Color Saliency Research Articles

Temporal and spatial analysis of event-related potentials in response to color saliency differences among various color vision types.

Human color vision exhibits significant diversity that cannot be fully explained by categorical classifications. Understanding how individuals with different color vision phenotypes perceive, recognize, and react to the same physical stimuli provides valuable insights into sensory characteristics. This study aimed to identify behavioral and neural differences between different color visions, primarily classified as typical trichromats and anomalous trichromats, in response to two chromatic stimuli, blue-green and red, during an attention-demanding oddball task. We analyzed the P3 component of event-related potentials (ERPs), associated with attention, and conducted a broad spatiotemporal exploration of neural differences. Behavioral responses were also analyzed to complement neural data. Participants included typical trichromats (n = 13) and anomalous trichromats (n = 5), and the chromatic stimuli were presented in an oddball paradigm. Typical trichromats exhibited faster potentiation from the occipital to parietal regions in response to the more salient red stimulus, particularly in the area overlapping with the P3 component. In contrast, anomalous trichromats revealed faster potentiation to the expected more salient blue-green stimulus in the occipital to parietal regions, with no other significant neural differences between stimuli. Comparisons between the color vision types showed no significant overall neural differences. The large variability in red-green sensitivity among anomalous trichromats, along with neural variability not fully explained by this sensitivity, likely contributed to the absence of clear neural distinctions based on color saliency. While reaction times were influenced by red-green sensitivity, neural signals showed ambiguity regarding saliency differences. These findings suggest that factors beyond red-green sensitivity influenced neural activity related to color perception and cognition in minority color vision phenotypes. Further research with larger sample sizes is needed to more comprehensively explore these neural dynamics and their broader implications.

Efficient fusion of spatio-temporal saliency for frame wise saliency identification

<p>Video saliency detection is a rapidly growing subject that has seen very few contributions. The most common technique used nowadays is to perform frame-by-frame saliency detection. The modified Spatio-temporal fusion method presented in this paper offers a novel approach to saliency detection and mapping. It uses frame-wise overall motion color saliency as well as pixel-based consistent Spatio-temporal diffusion for its temporal uniformity. Additionally, a variety of techniques is advocated as a way to increase the saliency maps' overall accuracy and precision. The video is divided into groups of frames, and each frame temporarily goes through diffusion and integration in order to compute the color saliency mapping, as covered in the proposed method section. Then, with the aid of a permutation matrix, the inter-group frame is used to format the pixel-based saliency fusion, after which the features, or the fusion of pixel saliency and color information, direct the diffusion of the spatiotemporal saliency. The result is tested using five publicly accessible global saliency evaluation metrics, and it is determined that the proposed algorithm outperforms numerous saliency detection techniques with an improvement in accuracy margin. The robustness, dependability, adaptability, and precision are all demonstrated by the results.</p>

Distinct mechanisms of attentional suppression: exploration of trait factors underlying cued- and learned-suppression

Attention allows us to focus on relevant information while ignoring distractions. Effective suppression of distracting information is crucial for efficient visual search. Recent studies have developed two paradigms to investigate attentional suppression: cued-suppression which is based on top-down control, and learned-suppression which is based on selection history. While both types of suppression reportedly engage proactive control, it remains unclear whether they rely on shared mechanisms. This study aimed to determine the relationship between cued- and learned-suppression. In a within-subjects design, 54 participants performed a cued-suppression task where pre-cues indicated upcoming target or distractor colors, and a learned-suppression task where a salient color distractor was present or absent. No significant correlation emerged between performance in the two tasks, suggesting distinct suppression mechanisms. Cued-suppression correlated with visual working memory capacity, indicating reliance on explicit control. In contrast, learned-suppression correlated with everyday distractibility, suggesting implicit control based on regularities. These results provide evidence for heterogeneous proactive control mechanisms underlying cued- and learned-suppression. While both engage inhibition, cued-suppression relies on deliberate top-down control modulated by working memory, whereas learned-suppression involves implicit suppression shaped by selection history and distractibility traits.

