Theories Of Visual Search Research Articles

On the timing of overt attention deployment: Eye-movement evidence for the priority accumulation framework.

Most visual-search theories assume that our attention is automatically allocated to the location with the highest priority at any given moment. The Priority Accumulation Framework (PAF) challenges this assumption. It suggests that the priority weight at each location accumulates across sequential events and that evidence for the presence of action-relevant information contributes to determining when attention is deployed to the location with the highest accumulated priority. Here, we tested these hypotheses for overt attention by recording first saccades in a free-viewing spatial-cueing task. We manipulated search difficulty (Experiments 1 and 2) and cue salience (Experiment 2). Standard theories posit that when oculomotor capture by the cue occurs, it is initiated before the search display appears; therefore, these theories predict that the cue's impact on the distribution of first saccades should be independent of search difficulty but influenced by the cue's saliency. By contrast, PAF posits that the cue can bias competition later, after processing of the search display has already started, and therefore predicts that such late impact should increase with both search difficulty and cue salience. The results fully supported PAF's predictions. Our account suggests a distinction between attentional capture and attentional-priority bias that resolves enduring inconsistencies in the attentional-capture literature. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Searching near and far: The attentional template incorporates viewing distance.

According to theories of visual search, observers generate a visual representation of the search target (the "attentional template") that guides spatial attention toward target-like visual input. In real-world vision, however, objects produce vastly different visual input depending on their location: your car produces a retinal image that is 10 times smaller when it is parked 50 compared to 5 m away. Across four experiments, we investigated whether the attentional template incorporates viewing distance when observers search for familiar object categories. On each trial, participants were precued to search for a car or person in the near or far plane of an outdoor scene. In "search trials," the scene reappeared and participants had to indicate whether the search target was present or absent. In intermixed "catch-trials," two silhouettes were briefly presented on either side of fixation (matching the shape and/or predicted size of the search target), one of which was followed by a probe-stimulus. We found that participants were more accurate at reporting the location (Experiments 1 and 2) and orientation (Experiment 3) of probe stimuli when they were presented at the location of size-matching silhouettes. Thus, attentional templates incorporate the predicted size of an object based on the current viewing distance. This was only the case, however, when silhouettes also matched the shape of the search target (Experiment 2). We conclude that attentional templates for finding objects in scenes are shaped by a combination of category-specific attributes (shape) and context-dependent expectations about the likely appearance (size) of these objects at the current viewing location. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Observers Efficiently Extract the Minimal and Maximal Element in Perceptual Magnitude Sets: Evidence for a Bipartite Format.

The mind represents abstract magnitude information, including time, space, and number, but in what format is this information stored? We show support for the bipartite format of perceptual magnitudes, in which the measured value on a dimension is scaled to the dynamic range of the input, leading to a privileged status for values at the lowest and highest end of the range. In six experiments with college undergraduates, we show that observers are faster and more accurate to find the endpoints (i.e., the minimum and maximum) than any of the inner values, even as the number of items increases beyond visual short-term memory limits. Our results show that length, size, and number are represented in a dynamic format that allows for comparison-free sorting, with endpoints represented with an immediately accessible status, consistent with the bipartite model of perceptual magnitudes. We discuss the implications for theories of visual search and ensemble perception.

Complex background information slows down parallel search efficiency by reducing the strength of interitem interactions.

In the laboratory, visual search is often studied using uniform backgrounds. This contrasts with search in daily life, where potential search items appear against more complex backgrounds. In the present study, we examined the effects of background complexity on a parallel visual search under conditions where objects are easily segregated from the background. Target-distractor similarity was sufficiently low such that search could unfold in parallel, as indexed by reaction times that increase logarithmically with set size. The results indicate that when backgrounds are relatively simple (sandy beach with water elements), search efficiency is comparable to search using a solid background. When backgrounds are more complex (child bedroom or checkerboard), logarithmic search slopes increase compared to search on solid backgrounds, especially at higher levels of target-distractor similarity. The results are discussed in terms of different theories of visual search. It is proposed that the complex visual information occurring in between distractors slows down individual distractor rejection times by weakening the strength of interitem interactions. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Incorporating the properties of peripheral vision into theories of visual search

Incorporating the properties of peripheral vision into theories of visual search

Color and Shape efficiency for outlier detection from automated to user evaluation

