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Problem statement: The “eye-brain” complex, which contributes maximally to visual perception, is no doubt a very interesting object for complexity study. In this review we shall try to present some of its aspects in perceiving brightness. It is a well-known fact that the perceived brightness of any surface depends on the brightness of the surfaces that surround it, a phenomenon termed as brightness induction. Several studies reveal that brightness contrast and brightness assimilation are two opposite phenomena in brightness induction. The former can be explained through the microscopic neural circuits that emanate from the retinal ganglion cells and converge on to primary visual cortex i.e. through a bottom-up approach, something which however fails till date to account for the later. In search of a unified theory of brightness induction, a top-down approach has often been suggested. However, the mechanism of brightness induction evident in several optical illusions, is not yet understood even after 200 years of intense research that saw George Berkeley, Maxwell, Helmholtz and the modern Gestalt school, that include both the intrinsic image theorists as well as the anchoring model theorists, following the “top-down” approach on one hand and Weber, Fechner, Mach, succeeded by the modern contrast theorists following the “bottom-up” approach on the other. Approach: In this review, we presented a historical perspective of the evolution of human concepts about the perception of brightness. We tried to capture the two essential philosophical trends among the scientists in understanding the phenomenon of brightness induction. The problems with idealist approach as well as the limitations of the mechanical materialist approach, have been pointed out in the light of the facts that, nature in general and complex systems in particular, are intrinsically dialectic in nature. Results: A proposal had been put forward that the path of dialectical materialism is the possible way out for the present philosophical crisis. Conclusion: Lateral inhibition based contrast theories need to be substantiated not only by the basic law of dialectics on which it rests upon viz., the unity of opposites, but also through the incorporation of the other dialectical laws like connectivity, quantity-quality transition and negation of the negation, so as to challenge all sorts of mysticisms in vision science and in brightness perception domain. Some recent researches both in experimental psychophysics as well as in mathematical modeling, that have been discussed or referred to in this review, are showing signs of such a development. In order to ensure that such synthesis should be dialectic and not eclectic, it would require identifying the proper mathematics towards quantitatively representing complex phenomena, a mathematics that can quantify the interaction between the part and the whole, through dialectical rules. |
