Singleton Search Research Articles

A Quantitative Analysis of the Taxonomy of Artistic Styles.

Classifying artists and their work as distinct art styles has been an important task of scholars in the field of art history. Due to its subjectivity, scholars often contradict one another. Our project investigated differences in aesthetic qualities of seven art styles through quantitative means. This was achieved with state-of-the-art deep-learning paradigms to generate new images resembling the style of an artist or entire era. We conducted psychological experiments to measure the behavior of subjects when viewing these new art images. Two different experiments were used: In an eye-tracking study, subjects viewed art-stylespecific generated images. Eye movements were recorded and then compared between art styles. In a visual singleton search study, subjects had to locate a style-outlier image among three images of an alternative style. Reaction time and accuracy were measured and analyzed. These experiments show that there are measurable differences in behavior when viewing images of varying art styles. From these differences, we constructed hierarchical clusterings relating art styles based on the different behaviors of subjects viewing the samples. Our study reveals a novel perspective on the classification of artworks into stylistic eras and motivates future research in the domain of empirical aesthetics through quantitative means.

Re-examining Maljkovic and Nakayama (1994): Conscious expectancy does affect the Priming of Pop-out effect.

Maljkovic and Nakayama (Memory & Cognition, 22(6), 657-672, 1994) observed that color singleton search performance was faster when the target and distractor colors repeated rather than switched across trials - an effect termed Priming of Pop-out (PoP). Two of the key results of this seminal study revealed that the PoP effect was not influenced by the knowledge of the probability of a target color change (Experiment 2), nor was it influenced by anticipating the upcoming target color by subvocalizing it (Experiment 4). Based on these findings they concluded that the PoP effect reflected the automatic priming due to the persistence of the target and distractor colors of the previous trial. Based on recent findings indicating that conscious expectancy may influence the PoP effect, as well as several bygone experimental practices in the original study (i.e., experimenter participants, no inferential statistics, etc.), we felt it worthwhile to evaluate whether their findings were observed when replicated in an empirically rigorous manner. Though the present study revealed that the PoP effect was robust, it was profoundly impacted by the knowledge of the probability of a target color switch (Experiment 1) and vocally anticipating the upcoming target color (Experiment 2). Overall, the results suggest that we should abandon the notion that the PoP effect only reflects the automatic priming of the previous target and distractor colors independent of conscious expectancy.

Attentional Access to Multiple Target Objects in Visual Search

Most investigations of visual search have focused on the discrimination between a search target and other task-irrelevant distractor objects (selection). The attentional limitations that arise when multiple target objects in the same display have to be processed simultaneously (access) remain poorly understood. Here, we employed behavioral and electrophysiological measures to investigate the factors that determine whether multiple target objects can be accessed in parallel. Performance and N2pc components were measured for search displays that contained either a single target or two target objects. When two target objects were present, they either had the same or different target-defining features. Participants reported whether search displays contained a single target, two targets with shared features, or two targets with different features. There were performance costs as well as reduced N2pc amplitudes for two-target/different relative to two-target/same displays, suggesting that access to multiple target objects defined by different features was impaired. These behavioral and electrophysiological costs were also observed in a task where all search display objects were physically different, but not during color or shape singleton search, confirming that they do not reflect a low-level perceptual grouping of physically identical targets. These results demonstrate strong feature-specific limitations of visual access, as proposed by the Boolean map theory of visual attention. They suggest that multiple target objects can be accessed in parallel only when they share task-relevant features and demonstrate that mechanisms of visual access can be studied with electrophysiological markers.

Spatial filtering restricts the attentional window during both singleton and feature-based visual search.

We investigated whether spatial filtering can restrict attentional selectivity during visual search to a currently task-relevant attentional window. While effective filtering has been demonstrated during singleton search, feature-based attention is believed to operate spatially globally across the entire visual field. To test whether spatial filtering depends on search mode, we assessed its efficiency both during feature-guided search with colour-defined targets and during singleton search tasks. Search displays were preceded by spatial cues. Participants responded to target objects at cued/relevant locations, and ignored them when they appeared on the uncued/irrelevant side. In four experiments, electrophysiological markers of attentional selection and distractor suppression (N2pc and PD components) were measured for relevant and irrelevant target-matching objects. During singleton search, N2pc components were triggered by relevant target singletons, but were entirely absent for singletons on the irrelevant side, demonstrating effective spatial filtering. Critically, similar results were found for feature-based search. N2pcs to irrelevant target-colour objects were either absent or strongly attenuated (when these objects were salient), indicating that the feature-based guidance of visual search can be restricted to relevant locations. The presence of PD components to salient objects on the irrelevant side during feature-based and singleton search suggests that spatial filtering involves active distractor suppression. These results challenge the assumption that feature-based attentional guidance is always spatially global. They suggest instead that when advance information about target locations becomes available, effective spatial filtering processes are activated transiently not only in singleton search, but also during search for feature-defined targets.