Testing the contributions of proactive target and distractor templates in visual search performance

ABSTRACT When searching for objects with particular visual features, performance is sometimes improved by the presence of a salient colour distractor, such as a red item among green objects. Attention to such distractors is thought to be suppressed when the visual system expects their specific features (e.g., redness), but a complication with this view is that distractor expectancies are generally accompanied by anticipated target features, with their own associated attentional facilitation. We tested the role of these mechanisms by separately manipulating the colour specificity of salient distractors and of targets, and thus the ability to build up feature-specific templates for each type of search item. Experiment 1 employed singleton distractors appearing in unpredictable colours, preventing the formation of a feature-specific suppression template. Nevertheless, evidence of suppression was unchanged, suggesting that it does not require a fixed, predictable distractor. In Experiment 2, the singleton colour remained fixed while the target colour varied. Without a constant target colour, markers of singleton suppression were effectively abolished. The pattern of results suggests that observed suppression effects are largely driven by global enhancement of the expected target colour, possibly in combination with a second-order suppression mechanism that is not dependent on specific distractor features.

Video saliency-recognition by applying custom spatio temporal fusion technique

<span lang="EN-US">Video saliency detection is a major growing field with quite few contributions to it. The general method available today is to conduct frame wise saliency detection and this leads to several complications, including an incoherent pixel-based saliency map, making it not so useful. This paper provides a novel solution to saliency detection and mapping with its custom spatio-temporal fusion method that uses frame wise overall motion colour saliency along with pixel-based consistent spatio-temporal diffusion for its temporal uniformity. In the proposed method section, it has been discussed how the video is fragmented into groups of frames and each frame undergoes diffusion and integration in a temporary fashion for the colour saliency mapping to be computed. Then the inter group frame are used to format the pixel-based saliency fusion, after which the features, that is, fusion of pixel saliency and colour information, guide the diffusion of the spatio temporal saliency. With this, the result has been tested with 5 publicly available global saliency evaluation metrics and it comes to conclusion that the proposed algorithm performs better than several state-of-the-art saliency detection methods with increase in accuracy with a good value margin. All the results display the robustness, reliability, versatility and accuracy.</span>

Inter-trial priming is not sufficient for feature-based distractor suppression

ABSTRACT Previous research has shown that observers can learn to suppress a salient distractor (e.g., a unique red item among green ones) when its salient feature (red) remains constant. Several authors suggested that such suppression builds up through repetition of the distractor’s salient feature via intertrial priming. Support for this account primarily comes from the finding that interference from a salient distractor is weaker when this distractor’s salient colour repeats on successive trials than when the distractor takes on the previous target’s colour. Here, we tested an alternative account, unrelated to distractor suppression, according to which this priming effect reflects increased distraction when the salient distractor shares the previous target’s colour rather than a decreased distraction when this distractor’s colour repeats. To dissociate the two accounts, we randomly selected the distractor and the other search items’ colours from four possible colours. Thus, on successive trials, the distractor and target colours could repeat, be new or swap. We found that relative to the new-colour condition, distractor interference increased when the distractor took on the previous target colour, but was unaffected by whether the distractor’s colour repeated. Our findings challenge the claim that intertrial priming accounts for distractor suppression.

Investigating the role of spatial filtering on distractor suppression.

In recent years, evidence has accumulated towards a distractor suppression mechanism that enables efficient selection of targets in a visual search task. According to these findings, the search for a target is faster in the presence of a salient distractor in a display among homogenous distractors as opposed to its absence. Studies have also shown that distractor suppression not only operates on the feature level but can also be spatially guided. The motivation of the current study was to examine if spatially guided distractor suppression can be goal-driven. We tested this across four experiments. In Experiment 1A, the task was to search for a shape target (e.g., a circle) and discriminate the orientation of the line within it. In some trials, a salient color distractor was presented in the display while participants were told that it appeared in one of the two locations on the horizontal axis (or the vertical axis, counterbalanced across participants). We expected enhanced distractor suppression when the salient distractor appeared within this "spatial filter" but did not find it since the target was also presented at the filtered locations. Experiment 1B replicated Experiment 1A, except that the target was always presented outside the filter; filtering enhanced search performance. In Experiment 2 even when the filter contained the salient distractor in only 65% of the filtered trials, filtering benefited search performance. In Experiment 3, the filter changed on every trial and did not benefit suppression.

