Perceptual Grouping Research Articles

Maintaining the status quo: the nature and role of policy stakeholders' perceptions of event value

PurposeThis paper explores event value from the perspective of policy stakeholders and discusses potential implications of this stakeholder group's perceptions of value on event policy, event evaluation and the public discourse on the value of events.Design/methodology/approachA thematic analysis is employed to analyze nine interviews from respondents who were deemed to fit the study criteria in the case of Östersund, Sweden.FindingsFindings indicate that value is portrayed in largely economic terms or in proxy-economic terms even though the respondents expressed awareness and concern for social aspects of value. Moreover, the article highlights the glaring omission of the relationship between policy stakeholders and the nature of evaluation efforts in the industry and academia.Originality/valueThe article addresses a still somewhat unexplored dynamics between influential policy stakeholders and how events are regarded in terms of their potential contribution to community development. To what degree does the way the events sector and the general public value events emanate from the way events have been instrumentalized in policy throughout history?

Temporal dynamics of the neural representation of hue and luminance polarity

Hue and luminance contrast are basic visual features. Here we use multivariate analyses of magnetoencephalography data to investigate the timing of the neural computations that extract them, and whether they depend on common neural circuits. We show that hue and luminance-contrast polarity can be decoded from MEG data and, with lower accuracy, both features can be decoded across changes in the other feature. These results are consistent with the existence of both common and separable neural mechanisms. The decoding time course is earlier and more temporally precise for luminance polarity than hue, a result that does not depend on task, suggesting that luminance contrast is an updating signal that separates visual events. Meanwhile, cross-temporal generalization is slightly greater for representations of hue compared to luminance polarity, providing a neural correlate of the preeminence of hue in perceptual grouping and memory. Finally, decoding of luminance polarity varies depending on the hues used to obtain training and testing data. The pattern of results is consistent with observations that luminance contrast is mediated by both L-M and S cone sub-cortical mechanisms.

Invited Session V: GABAergic function and dysfunction in visual perception: Abnormal processing of visual context in schizophrenia

People with schizophrenia (SZ) exhibit persistent deficits in visual processing including reduced contrast sensitivity and poor detection of complex image structure, such as contours. Over recent years accumulating psychophysical evidence indicates that vision in SZ is associated with a reduced influence of spatial context which in turn has been attributed to reduced spatial suppression in visual cortex. Compared to controls, people with SZ do not experience the same reduction in perceived contrast that occurs when targets are embedded in a high contrast background. This appears to be a cortical phenomenon: reduced influence of context is not limited to contrast but carries over to other image attributes (such as orientation) but not others (such as luminance). Finally, although patients poor processing of higher-order image structure has been attributed to differences in perceptual grouping, work from my lab indicates that abnormal processing of context may also contribute to patients' poor sensitivity for contours. It does this by (a) reducing their sensitivity to local orientation and (b) reducing their ability to discount irrelevant background structure. Taken together these results suggest that abnormal processing of context contributes to a range of visual processing deficits in SZ.

Neural correlates of local parallelism during naturalistic vision.

Human observers can rapidly perceive complex real-world scenes. Grouping visual elements into meaningful units is an integral part of this process. Yet, so far, the neural underpinnings of perceptual grouping have only been studied with simple lab stimuli. We here uncover the neural mechanisms of one important perceptual grouping cue, local parallelism. Using a new, image-computable algorithm for detecting local symmetry in line drawings and photographs, we manipulated the local parallelism content of real-world scenes. We decoded scene categories from patterns of brain activity obtained via functional magnetic resonance imaging (fMRI) in 38 human observers while they viewed the manipulated scenes. Decoding was significantly more accurate for scenes containing strong local parallelism compared to weak local parallelism in the parahippocampal place area (PPA), indicating a central role of parallelism in scene perception. To investigate the origin of the parallelism signal we performed a model-based fMRI analysis of the public BOLD5000 dataset, looking for voxels whose activation time course matches that of the locally parallel content of the 4916 photographs viewed by the participants in the experiment. We found a strong relationship with average local symmetry in visual areas V1-4, PPA, and retrosplenial cortex (RSC). Notably, the parallelism-related signal peaked first in V4, suggesting V4 as the site for extracting paralleism from the visual input. We conclude that local parallelism is a perceptual grouping cue that influences neuronal activity throughout the visual hierarchy, presumably starting at V4. Parallelism plays a key role in the representation of scene categories in PPA.

Perceptual grouping and detection of trial-unique emergent structures by pigeons.

