Publications

Individuating a single item presented within a continuous sequence of items requires segregating its signal from that of the other items. In contrast, representing a global aspect of the sequence, such as its average orientation, involves integration of information across time. Individuation and integration allow us to focus on individual events while maintaining an overall perception of our environment. To examine the relations between temporal averaging and individuation, we measured orientation averaging over short and long timescales using the same stimuli and orientation-estimation procedure previously used to measure individuation. Participants reported the average orientation of a sequence of three oriented items separated by either short (SOAs<150 ms) or long intervals (SOAs>150 ms). Analysis of the error distribution and mixture-modeling revealed distinct patterns of results for the different tasks and timescales, but also some similarities, particularly for the short timescale. In this timescale, the relative contribution of each individual item to the final response was similar across tasks, indicating the involvement of low-level factors operating regardless of the task. With the long timescale, the two tasks showed dissociable pattern across all performance aspects, except guessing rate, indicating that long-scale individuation and averaging engage mainly higher-level, task-related processes. Importantly, regardless of timescale, estimation errors in these tasks were best described by different models: in integration they primarily reflected unequal weighting of the averaged items, whereas in individuation they reflected imprecise target encoding with occasional misreports of distractors. Together, the findings reveal dissociable dynamics for integration and individuation.

Keywords: Vision, Temporal crowding, Individuation, Pooling, Averaging, Masking

Alterations in reward processing were proposed as a contributing factor to social and communication symptoms in autism. However, the nature of these alterations remains unclear, and it is debated whether reduced sensitivity to reward is a general phenomenon, specific to social contexts, or exists at all. Evidence for reduced sensitivity to reward primarily comes from neurobiological studies, yet it remains uncertain how these findings translate to autistic behavior. A key challenge in addressing this question lies in assessing and comparing behavioral responses to reward between autistic and non-autistic groups. Here, we addressed this issue by investigating the integration of monetary reward information into behavior through the framework of Bayesian perceptual decision-making, enabling a quantitative evaluation of the direct contribution of reward to decision-making. Autistic (n = 32) and non-autistic (n = 48) participants performed an orientation categorization task, while the monetary reward given per correct answer varied across categories. Using signal-detection theory, we estimated decision boundaries while accounting for sensory uncertainty and prior expectation. Our results reveal that autistic individuals adjust their decision boundaries in response to monetary reward in a suboptimal but typical manner. These findings challenge the hypothesis of generalized alteration of reward processing in autism.

Keywords: reward, autism, Bayesian perception, decision-making, suboptimality

Atypical metacognition has been suggested to underlie autistic phenotypes, given its role in social cognition and behavioural flexibility. However, no study has quantitatively assessed metacognitive abilities in autism. Here, we measured meta-uncertainty—the noise corrupting the estimates of one’s own decision uncertainty—in autism. In three experiments, autistic and non-autistic participants (N = 145) performed orientation categorisation tasks while simultaneously reporting their choice confidence. By independently manipulating each Bayesian component—sensory uncertainty, prior, and reward—and fitting a recently established process model, we assessed metacognitive abilities and their contingency on the Bayesian components while controlling for first-order decisions. Unlike non-autistic participants, autistic participants’ meta-uncertainty depended on which decision component was manipulated, and was lower than that of non-autistic participants specifically when decisions were adjusted for sensory uncertainty. These findings reveal that metacognition in autism is not generally reduced but rather enhanced for inferences that rely primarily on sensory information.