MECHANISMS OF ATTENTIONAL CONTROL AND SUPPRESSION IN AGING

Abstract Attentional control plays a crucial role in our daily lives by allowing our brains to selectively process relevant information while filtering out task-irrelevant distractions. Due to aging, older adults have demonstrated a heightened propensity to be more distractible. This decreased ability to regulate attention has been attributed to an inability to inhibit task-irrelevant salient stimuli. However, the specific mechanisms that underlie this age-related alteration remain unclear. In this study, we utilized a visual search paradigm that directly measures mechanisms of attentional suppression to test our hypothesis that older adults demonstrate reduced capabilities to suppress task-irrelevant information. Young adults (aged 18-35) and older adults (aged 50-80) were tasked to utilize goal-directed attentional control by fixating at a specific target shape. Critically, in some trials, individuals were exposed to a salient color shape that acted as a singleton distractor. While young adults show the ability to suppress attentional allocation to this salient distractor in this paradigm, we hypothesized that older adults would demonstrate attentional capture by this salient distractor. Our findings revealed that older adults made significantly fewer first-fixations towards the target, demonstrating a marked impairment with goal-directed attentional control. Surprisingly, older adults still made fewer fixations toward the distractor in comparison to non-targets, demonstrating that older adults sustained the ability to suppress irrelevant distractors. These findings raise important questions on the mechanisms that underlie increased distractibility in aging and oculomotor attentional control.

Different prioritization states of working memory representations affect visual searches: Evidence from an event-related potential study

Previous evidence has shown that the contents of working memory (WM) can bias visual selection. However, not much is known about how WM effects change when the WM representation is held in different prioritization states. Here, we investigated this problem using event-related potentials. Subjects maintained two colors in WM while performing a search task. One of the colors was retro-cued, indicating that it was 80 % likely to be the target of the memory test. During the search display, one of the distractors was a salient color singleton, and this singleton distractor could carry the same color as the cued WM representation, the uncued WM representation, or be irrelevant to the memory content. Behaviorally, the memory test performance was found to be better for the cued color than for the uncued color, and we observed lower search accuracy (ACC) and longer search reaction time (RT) when the singleton distractor matched the cued WM representation than when it matched an uncued or an irrelevant WM representation. Event-related potential (ERP) data showed that the P3 amplitude of cue-color distractor conditions was smaller than that of uncued-color distractor conditions and irrelevant-color distractor conditions. These findings clearly indicate that prioritizing an item for enhanced representational quality enables the item to bias attention to a greater extent.

Distinct roles of theta and alpha oscillations in the process of contingent attentional capture.

Visual spatial attention can be captured by a salient color singleton that is contingent on the target feature. A previous study reported that theta (4-7 Hz) and alpha (8-14 Hz) oscillations were related to contingent attentional capture, but the corresponding attentional mechanisms of these oscillations remain unclear. In this study, we analyzed the electroencephalogram data of our previous study to investigate the roles of capture-related theta and alpha oscillation activities. Different from the previous study that used color-changed placeholders as irrelevant cues, the present study adopted abrupt onsets of color singleton cues which tend to elicit phase-locked neural activities. In Experiment 1, participants completed a peripheral visual search task in which spatially uninformative color singleton cues were inside the spatial attentional window and a central rapid serial visual presentation (RSVP) task in which the same cues were outside the spatial attentional window. In Experiment 2, participants completed a color RSVP task and a size RSVP task in which the peripheral color singleton cues were contingent and not contingent on target feature, respectively. In Experiment 1, spatially uninformative color singleton cues elicited lateralized theta activities when they were contingent on target feature, irrespective of whether they were inside or outside the spatial attentional window. In contrast, the same color singleton cues elicited alpha lateralization only when they were inside the spatial attentional window. In Experiment 2, we further found that theta lateralization vanished if the color singleton cues were not contingent on target feature. These results suggest distinct roles of theta and alpha oscillations in the process of contingent attentional capture initiated by abrupt onsets of singleton cues. Theta activities may reflect global enhancement of target feature, while alpha activities may be related to attentional engagement to spatially relevant singleton cues. These lateralized neural oscillations, together with the distractor-elicited N2pc component, might consist of multiple stages of attentional processes during contingent attentional capture.

