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The influence of British and Chinese culture on the viewing of paintings from Western and East Asian traditions was explored in an old/new discrimination task. Accuracy data were considered alongside signal detection measures of sensitivity and bias. The results showed participant culture and painting tradition interacted but only with respect to response bias and not sensitivity. Eye movements were also recorded during encoding and discrimination. Paintings were split into regions of interest defined by faces, or the theme and context in order to analyse the eye movement data. With respect to the eye movement data, the results showed that a match between participant culture and painting tradition increased the viewing\ud of faces in paintings at the expense of the viewing of other locations, an effect interpreted as a manifestation of the Other Race Effect on the viewing of paintings. There was, however, no evidence of broader influence of culture on the eye movements made to paintings as might be expected if culture influenced the allocation of attention more generally. Taken together, these findings suggest culture influences the viewing of paintings but only in response to challenges to the encoding of faces.

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).

Participants' eye movements and electroencephalogram (EEG) signal were recorded as they read sentences displayed according to the gaze-contingent boundary paradigm. Two target words in each sentence were manipulated for lexical frequency (high vs. low frequency) and parafoveal preview of each target word (identical vs. string of random letters vs. string of Xs). Eye movement data revealed visual parafoveal-on-foveal (PoF) effects, as well as foveal visual and orthographic preview effects and word frequency effects. Fixation-related potentials (FRPs) showed visual and orthographic PoF effects as well as foveal visual and orthographic preview effects. Our results replicated the early preview positivity effect (Dimigen, Kliegl, & Sommer, 2012) in the X-string preview condition, and revealed different neural correlates associated with a preview comprised of a string of random letters relative to a string of Xs. The former effects seem likely to reflect difficulty associated with the integration of parafoveal and foveal information, as well as feature overlap, while the latter reflect inhibition, and potentially disruption, to processing underlying reading. Interestingly, and consistent with Kretzschmar, Schlesewsky, and Staub (2015), no frequency effect was reflected in the FRP measures. The findings provide insight into the neural correlates of parafoveal processing and written word recognition in reading and demonstrate the value of utilizing ecologically valid paradigms to study well established phenomena that occur as text is read naturally. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

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.

Image reproduction has expanded our knowledge of the world’s great art collections, but the viewing experience of a reproduction as against an actual work is altered. Images evoke a range of sensory, emotional and cognitive experiences that go beyond the merely visual. In particular, paintings displayed in galleries are presumed to hold preeminence for spectators over reproductions of them. We might be said to engage a range of senses in a more active manner in the presence of a painting. This preeminence emerges in the availability for inspection of information about physical relief that we can add to the colour, texture and form - information that is available in both paintings and reproductions. This study of Manet’s A Bar at the Folies Bergere by a team of artists and psychologists using eye-tracking technology tests this hypothesis, asking whether the availability of relief information changes the pattern of fixations for spectators viewing the picture. Four expert and four novice spectators viewed the original painting in situ at the Courtauld gallery, and sixteen novices viewed a to-scale reproduction of the picture. All spectators had their eye movements recorded as they verbally described the image and their response to 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.

In his Death and Disaster series, Andy Warhol repeated gruesome images of suicides and car crashes. The artist’s use of repetition has been discussed extensively but not in terms of its direct impact on the viewer’s perceptual and cognitive processing. This article considers the viewer’s affective experience resulting from repeated exposure to negative images in artworks from the Death and Disaster series. The authors put forward an account of the potential affective experience of Warholian repetition based on existing experimental findings and by way of the artist’s own remarks on the relationship between repetition and affect.

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.

This document contains all abstracts of the 20th European Conference on Eye Movements, August 18-22, 2019, in Alicante, Spain Video stream "Glimpses at 20th ECEM" : https://vimeo.com/user43478756

Previous research has demonstrated that when monitoring dynamically changing visual displays for color targets, contingencies between targets and distractors facilitate predictive target detection, and elevated intolerance of uncertainty (IU) and lower verbal working memory capacity (WMC) are associated with a higher false alarm rate (see Muhl-Richardson et al., 2018). The present study examined whether search in this type of task improved following placebo-controlled adaptive dual n-back working memory (WM) training or transcranial direct-current stimulation (tDCS) of the dorsolateral prefrontal cortex. It also attempted to replicate previous findings but at a high level of target prevalence. The results demonstrate a new benefit to predictive target detection, which was associated with faster response times, and identify elevated IU and verbal WMC were as significant predictors of a higher hit rate. We provide an account of these effects in terms of response criterion and perceptual sensitivity. WM training and tDCS were found not to benefit performance on our dynamic search task (and a range other cognitive tasks), adding to a mixed literature on the efficacy of these techniques. The results nonetheless extend our understanding of dynamic search tasks and have implications for the selection of personnel in a variety of real-world scenarios.