Keywords: autism, metacognition, decision-making, Bayesian perception

The Community Assessment of Psychic Experiences (CAPE-42) is a reliable tool to assess psychotic experiences (PEs) in clinical and non-clinical populations, in research and clinical settings. To investigate cultural differences in PEs and control for pathological behavior in non-clinical groups, we developed a Hebrew version of the CAPE-42 using translation/back-translation method. A total of 359 Hebrew-speaking Israelis participated in an online study comprising the CAPE-42, the Autistic Quotient (AQ), the Center for Epidemiological Study -Depression Scale (CES-D), and the Prodromal Questionnaire -Brief Version (PQ-B). We examined the psychometric properties of the Hebrew CAPE-42-including factor structure, internal consistency, gender invariance, and validity. We also investigated the independent and interaction effects of psychotic and autistic traits on depressive symptoms. Reliability analysis demonstrated very good internal consistency, and confirmatory factor analysis supported the eight-factor model-including depressive, social withdrawing, affective flattening, avolition, bizarre experiences, perceptual abnormalities, persecutory ideation, and magical thinking. Demonstrating its predictive and convergent validity, we found significant correlations with the CES-D and the PQ-B. The predictive model showed that both psychotic and autistic traits are independent predictors of depressive symptoms, without interacting. The Hebrew CAPE-42 offers a valuable instrument for investigating PEs in the Hebrew-speaking population and facilitates crosscultural studies.

Keywords: CAPE-42, Cross-validation, Hebrew, psychometric properties, psychosis

Background Alterations in sensory perception, a core phenotype of autism, are attributed to imbalanced integration of sensory information and prior knowledge during perceptual statistical (Bayesian) inference. This hypothesis has gained momentum in recent years, partly because it can be implemented both at the computational level, as in Bayesian perception, and at the level of canonical neural microcircuitry, as in predictive coding. However, empirical investigations have yielded conflicting results with evidence remaining limited. Critically, previous studies did not assess the independent contributions of priors and sensory uncertainty to the inference.

Method We addressed this gap by quantitatively assessing both the independent and interdependent contributions of priors and sensory uncertainty to perceptual decision-making in autistic and non-autistic individuals (N=126) during an orientation categorization task. Results Contrary to common views, autistic individuals integrated the two Bayesian components into their decision behavior, and did so indistinguishably from non-autistic individuals. Both groups adjusted their decision criteria in a suboptimal manner.

Limitations This study focuses on explicit priors in a perceptual categorization task and high-functioning adults. Thus, although the findings provide strong evidence against a general and basic alteration in prior integration in autism, they cannot rule out more specific cases of reduced prior effect – such as due to implicit prior learning, particular level of decision making (e.g., social), and level of functioning of the autistic person.

Conclusions These results reveal intact inference for autistic individuals during perceptual decision-making, challenging the notion that Bayesian computations are fundamentally altered in autism.

Keywords Autism spectrum disorder, Decision-making, Bayesian perception, Suboptimality

Crowding, our inability to identify a feature or object – the target – due to its proximity to adjacent features or objects – fankers – exhibits a notable inner-outer asymmetry. This asymmetry is characterized by the outer fanker – more peripheral – creating stronger interference than the inner one – closer to the fovea. But crowding is not uniform across diferent feature dimensions. For example, in the case of orientation, this asymmetry refects misreport errors: observers are more likely to misidentify the outer fanker as the target than the inner one. However, for spatial frequency (SF), observers tend to average the features of the target and fankers (Yashar et al., 2019). Here, we investigated whether and how the inner-outer asymmetry manifests across various feature dimensions: Gabor orientation and SF, as well as T-shape tilt and color. We reanalyzed continuous estimation reports data published by Yashar et al. (2019), focusing on a previously unanalyzed factor: the relative position of each flanker (inner vs. outer). We ft probabilistic models that assign variable weights to each flanker. Our analysis revealed that observers predominantly misreport the outer flanker as the target with Gabor orientation and T-shape tilt stimuli, and slightly so with color stimuli, whereas with Gabor SF, observers perform a weighted average of all features but also with a bias towards the outer flanker over the inner one. These findings suggest that an increased weighting on the more peripheral items is a general characteristic of crowding in peripheral vision.