The role of posterior parietal cortex and medial prefrontal cortex in distraction and mind-wandering

Distraction reflects a drift of attention away from the task at hand towards task-irrelevant external or internal information (mind-wandering). The right posterior parietal cortex (PPC) and the medial prefrontal cortex (mPFC) are known to mediate attention to external information and mind-wandering, respectively, but it is not clear whether they support each process selectively or rather they play similar roles in supporting both. In this study, participants performed a visual search task including salient color singleton distractors before and after receiving cathodal (inhibitory) transcranial direct current stimulation (tDCS) to the right PPC, the mPFC, or sham tDCS. Thought probes assessed the intensity and contents of mind-wandering during visual search. The results show that tDCS to the right PPC but not mPFC reduced the attentional capture by the singleton distractor during visual search. tDCS to both mPFC and PPC reduced mind-wandering, but only tDCS to the mPFC specifically reduced future-oriented mind-wandering. These results suggest that the right PPC and mPFC play a different role in directing attention towards task-irrelevant information. The PPC is involved in both external and internal distraction, possibly by mediating the disengagement of attention from the current task and its reorienting to salient information, be this a percept or a mental content (mind-wandering). By contrast, the mPFC uniquely supports mind-wandering, possibly by mediating the endogenous generation of future-oriented thoughts capable to draw attention inward, away from ongoing activities.

Video saliency-detection using custom spatiotemporal fusion method

There have been several researches done in the field of image saliency but not as much as in video saliency. In order to increase precision and accuracy during compression, reduce coding complexity and time consumption along with memory allocation problems with our proposed solution. It is a modified high-definition video compression (HEVC) pixel based consistent spatiotemporal diffusion with temporal uniformity. It involves taking apart the video into groups of frames, computing colour saliency, integrate temporal fusion, pixel saliency fusion is conducted and then colour information guides the diffusion process for the spatiotemporal mapping with the help of permutation matrix. The proposed solution is tested on a publicly available extensive dataset with five global saliency valuation metrics and is compared with several other state-of-the-art saliency detection methods. The results display and overall best performance amongst all other candidates.

Learned spatial suppression is not always proactive.

Learning to ignore distractors is critical for navigating the visual world. Research has suggested that a location frequently containing a salient distractor can be suppressed. How does such suppression work? Previous studies provided evidence for proactive suppression, but methodological limitations preclude firm conclusions. We sought to overcome these limitations with a new search-probe paradigm. On search trials, participants searched for a shape oddball target while a salient color singleton distractor frequently appeared in a high-probability location. On randomly interleaved probe trials, participants discriminated the orientation of a tilted bar presented briefly at one of the search locations, allowing us to index the spatial distribution of attention at the moment the search would have begun. Results on search trials replicated previous findings: reduced attentional capture when a salient distractor appeared in the high-probability location. However, critically, probe discrimination was no different at the high-probability and low-probability locations. We increased the incentive to ignore the high-probability location in Experiment 2 and found, strikingly, that probe discrimination accuracy was greater at the high-probability location. These results suggest that the high-probability location was initially selected before being suppressed, consistent with a reactive mechanism. Overall, the accuracy probe procedure demonstrates that learned spatial suppression is not always proactive, even when response time metrics seem consistent with such an inference. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