Abstract. Previous work showed that prior experience with discriminations requiring configural solutions (e.g., biconditional discrimination) confers an advantage for the learning of new configural discriminations (e.g., negative patterning) in comparison to prior experience with elemental discriminations. This effect is well established but its mechanism is not well understood. In the studies described below we assessed whether the saliences of configural and element cues were affected by prior training. We observed positive transfer to a new configural discrimination after configural pre-training but we were unable to find evidence for changes in cue salience using a signal-detection task. Our results confirm previous work by demonstrating experience-dependent flexibility in cue processing but they also suggest that this flexibility occurs at a point in the stimulus processing pipeline later than 1–2 s after the presentation of stimulus inputs. (138 words)

© 2018 John Wiley & Sons, Ltd. Target onsets in dynamically changing displays can be predicted when contingencies exist between different stimulus states over time. In the present study, we examined predictive monitoring when participants searched dynamically changing displays of numbers and colored squares for a color target, a number target, or both. Stimuli were presented in both contiguous and discrete spatial configurations. Response time (RT) and accuracy were recorded, and evidence of predictive monitoring was assessed via first fixations and refixations of target-predictive stimuli. RTs to target onsets and evidence of predictive monitoring were reduced in dual-target, relative to single-target, conditions. Further, predictive monitoring did not speed RTs but was influenced by display configuration. In particular, discrete displays impaired monitoring for number targets in the dual-target condition. Implications exist for real-world visual tasks involving multiple target categories and for visual display design.

Rummage search is the visual and haptic search of complex environments for targets. In this study, rummage search was explored using a novel analytic framework with expert dyads and novice dyads, as well as novice individuals. Participants sought an unknown number of targets placed in four rooms of a residential house. Some targets were plainly visible whereas others were hidden, and could only be found through haptic examination. Expert dyads were very good at the task, conducting a slowed, double-checking exhaustive search, while novices both failed to fixate potential target locations, and failed to carry out the appropriate action required to search those locations exhaustively. The novice dyads examined more than the novice individuals, but became more superficial in their search. We conclude that effective rummage searching is a skill enhanced by training.

Many real-world tasks now involve monitoring visual representations of data that change dynamically over time. Monitoring dynamically changing displays for the onset of targets can be done in two ways: detecting targets directly, post-onset, or predicting their onset from the prior state of distractors. In the present study, participants' eye movements were measured as they monitored arrays of 108 colored squares whose colors changed systematically over time. Across three experiments, the data show that participants detected the onset of targets both directly and predictively. Experiments 1 and 2 showed that predictive detection was only possible when supported by sequential color changes that followed a scale ordered in color space. Experiment 3 included measures of individual differences in working memory capacity (WMC) and anxious affect and a manipulation of target prevalence in the search task. It found that predictive monitoring for targets, and decisions about target onsets, were influenced by interactions between individual differences in verbal and spatial WMC and intolerance of uncertainty, a characteristic that reflects worry about uncertain future events. The results have implications for the selection of individuals tasked with monitoring dynamic visual displays for target onsets. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

We examined the influence of experience upon information-sampling and decision-making behaviour in a group of military personnel as they conducted risk assessments of scenes photographed from patrol routes during the recent conflict in Afghanistan. Their risk assessment was based on an evaluation of Potential Risk Indicators during examination of each scene. We found that both participant groups were equally likely to fixate Potential Risk Indicators, demonstrating similarity in the selectivity of their information-sampling. However, the inexperienced participants made more revisits to Potential Risk Indicators, had longer response times, and were more likely to decide that the scenes contained a high level of risk. Together, these results suggest that experience primarily modulates decision-making behaviour. We discuss potential routes to train personnel to conduct risk assessments in a more similar manner to experienced participants.