Keywords Visual periphery · Crowding · Inner-outer asymmetry · Object recognition

Peripheral letter recognition is fundamentally limited not by the visibility of letters but by the spacing between them, i.e., ‘crowding’. Crowding imposes a significant constraint on reading, however, the interplay between crowding and reading is not fully understood. Using a letter recognition task in varying display conditions, we investigated the effects of lexicality (words versus pseudowords), visual hemifield, and transitional letter probability (bigram/trigram frequency) among skilled readers (N ¼ 14. and N ¼ 13) in Hebrew e a script read from right to left. We observed two language-universal effects: a lexicality effect and a right hemifield (left hemisphere) advantage, as well as a strong language-specific effect e a left bigram advantage stemming from the right-to-left reading direction of Hebrew. The latter finding suggests that transitional probabilities are essential for parafoveal letter recognition. The results reveal that script-specific contextual information such as letter combination probabilities is used to accurately identify crowded letters.

Crowding refers to the failure to identify a peripheral object due to nearby objects (flankers). A hallmark of crowding is inner–outer asymmetry; that is, the outer flanker (more peripheral) produces stronger interference than the inner one. Here, by manipulating attention, we tested the predictions of two competing accounts: the attentional account, which predicts a positive attentional effect on the inner–outer asymmetry (i.e., attention to the outer flanker will increase asymmetry) and the receptive field size account, which predicts a negative attentional effect. In Experiment 1, observers estimated a Gabor target orientation. A peripheral pre-cue drew attention to one of three locations: target, inner flanker, or outer flanker. Probabilistic mixture modeling demonstrated asymmetry by showing that observers often misreported the outer-flanker orientation as the target. Interestingly, the outer cue led to a higher misreport rate of the outer flanker, and the inner cue led to a lower misreport rate of the outer flanker. Experiment 2 tested the effect of crowding and attention on incoherent object reports (i.e., binding errors, reporting the tilt of one presented item with the color of another item). In each trial, observers estimated both the tilt and color of the target. Attention merely increased coherent target reports, but not coherent flanker reports. The results suggest that the locus of spatial attention plays an essential role in crowding, as well as inner–outer asymmetry, and demonstrate that crowding and feature binding are closely related. However, our findings are inconsistent with the view that covert attention automatically binds features together.

Keywords: crowding, attention, binding, mixture model, asymmetry, color, orientation

Crowding refers to the failure to identify a peripheral object due to its proximity to other objects (flankers). This phenomenon can lead to reading and object recognition impairments and is associated with macular degeneration, amblyopia, and dyslexia. Crucially, the maximal target–flanker spacing required for the crowding interference (critical spacing) increases with eccentricity. This spacing is also larger when target and flankers appear along the horizontal meridian (radial arrangement) than when the flankers appear above and below the target (tangential arrangement). This phenomenon is known as radial–tangential anisotropy. Previous studies have demonstrated that transient attention can reduce crowding interference; however, it is still unclear whether and how attention interacts with radial–tangential anisotropy. To address this issue, we manipulated transient attention by using a cue at either the target (valid) or the fixation (neutral) location, in both radial and tangential target–flanker arrangements. Results showed that critical spacing was larger in the radial than in the tangential arrangement and that cueing the target location improved performance and reduced the critical spacing for both radial and tangential arrangements to the same extent. Together, our findings suggest that transient spatial attention plays an essential role in crowding but not in radial–tangential anisotropy.

Keywords: crowding, radial–tangential anisotropy, attention, critical spacing, spatial vision

Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on various perceptual tasks such as reading and facial recognition. While prevailing models suggest that crowding is a unitary phenomenon occurring at an early level of processing, recent studies have shown that crowding might also occur at higher levels of representation. Here we investigated whether local and global crowding interference co-occurs within the same display. To do so, we tested the distinctive contribution of local fanker features and global confgurations of the fankers on the pattern of crowding errors. Observers (n= 27) estimated the orientation of a target when presented alone or surrounded by fankers. Flankers were grouped into a global confguration, forming an illusory rectangle when aligned or a rectangular confguration when misaligned. We analyzed the error distributions by ftting probabilistic mixture models. Results showed that participants often misreported the orientation of a fanker instead of that of the target. Interestingly, in some trials the orientation of the global confguration was misreported. These results suggest that crowding occurs simultaneously across multiple levels of visual processing and crucially depends on the spatial confguration of the stimulus. Our results pose a challenge to models of crowding with an early single pooling stage and might be better explained by models which incorporate the possibility of multilevel crowding and account for complex target-fanker interactions.