A hierarchical approach based CBIR scheme using shape, texture, and color for accelerating retrieval process

In the traditional content-based image retrieval (CBIR) framework, images are retrieved based on the combined primitive features. However, such a kind of fusion is always not effective as one feature may overshadow other image feature. To overcome this issue, in this particular paper, we have suggested a hierarchical framework where features like color, texture, and shape are considered in a single hierarchy only. The main concern of the hierarchical system is the proper selection of the order of retrieving visual features. So, semantic-based image retrieval has been carried out. Here, at the first level, the salience map-based region of interest has been identified, and then edge histogram descriptor-based shape features are incorporated. In the second hierarchy, we have proposed a novel directional texture feature extraction based on the Tamura features’ directionality. Further, color is considered another primitive feature of an image, but human visual perception is not sensitive to each color. The image can be visualized by the salient colors, and in this work, we have developed a color image quantization-based approach. Now, to validate the system, extensive experimental results and its comparison with its contemporaries through Corel-1 K, GHIM-10 K, Olivia-2688, and Produce-1400 databases have been carried out.

Inversion of pop-out for a distracting feature dimension in monkey visual cortex

During visual search, it is important to reduce the interference of distracting objects in the scene. The neuronal responses elicited by the search target stimulus are typically enhanced. However, it is equally important to suppress the representations of distracting stimuli, especially if they are salient and capture attention. We trained monkeys to make an eye movement to a unique "pop-out" shape stimulus among an array of distracting stimuli. One of these distractors had a salient color that varied across trials and differed from the color of the other stimuli, causing it to also pop-out. The monkeys were able to select the pop-out shape target with high accuracy and actively avoided the pop-out color distractor. This behavioral pattern was reflected in the activity of neurons in area V4. Responses to the shape targets were enhanced, while the activity evoked by the pop-out color distractor was only briefly enhanced, directly followed by a sustained period of pronounced suppression. These behavioral and neuronal results demonstrate a cortical selection mechanism that rapidly inverts a pop-out signal to "pop-in" for an entire feature dimension thereby facilitating goal-directed visual search in the presence of salient distractors.

Effects of top-down and bottom-up attention on post-selection posterior contralateral negativity.

We examined the effect of combined top-down and bottom-up attentional control sources in easy and difficult visual search tasks. Applying a new analysis on previously acquired data, we focused on the sustained posterior contralateral negativity (SPCN) and the response-locked posterior contralateral negativity (RLpcN), to better understand processes following target selection. We used the signed-area approach to measure the negative area, where the signal was either locked to the target or the response onsets. We further split the RLpcN into an early and a late segment to capture the dynamics of selection and post-selection processes. In Experiment 1, participants reported the orientation of a uniquely tilted target. In Experiment 2, participants reported the position of a small gap within the uniquely tilted target. In both experiments, endogenous cues manipulated top-down attention (valid vs. neutral), and salient color singletons (either the target or a distractor) manipulated bottom-up attention. We hypothesized that the SPCN and the later segment of the RLpcN would be modulated by task difficulty and target salience, as they are associated with post-selection processes, such as response selection and working memory. The early segment of the RLpcN was hypothesized to be modulated by the cueing manipulation and presence of a salient distractor, as they affect target selection. An effect of distractor presence was observed on the early segment of the RLpcN, and our results further supported the hypotheses regarding the SPCN and the later segment of the RLpcN, providing novel insights into post-selection processes in visual search.

Color appearance of spatial patterns compared by direct estimation and conjoint measurement.