Detecting global patterns in the environment is essential to object perception and recognition. Consistent with this, pigeons have been shown to readily detect and locate geometrically arranged, structured targets embedded in randomized backgrounds. Here we show for the first time that pigeons can detect and localize trial-unique targets derived solely from global patterns resulting from periodicity, symmetry and their combination using randomly generated segments of black and white local elements. The results indicate pigeons can perceptually segment and detect a wide variety of emergent global structures and do so even when they are unique to each trial. The perceptual and cognitive mechanisms underlying this discrimination likely play important roles in the abilities of how pigeons, and likely other birds, detect and categorize the properties of natural objects at different spatial scales.

One Sketch for All: One-Shot Personalized Sketch Segmentation.

We present the first one-shot personalized sketch segmentation method. We aim to segment all sketches belonging to the same category provisioned with a single sketch with a given part annotation while (i) preserving the parts semantics embedded in the exemplar, and (ii) being robust to input style and abstraction. We refer to this scenario as personalized. With that, we importantly enable a much-desired personalization capability for downstream fine-grained sketch analysis tasks. To train a robust segmentation module, we deform the exemplar sketch to each of the available sketches of the same category. Our method generalizes to sketches not observed during training. Our central contribution is a sketch-specific hierarchical deformation network. Given a multi-level sketch-strokes encoding obtained via a graph convolutional network, our method estimates rigid-body transformation from the target to the exemplar, on the upper level. Finer deformation from the exemplar to the globally warped target sketch is further obtained through stroke-wise deformations, on the lower-level. Both levels of deformation are guided by mean squared distances between the keypoints learned without supervision, ensuring that the stroke semantics are preserved. We evaluate our method against the state-of-the-art segmentation and perceptual grouping baselines re-purposed for the one-shot setting and against two few-shot 3D shape segmentation methods. We show that our method outperforms all the alternatives by more than 10% on average. Ablation studies further demonstrate that our method is robust to personalization: changes in input part semantics and style differences.

Trajectory Grouping With Curvature Regularization for Tubular Structure Tracking.

Tubular structure tracking is a crucial task in the fields of computer vision and medical image analysis. The minimal paths-based approaches have exhibited their strong ability in tracing tubular structures, by which a tubular structure can be naturally modeled as a minimal geodesic path computed with a suitable geodesic metric. However, existing minimal paths-based tracing approaches still suffer from difficulties such as the shortcuts and short branches combination problems, especially when dealing with the images involving complicated tubular tree structures or background. In this paper, we introduce a new minimal paths-based model for minimally interactive tubular structure centerline extraction in conjunction with a perceptual grouping scheme. Basically, we take into account the prescribed tubular trajectories and curvature-penalized geodesic paths to seek suitable shortest paths. The proposed approach can benefit from the local smoothness prior on tubular structures and the global optimality of the used graph-based path searching scheme. Experimental results on both synthetic and real images prove that the proposed model indeed obtains outperformance comparing with the state-of-the-art minimal paths-based tubular structure tracing algorithms.

KL2 scholars' perceptions of factors contributing to sustained translational science career success.

Identifying the most effective ways to support career development of early stage investigators in clinical and translational science should yield benefits for the biomedical research community. Institutions with Clinical and Translational Science Awards (CTSA) offer KL2 programs to facilitate career development; however, the sustained impact has not been widely assessed. A survey comprised of quantitative and qualitative questions was sent to 2144 individuals that had previously received support through CTSA KL2 mechanisms. The 547 responses were analyzed with identifying information redacted. Respondents held MD (47%), PhD (36%), and MD/PhD (13%) degrees. After KL2 support was completed, physicians' time was divided 50% to research and 30% to patient care, whereas PhD respondents devoted 70% time to research. Funded research effort averaged 60% for the cohort. Respondents were satisfied with their career progression. More than 95% thought their current job was meaningful. Two-thirds felt confident or very confident in their ability to sustain a career in clinical and translational research. Factors cited as contributing to career success included protected time, mentoring, and collaborations. This first large systematic survey of KL2 alumni provides valuable insight into the group's perceptions of the program and outcome information. Former scholars are largely satisfied with their career choice and direction, national recognition of their expertise, and impact of their work. Importantly, they identified training activities that contributed to success. Our results and future analysis of the survey data should inform the framework for developing platforms to launch sustaining careers of translational scientists.

How do humans group non-rigid objects in multipleobject tracking?: Evidence from grouping by self-rotation.

