Search

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.

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.

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)

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).

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

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.

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).

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 Thatcher illusion (Thompson in Perception, 9, 483–484, 1980) is often explained as resulting from recognising a distortion of configural information when ‘Thatcherised’ faces are upright but not when inverted. However, recent behavioural studies suggest that there is an absence of perceptual configurality in upright Thatcherised faces (Donnelly et al. in Attention, Perception & Psychophysics, 74, 1475–1487, 2012) and both perceptual and decisional sources of configurality in behavioural tasks with Thatcherised stimuli (Mestry, Menneer et al. in Frontiers in Psychology, 3, 456, 2012). To examine sources linked to the behavioural experience of the illusion, we studied inversion and Thatcherisation of faces (comparing across conditions in which no features, the eyes, the mouth, or both features were Thatcherised) on a set of event-related potential (ERP) components. Effects of inversion were found at the N170, P2 and P3b. Effects of eye condition were restricted to the N170 generated in the right hemisphere. Critically, an interaction of orientation and eye Thatcherisation was found for the P3b amplitude. Results from an individual with acquired prosopagnosia who can discriminate Thatcherised from typical faces but cannot categorise them or perceive the illusion (Mestry, Donnelly et al. in Neuropsychologia, 50, 3410-3418, 2012) only differed from typical participants at the P3b component. Findings suggest the P3b links most directly to the experience of the illusion. Overall, the study showed evidence consistent with both perceptual and decisional sources and the need to consider both in relation to configurality. Electronic supplementary material The online version of this article (doi:10.3758/s13423-014-0705-3) contains supplementary material, which is available to authorized users.

Two experiments are reported to test the proposition that facial familiarity influences processing on a face classification task. Thatcherization was used to generate distorted versions of familiar and unfamiliar individuals. Using both a 2AFC (which is “odd”?) task to pairs of images (Experiment 1) and an “odd/normal” task to single images (Experiment 2), results were consistent and indicated that familiarity with the target face facilitated the face classification decision. These results accord with the proposal that familiarity influences the early visual processing of faces. Results are evaluated with respect to four theoretical developments of Valentine's (1991) face-space model, and can be accommodated with the two models that assume familiarity to be encoded within a region of face space.

Figure copying is often used to detect visuospatial neglect (VSN) in brain-damaged patients. We describe algorithms that enable the computation of parameters for describing figure-copying performance. The researcher can readily implement these algorithms on a computer using image analysis software, and they provide information on goodness-of-fit, relative to a standard model, as well as on dynamic aspects of subjects' performance in completing figure copies. To demonstrate the clinical utility of these algorithms, preliminary results from a group of right-hemisphere brain-damaged patients, some of whom have VSN, are compared with those for age-matched controls.

Previous research has shown that during visual search tasks target prevalence (the proportion of trials in which a target appears) influences both the probability that a target will be detected, and the speed at which participants will quit searching and provide an ‘absent’ response. When prevalence is low (e.g., target presented on 2 % of trials), participants are less likely to detect the target than when prevalence is higher (e.g., 50 % of trials). In the present set of experiments, we examined perceptual failures to detect low prevalence targets in visual search. We used a relative prevalence search task in order to be able to present an overall 50 % target prevalence and thereby prevent the results being accounted for by early quitting behavior. Participants searched for two targets, one of which appeared on 45 % of trials and another that appeared on 5 % of trials, leaving overall target prevalence at 50 %. In the first experiment, participants searched for two dissimilar targets; in the second experiment, participants searched for two similar targets. Overall, the results supported the notion that a reduction in prevalence primarily influenced perceptual failures of identification, rather than of selection. Together, these experiments add to a growing body of research exploring how and why observers fail to detect low prevalence targets, especially in real-world tasks in which some targets are more likely to appear than others.