The design of efficient representations is well established as a fruitful way to explore and analyze complex or large data. In these representations, data are encoded with various visual attributes depending on the needs of the representation itself. To make coherent design choices about visual attributes, the visual search field proposes guidelines based on the human brain’s perception of features. However, information visualization representations frequently need to depict more data than the amount these guidelines have been validated on. Since, the information visualization community has extended these guidelines to a wider parameter space.This paper contributes to this theme by extending visual search theories to an information visualization context. We consider a visual search task where subjects are asked to find an unknown outlier in a grid of randomly laid out distractors. Stimuli are defined by color and shape features for the purpose of visually encoding categorical data. The experimental protocol is made of a parameters space reduction step (i.e., sub-sampling) based on a machine learning model, and a user evaluation to validate hypotheses and measure capacity limits. The results show that the major difficulty factor is the number of visual attributes that are used to encode the outlier. When redundantly encoded, the display heterogeneity has no effect on the task. When encoded with one attribute, the difficulty depends on that attribute heterogeneity until its capacity limit (7 for color, 5 for shape) is reached. Finally, when encoded with two attributes simultaneously, performances drop drastically even with minor heterogeneity.

Search for the Unknown: Guidance of Visual Search in the Absence of an Active Template

Can you efficiently look for something even without knowing what it looks like? According to theories of visual search, the answer is no: A template of the search target must be maintained in an active state to guide search for potential locations of the target. Here, we tested the need for an active template by assessing a case in which this template is improbable: the search for a familiar face among unfamiliar ones when the identity of the target face is unknown. Because people are familiar with hundreds of faces, an active guiding template seems unlikely in this case. Nevertheless, participants (35 Israelis and 33 Germans) were able to guide their search as long as extrafoveal processing of the target features was possible. These results challenge current theories of visual search by showing that guidance can rely on long-term memory and extrafoveal processing rather than on an active search template.

A theory of visual search for targets added to natural backgrounds.

A theory of visual search for targets added to natural backgrounds.

A common neural network architecture for visual search and working memory

ABSTRACT Visual search and working memory (WM) are tightly linked cognitive processes. Theories of attentional selection assume that WM plays an important role in top-down guided visual search. However, computational models of visual search do not model WM. Here we show that an existing model of WM can utilize its mechanisms of rapid plasticity and pattern completion to perform visual search. In this model, a search template, like a memory item, is encoded into the network’s synaptic weights forming a momentary stable attractor. During search, recurrent activation between the template and visual inputs amplifies the target and suppresses non-matching features via mutual inhibition. While the model cannot outperform models designed specifically for search, it can, “off-the-shelf”, account for important characteristics. Notably, it produces search display set-size costs, repetition effects, and multiple-template search effects, qualitatively in line with empirical data. It is also informative that the model fails to produce some important aspects of visual search behaviour, such as suppression of repeated distractors. Also, without additional control structures for top-down guidance, the model lacks the ability to differentiate between encoding and searching for targets. The shared architecture bridges theories of visual search and visual WM, highlighting their common structure and their differences.

Effects of transcranial direct current stimulation over the posterior parietal cortex on novice X-ray screening performance

Existing theories of visual search are generally deduced from lab-based studies involving the identification of a target object among similar distractors. The role of the right parietal cortex in visual search is well-established. However, less is known about real-world visual search tasks, such as X-ray screening, which require targets to be disembedded from their background. Research has shown variations in the cognitive abilities required for these tasks and typical lab-based visual search tasks. Thus, the findings of traditional visual search studies do not always transfer into the applied domain. Although brain imaging studies have offered insights into visual search tasks involving disembedding, highlighting an association between the left parietal cortex and disembedding performance, no causal link has yet been established. To this end, we carried out a pilot study (n = 34, between-subjects) administering non-invasive brain stimulation over the posterior parietal cortex (PPC) prior to completing a security X-ray screening task. The findings suggested that anodal left PPC tDCS enhanced novice performance in X-ray screening over that of sham stimulation, in line with brain imaging findings. However, the efficacy of tDCS is under question, with a growing number of failed replications. With this in mind, this study aims to re-test our original hypothesis by examining the effects of left-side parietal stimulation on novice X-ray screener performance and comparing them to those of sham stimulation and of stimulation on a control site (right PPC). As such, this within-subjects study comprised three sessions (2 mA left PPC, 2 mA right PPC, low-intensity sham stimulation left PPC), to investigate effects of anodal tDCS on X-ray screening performance. The pre-registered analysis did not detect any significant differences between left PPC tDCS and sham tDCS or left PPC tDCS and right PPC tDCS on novice performance (d′) in X-ray screening. Further exploratory analyses detected no effects of left PPC tDCS on any other indices of performance in the X-ray security screening task (c, RTs and accuracy), or a disembedding control task (RTs and accuracy). The use of alternative stimulation techniques, with replicable behavioural effects on the parietal lobe (or a multi-technique approach), and well-powered studies with a systematic variation of stimulation parameters, could help to choose between two possible interpretations: that neither left nor right PPC are causally related to either tasks or that tDCS was ineffective. Finally, low-intensity sham stimulation (.016 mA), previously shown to outperform other sham conditions in between-subjects designs, was found to be ineffective for blinding participants in a within-subjects design. Our findings raise concerns for the current lack of optimal control conditions and add to the growing literature highlighting the need for replication in the field.

