Plato's Cave: The Gestalt View

The Gestalt View of Vision

The Gestalt Objection

The Gestalt movement in psychology emerged as a reaction to the "reductionist" view of perception which held that perception can be decomposed into elemental components, which can then be considered individually. This reductionist approach is still the prevailing view in [the conventional approach to visual processing.] The Gestaltists produced a large number of examples of perceptual phenomena which cannot be explained by the reductionist view. Nevertheless, computational models of vision continue to reflect reductionist architectures even though these architectures cannot address the Gestalt objection, and hold no promise in principle of ever addressing the Gestalt issues.

The Gestalt Laws

The Gestalt psychologists cataloged a number of laws of perceptual grouping which provide evidence for the nature of low-level visual processing, as well as a clue to the nature of the visual representation.

While it is possible in theory to implement these Gestalt laws using a reductionist architecture, in practice this can only be achieved in highly simplified examples, and tends to lead to a combinatorial explosion in the required computation. The Gestalt grouping laws suggest a totally different paradigm of computation from those proposed in the conventional view.

The Gestalt Models

In an attempt to explain the Gestalt laws of grouping, Gestalt theorists proposed models of perception involving analog field-like forces whereby the final global percept emerged by a parallel relaxation of multiple local forces in the manner of a soap bubble, whose spherical shape is not defined by a stored template or blueprint of the final shape, but rather it emerges naturally as a consequence of the multiple local forces in the skin of the bubble.

While the Gestalt insight about the mechanism of perception was right on target, Gestalt modelers were never able to define a system that made quantifiable predictions of the apperence of the final percept given any arbitrary input. It is for this reason that the Gestalt view of perception has fallen by the wayside of the mainstream of thinking in vision research.

The fundamental questions raised by the Gestalt movement have remained unanswered for so long that they are being forgotten, or considered irrelevent to the modern view of vision. Nevertheless the Gestalt challenge to the reductionist view remains as valid as it ever was.

Any model of vision which does not address the Gestalt issues is worse than a non-solution; it is a diversion from the real questions of visual perception.

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