Autism is a neurodevelopmental disorder of unknown etiology. Recently, there has been a growing interest in sensory processing in autism as a core phenotype. However, basic questions remain unanswered. Here, we review the major findings and models of perception in autism and point to methodological issues that have led to conflicting results. We show that popular models of perception in autism, such as the reduced prior hypothesis, cannot explain the many and varied findings. To resolve these issues, we point to the benefits of using rigorous psychophysical methods to study perception in autism. We advocate for perceptual models that provide a detailed explanation of behavior while also taking into account factors such as context, learning, and attention. Furthermore, we demonstrate the importance of tracking changes over the course of development to reveal the causal pathways and compensatory mechanisms. We finally propose a developmental perceptual narrowing account of the condition.

Keywords: autism, perception, psychophysics, sensory processing, Bayesian, development, perceptual illusions, perceptual narrowing

Crowding refers to the failure to identify a peripheral object due to nearby objects (flankers). A hallmark of crowding is inner-outer asymmetry; i.e., the outer flanker (more peripheral) produces stronger interference than the inner one. Here, by manipulating attention, we tested the predictions of two competing accounts: the attentional account, which predicts a positive attentional effect on the inner-outer asymmetry (i.e., attention to the outer flanker will increase asymmetry) and the receptive field size account, which predicts a negative attentional effect. In Experiment 1, observers estimated a Gabor target orientation. A peripheral pre-cue drew attention to one of three locations: target, inner flanker or outer flanker. Probabilistic mixture modeling demonstrated asymmetry by showing that observers often misreported the outerflanker orientation as the target. Interestingly, the outer cue led to a higher misreport rate of the outer flanker, and the inner cue led to a lower misreport rate of the outer flanker. Experiment 2 tested the effect of crowding and attention on incoherent object reports (i.e., binding errors – reporting the tilt of one presented item with the color of another item). In each trial, observers estimated both the tilt and color of the target. Attention merely increased coherent target reports, but not coherent flanker reports. The results suggest that the locus of spatial attention plays an essential role in crowding as well as inner-outer asymmetry and demonstrate that crowding and feature binding are closely related. However, our findings are inconsistent with the view that covert attention automatically binds features together.

Keywords: crowding; attention; binding; mixture model; asymmetry; color; orientation

Crowding refers to the failure to identify a peripheral object due to its proximity to other objects (flankers). This phenomenon can lead to reading and object recognition impairments, and is associated with macular degeneration, amblyopia, and dyslexia. Crucially, the minimal target-flanker spacing required for the crowding interference (critical spacing) increases with eccentricity. This spacing is also larger when target and flankers appear along the horizontal meridian (radial arrangement) than when the flankers appear above and below the target (tangential arrangement). This phenomenon is known as radial– tangential anisotropy. Previous studies have demonstrated that transient attention can reduce crowding interference. However, it is still unclear whether and how attention interacts with the radial–tangential anisotropy. To address this issue, we manipulated transient attention by using a cue either at the target (valid) or fixation (neutral) location, in both radial and tangential target-flanker arrangements. Results showed that critical spacing was larger in the radial than in the tangential arrangement, and that cueing the target location improved performance and reduced the critical spacing for both radial and tangential arrangements, to the same extent. Together, our findings suggest that transient spatial attention plays an essential role in crowding but not in the radial-tangential anisotropy.

Keywords: crowding, radial-tangential anisotropy, attention, critical spacing, spatial vision

Crowding, the failure to identify a peripheral item in clutter, is an essential bottleneck in visual information processing. A hallmark characteristic of crowding is the inner–outer asymmetry in which the outer fanker (more eccentric) produces stronger interference than the inner one (closer to the fovea). We tested the contribution of the inner-outer asymmetry to the pattern of crowding errors in a typical radial crowding display in which both fankers are presented simultaneously on the horizontal meridian. In two experiments, observers were asked to estimate the orientation of a Gabor target. Instead of the target, observers reported the outer fanker much more frequently than the inner one. When the target was the outer Gabor, crowding was reduced. Furthermore, when there were four fankers, two on each side of the target, observers misreported the outer fanker adjacent to the target, not the outermost fanker. Model comparisons suggested that orientation crowding refects sampling over a weighted sum of the represented features, in which the outer fanker is more heavily weighted compared to the inner one. Our fndings reveal a counterintuitive phenomenon: in a radial arrangement of orientation crowding, within a region of selection, the outer item dominates appearance more than the inner one.

