Differences in multiple‐target visual search performance between non‐professional and professional searchers due to decision‐making criteria

Professional visual searches, such as those conducted by airport security personnel, often demand highly accurate performance. As many factors can hinder accuracy, it is critical to understand the potential influences. Here, we examined how explicit decision‐making criteria might affect multiple‐target search performance. Non‐professional searchers (college undergraduates) and professional searchers (airport security officers) classified trials as ‘safe’ or ‘dangerous’, in one of two conditions. Those in the ‘one = dangerous’ condition classified trials as dangerous if they found one or two targets, and those in the ‘one = safe’ condition only classified trials as dangerous if they found two targets. The data suggest an important role of context that may be mediated by experience; non‐professional searchers were more likely to miss a second target in the one = dangerous condition (i.e., when finding a second found target did not change the classification), whereas professional searchers were more likely to miss a second in the one = safe condition.     

Anticipatory anxiety hinders detection of a second target in dual-target search

Professional visual searches (e.g., baggage screenings, military searches, radiological examinations) are often conducted in high-pressure environments and require focus on multiple visual targets. Yet laboratory studies of visual search tend to be conducted in emotionally neutral settings with only one possible target per display. In the experiment reported here, we looked to better emulate high-pressure search conditions by presenting searchers with arrays that contained between zero and two targets while inducing anticipatory anxiety via a threat-of-shock paradigm. Under conditions of anticipatory anxiety, dual-target performance was negatively affected, but single-target performance and time on task were unaffected. These results suggest that multiple-target searches may be a more sensitive instrument to measure the effect of environmental factors on visual cognition than single-target searches are. Further, the effect of anticipatory anxiety was modulated by individual differences in state anxiety levels of participants prior to the experiment. These results have implications for both the laboratory study of visual search and the management and assessment of professional searchers.     

A bayesian optimal foraging model of human visual search

Real-world visual searches often contain a variable and unknown number of targets. Such searches present difficult metacognitive challenges, as searchers must decide when to stop looking for additional targets, which results in high miss rates in multiple-target searches. In the study reported here, we quantified human strategies in multiple-target search via an ecological optimal foraging model and investigated whether searchers adapt their strategies to complex target-distribution statistics. Separate groups of individuals searched displays with the number of targets per trial sampled from different geometric distributions but with the same overall target prevalence. As predicted by optimal foraging theory, results showed that individuals searched longer when they expected more targets to be present and adjusted their expectations on-line during each search by taking into account the higher-order, across-trial target distributions. However, compared with modeled ideal observers, participants systematically responded as if the target distribution were more uniform than it was, which suggests that training could improve multiple-target search performance.     

Person perception informs understanding of cognition during visual search

Does person perception—the impressions we form from watching others—hold clues to the mental states of people engaged in cognitive tasks? We investigated this with a two-phase method: In Phase 1, participants searched on a computer screen (Experiment 1) or in an office (Experiment 2); in Phase 2, other participants rated the searchers’ video-recorded behavior. The results showed that blind raters are sensitive to individual differences in search proficiency and search strategy, as well as to environmental factors affecting search difficulty. Also, different behaviors were linked to search success in each setting: Eye movement frequency predicted successful search on a computer screen; head movement frequency predicted search success in an office. In both settings, an active search strategy and positive emotional expressions were linked to search success. These data indicate that person perception informs cognition beyond the scope of performance measures, offering the potential for new measurements of cognition that are both rich and unobtrusive.     

场景情境和目标模板在视觉搜索中的交互作用

以真实场景图像中的物体搜索为实验任务, 操纵场景情境和目标模板, 采用眼动技术将搜索过程分为起始阶段、扫描阶段和确认阶段, 考察场景情境和目标模板对视觉搜索过程的影响机制。结果发现, 场景情境和目标模板的作用方式及时间点不同, 二者交互影响搜索的正确率和反应时, 仅场景情境影响起始阶段的时间, 随后二者交互影响扫描阶段和确认阶段的时间及主要眼动指标。作者由此提出了场景情境和目标模板在视觉搜索中的交互作用模型。     

Training older adults to search more effectively: scanning strategy and visual search in dynamic displays

The authors examined the ability of older adults to modify their search strategies to detect changes in dynamic displays. Older adults who made few eye movements during search (i.e., covert searchers) were faster and more accurate compared with individuals who made many eye movements (i.e., overt searchers). When overt searchers were instructed to adopt a covert search strategy, target detection performance increased to the level of natural covert searchers. Similarly, covert searchers instructed to search overtly exhibited a decrease in target detection performance. These data suggest that with instructions and minimal practice, older adults can ameliorate the cost of a poor search strategy.     