On the link between attentional search and the oculomotor system: Is preattentive search restricted to the range of eye movements?

It has been proposed that covert visual search can be fast, efficient, and stimulus driven, particularly when the target is defined by a salient single feature, or slow, inefficient, and effortful when the target is defined by a nonsalient conjunction of features. This distinction between fast, stimulus-driven orienting and slow, effortful orienting can be related to the distinction between exogenous spatial attention and endogenous spatial attention. Several studies have shown that exogenous, covert orienting is limited to the range of saccadic eye movements, whereas covert endogenous orienting is independent of the range of saccadic eye movements. The current study examined whether covert visual search is affected in a similar way. Experiment 1 showed that covert visual search for feature singletons was impaired when stimuli were presented beyond the range of saccadic eye movements, whereas conjunction search was unaffected by array position. Experiment 2 replicated and extended this effect by measuring search times at 6 eccentricities. The impairment in covert feature search emerged only when stimuli crossed the effective oculomotor range and remained stable for locations further into the periphery, ruling out the possibility that the results of Experiment 1 were due to a failure to fully compensate for the effects of cortical magnification. The findings are interpreted in terms of biased competition and oculomotor theories of spatial attention. It is concluded that, as with covert exogenous orienting, biological constraints on overt orienting in the oculomotor system constrain covert, preattentive search.

A bilateral N2pc (N2pcb) component is elicited by search targets displayed on the vertical midline.

The study of visually elicited event-related potentials (ERPs) detected at posterior recording sites during visual search has enormously advanced our knowledge about how and when visuo-spatial attention locks onto one or more laterally presented target objects. The N2pc component to lateral targets has been pivotal to further our understanding of the mechanisms and time course of target selection in visual search. However, the N2pc cannot track visuo-spatial attention deployment to targets displayed along the vertical midline. Here, we introduce a new ERP marker (N2pcb component) that is elicited during the selection of such midline targets. In line with retinal and callosal projections from striate to ventral extrastriate cortex, this component reflects an enhanced negativity elicited by midline targets over both posterior hemispheres. By comparing the attentional selection of lateral and midline targets in a singleton search condition and a feature search condition, we show that the N2pcb is triggered at the same time as the N2pc to lateral targets, and shows the same onset latency difference between singleton and feature search. We conclude that the N2pcb and N2pc components reflect the same attentional target selection processes in visual search.

Target templates in singleton search vs. feature-based search modes

ABSTRACTIt is well-known that visual attention can be tuned in a top-down controlled manner to various attributes. Amongst other search strategies, previous research has identified a feature search mode in which attention is tuned to the target feature (e.g., colour) vs. a singleton search mode, where all salient items can attract attention. A short review of the literature reveals that singleton search mode is not regularly applied in single-target search, but could play a role in two-target search. Here we critically tested whether results suggesting singleton search could alternatively be due to top-down tuning to different attributes of the targets (e.g., luminance). The results of the first experiment show a mixture of attentional tuning to the target colours (red, green), as well as luminance (darker), and residual singleton capture. A second experiment shows that such mixed results can be obtained in the standard paradigm, with only small changes to the stimuli. These results cannot be coherently described within a single mental representation, and are therefore difficult to reconcile with the notion of a target template. Non-representational theories such as feature map theories seem better equipped to explain mixed search results, which could be a decisive weakness of representational theories.

Cueing distraction: electrophysiological evidence for anticipatory active suppression of distractor location.

It is well known that processing at upcoming target locations can be facilitated, but mixed results have been obtained regarding the inhibition of irrelevant locations when advance information about distractors is available on a trial-to-trial basis. Here, we provide electrophysiological evidence that distractor locations can be anticipatorily suppressed. In an additional singleton search task, distractor cues were presented before the search display, which were either fully predictive or non-predictive of the location of the upcoming salient colour distractor. The PD component of the event-related potential, a marker of active suppression, was elicited by lateral singletons and smaller following predictive than non-predictive cues, indicating that less suppression was required upon presentation of the distractor when its location was known in advance. Presumably, excitability of regions processing the predictively cued locations was anticipatorily reduced to prevent distraction. This idea was further supported by the finding that larger individual cueing benefits in reaction time were associated with stronger reductions of the PD. There was no behavioural benefit at the group level, however, and implications for the role of individual differences and for the measurement of inhibition in distractor cueing tasks are discussed. The enhancement of target locations, reflected by the NT component, was not modulated by the predictiveness of the cues. Overall, our findings add to a growing literature highlighting the importance of inhibitory mechanisms for the guidance of spatial attention by showing that irrelevant locations can be anticipatorily suppressed in a top-down fashion, reducing the impact of even salient stimuli.