Humans often fail to identify a target because of nearby flankers. The nature and stages at which this crowding occurs are unclear, and whether crowding operates via a common mechanism across visual dimensions is unknown. Using a dual-estimation report (N = 42), we quantitatively assessed the processing of features alone and in conjunction with another feature both within and between dimensions. Under crowding, observers misreported colors and orientations (i.e., reported a flanker value instead of the target’s value) but averaged the target’s and flankers’ spatial frequencies (SFs). Interestingly, whereas orientation and color errors were independent, orientation and SF errors were interdependent. These qualitative differences of errors across dimensions revealed a tight link between crowding and feature binding, which is contingent on the type of feature dimension. These results and a computational model suggest that crowding and misbinding are due to pooling across a joint coding of orientations and SFs but not of colors.

Keywords: crowding, feature binding, spatial integration, color, spatial frequency, orientation, estimation, open data, open materials

Training can modify the visual system to produce a substantial improvement on perceptual tasks and therefore has applications for treating visual deficits. Visual perceptual learning (VPL) is often specific to the trained feature, which gives insight into processes underlying brain plasticity, but limits VPL’s effectiveness in rehabilitation. Under what circumstances VPL transfers to untrained stimuli is poorly understood. Here we report a qualitatively new phenomenon: intrinsic variation in the representation of features determines the transfer of VPL. Orientations around cardinal are represented more reliably than orientations around oblique in V1, which has been linked to behavioral consequences such as visual search asymmetries. We studied VPL for visual search of near-cardinal or oblique targets among distractors of the other orientation while controlling for other display and task attributes, including task precision, task difficulty, and stimulus exposure. Learning was the same in all training conditions; however, transfer depended on the orientation of the target, with full transfer of learning from near-cardinal to oblique targets but not the reverse. To evaluate the idea that representational reliability was the key difference between the orientations in determining VPL transfer, we created a model that combined orientation-dependent reliability, improvement of reliability with learning, and an optimal search strategy. Modeling suggested that not only search asymmetries but also the asymmetric transfer of VPL depended on preexisting differences between the reliability of near-cardinal and oblique representations. Transfer asymmetries in model behavior also depended on having different learning rates for targets and distractors, such that greater learning for low-reliability distractors facilitated transfer. These findings suggest that training on sensory features with intrinsically low reliability may maximize the generalizability of learning in complex visual environments.

People perform better in visual search when the target feature repeats across trials (intertrial feature priming [IFP]). Here, we investigated whether repetition of a feature singleton’s color modulates stimulus-driven shifts of spatial attention by presenting a probe stimulus immediately after each singleton display. The task alternated every two trials between a probe discrimination task and a singleton search task. We measured both stimulus-driven spatial attention (via the distance between the probe and singleton) and IFP (via repetition of the singleton’s color). Color repetition facilitated search performance (IFP effect) when the set size was small. When the probe appeared at the singleton’s location, performance was better than at the opposite location (stimulus-driven attention effect). The magnitude of this attention effect increased with the singleton’s set size (which increases its saliency) but did not depend on whether the singleton’s color repeated across trials, even when the previous singleton had been attended as a search target. Thus, our findings show that repetition of a salient singleton’s color affects performance when the singleton is task relevant and voluntarily attended (as in search trials). However, color repetition does not affect performance when the singleton becomes irrelevant to the current task, even though the singleton does capture attention (as in probe trials). Therefore, color repetition per se does not make a singleton more salient for stimulusdriven attention. Rather, we suggest that IFP requires voluntary selection of color singletons in each consecutive trial.