The relative contribution of scene context and target features to visual search in scenes

Many experiments have shown that knowing a targets visual features improves search performance over knowing the target name. Other experiments have shown that scene context can facilitate object search in natural scenes. In this study, we investigated how scene context and target features affect search performance. We examined two possible sources of information from scene context—the scenes gist and the visual details of the scene—and how they potentially interact with target-feature information. Prior to commencing search, participants were shown a scene and a target cue depicting either a picture or the category name (or no-information control). Using eye movement measures, we investigated how the target features and scene context influenced two components of search: early attentional guidance processes and later verification processes involved in the identification of the target. We found that both scene context and target features improved guidance, but that target features also improved speed of target recognition. Furthermore, we found that a scenes visual details played an important role in improving guidance, much more so than did the scenes gist alone.     

Does prism adaptation affect visual search in spatial neglect patients: A systematic review

Prism adaptation (PA) is a widely used intervention for (visuo‐)spatial neglect. PA‐induced improvements can be assessed by visual search tasks. It remains unclear which outcome measures are the most sensitive for the effects of PA in neglect. In this review, we aimed to evaluate PA effects on visual search measures. A systematic literature search was completed regarding PA intervention studies focusing on patients with neglect using visual search tasks. Information about study content and effectiveness was extracted. Out of 403 identified studies, 30 met the inclusion criteria. The quality of the studies was evaluated: Rankings were moderate‐to‐high for 7, and low for 23 studies. As feature search was only performed by five studies, low‐to‐moderate ranking, we were limited in drawing firm conclusions about the PA effect on feature search. All moderate‐to‐high‐ranking studies investigated cancellation by measuring only omissions or hits. These studies found an overall improvement after PA. Measuring perseverations and total task duration provides more specific information about visual search. The two (low ranking) studies that measured this found an improvement after PA on perseverations and duration (while accuracy improved for one study and remained the same for the other). This review suggests there is an overall effect of PA on visual search, although complex visual search tasks and specific visual search measures are lacking. Suggestions for search measures that give insight in subcomponents of visual search are provided for future studies, such as perseverations, search path intersections, search consistency and using a speed–accuracy trade‐off.     

Intertrial temporal contextual cuing: association across successive visual search trials guides spatial attention

Contextual cuing refers to the facilitation of performance in visual search due to the repetition of the same displays. Whereas previous studies have focused on contextual cuing within single-search trials, this study tested whether 1 trial facilitates visual search of the next trial. Participants searched for a T among Ls. In the training phase, the spatial layout on trial N=1 was predictive of the target location on trial N. In the testing phase, the predictive value was removed. Results revealed an intertrial temporal contextual cuing effect: Search speed became progressively shorter in the training phase, but it significantly lengthened during testing. The authors conclude that the visual system is capable of retaining spatial contextual memory established earlier to facilitate perception.     

The role of priming in conjunctive visual search

To assess the role of priming in conjunctive visual search tasks, we systematically varied the consistency of the target and distractor identity between different conditions. Search was fastest in the standard conjunctive search paradigm where identities remained constant. Search was slowest when potential target identity varied predictably for each successive trial (the 'switch' condition). The role of priming was also demonstrated on a trial-by-trial basis in a 'streak' condition where target and distractor identity was unpredictable yet was consistent within streaks. When the target to be found was the same for a few trials in a row, search performance became similar to that when the potential target was the same on all trials. A similar pattern was found for the target absent trials, suggesting that priming is based on the whole search array rather than just the target in each case. Further analysis indicated that the effects of priming are sufficiently strong to account for the advantage seen for the conjunctive search task. We conclude that the role of priming in visual search is underestimated in current theories of visual search and that differences in search times often attributed to top-down guidance may instead reflect the benefits of priming.     

You detect while I search: examining visual search efficiency in a joint search task

Numerous factors impact attentional allocation, with behaviour being strongly influenced by the interaction between individual intent and our visual environment. Traditionally, visual search efficiency has been studied under solo search conditions. Here, we propose a novel joint search paradigm where one individual controls the visual input available to another individual via a gaze contingent window (e.g., Participant 1 controls the window with their eye movements and Participant 2 – in an adjoining room – sees only stimuli that Participant 1 is fixating and responds to the target accordingly). Pairs of participants completed three blocks of a detection task that required them to: (1) search and detect the target individually, (2) search the display while their partner performed the detection task, or (3) detect while their partner searched. Search was most accurate when the person detecting was doing so for the second time while the person controlling the visual input was doing so for the first time, even when compared to participants with advanced solo or joint task experience (Experiments 2 and 3). Through surrendering control of one’s search strategy, we posit that there is a benefit of a reduced working memory load for the detector resulting in more accurate search. This paradigm creates a counterintuitive speed/accuracy trade-off which combines the heightened ability that comes from task experience (discrimination task) with the slower performance times associated with a novel task (the initial search) to create a potentially more efficient method of visual search.     

