The computational brain: Patricia S. Churchland and Terrence J. Sejnowski (MIT Press, Cambridge, MA, 1992); xi, 544 pages, $39.95

In 1912, Max Wertheimer published his paper on phi motion, widely recognized as the start of Gestalt psychology. Because of its continued relevance in modern psychology, this centennial anniversary is an excellent opportunity to take stock of what Gestalt psychology has offered and how it has changed since its inception. We first introduce the key findings and ideas in the Berlin school of Gestalt psychology, and then briefly sketch its development, rise, and fall. Next, we discuss its empirical and conceptual problems, and indicate how they are addressed in contemporary research on perceptual grouping and figure–ground organization. In particular, we review the principles of grouping, both classical (e.g., proximity, similarity, common fate, good continuation, closure, symmetry, parallelism) and new (e.g., synchrony, common region, element and uniform connectedness), and their role in contour integration and completion. We then review classic and new image-based principles of figure–ground organization, how it is influenced by past experience and attention, and how it relates to shape and depth perception. After an integrated review of the neural mechanisms involved in contour grouping, border ownership, and figure–ground perception, we conclude by evaluating what modern vision science has offered compared to traditional Gestalt psychology, whether we can speak of a Gestalt revival, and where the remaining limitations and challenges lie. A better integration of this research tradition with the rest of vision science requires further progress regarding the conceptual and theoretical foundations of the Gestalt approach, which is the focus of a second review article.

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A Century of Gestalt Psychology in Visual Perception I. Perceptual Grouping and Figure-Ground Organization

It is widely agreed that the human face is processed differently from other objects. However there is a lack of consensus on what is meant by a wide array of terms used to describe this “special” face processing (e.g. holistic and configural) and the perceptually relevant information within a face (e.g. relational properties and configuration). This paper will review existing models of holistic/configural processing, discuss how they differ from one another conceptually and review the wide variety of measures used to tap into these concepts. In general we favour a model where holistic processing of a face includes some or all of the inter-relations between features and has separate coding for features. However, some aspects of the model remain unclear. We propose the use of moving faces as a way of clarifying what types of information are included in the holistic representation of a face.

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A Review and Clarification of the Terms “holistic,” “configural,” and “relational” in the Face Perception Literature

The Architecture Of Cognition

Bile duct injuries are the main serious technical complication of laparoscopic cholecystectomy. 1,2 Data are insufficient to determine precisely the frequency of bile duct injuries, but a reasonable estimate is one in 1,000 cases. 2 A decade ago, as the technique of laparoscopic cholecystectomy was first being learned by otherwise fully trained, practicing surgeons, the injury rate was noted to be greater during an individual’s first dozen cases than in subsequent ones. 2 This learning curve contribution is now much less important, for surgical residents learn the procedure under direct supervision of more experienced surgeons.

Surgeons have always analyzed their technical complications for insights that might be translated into improved performance. In the past the information available from such reviews could rarely go much beyond a tabulation of results. An understanding of the root causes of technical complications remained elusive. This report takes analysis of technical complications to greater depths, for it integrates the findings of videotapes of operations involving bile duct injuries, operative notes dictated after the operation had been completed but before an injury had become apparent, and conceptual tools of human factors research and the cognitive science of human error.

Causes and Prevention of Laparoscopic Bile Duct Injuries: Analysis of 252 Cases From a Human Factors and Cognitive Psychology Perspective

Our first review article (Wagemans et al., 2012) on the occasion of the centennial anniversary of Gestalt psychology focused on perceptual grouping and figure-ground organization. It concluded that further progress requires a reconsideration of the conceptual and theoretical foundations of the Gestalt approach, which is provided here. In particular, we review contemporary formulations of holism within an information-processing framework, allowing for operational definitions (e.g., integral dimensions, emergent features, configural superiority, global precedence, primacy of holistic/configural properties) and a refined understanding of its psychological implications (e.g., at the level of attention, perception, and decision). We also review 4 lines of theoretical progress regarding the law of Pragnanz-the brain's tendency of being attracted towards states corresponding to the simplest possible organization, given the available stimulation. The first considers the brain as a complex adaptive system and explains how self-organization solves the conundrum of trading between robustness and flexibility of perceptual states. The second specifies the economy principle in terms of optimization of neural resources, showing that elementary sensors working independently to minimize uncertainty can respond optimally at the system level. The third considers how Gestalt percepts (e.g., groups, objects) are optimal given the available stimulation, with optimality specified in Bayesian terms. Fourth, structural information theory explains how a Gestaltist visual system that focuses on internal coding efficiency yields external veridicality as a side effect. To answer the fundamental question of why things look as they do, a further synthesis of these complementary perspectives is required.