Flipped on its Head: Deep Learning-Based Saliency Finds Asymmetry in the Opposite Direction Expected for Singleton Search of Flipped and Canonical Targets

Flipped on its Head: Deep Learning-Based Saliency Finds Asymmetry in the Opposite Direction Expected for Singleton Search of Flipped and Canonical Targets

Expectations and perceptual priming in a visual search task: Evidence from eye movements and behavior.

An extensive amount of research indicates that repeating target and distractor features facilitates pop-out search while switching these features slows the search. Following the seminal study by Maljkovic and Nakayama (1994), this "priming of pop-out" effect (PoP) has been widely described as an automatic bottom-up process that is independent of the observers' expectations. At the same time, numerous studies highlight the crucial role of expectations in visual attention deployment. Our experiment shows that in contrast to previous claims, PoP in a classic color singleton search task is a mix of automatic processing and expectations. Participants searched for a uniquely colored diamond among 2 same-colored distractors. Target color sequences were either predictable (e.g., 2 red-target-green-distractors trials, followed by 2 green-target-red-distractors trials, and so on) or random. Responses were faster in predictable color sequences than randomly changing ones with equal number of repetitions of target colors on preceding trials. Analyses of observers' eye movements showed that predictability of target color affected both latency and accuracy of the first saccade during a search trial. Our results support the idea that PoP is governed not only by automatic effects from previous target or distractor features but also by top-down expectations. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Taking a closer look at visual search: Just how feature-agnostic is singleton detection mode?

Singleton detection mode is a state in which spatial attention is set to prioritize any objects that differ from all other objects present on any feature dimension. Relatively little research has been devoted to confirming the consequences such a search mode has for stimulus processing. It is often implied that when observers employ singleton detection mode, all singletons capture attention equally, and when observers search for a single feature, only that feature captures attention. The experiment presented here contradicts these implications. We had observers search for colored singleton targets preceded by spatially uninformative colored singleton cues, and we recorded stimulus-evoked neural responses using electroencephalography (EEG). When observers had to respond to targets defined by two possible colors (a task intended to encourage singleton detection mode), cue validity effects were apparent for both target-color cues and irrelevant-color cues, and these effects were accompanied by an N2pc in the EEG data. Importantly, however, the target-color cues evoked significantly larger cue validity effects and N2pc components than did the irrelevant-color cues. In contrast, when observers had to respond to targets defined by one color (a task intended to encourage feature search mode), only cues of that color evoked a cue validity effect. Interestingly, the N2pcs produced by irrelevant cues did not differ between feature and singleton search, suggesting that the behavioral difference was not due to different attentional orienting. Rather, we suggest that behavioral singleton capture is due to a diminished same-location cost being produced by irrelevant-color cues.

Strategic visual imagery and automatic priming effects in pop-out visual search.

Priming of Pop-out (PoP) is defined by faster responses in singleton search when the target repeats across trials than when it switches. In a recent study, it was shown that the PoP effect can be reversed using visual imagery (Cochrane, Nwabuike, Thomson, & Milliken, 2018). The goal of the current study was to pinpoint the procedural constraints necessary to observe the imagery-induced reversal of PoP. Across four experiments the reversal of the PoP effect (i) depended critically on the response-stimulus interval between trials, (ii) was remarkably stable across long experimental sessions, (iii) was observed within trial-pairs when participants engaged in visual imagery, but not between trial-pairs when participants did not, and (iv) appeared to be more robust with self-paced trial-pairs than with a long continuous run of trials. Together, these results offer strong confirmation of the idea that self-generated visual imagery can produce robust reversals of the PoP effect.

How to inhibit a distractor location? Statistical learning versus active, top-down suppression.

Recently, Wang and Theeuwes (Journal of Experimental Psychology: Human Perception and Performance, 44(1), 13-17, 2018a) demonstrated the role of lingering selection biases in an additional singleton search task in which the distractor singleton appeared much more often in one location than in all other locations. For this location, there was less capture and selection efficiency was reduced. It was argued that statistical learning induces plasticity within the spatial priority map such that particular locations that are high likely to contain a distractor are suppressed relative to all other locations. The current study replicated these findings regarding statistical learning (Experiment 1) and investigated whether similar effects can be obtained by cueing the distractor location in a top-down way on a trial-by-trial basis. The results show that top-down cueing of the distractor location with long (1,500 ms; Experiment 2) and short stimulus-onset symmetries (SOAs) (600 ms; Experiment 3) does not result in suppression: The amount of capture nor the efficiency of selection was affected by the cue. If anything, we found an attentional benefit (instead of the suppression) for the short SOA. We argue that through statistical learning, weights within the attentional priority map are changed such that one location containing a salient distractor is suppressed relative to all other locations. Our cueing experiments show that this effect cannot be accomplished by active, top-down suppression. Consequences for recent theories of distractor suppression are discussed.