Keywords: visual search, intertrial priming, feature singleton, saliency, stimulus-driven attention, goal-driven attention

How are features integrated (bound) into objects and how can this process be facilitated? Here we investigated the role of rapid perceptual learning in feature binding and its long-lasting effects. By isolating the contributions of individual features from their conjunctions between training and test displays, we demonstrate for the first time that training can rapidly and substantially improve feature binding. Observers trained on a conjunction search task consisting of a rapid display with one targetconjunction, then tested with a new target-conjunction. Features were the same between training and test displays. Learning transferred to the new target when its conjunction was presented as a distractor, but not when only its component features were presented in different conjunction distractors during training. Training improvement lasted for up to 16 months, but, in all conditions, it was specific to the trained target. Our findings suggest that with short training observers’ ability to bind two specific features into an object is improved, and that this learning effect can last for over a year. Moreover, our findings show that while the short-term learning effect reflects activation of presented items and their binding, long-term consolidation is task specific.

Keywords: Feature binding Perceptual learning Conjunction search Visual search

Crowding is the failure to identify an object in the peripheral visual field in the presence of nearby objects. Recent studies have shown that crowding can be alleviated after several days of training, but the processes underlying this improvement are still unclear. Here we tested whether a few hundred trials within a short period of training can alleviate crowding, whether the learning is location specific, and whether the improvement reflects facilitation by target enhancement or flankers suppression. Observers were asked to identify the orientation of a letter in the periphery surrounded by two flanker letters. Observers were tested before (pretest) and after (posttest) training (600 trials). In Experiment 1 we tested whether learning is location specific or can transfer to a different location; the training and test occurred at the same or different hemifields. In a control experiment, we ruled out alternative explanations for the learning effect in Experiment 1. In Experiment 2, we assessed different components of feature selection by training with either the same flanker polarity as the pre/posttest but opposite polarity group (flanker polarity group) or the same target polarity as the pre/posttest but opposite flanker polarity (target polarity group). Following training, overall performance increased in all four conditions, but only the same-location group (Experiment 1) and the same flanker polarity (Experiment 2) showed a significant reduction in crowding as assessed by the distance at which the flankers no longer interfere with target identification, that is, the critical spacing. These results show that training can rapidly reduce crowding and that improvement primarily reflects learning to ignore the irrelevant flankers. Remarkably, in the two conditions in which training significantly reduced crowding, the benefit of short training persisted for up to a year.

Keywords: crowding, perceptual learning, contrast polarity

Visual search is considerably speeded when the target’s characteristics remain constant across successive selections. Here, we investigated whether such inter-trial priming increases the target’s attentional priority, by examining whether target repetition reduces search efficiency during serial search. As the study of inter-trial priming requires the target and distractors to exchange roles unpredictably, it has mostly been confined to singleton searches, which typically yield efficient search. We therefore resorted to two singleton searches known to yield relatively inefficient performance, that is, searches in which the target does not pop out. Participants searched for a veridical angry face among neutral ones or vice-versa, either upright or inverted (Experiment 1) or for a Q among Os or vice-versa (Experiment 2). In both experiments, we found substantial intertrial priming that did not improve search efficiency. In addition, intertrial priming was asymmetric and occurred only when the more salient target repeated. We conclude that intertrial priming does not modulate attentional priority allocation and that it occurs in asymmetric search only when the target is characterized by an additional feature that is consciously perceived.

Keywords: priming of pop-out, inter-trial priming, search asymmetry, preattentive processing, attentional priority allocation, serial search, visual search

Perception and motor control jointly act to meet our current needs. Recent evidence shows that the generation of motor action significantly affects perception. Here, we examined the role of motor response in inter-trial priming, namely, in Priming of Pop-out (PoP): when searching for a singleton target, performance is improved when the target and distractors features repeat on consecutive search trials than when they switch. Although recent studies have shown an interaction between motor response and PoP, the role of motor action on priming has not been fully characterized. Here we investigated whether motor action is necessary during encoding, for PoP to be observed. On go trials, observers searched for a color singleton target and responded to its shape, while on no-go trials they passively watched the display instead of responding to the target. We observed PoP even when the previous trial had been a no-go trial, suggesting that encoding of search-relevant attributes in pop-out displays is not contingent on motor response. Nevertheless, the repetition effect was larger after a go trial than after a no-go trial, supporting the dual-stage model of PoP, according to which this effect involves both a perceptual and a motor component.

