Structural salience and the nonaccidentality of a gestalt.

The processes of perceptual organization and social categorization share the goal of simplifying and structuring the world, though they have traditionally been studied within separate branches of psychology. Drawing on embodied cognition, this perspective suggests that both processes stem from bodily experiences. Early sensorimotor experiences, such as being held in proximity or rocked in synchrony, may have shaped the principles of perceptual organization and provide the foundations for social categorization. To integrate these domains, a triadic embodied model is proposed, linking bodily experience, perceptual organization, and social categorization as dynamically interacting vertices. The model allows bidirectional influences, whereby each element can prime and reinforce the others, and may also involve activation of metaphorical concepts. It further explains how cultural context can bias these interconnections. The model situates social categorization along a continuum of representational depth, from shallow symbolic tagging to deep embodied simulation. While prior work has demonstrated dyadic links between bodily experience, perceptual organization, and social categorization, the present article explicitly integrates these domains in a unified model, offering new directions for understanding how people structure their physical and social world.

A principal challenge for both human and machine vision systems is to integrate and organize the diversity of cues received from the environment into the coherent global representations required to make good decisions and take effective actions. This conference brings together an interdisciplinary roster of leading researchers in both biological and computer vision to report and discuss the latest research on this process of perceptual organization.

In the previous chapter, I specified perceptual organization as an autonomous process that enables us to perceive scenes as structured wholes consisting of objects arranged in space. Because any scene can be interpreted in numerous ways, it is amazing not only that the visual system usually has a clear preference for only one interpretation, but also that this interpretation usually is sufficiently veridical to guide us through the world. Indeed, it is true that visual illusions show that what we see is not always what we look at, but a fair degree of veridicality seems necessary — otherwise, our visual system would probably not have survived during evolution. In this chapter, expanding on van der Helm (2000), I assess what degree of veridicality vision might achieve by aiming at simplicity. To this end, I elaborate on three related issues, which I next introduce briefly. S implicity versus likelihood . The main issue is whether the perceptual organization process is guided by the likelihood principle (von Helmholtz, 1909/1962) or by the simplicity principle (Hochberg & McAlister, 1953). Both principles take this process as a form of unconscious inference yielding interpretations which persons subjectively believe are most likely to be true. The question, however, is what drives this unconscious inference, and as I indicate next, the two principles differ fundamentally in this respect. The likelihood principle, on the one hand, aims explicitly at a high degree of veridicality in the external world.

Part I : Perceptual Organization and Classification Processes

Perceptual organization concerns the organization of people’s perception into meaningful, structured entities—often wholes containing parts, with specific interrelationships among the parts as well as specific relationships between the parts and the wholes. It embraces a wide variety of distinct processes, which often occur together in everyday life and lead to interesting perceptual experiences by their interactions. The best-known perceptual organization processes are perceptual grouping and figure-ground organization, which appear to be determined by characteristic principles or laws, such as grouping by proximity, similarity, good continuation, area, convexity, symmetry, and so forth. Other important phenomena of perceptual organization include perceptual multi-stability (i.e., the fact that the same stimulus can give rise to multiple competing percepts that switch over time), visual illusions, the role of reference frames, and the role of context. Gestalt psychology has contributed deep insights into the way people’s perception of the world is organized, although it has also been criticized for its emphasis on subjective experiences and its sometimes vague and non-quantitative descriptions of the Gestalt principles. Because perceptual organization essentially concerns visual awareness, however, phenomenology is needed to describe what is experienced. This ultimately remains the basis for research on perceptual organization even when it is aimed at quantifying the principles of perceptual organization and identifying the neural correlates or mechanisms underlying perceptual organization.

Perceptual organization represents an intermediate level of visual processing, subordinate to higher-order processes such as object recognition. Previous studies of perceptual organization in aging are inconclusive, varying in the cognitive capacities measured and the nature of the stimulus. To determine characteristics of perceptual organization in aging, young and elderly participants discriminated patterns organized by basic visual components: line-orientation, color, flicker, or motion. Psychophysical measurements determined organization thresholds and processing times. Age-related impairment occurred with line-orientation and flicker, but not color and motion. These results indicate that perceptual organization capacities in aging depend on the stimulus feature upon which organization is based.

Every object acquires its shape from some kind of generative process, such as manufacture, biological growth, or self-organization, in response to external forces. Inferring such generative processes from an observed shape is computationally challenging because a given process can lead to radically different shapes, and similar shapes can result from different generative processes. Here, we suggest that in some cases, generative processes endow objects with distinctive statistical features that observers can use to classify objects according to what has been done to them. We found that from the very first trials in an eight-alternative forced-choice classification task, observers were extremely good at classifying unfamiliar objects by the transformations that had shaped them. Further experiments show that the shape features underlying this ability are distinct from Euclidean shape similarity and that observers can separate and voluntarily respond to both aspects of objects. Our findings suggest that perceptual organization processes allow us to identify salient statistical shape features that are diagnostic of generative processes. By so doing, we can classify objects we have never seen before according to the processes that shaped them.

In our complex acoustic environment, we are confronted with a mixture of sounds produced by several simultaneous sources. However, we rarely perceive these sounds as incomprehensible noise. Our brain uses perceptual organization processes to independently follow the emission of each sound source over time. If the acoustic properties exploited in these processes are well-established, the neurophysiological mechanisms involved in auditory scene analysis remain unclear and have recently raised more interest. Here, we review the studies investigating these mechanisms using electrophysiological recordings from the cochlear nucleus to the auditory cortex, in animals and humans. Their findings reveal that basic mechanisms such as frequency selectivity, forward suppression and multi-second habituation shape the automatic brain responses to sounds in a way that can account for several important characteristics of perceptual organization of both simultaneous and successive sounds. One challenging question remains unresolved: how are the resulting activity patterns integrated to yield the corresponding conscious percepts?