http://www.vcl.salk.edu/~gepshtein/Wagemans_etal_II_PsyhBulletin2012.pdf

A century of Gestalt psychology in visual perception: II. Conceptual and theoretical foundations.

Until recently, the transformational approach provided the only available formal analysis of visual regularities like repetition and mirror symmetry. This theoretical study presents a new analysis, based on the recently developed concept of holographic regularity. This concept applies to the intrinsic character of regularity and specifies the unique formal status of perceptually relevant regularities. The crucial point is that the two analyses imply the same structure for repetition but a different structure for mirror symmetry. Transformationally, mirror symmetry is an all-or-nothing property, whereas holographically, it is a graded property. This difference pervades the understanding of both perfect regularities and perturbed regularities. Whereas the transformational approach explains hardly any goodness phenomenon, the holographic approach explains a wide variety of goodness phenomena in a coherent way that is ecologically plausible as well.

Goodness of Visual Regularities: A Nontransformational Approach

The phenomenon of visual occlusion has frequently been studied by means of two-dimensional line drawings. These drawings may elicit various interpretations. Sometimes a mosaic of shapes is seen, sometimes a shape that partly occludes another shape. In the latter case, observers often have a clear idea about the form of the partly occluded shape. Local and global pattern aspects both seem to be decisive with respect to the preferred interpretation. An attempt is made to integrate these aspects by applying the global-minimum principle to the perceptual complexity of three distinct components of those pattern interpretations: (i) The internal structure, dealing with each of the shapes separately, (ii) the external structure, dealing with the positional relation between these shapes, and (iii) the virtual structure, dealing with the occluded parts of the shapes. The perceptual complexity of each of these three components can be expressed in terms of structural information. The hypothesis that the perceptually preferred interpretation is the one for which the total information load is minimal is tested on many patterns stemming from different studies on pattern completion.

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Integrating Global and Local Aspects of Visual Occlusion

In this paper the author traces the origins of the Martin Centre work in urban and regional studies back to the geometrical explorations of grids and buildings by Sir Leslie Martin and Lionel March. That work encouraged the author and his colleagues to look for a deeper understanding in order to forecast how people would use proposed layouts for cities, and thus evaluate them. The sources of understanding came from other disciplines such as economics, engineering, geography, and planning which, combined with the physical understanding of the buildings, towns, and networks, provided the basis for the development of comprehensive models of cities and regions. This understanding is embodied in the operational software of the MEPLAN model which is used extensively in practice. The author concludes by taking stock of what has been achieved and argues for the need to improve the knowledge of the supply aspects in the urban system and to simplify the operations of the model without losing its comprehensiveness.

Serial pattern complexity: irregularity and hierarchy.

It is widely assumed that symmetry is an important visual primitive, probably encoded without the need for attention. Julesz's (1981) definition of effortless perception, which states that any stimulus property perceived for exposure durations of 160 msec or less is detected preattentively, contributed greatly to this belief. Single pattern studies confirm that symmetry is detected within this limit. In the present study, however, Julesz's operationalization is compared with the multiple pattern visual search task, to see whether symmetry as a wholistic property is detected in parallel. The results show that symmetry detection times are highly dependent on the number of distractor patterns. The findings are similar for dot patterns, wire polygons, solid block shapes, and simple parentheses. We conclude that symmetry detection per se requires selective attention, but that some related grouping or segmentation mechanism may operate preattentively.

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Peter A. van der Helm

Papers

A century of Gestalt psychology in visual perception: II. Conceptual and theoretical foundations.

Goodness of Visual Regularities: A Nontransformational Approach

Integrating Global and Local Aspects of Visual Occlusion

Serial pattern complexity: irregularity and hierarchy.

Symmetry and selective attention: A dissociation between effortless perception and serial search