OBJECTIVE: Rehabilitation of hearing is complicated in patients with profound bilateral hearing loss in the presence of sporadic vestibular schwannoma (VS) or neurofibromatosis 2 (NF2), especially if the tumor does not need to be removed. We present the outcome of patients who have had a cochlear implant in the tumor affected ear without removal of the primary tumor. DESIGN: This is a retrospective multicentre study investigating outcomes of cochlear implantation in profoundly deaf patients with vestibular schwannoma in the implanted ear. MATERIALS AND METHODS: Out of 11 implanted patients, 5 required no treatment for their tumor, whereas 6 had previously undergone radiotherapy. Nine patients experienced NF2, and 2 had unilateral VS in the only hearing ear. Postoperative hearing was assessed with open and closed set speech discrimination, including City University of New York (CUNY) in noise and Bamford, Kowal and Bench (BKB) sentence scores. RESULTS: Patients with untreated lesions experienced marked improvement in their BKB and CUNY scores in the implanted ear and were daily cochlear implant users. The improvement was less consistent in the patients who had radiotherapy where only 1 patient attained open set speech discrimination. CONCLUSION: Patients with unilateral VS (sporadic or those affected with NF2) whose tumor status was stable, benefited from cochlear implantation in their tumor-affected ear. Patients who had radiotherapy also benefited from CI, but their outcomes were variable.

Atypical face processing plays a key role in social interaction difficulties encountered by individuals with autism. In the current fMRI study, the Thatcher illusion was used to investigate several aspects of face processing in 20 young adults with high-functioning autism spectrum disorder (ASD) and 20 matched neurotypical controls. “Thatcherized” stimuli were modified at either the eyes or the mouth and participants discriminated between pairs of faces while cued to attend to either of these features in upright and inverted orientation. Behavioral data confirmed sensitivity to the illusion and intact configural processing in ASD. Directing attention towards the eyes vs. the mouth in upright faces in ASD led to (1) improved discrimination accuracy; (2) increased activation in areas involved in social and emotional processing; (3) increased activation in subcortical face-processing areas. Our findings show that when explicitly cued to attend to the eyes, activation of cortical areas involved in face processing, including its social and emotional aspects, can be enhanced in autism. This suggests that impairments in face processing in autism may be caused by a deficit in social attention, and that giving specific cues to attend to the eye-region when performing behavioral therapies aimed at improving social skills may result in a better outcome.

Detection of the Thatcher illusion (Thompson, Perception, 9:483–484, 1980) is widely upheld as being dependent on configural processing (e.g., Bartlett & Searcy, Cognitive Psychology, 25:281–316, 1993; Boutsen, Humphreys, Praamstra, & Warbrick, NeuroImage, 32:352–367, 2006; Donnelly & Hadwin, Visual Cognition, 10:1001–1017, 2003; Leder & Bruce, Quarterly Journal of Experimental Psychology, 53A:513–536, 2000; Lewis, Perception, 30:769–774, 2001; Maurer, Grand, & Mondloch, Trends in Cognitive Sciences, 6:255–260, 2002; Sturzel & Spillmann, Perception, 29:937–942, 2000). Given that supercapacity processing accompanies configural processing (see Wenger & Townsend, 2001), supercapacity processing should occur in the processing of Thatcherised upright faces. The purpose of this study was to test for evidence that the grotesqueness of upright Thatcherised faces results from supercapacity processing. Two tasks were employed: categorisation of a single face as odd or normal, and a same/different task for sequentially presented faces. The stimuli were typical faces, partially Thatcherised faces (either eyes or mouth inverted) and fully Thatcherised faces. All of the faces were presented upright. The data from both experiments were analysed using mean response times and a number of capacity measures (capacity coefficient, the Miller and Grice inequalities, and the proportional-hazards ratio). The results of both experiments demonstrated some evidence of a redundancy gain for the redundant-target condition over the single-target condition, especially in the response times in Experiment 1. However, there was very limited evidence, in either experiment, that the redundancy gains resulted from supercapacity processing. We concluded that the oddity signalled by inversion of eyes and mouths does not arise from positive interdependencies between these features.

Eye movements were monitored to examine search efficiency and infer how color is mentally represented to guide search for multiple targets. Observers located a single color target very efficiently by fixating colors similar to the target. However, simultaneous search for 2 colors produced a dual-target cost. In addition, as the similarity between the 2 target colors decreased, search efficiency suffered, resulting in more fixations on colors dissimilar to both target colors, which we describe as a "split-target cost." The patterns of fixations provide evidence to the type of mental representations guiding search. When the 2 targets are dissimilar, they are apparently encoded as separate and discrete representations. The fixation patterns for more similar targets can be explained with either 2 discrete target representations or a single, unitary range containing the target colors as well as the colors between them in color space.