Curvature effect on stabilization of cellular detonations in channel, circular arc and spherical shell geometries

How do we perceptually and cognitively organize incoming stimulation? A century ago, Gestalt psychologists posited the law of Prägnanz: psychological organization will always be as 'good' as possible given the prevailing conditions. To make the Prägnanz law a useful statement, it needs to be specified further (a) what a 'good' psychological organization entails, (b) how the Prägnanz tendency can be realized, and (c) which conditions need to be taken into account. Although the Gestalt school did provide answers to these questions, modern-day mentions of Prägnanz or good Gestalt often lack these clarifications. The concept of Prägnanz has been (mis)understood in many different ways, and by looking back on the rich history of the concept, we will attempt to present a more fine-grained view and promote a renewed understanding of the central role of Prägnanz in visual perception and beyond. We review Gestalt psychology's answers to the questions listed above, and also discuss the four main uses of the Prägnanz concept in more detail: (a) a Prägnanz tendency in each organizational process, (b) Prägnanz as a property of a Gestalt, (c) Prägnanz steps as internal reference points, and (d) Prägnanz in relation to aesthetic appreciation. As a key takeaway, Prägnanz is a multifaceted Gestalt psychological concept indicating the "goodness" of an experienced organization. Both the removal of unnecessary details and the emphasis on characteristic features of the overall organization compared to a reference organization can contribute to the emergence of a 'better' Gestalt. The stimulus constellation is not the only factor in determining the goodness of an organization, also the stimulus' interaction with an individual in a specific spatial and temporal context plays a role. Taking the ideas on Prägnanz as a generative framework and keeping the original Gestalt psychological context in mind, future research on perceptual organization can improve our understanding of the principles underlying psychological organization by further specifying how different organizational principles interact in concrete situations. Public significance statement: This paper reviews what a 'good' psychological organization entails, and how the incoming stimulation is clarified in human perception to achieve the best possible psychological organization. The review debunks common misconceptions on the meaning of "goodness" and synthesizes the most important perspectives and developments on "goodness" from its conception until now.

Little is known about how people comprehend mathematical expressions. In the present study we investigate the internal representations used by experienced users of mathematics to encode algebraic expressions. Initially, a memory recognition task was conducted that examined the role of mathematical syntax in the encoding of algebraic expressions. The results indicate that participants could more readily identify those parts of a previously seen expression that were syntactically well formed than those that were not well formed, suggesting that syntax plays an important role. To determine the level of syntactic structure involved, a second recognition task was conducted. The results indicate that algebraic expressions are encoded into components that represent the phrasal constituents of the expression. However, the results of these experiments did not rule out the possibility that the visual processes of perceptual organization were used to encode the expressions, or that the data were a consequence of a mathematical "lexicon" of common mathematical "phrases". Three further experiments were conducted to examine this, the results of which indicate that the encoding of algebraic expressions is based primarily on processes that occur beyond the level of visual or "lexical" processing. This is consistent with our finding that syntactic structure plays a key role.

Three lower level layers of the hierarchical machine perception system are described, and experimental results are provided. The system is based on agile camera and aimed at automatic recognition of simple geometric scenes, made of crafted manipulation objects. The primary process of grouping the edgelets on the image is described. Two methods of edgelet grouping are compared, namely a Hough transform based method and a method based on LSR. Some modifications to both methods have been proposed. Next, a process of perceptual grouping of elementary features, short segments, is described. Three approaches to feature fusion are addressed: one based on crisp, geometrical, heuristic conditions, the second based on fuzzified conditions and the third one based on Dempster-Shafer theory. The results obtained with the three methods are compared and presented on the example image of a real scene. Higher layer issues, namely a problem of contour closing and of separating particular objects (in the case of occlusions) are briefly discussed. Some preliminary results in that area are reported.

After an initial stage of local analysis within the retina and early visual pathways, the human visual system creates a structured representation of the visual scene by co-selecting image elements that are part of behaviorally relevant objects. The mechanisms underlying this perceptual organization process are only partially understood. We here investigate the time-course of perceptual grouping of two-dimensional image-regions by measuring the reaction times of human participants and report that it is associated with the gradual spread of object-based attention. Attention spreads fastest over large and homogeneous areas and is slowed down at locations that require small-scale processing. We find that the time-course of the object-based selection process is well explained by a 'growth-cone' model, which selects surface elements in an incremental, scale-dependent manner. We discuss how the visual cortical hierarchy can implement this scale-dependent spread of object-based attention, leveraging the different receptive field sizes in distinct cortical areas.

Visual perception of complex shape-transforming processes

The crowding effect refers to stronger deficits in linear acuity (e.g., letters in a line) than in single letter acuity in amblyopia. The current work investigated whether the salience of a global structure in which the target for identification is embedded influences the crowding effect in amblyopia. Compound shapes were presented to the amblyopic and fellow eyes respectively of 12 anisometropic amblyopes. The compound stimuli were presented on either a blank or a cross background so that the salience of global structures were manipulated. Reaction times (RTs) and response error rates were recorded when subjects identified global or local shapes, respectively. RTs were shorter to global than local shapes for both the amblyopic and the fellow eyes. The global RT advantage was larger for the amblyopic than the fellow eye. Interestingly, when viewing the stimuli with the amblyopic eye, subjects made more errors to local targets when the compound stimuli were presented against the blank than the cross background. The results suggest that the salience of global structures of visual stimuli contributes to the crowding effect in amblyopia.