Participants judged 94 portraits painted by Édouard Manet (70), Gustave Courbet (12) and Henri Fantin-Latour (12) for horizontal and vertical pupil misalignment and gaze ambiguity (Experiment 1) and focal point of gaze (Experiment 2). Eye movements were also measured as participants considered the extent to which sitters in the same portraits acknowledged viewers (spectators; Experiment 3). The results showed Manet portraits to be frequently painted with misaligned pupils that are associated with gaze ambiguity, especially when misaligned on the vertical axis. This ambiguity of gaze was associated with the average focal point of gaze as being judged further up and to the left of the centre for ambiguous relative to non-ambiguous portraits. These decisions in relation to portraits displaying ambiguous gaze were associated with increased eye-movements to the eye region relative to those portraits not displaying ambiguity. Finally, ratings of acknowledgement taken in Experiment 3 correlated with those of gaze ambiguity taken in Experiment 1. The results are interpreted in terms of the role of eye gaze in influencing spectatorship of portraits and, specifically, Fried’s theory of the ‘double relation’ (Fried 1980; Fried 1996) between painting and spectator in the paintings of Manet.

Previous research shows that visual search for two different targets is less efficient than search for a single target. Stroud, Menneer, Cave, and Donnelly concluded that two target colours are represented separately based on modelling 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.

The Functional Visual Field (FVF) offers explanatory power. To us, it relates to existing literature on the flexibility of attentional focus in visual search and reading (Eriksen & St. James 1986; McConkie & Rayner 1975). The target article promotes reflection on existing findings. Here we consider the FVF as a mechanism in the Prevalence Effect (PE) in visual search.

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

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

A number of real-world search tasks (i.e. police search, detection of improvised explosive devices (IEDs)) require searchers to search exhaustively across open ground. In the present study, we simulated this problem by asking individuals (Experiments 1a and 1b) and dyads (Experiment 2) to search for coin targets pseudo-randomly located in a bounded area of open grassland terrain. In Experiment 1a, accuracy, search time, and the route used to search an area were measured. Participants tended to use an ‘S’-shaped pattern with a common width of search lane. Increased accuracy was associated with slower, but also variable, search speed, though only when participants moved along the length (as opposed to across the width) of the search area. Experiment 1b varied the number of targets available within the bounded search area and in doing so varied target prevalence and density. The results confirmed that the route taken in Experiment 1a generalizes across variations in target prevalence/density. In Experiment 2, accuracy, search time, and the search strategy used by dyads was measured. While dyads were more accurate than individuals, dyads that opted to conduct two independent searches were more accurate than those who opted to split the search space. The implications of these results for individuals and dyads when searching for targets in open space are discussed.

The proportion of trials on which a target is presented (referred to as the target prevalence) during visual search influences the probability that the target will be detected. As prevalence increases, participants become biased toward reporting that the target is present. This bias results in an increase in detection rates for the target, coupled with an increased likelihood of making a false alarm. Previous work has demonstrated that, as prevalence increases, participants spend an increasing period of time searching on target-absent trials. The goal of the present study was to determine the information processing during the additional time spent searching on target-absent trials as prevalence increased. We recorded participants' eye movement behavior as they were engaged in low-prevalence (25% target-present trials), medium-prevalence (50%), or high-prevalence (75%) search. Increased prevalence primarily influenced search by increasing the time spent examining objects in the display, rather than by increasing the proportion of objects examined in each display. In addition, the additional time spent examining objects in high-prevalence target-absent trials was the result of revisiting objects. We discuss the implications of these results in relation to current models of search as well as ongoing efforts to alleviate the prevalence effect.

Right visual field-left hemisphere (RVF-LH) and left visual field-right hemisphere (LVF-RH) specialisations found for categorical and coordinate visuospatial judgements, respectively, are thought to demonstrate two different perceptual processes. In the current experiment, we used signal detection theory to investigate categorical and coordinate processes, and to explore the relationship between response time (RT), sensitivity and bias measures. We found a LVF-RH advantage for the processing of categorical spatial relations when this effect was indexed by sensitivity. We also found that task influenced response bias in RVF-LH trials, but not in LVF-RH trials. Increased sensitivity was correlated with faster responses in the coordinate task but slower responses in the categorical task, and faster RTs when responding liberally in RVF-LH but not LVF-RH categorical trials. By analysing signal detection measures alongside RT, the findings suggest that differences in sensitivity and response bias may contribute to typical task by hemisphere effects in RT.