In the present study, we explored the proposition that an individual’s capacity for threat detection is related to his or her trait anxiety. Using a redundant signals paradigm with concurrent measurements of reaction times and eye movements, participants indicated the presence or absence of an emotional target face (angry or happy) in displays containing no targets, one target, or two targets. We used estimates of the orderings on the hazard functions of the RT distributions as measures of processing capacity (Townsend & Ashby, 1978; Wenger & Gibson, Journal of Experimental Psychology. Human Perception and Performance, 30,708–719, 2004) to assess whether self-reported anxiety and the affective state of the face interacted with the level of perceptual load (i.e., the number of targets). Results indicated that anxiety was associated with fewer eye movements and increased processing capacity to detect multiple (vs. single) threatening faces. The data are consistent with anxiety influencing threat detection via a broadly tuned attentional mechanism (Eysenck, Derakshan, Santos, & Calvo, Emotion, 7,336–353, 2007).

The discrimination of thatcherized faces from typical faces was explored in two simultaneous alternative forced choice tasks. Reaction times (RTs) and errors were measured in a behavioural task. Brain activation was measured in an equivalent fMRI task. In both tasks, participants were tested with upright and inverted faces. Participants were also tested on churches in the behavioural task. The behavioural task confirmed the face specificity of the illusion (by comparing inversion effects for faces against churches) but also demonstrated that the discrimination was primarily, although not exclusively, driven by attending to eyes. The fMRI task showed that, relative to inverted faces, upright grotesque faces are discriminated via activation of a network of emotion/social evaluation processing areas. On the other hand, discrimination of inverted thatcherized faces was associated with increased activation of brain areas that are typically involved in perceptual processing of faces., PLoS ONE, 6 (8), ISSN:1932-6203

We report data contrasting the processing of facial identity from static photographs, and facial expression from static and moving images, in two patients with face processing impairments. One patient is markedly impaired at perceiving facial identity and he is poor at discriminating facial expression and gender from static photographs of faces. In contrast, he performs normally when required to make judgements of facial expression and gender to faces depicted by sets of moving light dots. The second patient is relatively good at perceiving facial identity, but poor at judging emotional expression from both static and moving faces. The data are consistent with the existence of separate processes for encoding face identity and facial expression, and, furthermore, indicate the separate encoding of expression from moving and static images.

Previous studies have demonstrated a dual-target cost in visual search. In the current study, the relationship between search for one and search for two targets was investigated to examine the effects of target prevalence and practice. Color-shape conjunction stimuli were used with response time, accuracy and signal detection measures. Performance was lower in dual-target search compared with the combined performance for two independent single-target searches. The cost in response time slope disappeared with practice, but the cost in accuracy remained. Sensitivity was lower and the decision criterion more conservative in dual-target search than in single-target searches, suggesting that the representation of the target was less effective in dual-target search than in single-target search. Manipulation of target prevalence induced a bias in favor of the more likely correct response: target-present responses were likely under high target prevalence and target-absent responses were likely under low target prevalence. The prevalence effect was greater in dual-target search than single-target search, causing the dual-target cost to be larger under target prevalences that differed from 50%. These findings are important for applied tasks in which targets appear rarely and can differ from each other. For example, the low target prevalence in X-ray security searches may magnify the dual-target cost implicated in previous research with X-ray images (see Menneer, Cave, & Donnelly, 2009). Such a result would increase the need for security personnel to consider alternatives to dual-target search, such as specialization in detecting one target type or training to encourage independent searches for each target.

The probability of target presentation in visual search tasks influences target detection performance: thisis known as the prevalence effect (Wolfe et al., 2005). Additionally, searching for several targets simultaneouslyreduces search performance: this is known as the dual-target cost (DTC: Menneer et al., 2007).The interaction between the DTC and prevalence effect was investigated in a single study by presentingone target in dual-target search at a higher level of prevalence than the other target (Target A: 45% Prevalence;Target B: 5% Prevalence). An overall DTC was found for both RTs and response accuracy. Furthermore,there was an effect of target prevalence in dual-target search, suggesting that, when one target ispresented at a higher level of prevalence than the other, both the dual-target cost and the prevalenceeffect contribute to decrements in performance. The implications for airport X-ray screening arediscussed.