Multiple attentional sets while monitoring rapid serial visual presentations.

The present study examined whether observers are able to establish multiple attentional sets to concurrently monitor two different spatial locations. Observers identified a target letter in red or cyan among nontarget letters of other heterogeneous colours during a temporal feature search. A peripheral distractor display consisted of one item of either the same colour as the current target, and the other potential target colour, or an irrelevant colour that could never be the target. They identified an odd-ball colour letter among homogenous colours during a singleton search. The results revealed that observers maintained multiple attentional sets for detecting two singletons or for targets involving two (or three) features. However, they were unable to maintain a mixture of sets. Moreover, exposure to a distractor containing feature that corresponded to a feature of the current target was advantageous for target identification. The presence or absence of this set-specific capture depended on top-down knowledge and did not occur automatically in the singleton-detection stream. These results demonstrate a limitation in the flexibility of attentional sets. Although two singleton detections were possible, multiple attentional templates for a more complex attentional set could not be maintained concurrently when monitoring multiple rapid serial visual presentations.

The width of the functional viewing field is sensitive to distractor-target similarity even in efficient singleton search

The width of the functional viewing field is sensitive to distractor-target similarity even in efficient singleton search

Feature singletons attract spatial attention independently of feature priming.

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 stimulus-driven attention. Rather, we suggest that IFP requires voluntary selection of color singletons in each consecutive trial.

Stronger interference from distractors in the right hemifield during visual search

ABSTRACTThe orientation-bias hypothesis states that there is a bias to attend to the right visual hemifield (RVF) when there is spatial competition between stimuli in the left and right hemifield [Pollmann, S. (1996). A pop-out induced extinction-like phenomenon in neurologically intact subjects. Neuropsychologia, 34(5), 413–425. doi:10.1016/0028-3932(95)00125-5]. In support of this hypothesis, stronger interference was reported for RVF distractors with contralateral targets. In contrast, previous studies using rapid serial visual presentation (RSVP) found stronger interference from distractors in the left visual hemifield (LVF). We used the additional singleton paradigm to test whether this discrepancy was due to the different distractor features that were employed (colour vs. orientation). Interference from the colour distractor with contralateral targets was larger in the RVF than in the LVF. However, the asymmetrical interference disappeared when observers had to search for an inconspicuous colour target instead of the inconspicuous shape target. We suggest that the LVF orienting-bias is limited to situations where search is driven by bottom-up saliency (singleton search) instead of top-down search goals (feature search). In contrast, analysis of the literature suggests the opposite for the LVF bias in RSVP tasks. Thus, the attentional asymmetry may depend on whether the task involves temporal or spatial competition, and whether search is based on bottom-up or top-down signals.

Search for Capacity-Limited and Super-Capacity Search.

The present study investigated capacity limitations of visual search. In a series of experiments, participants searched for a singleton target among homogenous distractors, a conjunction target defined by combination of two features, or a feature target among heterogeneous distractors. Using the simultaneous-sequential paradigm, I found that singleton search proceeded in a capacity-unlimited manner. By contrast, the performance of the conjunction search was found to depend on a capacity-limited process. For feature searches, the performance of searching for a specific color was not affected by how the stimuli were presented, while the orientation search performance was enhanced as the number of distractors simultaneously presented with the target increased. These results imply that distinct colors are individually coded, whereas multiple orientations are encoded as an ensemble in a structured way. Taken together, the present study clarifies which type of search process are capacity-limited and reveals how this limit can be overcome.

The role of crowding on feature singleton search

The role of crowding on feature singleton search

Building ensemble representations: How the shape of preceding distractor distributions affects visual search

Perception allows us to extract information about regularities in the environment. Observers can quickly determine summary statistics of a group of objects and detect outliers. The existing body of research has, however, not revealed how such ensemble representations develop over time. Moreover, the correspondence between the physical distribution of features in the external world and their potential internal representation as a probability density function (PDF) by the visual system is still unknown. Here, for the first time we demonstrate that such internal PDFs are built during visual search and show how they can be assessed with repetition and role-reversal effects. Using singleton search for an oddly oriented target line among differently oriented distractors (a priming of pop-out paradigm), we test how different properties of previously observed distractor distributions (mean, variability, and shape) influence search times. Our results indicate that observers learn properties of distractor distributions over and above mean and variance; in fact, response times also depend on the shape of the preceding distractor distribution. Response times decrease as a function of target distance from the mean of preceding Gaussian distractor distributions, and the decrease is steeper when preceding distributions have small standard deviations. When preceding distributions are uniform, however, this decrease in response times can be described by a two-piece function corresponding to the uniform distribution PDF. Moreover, following skewed distributions response times function is skewed in accordance with the skew in distributions. Indeed, internal PDFs seem to be specifically tuned to the observed feature distribution.