In Chapter 1 we claimed that the contribution of new techniques or methodologies to perceptual research and theory was very considerable. It is hoped that readers will now agree with this claim, after having read about the wide range of techniques reviewed in this volume. Laser scans of the environment, habituation techniques with infants, virtual reality rooms, analyses of optical flow, the creation of pi numbers, fMRI scans, connectionist modelling, spatial frequency analysis, image processing by Gaussian and Gabor filters - each of these has contributed importantly to the work described in the relevant chapters.
Six very different approaches to theorizing in perception have been discussed. At this point a brief evaluative summary will be given of each approach. This will be followed by a general discussion of the problems facing theorists in the general area of visual perception.
The Gestalt theory (Chapter 2) was based upon the numerous discoveries made by proponents of this approach. The Gestalt theorists believed strongly in the dynamic nature of perceiving and the tendency for perception to tend towards coherent, meaningful and simple solutions. The Gestalt demonstrations of the emergent properties of stimulus interactions present an important challenge to all future theories of visual perception. The decision of the Gestalt theorists to concentrate upon strong, reliable effects may provide a lesson for others who wish to make discoveries about perceptual systems. Finally, the emphasis upon phenomenological aspects of perception, which was such an important part of the Gestalt approach, is something that continues to stimulate debate among contemporary theorists: what is it that theories of perception are trying to explain?
The weaknesses of the Gestalt movement lie mainly in the naive approach to theory and explanation. As was shown in Chapter 2, the Gestalt theorists sometimes fell into the trap of mistaking description for explanation. Gestalt theory was, for the most part, not predictive. And when the Gestalt theorists attempted some sort of explanation of the effects they had discovered, they