A series of visual search experiments are reported examining pattern processing in a visual agnosic patient. We examined search for targets defined by: (I) the combination of their features relative to homogeneous distractors; (2) the combination of their features relative to heterogeneous distractors; and (3) a single feature difference relative to the distractors (their orientation). Normal subjects demonstrate evidence of spatially parallel search when combined-feature targets are detected against homogeneous distractors, and when targets are defined by a salient feature difference. There are non-linear effects of the number of distractors present, and absent responses can be as fast as present. In contrast, search times for combined-feature targets amongst heterogeneous distractors increase linearly with display size, with the slope for absent responses about twice that for present. The contrast between search for combined-feature targets amongst homogeneous and heterogeneous distractors can be attributed to the effects of grouping between distractors and between distractors and targets (Duncan & Humphreys, 1989, 1992; Humphreys & Muller, in press). Grouping between homogeneous distractors facilitates search. An agnosic patient, HJA, showed normal search functions for single-feature targets and for combined-feature targets amongst heterogeneous distractors. However, he was impaired at search for combined-feature targets amongst homogeneous distractors. This suggests that HJA is selectively impaired at grouping conjunctions of form features. The relations between HJA's agnosia and his problem in the parallel grouping of form conjunctions are discussed, as are the implications of the work for understanding normal vision.

This study used an emotional face stroop task to investigate the effects of self-report trait anxiety, social concern and chronological age on reaction time to match coloured outlines of angry, happy and neutral faces (and control faces with scrambled features) with coloured buttons in a community sample of 74 children aged six to twelve years. The results showed an interference of colour matching for angry (relative to neutral) faces in children with elevated social concern. The same effect was not found for happy or control faces. In addition, the results suggest that selective attention to angry faces in children with social concern was not significantly moderated by age.

Previous research on object superiority effects has shown that certain contexts enhance the recognition of an object part. However, those contexts would not normally be called objects. The present study discusses object superiority within more general issues of object recognition. By using what we call ‘complete’ probes, superiority effects were extended to exposure durations much longer than those used in previous research. Experiments 1 and 2 found that complete probes gave stable superiorities at 250 msec and even 2-sec stimulus exposures. These object superiority effects were found for both objects (faces and chairs) investigated. Experiment 3 showed that object superiorities established with complete probes were not necessarily greater than those for part probes. The experiments stress the role of spatial arrangement of object parts in accessing stored information. It is argued that a successful match of a structural description to a representation in long-term memory influences stimulus processing by allowing the formation of higher level features.

The relationship between children's anxiety and cognitive biases was examined in two tasks. A group of 50 children aged 10 to 11 years (mean = 11 years, SD = 3.71 months) was given two tasks. The first tested children's selective attention (SA) to threat in an emotional Stroop task. The second explored facial processing biases using morphed angry-neutral and happy-neutral emotional expressions that varied in intensity. Faces with varying levels of emotion (25% emotion–75% neutral, 50% emotion–50% neutral, 100% emotion–0% neutral [prototype] and 150% emotion–0% neutral [caricature]) were judged as being angry or happy. Results support previous work highlighting a link between anxiety and SA to threat. In addition, increased anxiety in late childhood is associated with decreased ability to discriminate facial expression. Finally, lack of discrimination in the emotional expression task was related to lack of inhibition to threat in the Stroop task.

Three experiments investigated visual search for targets that differed from distractors in colour, size, or orientation. In one condition the target was defined by a conjunction of these features, while in the other condition the target was the odd one out. In all experiments, 6–7- and 9–10-year-old children were compared with young adults. Experiment 1 showed that children's search differed from adults’ search in two ways. In conjunction searches children searched more slowly and took longer to reject trials when no target was present. In the odd-one-out experiments, 6–7-year-old children were slower to respond to size targets than to orientation targets, and slower for orientation targets than for colour targets. Both the other groups showed no difference in their rate of responding to colour and orientation. Experiments 2 and 3 highlighted that these results were not a function of either differential density across set sizes (Experiment 2) or discriminability of orientation and colour (Experiment 3). Across all three experiments, the results of both conjunction and odd-one-out searches highlighted a development in visual search from middle to late childhood.

Background: This study presents two experiments that investigated whether children with autism were susceptible to the Thatcher illusion. Perception of the Thatcher illusion requires being able to compute second-order configural relations for facial stimuli. Method: In both experiments children with autism were matched for non-verbal and verbal ability with a group of children with moderate (non-specific) mental retardation (MLD) and a group of typically developing children respectively. Participants were asked to detect the ‘unusual’ face in a two-alternative-forced-choice version of the Margaret Thatcher illusion with grey-scale (Experiment 1) and monochrome ‘Mooney’ face images (Experiment 2). In Experiment 1 participants also performed a control task where buildings had been doctored in the same way as the facial stimuli. Results: Children with autism were as susceptible to the Thatcher illusion as both control groups, in terms of accuracy and reaction time to make decisions about which face was unusual. Children with autism performed more accurately than children with MLD in the buildings task. Conclusion: Children with autism are able to compute second-order configural features in faces and exhibit no difference in face processing, relative to appropriate control groups.