Previous studies on perceptual grouping found that people can use spatiotemporal and featural information to group spatially separated rigid objects into a unit while tracking moving objects. However, few studies have tested the role of objects' self-motion information in perceptual grouping, although it is of great significance to the motion perception in the three-dimensional space. In natural environments, objects always move in translation and rotation at the same time. The self-rotation of the objects seriously destroys objects' rigidity and topology, creates conflicting movement signals and results in crowding effects. Thus, this study sought to examine the specific role played by self-rotation information on grouping spatially separated non-rigid objects through a modified multiple object tracking (MOT) paradigm with self-rotating objects. Experiment 1 found that people could use self-rotation information to group spatially separated non-rigid objects, even though this information was deleterious for attentive tracking and irrelevant to the task requirements, and people seemed to use it strategically rather than automatically. Experiment 2 provided stronger evidence that this grouping advantage did come from the self-rotation per se rather than surface-level cues arising from self-rotation (e.g. similar 2D motion signals and common shapes). Experiment 3 changed the stimuli to more natural 3D cubes to strengthen the impression of self-rotation and again found that self-rotation improved grouping. Finally, Experiment 4 demonstrated that grouping by self-rotation and grouping by changing shape were statistically comparable but additive, suggesting that they were two different sources of the object information. Thus, grouping by self-rotation mainly benefited from the perceptual differences in motion flow fields rather than in deformation. Overall, this study is the first attempt to identify self-motion as a new feature that people can use to group objects in dynamic scenes and shed light on debates about what entities/units we group and what kinds of information about a target we process while tracking objects.

Misaligned dynamic faces are processed holistically

It was recently proposed that both experience-driven and object-based perceptual grouping contribute to holistic face processing. We investigated whether motion—as a common fate perceptual grouping cue—could enhance the holistic processing of misaligned faces. We manipulated alignment and motion (dynamic and static) of study and test faces in a modified complete composite task in which the congruency effect was regarded as an indicator of holistic processing. Participants made same-different judgments about the top halves of two sequentially presented composite faces. We observed that when the study faces were dynamic, regardless of whether the test faces were dynamic or static, misaligned-misaligned face pairs were processed holistically. When the study faces were static, misaligned-misaligned face pairs showed no holistic processing, and neither did inverted faces. These results indicate that motion can promote the holistic processing of misaligned faces. Our findings provide important insights into different types of holistic face processing, and we discuss these types as well as their relationships with each other in depth.

Music reading expertise affects visual change detection: Evidence from a music-related flicker paradigm.

To study the mechanisms and boundary conditions of expertise effects on change detection, we introduced a novel music-related variant of the flicker paradigm. Specifically, we monitored the eye movements of expert musicians (with 10 years of music experience) and non-musicians (who could not read music) while they located changes across two rapidly alternating versions of a music score, with a blank screen presented between each screen change. Relative to the non-musicians, experts were faster at change detection, with shorter fixations and larger saccade amplitudes. Expertise effects on accuracy and saccade amplitude were magnified for visually complex relative to simple music scores. Consistent with the assumptions of chunking and template theories of expertise, our results suggest that expert musicians can use chunking (i.e., perceptual grouping) mechanisms to facilitate perceptual encoding during change detection.

The Grouping-Induced Numerosity Illusion Is Attention-Dependent.

Perceptual grouping and visual attention are two mechanisms that help to segregate visual input into meaningful objects. Here we report how perceptual grouping, which affects perceived numerosity, is reduced when visual attention is engaged in a concurrent visual task. We asked participants to judge the numerosity of clouds of dot-pairs connected by thin lines, known to cause underestimation of numerosity, while simultaneously performing a color conjunction task. Diverting attention to the concomitant visual distractor significantly reduced the grouping-induced numerosity biases. Moreover, while the magnitude of the illusion under free viewing covaried strongly with AQ-defined autistic traits, under conditions of divided attention the relationship was much reduced. These results suggest that divided attention modulates the perceptual grouping of elements by connectedness and that it is independent of the perceptual style of participants.