Perceptual scales of color saturation obtained by direct estimation (DE) and maximum likelihood conjoint measurement (MLCM) were compared for red checkerboard patterns and uniform red squares. For the DE task, observers were asked to rate the saturation level as a percentage, indicating the chromatic sensation for each pattern and contrast. For the MLCM procedure, observers judged on each trial which of two stimuli that varied in chromatic contrast and/or spatial pattern evoked the most salient color. In separate experiments, patterns varying only in luminance contrast were also tested. The MLCM data confirmed previous results reported with DE indicating that the slope of the checkerboard scale with cone contrast levels is steeper than that for the uniform square. Similar results were obtained with patterns modulated only in luminance. DE methods were relatively more variable within an observer, reflecting observer uncertainty, while MLCM scales showed greater relative variability across observers, perhaps reflecting individual differences in the appearance of the stimuli. MLCM provides a reliable scaling method, based only on ordinal judgments between pairs of stimuli and that provides less opportunity for subject-specific biases and strategies to intervene in perceptual judgements.

Pixel-Domain Just Noticeable Difference Modeling with Heterogeneous Color Features.

With the rapidly emerging user-generated images, perception compression for color image is an inevitable mission. Whilst in existing just noticeable difference (JND) models, color-oriented features are not fully taken into account for coinciding with HVS perception characteristics, such as sensitivity, attention, and masking. To fully imitate the color perception process, we extract color-related feature parameters as local features, including color edge intensity and color complexity, as well as region-wise features, including color area proportion, color distribution position and color distribution dispersion, and inherent feature irrelevant to color content called color perception difference. Then, the potential interaction among them is analyzed and modeled as color contrast intensity. To utilize them, color uncertainty and color saliency are envisaged to emanate from feature integration in the information communication framework. Finally, color and uncertainty saliency models are applied to improve the conventional JND model, taking the masking and attention effect into consideration. Subjective and objective experiments validate the effectiveness of the proposed model, delivering superior noise concealment capacity compared with start-of-the-art works.

Contextualising the bizarre: The integrated functioning of rib puncture as an antipredator defence in the Iberian ribbed newt (Pleurodeles waltl)

Abstract Numerous prey traits are the result of the pervasive evolutionary pressure imposed by predators. Mirroring their fundamental role in the fitness of prey, some antipredator defences can evolve into elaborate strategies. Such is the case of the Iberian ribbed newt (Pleurodeles waltl), a semiaquatic urodele that inhabits multiple types of inland waterbodies in central and southern Iberian Peninsula and north‐western Africa. It possesses sharp, protractile ribs, which can thwart predators by emerging through skin ‘warts’ they pierce, becoming impregnated with the toxicants these warts produce, and making the newts difficult to swallow. Plus, the orange colour of these warts contrasts with the predominantly dull dorsum. In this work, I studied the interactions between the number of these warts, the saliency of wart colour against dorsum colour of each individual (i.e., the difference in colour between the warts and the dorsum), rib response time (i.e., the time needed for the ribs to emerge in response to a standardised stimulus), body size, and locomotor performance in males and females in either their aquatic or terrestrial stage. I also conducted a field experiment to determine whether predators more frequently attacked plasticine models with conspicuous or inconspicuous warts. I found that wart colour saliency functions as a decoy, attracting predator attacks towards this well‐protected body part. Plus, many of the antipredator defences studied, namely the number of warts, their colour saliency, rib response time, body size, and locomotor performance, were interrelated. Accordingly, more salient warts indicated a faster rib response, suggesting that these defences are coordinated with each other. Plus, locomotion was considerably slower in the terrestrial than in the aquatic stage. Moreover, warts were more salient, and thus more efficient attracting predator attacks, in newts in the slower terrestrial stage. However, rib response was faster in the aquatic stage, which coincides with the newt's activity peak, and therefore with the height of its conspicuousness to predators. Remarkably, faster newts display less salient warts and a slower rib response, which suggests a trade‐off between both defences. Nonetheless, some of these trends are reversed in females, among which faster individuals also display a faster rib response. This could be a likely consequence of reduced predation pressure. These results further the understanding of how prey integrate and tune multiple antipredator defences according to factors that influence predation pressure, such as sex and life stage.

Color saliency and attention change represented by neural processing in individuals with various color visions

Color saliency and attention change represented by neural processing in individuals with various color visions