Keywords: Spatial attention Inter-trial priming Motor response Visual search Implicit encoding Visual short-term memory

Explicit expectations can guide attention toward the time at which an upcoming target is likely to appear. However, in real-life situations, explicit preknowledge of upcoming events’ temporal occurrence is rarely provided. We investigated whether implicit memory traces can guide attention in time, as they guide attention to recently attended features and locations (priming of pop-out and priming of location; V. Maljkovic & K. Nakayama, 1994, Priming of pop-out: I. Role of features, Memory & Cognition, Vol. 22, pp. 657– 672; V. Maljkovic & K. Nakayama, 1996, Priming of pop-out: II. The role of position, Perception & Psychophysics, Vol. 58, pp. 977–991). Using a rapid serial visual presentation task, we show a temporal position priming (TPP) effect by which search performance is speeded when the target temporal position within the visual stream happens to repeat on consecutive trials. We show that such repetition priming is one of the mechanisms that underlie the much-studied sequential effect of the foreperiod. We further demonstrate that the learned association that gives rise to TPP does not require the selection or execution of a motor response and that it affects perceptual stages of visual processing. The relations between these findings and existing accounts of the sequential effect as well as with other intertrial priming effects in visual search are discussed.

Keywords: attention, intertrial priming, time assessment, rapid serial visual presentation (RSVP), sequential effect

In search for a singleton target, performance is considerably improved when the target and distractors repeat than when they switch roles, an effect called priming of pop-out or PoP (Maljkovic & Nakayama, 1994). Although this phenomenon has been replicated across a variety of dimensions, orientation PoP has proved to be volatile. Recent research has shown that target activation and distractor inhibition mechanisms underlie PoP (Lamy, Antebi, et al., 2008). Relying on this finding, we show that unlike in color and shape search, only distractor inhibition processes contribute to PoP in orientation search, which resolves the apparent inconstancies in the literature. The implications of this finding for mechanisms underlying PoP and orientation singleton search are discussed.

Keywords: Inter-trial priming Priming of pop-out Visual search Target activation Distractor inhibition Orientation singleton search

Numerous studies have shown that repetition of search-relevant attributes facilitates visual search performance. For example, Maljkovic and Nakayama (1994) showed that when observers search for a target defined by its color and report its shape, repetition of the target color speeds search, an effect known as priming of pop-out. While intertrial feature priming in search was initially thought to affect perceptual processes, the idea that it also affects postselection stages of processing is increasingly acknowledged. However, because in previous studies repetition of the motor response has typically been confounded with repetition of the response feature, it is not clear what mechanisms underlie the postselection effect of intertrial priming. In the present study, we dissociated the two repetition types. The results showed that repetition of the target-defining attribute from the previous trial affects selection of the motor response but not discrimination of the response attribute. The implications for current accounts of intertrial priming are discussed.

Keywords: Visual search . Attention . Memory. Repetition effects. Response selection

Previous research has shown that intertrial repetition of target and distractors task-relevant properties speeds visual search performance, an effect known as priming of pop-out (PoP). Recent accounts suggest that such priming results, at least in part, from a mechanism that speeds post-selectional, responserelated processes, the marker of which is an interaction between repetition of the target and distractor features and repetition of the response from the previous trial. However, this response-based component of inter-trial priming has been elusive, and it remains unclear what its boundary conditions might be. In addition, what information is represented in the episodic memory traces that underlie the responsebased component has not yet been characterized.

Here, we show that the response-based component of feature priming reflects an episodic memory retrieval mechanism that is not mandatory or automatic but may be described as a heuristic that subjects sometimes use, in particular when the overall difficulty of the search task is high. In addition, we show that the conjunction of the target and distractor features forms the context that is reactivated during episodic retrieval. Finally, we show that target–distractor discriminability is an important modulator of the selection-based component. The findings are discussed within the framework of the dual-stage model of inter-trial priming (Lamy, Yashar, & Ruderman, 2010).