Coarse-to-fine eye movement behavior during visual search

It has previously been argued that, during visual search, eye movement behavior is indicative of an underlying scanning “strategy” that starts on a global, or “coarse,” scale but then progressively focuses to a more local, or “fine,” scale. This conclusion is motivated by the finding that, as a trial progresses, fixation durations tend to increase and saccade amplitudes tend to decrease. In the present study, we replicate these effects but offer an alternative explanation for them—that they emerge from a few stochastic factors that control eye movement behavior. We report the results of a simulation supporting this hypothesis and discuss implications for future models of visual search.     

Rewarding context accelerates implicit guidance in visual search

It is well known that observers can implicitly learn the spatial context of complex visual searches, such that future searches through repeated contexts are completed faster than those through novel contexts, even though observers remain at chance at discriminating repeated from new contexts. This contextual-cueing effect arises quickly (within less than five exposures) and asymptotes within 30 exposures to repeated contexts. In spite of being a robust effect (its magnitude is over 100 ms at the asymptotic level), the effect is implicit: Participants are usually at chance at discriminating old from new contexts at the end of an experiment, in spite of having seen each repeated context more than 30 times throughout a 50-min experiment. Here, we demonstrate that the speed at which the contextual-cueing effect arises can be modulated by external rewards associated with the search contexts (not with the performance itself). Following each visual search trial (and irrespective of a participant’s search speed on the trial), we provided a reward, a penalty, or no feedback to the participant. Crucially, the type of feedback obtained was associated with the specific contexts, such that some repeated contexts were always associated with reward, and others were always associated with penalties. Implicit learning occurred fastest for contexts associated with positive feedback, though penalizing contexts also showed a learning benefit. Consistent feedback also produced faster learning than did variable feedback, though unexpected penalties produced the largest immediate effects on search performance.     

Scale of attentional focus in visual search

The effects of the spatial scale of attention on feature and conjunction search were examined in two experiments. Adult participants in three age groups—young, young-old, and old-old—were given precues of varying validity and precision in indicating the location of a target letter subsequently presented in a visual array. Systematic decreases in the size of a valid precue (toward the size of the target) progressively facilitated both feature and conjunction search, with a greater benefit accruing to conjunction search. Age-related slowing in conjunction search was mitigated by precise (small and valid) precues, presumably because they reduced the need for participants in the young-old group to focus and to shift attention. Nevertheless, this benefit was reduced in the old-old group. The effects of valid location precue size varied with cue-target stimulus onset asynchrony (SOA) in a manner that interacted with search difficulty: Effects of cue size developed more rapidly in feature search but more slowly in conjunction search. Finally, when precues were invalid for target location, search was faster with larger sized precues. Thus, in both easy feature search and hard conjunction search, the scale of visuospatial attention modulates the speed of visual search. Furthermore, when the SOA is sufficiently long for cue effects to develop, the ability to dynamically adjust the scale of visuospatial attention appears to decline in advanced age. These results go beyond current models in suggesting that visuospatial attention possesses two dynamic properties—shifting in space and varying in scale—that are deployed independently, depending on task demands.     

Hiding and finding: The relationship between visual concealment and visual search

As an initial step toward developing a theory of visual concealment, we assessed whether people would use factors known to influence visual search difficulty when the degree of concealment of objects among distractors was varied. In Experiment 1, participants arranged search objects (shapes, emotional faces, and graphemes) to create displays in which the targets were in plain sight but were either easy or hard to find. Analyses of easy and hard displays created during Experiment 1 revealed that the participants reliably used factors known to influence search difficulty (e.g., eccentricity, target—distractor similarity, presence/absence of a feature) to vary the difficulty of search across displays. In Experiment 2, a new participant group searched for the targets in the displays created by the participants in Experiment 1. Results indicated that search was more difficult in the hard than in the easy condition. In Experiments 3 and 4, participants used presence versus absence of a feature to vary search difficulty with several novel stimulus sets. Taken together, the results reveal a close link between the factors that govern concealment and the factors known to influence search difficulty, suggesting that a visual search theory can be extended to form the basis of a theory of visual concealment.     