Focal lung pathology detection in radiology: Is there an effect of experience on visual search behavior?

In radiology, 60% to 80% of diagnostic errors are perceptual. The use of more efficient visual search behaviors is expected to reduce these errors. We collected eye-tracking data from participants with different levels of experience when interpreting chest X-rays during the completion of a pathology-detection task. Eye-tracking measures were assessed in the context of three existing visual search theories from the literature to understand the association between visual search behavior and underlying processes: the long-term working memory theory, the information-reduction hypothesis, and the holistic model of image perception. The most experienced participants (radiology residents) showed the highest level of performance, albeit their visual search behaviors did not differ from the intermediate group. This suggests that radiology residents better processed the represented information on the X-ray, using a visual search strategy similar to the intermediate group. Since similar visual search resulted in more information extraction in the radiology residents compared with the intermediates, we suggest that this result might support the long-term working memory theory. Furthermore, compared with novices, intermediates and radiology residents fixated longer on areas that were more important to avoid missing any pathology, which possibly confirmsthe information-reduction hypothesis. Finally, the larger distances between fixations observed in more experienced participants could support theholistic model of image perception. In addition, measures of generic skills were related to a lower time cost for switching between global and local information processing. Our findings suggest that the three theories may be complementary in chest X-ray interpretation. Therefore, a unified theory explaining perceptual-cognitive superiority in radiology is considered.

A target contrast signal theory of parallel processing in goal-directed search.

Feature Integration Theory (FIT) set out the groundwork for much of the work in visual cognition since its publication. One of the most important legacies of this theory has been the emphasis on feature-specific processing. Nowadays, visual features are thought of as a sort of currency of visual attention (e.g., features can be attended, processing of attended features is enhanced), and attended features are thought to guide attention towards likely targets in a scene. Here we propose an alternative theory - the Target Contrast Signal Theory - based on the idea that when we search for a specific target, it is not the target-specific features that guide our attention towards the target; rather, what determines behavior is the result of an active comparison between the target template in mind and every element present in the scene. This comparison occurs in parallel and is aimed at rejecting from consideration items that peripheral vision can confidently reject as being non-targets. The speed at which each item is evaluated is determined by the overall contrast between that item and the target template. We present computational simulations to demonstrate the workings of the theory as well as eye-movement data that support core predictions of the theory. The theory is discussed in the context of FIT and other important theories of visual search.

A theoretical attempt to revive the serial/parallel-search dichotomy.

A core distinction in Anne Treisman's feature-integration theory (FIT) is in that between parallel and serial search. We outline this dichotomy and selectively review the reasons why it has largely been abandoned in the visual-search community-namely, its theoretical dispensability, failure to find reliable yardsticks for differentiating parallel and serial search, and falsification of core predictions. We then go on to introduce a new theoretical framework that, we argue, clears up some of the theoretical confusion by merging FIT with various competing theories. This framework's core feature is the distinction between and characterization of two fundamentally different search modes: one in which attention is guided to a single item via a priority map (priority guidance), and one in which clumps of multiple items are scanned in parallel in a spatially systematic order (clump scanning). Finally, we will elaborate how this new theoretical framework can resolve current controversies in the literature and how it relates to other existing theories. We (somewhat optimistically) believe that the outcome of this theoretical exercise is a unification of theories of visual search that can explain, or at least is consistent with, all phenomena reported in the visual-search literature that have previously been accounted for by various conflicting theories.