In three experiments participants viewed pairs of overlapping transparent faces, with one face upright and the other oriented, and they reported which face was dominant. In each trial, an upright face was presented with a face at 45, 90, 135 or 180 degrees, with transparency set using a linear weighted algorithm, so that relative contrast across faces was biased in favour of oriented faces. Exposure duration was restricted in experiment 1 to 250, 500 or 1000 ms, but was unlimited in experiments 2 and 3. Adults were tested in experiments 1 and 2 and children aged 6-9 years of age were tested in experiment 3. Irrespective of exposure duration, the results showed the probability of dominance being ceded by oriented faces to upright faces was a function of orientation. In comparable conditions, the function found with young children was flatter than with adults. These patterns, and those of earlier perceptual studies, can be explained by the distribution of different orientation tunings found in physiological studies of inferotemporal cortex in macaques.

This study presents two experiments that investigated the relationship between 7- and 10-year-olds' levels of self-report trait anxiety and depression and their visual search for threatening (angry faces) and non-threatening (happy and neutral faces) stimuli.In both experiments a visual search paradigm was used to measure participants' reaction times to detect the presence or absence of angry, happy or neutral schematic faces (Experiment 1) or cartoon drawings (Experiment 2). On target present trials, a target face was displayed alongside three, five or seven distractor items. On target absent trials all items were distractors.Both experiments demonstrated that on target absent (but not present) trials, increased levels of anxiety produced significantly faster search times in the angry face condition, but not in the neutral condition. In Experiment 2 there was some trend towards significance between anxiety and searches for happy faces in absent trials. There were no effects of depression on search times in any condition.The results support previous work highlighting a specific link between anxiety and attention to threat in childhood.

We report evidence from three sets of experiments dealing with spatially parallel grouping of parts in single objects. A first set of experiments demonstrates that parts can be encoded in a spatially parallel manner in three-dimensional (3-D) objects, while there is a serial selection of parts across objects. A second set of experiments further shows that grouping in 3-D is less affected by eliminating collinearity between the parts of objects than grouping in two dimensions, suggesting that 3-D constraints operate directly on visual grouping. A final pair of experiments demonstrates that rotating the elements in the plane, to make a physically unstable 3-D object, disrupts the benefit found with 3-D stimuli when collinearity is eliminated. The evidence indicates that there is rapid and spatially parallel encoding of 3-D object descriptions in vision.

Objective: To determine whether a computer-based method for recording standardized assessment of neglect identifies abnormalities in the ‘process’ as well as in the ‘outcome’ of such tasks. Design: Prospective sequential assessment of patients admitted to a stroke rehabilitation unit. Subjects: All consecutive patients with right-sided cerebrovascular accident confirmed on computerized tomography (CT) scan including 30 patients with neglect, 57 patients without neglect. An age-matched control group of 13 subjects. Intervention: All patients were tested using the standard Rivermead Behavioural Inattention Test (BIT) and by computer recording of two standard tests for assessing neglect (line bisection and Albert's test). Age-matched controls were tested using computer recording of the two standard tests. Main outcome measures: Neglect was defined using the BIT with a cut-off score of 129. Computer recording measured the ‘outcome’ of tasks, i.e. the deviation from midline and omissions in cancellation, as well as the ‘process’ of tasks, i.e. time between cancellations, components of cancellation time including premovement, movement and drawing time, and the starting point for cancellation. Results: The computer recording identified significant differences in ‘outcome’ and ‘process’ which distinguished neglect from non-neglect patients. There were significant differences between non-neglect patients and age-matched controls with regard to ‘process’ measures but not with regard to ‘outcome’ measures. Conclusions: Computer recording of standard tests for assessing neglect identifies novel impairments with regard to the process of carrying out tasks. These impairments may be used to investigate changes in neglect with time, the response of neglect to treatment and to explore further the neuropsychological changes associated with neglect in stroke patients.