Unsupervised Image Segmentation by Mutual Information Maximization and Adversarial Regularization

Semantic segmentation is one of the basic, yet essential scene understanding tasks for an autonomous agent. The recent developments in supervised machine learning and neural networks have enjoyed great success in enhancing the performance of the state-of-the-art techniques for this task. However, their superior performance is highly reliant on the availability of a large-scale annotated dataset. In this letter, we propose a novel fully unsupervised semantic segmentation method, the so-called Information Maximization and Adversarial Regularization Segmentation (InMARS). Inspired by human perception which parses a scene into perceptual groups, rather than analyzing each pixel individually, our proposed approach first partitions an input image into meaningful regions (also known as superpixels). Next, it utilizes Mutual-Information-Maximization followed by an adversarial training strategy to cluster these regions into semantically meaningful classes. To customize an adversarial training scheme for the problem, we incorporate adversarial pixel noise along with spatial perturbations to impose photometrical and geometrical invariance on the deep neural network. Our experiments demonstrate that our method achieves the state-of-the-art performance on two commonly used unsupervised semantic segmentation datasets, COCO-Stuff, and Potsdam.

Grouping strategies in numerosity perception between intrinsic and extrinsic grouping cues

The number of items in an array can be quickly and accurately estimated by dividing the array into subgroups, in a strategy termed “groupitizing.” For example, when memorizing a telephone number, it is better to do so by divide the number into several segments. Different forms of visual grouping can affect the precision of the enumeration of a large set of items. Previous studies have found that when groupitizing, enumeration precision is improved by grouping arrays using visual proximity and color similarity. Based on Gestalt theory, Palmer (Cognit Psychol 24:436, 1992) divided perceptual grouping into intrinsic (e.g., proximity, similarity) and extrinsic (e.g., connectedness, common region) principles. Studies have investigated groupitizing effects on intrinsic grouping. However, to the best of our knowledge, no study has explored groupitizing effects for extrinsic grouping cues. Therefore, this study explored whether extrinsic grouping cues differed from intrinsic grouping cues for groupitizing effects in numerosity perception. The results showed that both extrinsic and intrinsic grouping cues improved enumeration precision. However, extrinsic grouping was more accurate in terms of the sensory precision of the numerosity perception.

Gaming and non-gaming memorable tourism experiences: How do they influence young and mature tourists’ behavioural intentions?

Many gaming tourist destinations are now tending to provide more non-gaming activities to evolve their image for diversifying their tourism market. When tourists visit a gaming tourist destination, they can obtain memorable tourism experiences (MTEs) from both gaming and non-gaming activities. However, previous studies on MTEs have only focused on all memorable experiences as a whole. This study aims to construct a research model that links gaming MTEs and non-gaming MTEs with the destination image, overall satisfaction, and behavioural intentions to understand how gaming MTEs and non-gaming MTEs work together to influence tourists' behaviours. The results of this study indicate that non-gaming MTEs have a stronger impact than gaming MTEs on the destination image, both gaming and non-gaming MTEs influence tourists' revisit intention, but gaming MTEs have no significant influence on overall satisfaction and word-of-mouth. This study then applies multi-group analysis to compare the results from two age groups. The results indicate that gaming MTEs do not influence the young group's perception of the destination image. This study helps gaming destinations to establish marketing strategies by providing non-gaming MTEs to build a positive destination image and word-of-mouth publicity. It also recommends that casino operators enhance their gaming MTEs to attract repeat visitors.

Young chicks rely on symmetry/asymmetry in perceptual grouping to discriminate sets of elements.

Grouping sets of elements into smaller, equal-sized, subsets constitutes a perceptual strategy employed by humans and other animals to enhance cognitive performance. Here, we show that day-old chicks can solve extremely complex numerical discriminations (Exp.1), and that their performance can be enhanced by the presence of symmetrical/asymmetrical colour grouping (Exp.2 versus Exp.3). Newborn chicks were habituated for 1 h to even numerosities (sets of elements presented on a screen) and then tested for their spontaneous choice among what for humans would be considered a prime and a non-prime odd numerosity. Chicks discriminated and preferred the prime over the composite set of elements irrespective of its relative magnitude (i.e. 7 versus 9 and 11 versus 9). We discuss this result in terms of novelty preference. By employing a more complex contrast (i.e. 13 versus 15), we investigated the limits of such a mechanism and showed that induced grouping positively affects chicks' performance. Our results suggest the existence of a spontaneous mechanism that enables chicks to create symmetrical (i.e. same-sized) subgroups of sets of elements. Chicks preferentially inspected numerosities for which same-sized grouping is never possible (i.e. the prime numerosity) rather than numerosities allowing for symmetrical grouping (i.e. composite).