Medium versus difficult visual search: How a quantitative change in the functional visual field leads to a qualitative difference in performance

The dominant theories of visual search assume that search is a process involving comparisons of individual items against a target description that is based on the properties of the target in isolation. Here, we present four experiments that demonstrate that this holds true only in difficult search. In medium search it seems that the relation between the target and neighbouring items is also part of the target description. We used two sets of oriented lines to construct the search items. The cardinal set contained horizontal and vertical lines, the diagonal set contained left diagonal and right diagonal lines. In all experiments, participants knew the identity of the target and the line set used to construct it. In difficult search this knowledge allowed performance to improve in displays where only half of the search items came from the same line set as the target (50% eligibility), relative to displays where all items did (100% eligibility). However, in medium search, performance was actually poorer for 50% eligibility, especially on target-absent trials. This opposite effect of ineligible items in medium search and difficult search is hard to reconcile with theories based on individual items. It is more in line with theories that conceive search as a sequence of fixations where the number of items processed during a fixation depends on the difficulty of the search task: When search is medium, multiple items are processed per fixation. But when search is difficult, only a single item is processed.

Microsaccades reveal the temporal dynamics of template and response preparation during visual search.

Theories of visual search assume that selection is driven by an active template representation of the target object. Earlier studies suggest that template activation occurs prior to search, before the matching input appears in view, but the temporal dynamics of such pre-activation remain unclear. We demonstrate that microsaccades reflect the preparation process for visual search, in terms of both template-specific activation of target features (what to search for) and general preparation to respond (when to start searching). Participants memorized a target color (i.e. the template) for an upcoming search task. During the delay, we presented an irrelevant Rapid Serial Visual Presentation (RSVP) of lateralized colored disks and manipulated the length of the delay in blocks of long (4650 ms) and short (2790 ms) trials. Crucially, at different time points into the delay, the template color was inserted in the RSVP, allowing us to measure specific attentional biases towards this template location as a function of time. Results revealed a general suppression of saccade production in preparation to search: the closer in time to the task, the fewer saccades the participants made. Strikingly, this suppression was stronger when a template-matching disk was present. Moreover, in the time points where a template-matching disk was presented, relatively more and larger saccades went to the matching disk than to an irrelevant color, an effect that also became stronger near the end of the delay. We conclude that observers adapt search template activation to the anticipated moment of search, and that microsaccades track the dynamics of preparing for selection in visual search tasks. Meeting abstract presented at VSS 2018

Adding depth to overlapping displays can improve visual search performance.

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

Which kind of attention is captured by cues with the relative target colour?

ABSTRACTMost theories of visual search maintain that attention is selectively tuned to the attributes of the search target (e.g., orange). Conversely, according to the relational account, attention is biased to the relative feature of the target (e.g., redder). However, previous studies that supported the relational account mainly measured mean response times. Hence, the results might not reflect early, perceptual mechanisms (e.g., signal enhancement) but later, decision-based mechanisms (channel selection). The current study tested the relational account against feature-specific theories in a spatial cueing task, in which the targets were backward-masked, and target identification accuracy was measured. The first experiment corroborated earlier results, demonstrating that relational effects are due to signal enhancement. In the second experiment, we chose highly discriminable colours along the blue–red continuum, and obtained results that were more consistent with broad feature-specific rather than relational tuning. The implications of these findings for current theories of attention are discussed.

Fixations are not all created equal: An objection to mindless visual search.

This call to revolution in theories of visual search does not go far enough. Treating fixations as uniform is an oversimplification that obscures the critical role of the mind. We remind readers that what happens during a fixation depends on mindset, as shown in studies of search strategy and of humans' ability to rapidly resume search following an interruption.

Cognitive architecture enables comprehensive predictive models of visual search.

With a simple demonstration model, Hulleman & Olivers (H&O) effectively argue that theories of visual search need an overhaul. We point to related literature in which visual search is modeled in even more detail through the use of computational cognitive architectures that incorporate fundamental perceptual, cognitive, and motor mechanisms; the result of such work thus far bolsters their arguments considerably.

The "item" as a window into how prior knowledge guides visual search.

We challenge the central idea proposed in Hulleman & Olivers (H&O) by arguing that the "item" is still useful for understanding visual search and for developing new theoretical frameworks. The "item" is a flexible unit that represents not only an individual object, but also a bundle of objects that are grouped based on prior knowledge. Uncovering how the "item" is represented based on prior knowledge is essential for advancing theories of visual search.