We describe a set of algorithms that enhance the sensitivity of cancellation tests used in assessing visuospatial neglect. The algorithms can be readily implemented on a computer and can provide temporal and nontemporal data on strategies used during cancellation. We also present preliminary results from a group of 68 right-hemisphere brain-damaged patients and 12 age-matched control participants, which demonstrate the clinical significance of the measures we have defined.

In five experiments, we investigated the extent to which form (shape) and metric attributes (three-dimensional, 3-D, orientation), both defined by relations between line elements, are processed in early vision. Search for a target defined by an abstract property of form (i.e., impossibility) was slow and serial. In contrast, search for a 3-D orientation target was considerably easier. Subsequent experiments suggest that this difference reflects the fact that 3-D orientation is derivable from localized sets of lines, whereas impossibility is an idiosyncratic property of the complete set of relations between lines. We conclude that only "gross" aspects of form are available in early vision as the complete set of line relations is not processed preattentively. However, localized processing of line relations is sufficient to derive 3-D orientation.

We report three experiments which investigate the lateralization of categorical and coordinate processing. In all experiments, participants judged the position of a dot relative to a line. We manipulated display luminance (controlling for contrast), polarity (black-on-white versus white-on-black displays), and exposure duration (100, 150, and 200 ms). The results showed a left visual field-right hemisphere advantage for coordinate judgments, but only under highly prescribed conditions. We argue that stimulus and procedural factors are critical in determining the hemisphere by task interaction.

The visual system analyses information by decomposing complex objects into simple components (visual features) that are widely distributed across the cortex. When several objects are present simultaneously in the visual field, a mechanism is required to group (bind) together visual features that belong to each object and to separate (segment) them from features of other objects. An attractive scheme for binding visual features into a coherent percept consists of synchronizing the activity of their neural representations. If synchrony is important in binding, one would expect that binding and segmentation are facilitated by visual displays that are temporally manipulated to induce stimulus-dependent synchrony. Here we show that visual grouping is indeed facilitated when elements of one percept are presented at the same time as each other and are temporally separated (on a scale below the integration time of the visual system) from elements of another percept or from background elements. Our results indicate that binding is due to a global mechanism of grouping caused by synchronous neural activation, and not to a local mechanism of motion computation.

Three experiments are reported which investigate the categorisation of faces and scrambled faces in a face/scrambled face decision task. Three kinds of stimuli were presented in upright and inverted orientations; faces, highly scrambled faces (all features out of position) and moderately scrambled faces (two features out of position). Experiment 1 demonstrated that faces and highly scrambled faces are categorised equally quickly and both types of stimulus were categorised faster than moderately scrambled faces. These results held for both upright and inverted presentations. It is argued that for both upright and inverted presentations, faces are categorised by being matched in parallel to a stored mental representation of a face. In contrast scrambled faces are categorised following a serial search of facial features which is probably self-terminating. Experiment 2 demonstrates that the results of Experiment 1 hold when facial features are replaced by other objects which retain the same global shape as facial features and suggest that faces are categorised using a coarsely coded visual description. Experiment 3 demonstrates the importance of stimulus outline on the categorisation of both moderately and highly scrambled faces but not real faces. The results are discussed in terms of the stimulus information used, and the effect of inversion, on face categorisation.

Evidence from visual-search experiments is discussed that indicates that there is spatially parallel encoding based on three-dimensional (3-D) spatial relations between complex image features. In one paradigm, subjects had to detect an odd part of cube-like figures, formed by grouping of corner junctions. Performance with cube-like figures was unaffected by the number of corner junctions present, though performance was affected when the corners did not configure into a cube. It is suggested from the data that junctions can be grouped to form 3-D shapes in a spatially parallel manner. Further, performance with cube-like figures was more robust to noncollinearity between junctions than was performance when junctions grouped to form two-dimensional planes. In the second paradigm, subjects searched for targets defined by their size. Performance was affected by a size illusion, induced by linear-perspective cues from local background neighbourhoods. Search was made more efficient when the size illusion was consistent with the real size difference between targets and nontargets, and it was made less efficient when the size illusion was inconsistent with the real size difference. This last result occurred even though search was little affected by the display size in a control condition. We suggest that early, parallel visual processes are influenced by 3-D spatial relations between visual elements, that grouping based on 3-D spatial relations is relatively robust to noncollinearity between junctions, and that, at least in some circumstances, 3-D relations dominate those coded in two-dimensions.