Theoretical frameworks of anxiety propose that attentional biases to threat-related stimuli cause or maintain anxious states. The current paper draws on theoretical frameworks and key empirical studies to outline the distinctive attentional processes highlighted as being important in understanding anxiety. We develop a conceptual framework to make a distinction between two attentional biases: selective attention to threat and hypervigilance for threat. We suggest that these biases each have a different purpose and can account for the typical patterns of facilitated and impaired attention evident in anxious individuals. The framework is novel in its specification of the eye movement behavior associated with these attentional biases. We highlight that selective attention involves narrowing overt attention onto threat to ensure that these stimuli receive processing priority, leading to rapid engagement with task-relevant threat and delayed disengagement from task-irrelevant threat. We show that hypervigilance operates in the presence and absence of threat and involves monitoring for potential dangers via attentional broadening or excessive scanning of the environment with numerous eye movements, leading to improved threat detection and increased distraction from task-irrelevant threat. We conclude that future research could usefully employ eye movement measures to more clearly understand the diverse roles of attention in anxiety.

Participants’ eye movements (EMs) and EEG signal were simultaneously recorded to examine foveal and parafoveal processing during sentence reading. All the words in the sentence were manipulated for inter-word spacing (intact spaces vs. spaces replaced by a random letter) and parafoveal preview (identical preview vs. random letter string preview). We observed disruption for unspaced text and invalid preview conditions in both EMs and fixation-related potentials (FRPs). Unspaced and invalid preview conditions received longer reading times than spaced and valid preview conditions. In addition, the FRP data showed that unspaced previews disrupted reading in earlier time windows of analysis, compared to string preview conditions. Moreover, the effect of parafoveal preview was greater for spaced relative to unspaced conditions, in both EMs and FRPs. These findings replicate well-established preview effects, provide novel insight into the neural correlates of reading with and without inter-word spacing and suggest that spatial selection precedes lexical processing. peerReviewed

We report data from a prosopagnosic patient (PHD), and aged-matched control participants, from experiments where participants categorised individually presented emotional faces (Experiment 1) and Thatcherised (from typical) faces (Experiment 2). In Experiment 2 participants also discriminated between simultaneously presented Thatcherised and typical faces. PHD was at chance categorising Thatcherised from typical faces. He was, however, able to discriminate between Thatcherised and typical faces, and partially able to categorise emotional faces. The results are discussed in terms of a loss of configural processing but preserved feature processing in PHD. The loss of configural processing impacts his categorisation of Thatcherised and typical faces, and his emotion processing, while his preserved feature processing supports his ability to categorise some emotional faces and his ability to discriminate between Thatcherised and typical faces.Keywords: Prosopagnosia; Configural processing; Emotion; Thatcher illusion; Face processing.

Searching simultaneously for metal threats (guns and knives) and improvised explosive devices (IEDs) in X-ray images is less effective than 2 independent single-target searches, 1 for metal threats and 1 for IEDs. The goals of this study were to (a) replicate this dual-target cost for categorical targets and to determine whether the cost remains when X-ray images overlap, (b) determine the role of attentional guidance in this dual-target cost by measuring eye movements, and (c) determine the effect of practice on guidance. Untrained participants conducted 5,376 trials of visual search of X-ray images, each specializing in single-target search for metal threats, single-target search for IEDs, or dual-target search for both. In dual-target search, only 1 target (metal threat or IED) at most appeared on any 1 trial. Eye movements, response time, and accuracy were compared across single-target and dual-target searches. Results showed a dual-target cost in response time, accuracy, and guidance, with fewer fixations to target-color objects and disproportionately more to non-target-color objects, compared with single-target search. Such reduction in guidance explains why targets are missed in dual-target search, which was particularly noticeable when objects overlapped. After extensive practice, accuracy, response time, and guidance remained better in single-target search than in dual-target search. The results indicate that, when 2 different target representations are required for search, both representations cannot be maintained as accurately as in separate single-target searches. They suggest that baggage X-ray security screeners should specialize in one type of threat, or be trained to conduct 2 independent searches, 1 for each threat item.

