did not consistently change with load. Using machine learning, we were able to predict the load condition from fixation duration alone. These results suggest monitoring fixation duration may be useful in the design of systems to track users' attentional states and predict impaired user responses to stimuli outside of the focus of attention.

Initial Maintenance of Attention to Threat in Children with Social Anxiety Disorder? Findings from an Eye-Tracking Experiment

Background

Attentional biases are assumed to be a core feature in the etiology and maintenance of clinical anxiety. The present study focuses on initial maintenance of attention to threat, one of three attentional components investigated the least, particularly in child anxiety.

Methods

Angry and neutral facial expressions were presented in a free-viewing task, while eye-movements were recorded. Participants were N = 96 school-aged children, with n = 50 children with a clinical social anxiety disorder (SAD) and n = 46 healthy control children (HC). Prior to the task, social stress was induced in half of participating children to investigate the impact of increased levels of distress on initial attention allocation.

Results

The length of first fixation to angry faces in children with SAD neither differed from the length of first fixation to neutral faces nor the length of first fixation to angry faces in HC children. Furthermore, this variable was not affected by a stress induction procedure. However, children with SAD initially fixated longer on faces than HC children.

Conclusion

Our findings provide evidence for difficulties disengaging attention from faces. This may indicate that attention allocation is determined by the social nature of the stimuli rather than by the specific emotional valence.

Dwelling on simple stimuli in visual search

Research and theories on visual search often focus on visual guidance to explain differences in search. Guidance is the tuning of attention to target features and facilitates search because distractors that do not show target features can be more effectively ignored (skipping). As a general rule, the better the guidance is, the more efficient search is. Correspondingly, behavioral experiments often interpreted differences in efficiency as reflecting varying degrees of attentional guidance. But other factors such as the time spent on processing a distractor (dwelling) or multiple visits to the same stimulus in a search display (revisiting) are also involved in determining search efficiency. While there is some research showing that dwelling and revisiting modulate search times in addition to skipping, the corresponding studies used complex naturalistic and category-defined stimuli. The present study tests whether results from prior research can be generalized to more simple stimuli, where target-distractor similarity, a strong factor influencing search performance, can be manipulated in a detailed fashion. Thus, in the present study, simple stimuli with varying degrees of target-distractor similarity were used to deliver conclusive evidence for the contribution of dwelling and revisiting to search performance. The results have theoretical and methodological implications: They imply that visual search models should not treat dwelling and revisiting as constants across varying levels of search efficiency and that behavioral search experiments are equivocal with respect to the responsible processing mechanisms underlying more versus less efficient search. We also suggest that eye-tracking methods may be used to disentangle different search components such as skipping, dwelling, and revisiting.

Dwelling on distractors varying in target-distractor similarity

Present day models of visual search focus on explaining search efficiency by visual guidance: The target guides attention to the target's position better in more efficient than in less efficient search. The time spent processing the distractor, however, is set to a constant in these models. In contrast to this assumption, recent studies found that dwelling on distractors is longer in more inefficient search. Previous experiments in support of this contention all presented the same distractors across all conditions, while varying the targets. While this procedure has its virtues, it confounds the manipulation of search efficiency with target type. Here we use the same targets over the entire experiment, while varying search efficiency by presenting different types of distractors. Eye fixation behavior was used to infer the amount of distractor dwelling, skipping, and revisiting. The results replicate previous results, with similarity affecting dwelling, and dwelling in turn affecting search performance. A regression analysis confirmed that variations in dwelling account for a large amount of variance in search speed, and that the similarity effect in dwelling accounts for the similarity effect in overall search performance.

Developmental effects of stimulus gender and the social context in which it appears on threat detection

This study used a hands-free eye-tracking visual search (VS) task to examine possible developmental differences in target detection. Thirty-two young adults and 27 youth were asked to detect a fearful face (male or female) among a crowd of either neutral or happy faces. Fearful male faces were detected faster than fearful female faces, but only by young adults and only when displayed among neutral faces. Additionally, young adults had shorter scanpath lengths prior to the target detection. Finally, a strong negative correlation emerged between age and detection speed for a male target in a neutral crowd. Using this age-matched VS task, the study found age differences in the way individuals detect a threat in a social-related contextual environment, pointing to subtle differences in the emotion-attention interplay during the course of development. Statement of contribution What is already known on this subject? Visual search of threat detection is critical for survival, specifically regarding expressive faces. Visual search efficiency is affected by both stimulus-driven and higher goal-directed processes. Stimuli and contextual features affect threat speed detection. What does this study add? A novel task was designed to examine age-related differences in visual search. Specific stimuli gender and contextual features yielded age-related differences in threat detection. The study further demonstrates the subtle developmental differences in attention-emotion interaction.