Keywords: Visual search Attention Intertrial priming Priming of pop-out Episodic retrieval

Implicit short-term memory plays an important role in visual search. For instance, singleton search is faster when the target and distractor features repeat on two consecutive trials than when they switch, an effect called Priming of Popout (PoP). However, whether or not PoP facilitates early perceptual/attentional processes remains controversial. To resolve discrepancies between existing findings, we tested the hypothesis that early effects of PoP occur only if attention is focused/engaged on the target. We measured search accuracy using brief displays for a fine discrimination task, which required focused attention, and for a left/right hemifield localization task, which did not. We found that PoP effects on accuracy occur only in the discrimination task. The theoretical implications are discussed.

Keywords: attention, masking, detection/discrimination, memory, visual acuity, search

Recent research has demonstrated that what observers attend to at a given time affects how their attention is deployed in the few moments that follow. When an observer searches for a discrepant target, repetition of the target feature from the previous trial speeds search, an effect known as priming of pop-out (PoP). Previous PoP studies have relied exclusively on spatial search tasks. Here, using a rapid serial visual presentation task, we show that PoP also occurs when temporal uncertainty makes search necessary, and that when spatial and temporal search trials are interleaved, the PoP effect transfers from one task to the other. The results suggest that common mechanisms of target-feature activation and distractor-feature inhibition underlie spatial and temporal visual search. They elucidate the role of PoP in visual search by showing that it speeds engagement of attention to the selected target, rather than earlier stages involving target localization and attention focusing.

Keywords: attention, visual search, priming of pop-out, temporal search, intertrial priming

The study of inter-trial effects in visual search has generated an increasing amount of research in recent years. However, the mechanisms underlying these effects are still a matter of debate. Two rival accounts have been suggested. One view stipulates that inter-trial effects facilitate early perceptual/attentional processes, whereas the other proposes that it affects post-perceptual response-related processes. Here, we focused on the priming of pop-out effect (PoP, Maljkovic & Nakayama, 1994), which refers to the well-established finding that performance on singleton search is faster when the target and distractors features repeat on two consecutive trials than when they switch. We set out to resolve the current controversy surrounding PoP by suggesting a dual-stage account, according to which PoP speeds both an early perceptual stage and a later, response-related stage of visual search. We were able to dissociate the hypothesized components of PoP by tracking their time course.

Keywords: Priming of pop-out, Inter-trial priming, Visual search, Attention

The presence of an irrelevant singleton disrupts search for a singleton target substantially more when the target feature varies unpredictably (mixed-singleton search) than when it is known in advance (fixedsingleton search). This finding suggests that advance knowledge of the target feature guides singleton search. Pinto et al. [Pinto, Y., Olivers, C. N. L., & Theeuwes, J. (2005). Target uncertainty does not lead to more distraction by singletons: Intertrial priming does. Perception & Psychophysics, 67, 1354–1361] proposed an alternative account, according to which this difference results from inter-trial priming effects. They based their argument on the finding that distractor interference is reduced when the singleton target feature repeats vs. switches from one trial to the next. However, Lamy et al. [Lamy, D., Carmel, T., Egeth, H., & Leber, A. (2006). Effects of search mode and inter-trial priming on singleton search. Perception & Psychophysics, 68, 919–932] reported no such modulation of distractor interference by target-feature repetition. Here, we show that differences in design (blocking conditions of distractor presence in the former study vs. randomly mixing them in the latter) account for this discrepancy. We conclude that the different task demands induced by the blocked distractor-present and distractorabsent conditions rather than distractor presence per se interact with intertrial priming effects. These findings argue against the claim that singleton search relies exclusively on stimulus-driven factors and suggest that preknowledge of the target feature, when available, can guide attention. In addition, the present results challenge the ambiguity hypothesis of intertrial priming, according to which increased competition for attentional selection boosts inter-trial priming effects.

Keywords: Visual search, Intertrial priming Attentional capture