The Thatcher illusion (Thompson, 1980) is considered to be a prototypical illustration of the notion that face perception is dependent on configural processes and representations. We explored this idea by examining the relative contributions of perceptual and decisional processes to the ability of observers to identify the orientation of two classes of forms-faces and churches-and a set of their component features. Observers were presented with upright and inverted images of faces and churches in which the components (eyes, mouth, windows, doors) were presented either upright or inverted. Observers first rated the subjective grotesqueness of all of the images and then performed a complete identification task in which they had to identify the orientation of the overall form and the orientation of each of the interior features. Grotesqueness ratings for both classes of image showed the standard modulation of rated grotesqueness as a function of orientation. The complete identification results revealed violations of both perceptual and decisional separability but failed to reveal any violations of within-stimulus (perceptual) independence. In addition, exploration of a simple bivariate Gaussian signal detection model of the relationship between identification performance and judged grotesqueness suggests that within-stimulus violations of perceptual independence on their own are insufficient for producing the illusion. This lack of evidence for within-stimulus configurality suggests the need for a critical reevaluation of the role of configural processing in the Thatcher illusion. (PsycINFO Database Record (c) 2011 APA, all rights reserved).

Recent studies have shown that the prevalence of target presentation in visual search has an impact on target detection rates, and also that searching for two targets leads to a decrement in performance (the “dual-target cost”). In the present experiments, we added to previous work that has examined the interaction between the prevalence effect and dual-target cost, and also to previous work that has examined a full range of prevalence levels. We found no interaction between the dual-target cost and prevalence effect, though the response criterion in dual-target search did interact with target prevalence in an unexpected manner. Furthermore, we detected anasymmetry in the prevalence effect: It was more marked for high than low prevalence. Implications for real-world tasks are discussed.

With the use of X-ray images, performance in the simultaneous search for two target categories was compared with performance in two independent searches, one for each category. In all cases, displays contained one target at most. Dual-target search, for both categories simultaneously, produced a cost in accuracy, although the magnitude of this dual-target cost was affected by the nature of the targets. When target feature sets shared values, accuracy in dual-target search was equivalent to that in the less accurate of the two single-target searches. However, when targets comprised different feature sets, accuracy in dual-target search was lower than in either single-target search. These results held after practice. In conclusion, dual-target search performance depends on the target representations required for search. When combined representations contain conflicting values within the most informative feature dimensions, then there is a cost in performance. When target representations share features, the search can be guided by the common values so that resources are not wasted on irrelevant distractors. The implication is that security screener performance might be improved by specializing in searching for threat categories that share features. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

Previous experiments have shown that objects are recognized more readily in a semantically consistent visual context. However, the benefit from context could be explained by response bias, and may not reflect the influence of context on the perceptual processes of recognition. We conducted a six-alternative forced-choice experiment to measure semantic and perceptual errors. A target object appeared briefly, surrounded by four context objects. The target was more accurately identified when the context consisted of objects semantically related to the target. The large number of semantic errors, which increased when the context presentation preceded the target, showed that response bias did account for a proportion of the context effect. Nevertheless, significant facilitation was still present after a bias correction. Recognition of an object can be affected by context not only when it is embedded in a coherent naturalistic scene, but also when it is simply near other related objects. Materials associated with this article may be accessed at www.psychonomic.org/archive.

The cost of searching for two visual targets simultaneously was compared against two separate single-target searches using exposure time and accuracy measures within a staircase procedure. Dual-target search for all stimuli (colour, shape and orientation) exhibited a loss of accuracy for one target. For orientation and shape, this dual-target cost in accuracy was extreme, with chance-level performance on one target. For colour, dual-target search exhibited an additional cost in search time, with search requiring a longer exposure than the summed time required for two single-target searches. An additional search-time cost was also found for orientation targets when irrelevant colour variation was added to the display. In conclusion, dual-target search for dissimilar targets is accompanied by an accuracy cost. Furthermore, colour variation, whether task-relevant or not, leads to an additional cost in processing speed. The results suggest that a divided-effort strategy would improve performance in search tasks such as X-ray baggage screening.