Effects of correct and transformed visual feedback on rhythmic visuo-motor tracking: tracking performance and visual search behavior

The effects of correct and transformed visual feedback on rhythmic unimanual visuo-motor tracking were examined, focusing on tracking performance (accuracy and stability) and visual search behavior. Twelve participants (reduced to 9 in the analyses) manually tracked an oscillating visual target signal in phase (by moving the hand in the same direction as the target signal) and in antiphase (by moving the hand in the opposite direction), while the frequency of the target signal was gradually increased to probe pattern stability. Besides a control condition without feedback, correct feedback (representing the actual hand movement) or mirrored feedback (representing the hand movement transformed by 180 degrees) were provided during tracking, resulting in either in-phase or antiphase visual motion of the target and feedback signal, depending on the tracking mode performed. The quality (accuracy and stability) of in-phase tracking was hardly affected by the two forms of feedback, whereas antiphase tracking clearly benefited from mirrored feedback but not from correct feedback. This finding extends previous results indicating that the performance of visuo-motor coordination tasks is aided by visual feedback manipulations resulting in coherently grouped (i.e., in-phase) visual motion structures. Further insights into visuo-motor tracking with and without feedback were garnered from the visual search patterns accompanying task performance. Smooth pursuit eye movements only occurred at lower oscillation frequencies and prevailed during in-phase tracking and when target and feedback signal moved in phase. At higher frequencies, point-of-gaze was fixated at a location that depended on the feedback provided and the resulting visual motion structures. During in-phase tracking the mirrored feedback was ignored, which explains why performance was not affected in this condition. Point-of-gaze fixations at one of the end-points were accompanied by reduced motor variability at this location, reflecting a form of visuo-motor anchoring that may support the pick up of discrete information as well as the control of hand movements to a desired location.     

Differential central resource demands of memory scanning and visual search: The role of consistent and varied mapping

In this paper we compare the effect of mapping on the central resource requirements of two search processes. With consistent mapping of items to the role of either target or distractor, search becomes very efficient; with varied mapping (each item serves as both a target and a distractor in the same experiment), search is less efficient. One interpretation of this effect of manipulating the consistency of mapping is that search under varied mapping requires limited capacity central resources but the requirement for these resources is reduced with consistent mapping. We tested this interpretation by varying the consistency of mapping in memory scanning (Experiments 1 and 2) and in visual search (Experiments 3 and 4) as the second of two tasks in the psychological refractory period (PRP) paradigm. Responses were location based, rather than present/absent judgements, and a target was present on every trial. The results indicated that there was less of a requirement for central resources with consistent mapping than with varied mapping in both memory scanning and in visual search; however, the effect of the mapping manipulation on central resource requirements was different for memory scanning than for visual search. Memory scanning was not done in parallel with a resource-demanding stage of a second task under varied mapping, but was done in parallel with this stage under consistent mapping. Part of visual search under both types of mapping was done in parallel with a resource-demanding stage of a second task and part was not; consistent mapping reduced the duration of the stage of processing that could not be carried out in parallel. We conclude that under consistent mapping, switching among items in memory becomes less controlled and therefore has less of a requirement for central resources than under varied mapping. In visual search, however, consistent mapping improves performance by facilitating the comparison of the target item to items in the search array.     

Rare,but obviously there: Effects of target frequency and salience on visual search accuracy

Accuracy can be extremely important for many visual search tasks. However, numerous factors work to undermine successful search. Several negative influences on search have been well studied, yet one potentially influential factor has gone almost entirely unexplored—namely, how is search performance affected by the likelihood that a specific target might appear? A recent study demonstrated that when specific targets appear infrequently (i.e., once in every thousand trials) they were, on average, not often found. Even so, some infrequently appearing targets were actually found quite often, suggesting that the targets' frequency is not the only factor at play. Here, we investigated whether salience (i.e., the extent to which an item stands out during search) could explain why some infrequent targets are easily found whereas others are almost never found. Using the mobile application Airport Scanner, we assessed how individual target frequency and salience interacted in a visual search task that included a wide array of targets and millions of trials. Target frequency and salience were both significant predictors of search accuracy, although target frequency explained more of the accuracy variance. Further, when examining only the rarest target items (those that appeared on less than 0.15% of all trials), there was a significant relationship between salience and accuracy such that less salient items were less likely to be found. Beyond implications for search theory, these data suggest significant vulnerability for real-world searches that involve targets that are both infrequent and hard-to-spot.     

Independence of speed and accuracy in visual search: evidence for separate mechanisms.

Data from two studies that tested children's attention using visual search for a series of targets in a complex display and a sustained-attention task waiting for signals in a similar display were subjected to Factor Analysis to explore previous indications that speed and accuracy (the number of false alarms to nontargets) on this task reflect different mechanisms. The two factors identified confirmed the separation of these two measures and also suggested that the speed factor was related to Mental Age, while the accuracy factor was related to ratings of attentional ability. It is suggested that ratings of attentional ability reflect the efficiency of executive functions, displayed in the ability to inhibit responses to nontargets in these tasks, while speed of search is related to processing speed in the nervous system. Therefore intelligence and attentional ability depend on different underlying features of the nervous system.