Anytime collaborative brain\u2013computer interfaces for enhancing perceptual group decision-making

In this paper we present, and test in two realistic environments, collaborative Brain-Computer Interfaces (cBCIs) that can significantly increase both the speed and the accuracy of perceptual group decision-making. The key distinguishing features of this work are: (1) our cBCIs combine behavioural, physiological and neural data in such a way as to be able to provide a group decision at any time after the quickest team member casts their vote, but the quality of a cBCI-assisted decision improves monotonically the longer the group decision can wait; (2) we apply our cBCIs to two realistic scenarios of military relevance (patrolling a dark corridor and manning an outpost at night where users need to identify any unidentified characters that appear) in which decisions are based on information conveyed through video feeds; and (3) our cBCIs exploit Event-Related Potentials (ERPs) elicited in brain activity by the appearance of potential threats but, uniquely, the appearance time is estimated automatically by the system (rather than being unrealistically provided to it). As a result of these elements, in the two test environments, groups assisted by our cBCIs make both more accurate and faster decisions than when individual decisions are integrated in more traditional manners.

Cortical Synchrony as a Mechanism of Collinear Facilitation and Suppression in Early Visual Cortex.

Stimulus-induced oscillations and synchrony among neuronal populations in visual cortex are well-established phenomena. Their functional role in cognition are, however, not well-understood. Recent studies have suggested that neural synchrony may underlie perceptual grouping as stimulus-frequency relationships and stimulus-dependent lateral connectivity profiles can determine the success or failure of synchronization among neuronal groups encoding different stimulus elements. We suggest that the same mechanism accounts for collinear facilitation and suppression effects where the detectability of a target Gabor stimulus is improved or diminished by the presence of collinear flanking Gabor stimuli. We propose a model of oscillators which represent three neuronal populations in visual cortex with distinct receptive fields reflecting the target and two flankers, respectively, and whose connectivity is determined by the collinearity of the presented Gabor stimuli. Our model simulations confirm that neuronal synchrony can indeed explain known collinear facilitation and suppression effects for attended and unattended stimuli.

Communicating group norms through election results.

In a representative democracy, leaders (ideally) who are elected through the electorates should indicate consensus that the newly elected leader truly does represent the majority of the nation or the group. That is, once elected, can the ensuing perceptions of the electorate's consensus provide the newly elected leader with a sense of legitimacy and the ability to represent the group? Two experiments demonstrate that the perceptions of group consensus stemming from democratic elections can imbue newly elected leaders (even if they were once deviant) with legitimacy. Study 1 (N = 158) demonstrates that normative leaders are perceived as more legitimate than deviant leaders when elected with high voting consensus, which increased the perceived prototypicality of the normative leader through greater perceptions of legitimacy. Study 2 (N = 182) showed that newly elected leaders (vs. candidates) are perceived as more legitimate, which in turn, increases the group's perceptions of the once deviant leader's prototypicality, granted that the leader is democratically elected. Results suggest that democratic elections create conditions under which once deviant leaders can gain in perceived prototypicality and create lasting changes to the group identity.

Behavioral Approaches to Study Top-Down Influences on Active Listening.

The massive network of descending corticofugal projections has been long-recognized by anatomists, but their functional contributions to sound processing and auditory-guided behaviors remain a mystery. Most efforts to characterize the auditory corticofugal system have been inductive; wherein function is inferred from a few studies employing a wide range of methods to manipulate varying limbs of the descending system in a variety of species and preparations. An alternative approach, which we focus on here, is to first establish auditory-guided behaviors that reflect the contribution of top-down influences on auditory perception. To this end, we postulate that auditory corticofugal systems may contribute to active listening behaviors in which the timing of bottom-up sound cues can be predicted from top-down signals arising from cross-modal cues, temporal integration, or self-initiated movements. Here, we describe a behavioral framework for investigating how auditory perceptual performance is enhanced when subjects can anticipate the timing of upcoming target sounds. Our first paradigm, studied both in human subjects and mice, reports species-specific differences in visually cued expectation of sound onset in a signal-in-noise detection task. A second paradigm performed in mice reveals the benefits of temporal regularity as a perceptual grouping cue when detecting repeating target tones in complex background noise. A final behavioral approach demonstrates significant improvements in frequency discrimination threshold and perceptual sensitivity when auditory targets are presented at a predictable temporal interval following motor self-initiation of the trial. Collectively, these three behavioral approaches identify paradigms to study top-down influences on sound perception that are amenable to head-fixed preparations in genetically tractable animals, where it is possible to monitor and manipulate particular nodes of the descending auditory pathway with unparalleled precision.