GESTALT PSYCHOLOGY AND

Transcription

1 GESTALT PSYCHOLOGY AND CONTEMPORARY VISION SCIENCE: PROBLEMS, CHALLENGES, PROSPECTS JOHAN WAGEMANS LABORATORY OF EXPERIMENTAL PSYCHOLOGY UNIVERSITY OF LEUVEN, BELGIUM GTA 2013, KARLSRUHE

2 A century of Gestalt psychology in visual perception 2 extensive reviews published last year Wagemans, J., Elder, J. H., Kubovy, M., Palmer, S. E., Peterson, M. A., Singh, M., & von der Heydt, R. (2012). A century of Gestalt psychology in visual perception: I. Perceptual grouping and figure-ground organization. Psychological Bulletin, 138(6), doi: /a (46 pages) Wagemans, J., Feldman, J., Gepshtein, S., Kimchi, R., Pomerantz, J. R., van der Helm, P., & van Leeuwen, C. (2012). A century of Gestalt psychology in visual perception: II. Conceptual and theoretical foundations. Psychological Bulletin, 138(6), doi: /a (35 pages)

3 Paper I

4 Paper I: Contents Historical part key findings and ideas in the Berlin school of Gestalt psychology development, rise, and fall empirical and conceptual problems Perceptual grouping classical principles (e.g., proximity, similarity, common fate, good continuation, closure, symmetry, parallelism) new principles (e.g., synchrony, common region, element and uniform connectedness) their role in contour integration and completion Figure-ground organization classic and new image-based principles influences of past experience and attention relations to shape and depth perception Neural mechanisms involved in contour grouping, border-ownership, and figure-ground perception

5 Paper I: Conclusions what modern vision science has offered compared to traditional Gestalt psychology a Gestalt revival remaining limitations and challenges general conclusion: 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

6 Paper II

7 Paper II: Contents contemporary formulations of holism within an information-processing framework operational definitions (e.g., integral dimensions, emergent features, configural superiority, global precedence, primacy of holistic/configural properties) refined understanding of its psychological implications (e.g., at the level of attention, perception, and decision) four lines of theoretical progress regarding the law of Prägnanz the brain s tendency of being attracted towards states corresponding to the simplest possible organization, given the available stimulation

8 Aim of this talk Evaluative analysis of 100 years of Gestalt psychology in relation to vision science problems challenges prospects Some conclusions

9 Problems Gestalt theory was criticized for formulating new laws for every factor that influenced perceptual organization, and with little precision. To avoid a proliferation of laws, Prägnanz was proposed as the fundamental law encompassing all the others but its formulation was left intentionally vague: psychological organization will always be as good as the prevailing conditions allow (Koffka, 1935, p. 110) [o]ne recognizes a resultant good Gestalt simply by its own inner necessity (Wertheimer, 1923/1938, p. 83).

10 Problems Inspiration was sought in physical phenomena that appeared to show similar global effects, in order to formulate field models of electric currents in the brain, which were supposed to be structurally and functionally isomorphic to the experienced Gestalts (Köhler, 1920). Köhler s electrical field theory was proven wrong by Lashley s and Sperry s experiments and the underlying notion of psychophysical isomorphism not productive. No alternatives were found to replace the physical but nonmechanistic foundations of Gestalt theory. With no testable quantitative models and no plausible neural underpinning, the Gestalt principles remained mere descriptions of interesting perceptual phenomena.

11 Problems Claims about Gestalt principles being preattentive, innate, and independent of experience appeared exaggerated: principles of grouping seem to operate at multiple levels and figure-ground segregation can also be affected by attention infants are already capable of grouping according to at least some grouping principles, but developmental trends regarding other grouping principles indicate that visual experience does play a role as well recent studies with adult observers showed that past experience can exert an influence on several aspects of figure-ground perception

12 Challenges Several Gestalt notions do not fit well with the rest of what we know about vision. Modern vision science appears to be incommensurate with the fundamental formula of Gestalt theory (Wertheimer, 1924/1938, p. 2) There are wholes, the behavior of which is not determined by that of their individual elements, but where the part-processes are themselves determined by the intrinsic nature of the whole. How can we understand the relationships between parts and wholes in light of the visual cortical hierarchy and dynamics?

13 Challenges The convergence between psychophysical results and natural image statistics seems to indicate that the visual system is tuned to the properties of its environment. How can internal laws based on a general minimum principle yield veridicality in the external world (or the behavioral suitability or survival value of vision)? Establishing an integration of Gestalt theory within modern vision science provides serious challenges.

14 Prospects 4 building blocks of a synthesis: 1. the brain as a complex adaptive system: explains how self-organization solves the trade-off between robustness and flexibility of perceptual states 2. the economy principle in terms of optimization of neural resources: shows that elementary sensors working independently to minimize uncertainty can respond optimally at the system level 3. Gestalt percepts (e.g., groups, objects) are optimal given the available stimulation, with optimality specified in Bayesian terms 4. Structural Information Theory: explains how a Gestaltist visual system that focuses on internal coding efficiency yields external veridicality as a side-effect

15 Conclusions Gestalt theory is still relevant to current psychology/vision science in several ways: proper emphasis on the emergence of structure in perceptual experience and the subjective nature of phenomenal awareness continuing challenge to some of the fundamental assumptions of mainstream vision science and cognitive neuroscience progress has been tremendous compared to the situation of 100 years ago

16 Conclusions building on a research tradition of more than a century, we can now reconsider some of the old puzzles at a much more advanced scientific level the challenge remains to better integrate this research tradition with the rest of vision science building blocks of a possible synthesis are available general conclusion: to answer the fundamental question of why things look as they do, a further synthesis of these complementary perspectives is required

17 THANK YOU