Visual Perception of Surfaces: A Biological Theory

Abstract

There is a wealth of anatomical and psychological evidence which suggests that when you look at an object in the visual field, its various attributes such as color, motion, depth, and “form” are extracted by separate channels in the visual system. If so, how are these different attributes put back together again to create a unified picture of the object? And, in the case of a rapidly moving object, how is such perfect synchrony maintained between different features on its surface if it is indeed true that they are being extracted separately? In this essay, I shall suggest that this synchrony arises from a mechanism that I call capture. The visual system seems to extract certain conspicuous image features (such as occlusion boundaries), and the signal derived from these is then blindly attributed to features throughout the surface of the object. This implies that visual perception (especially in the periphery) is highly sketchy and impressionistic and that much of the richness and clarity that we experience is really an illusion.

I doubt if we can ever guess what Natural Selection has achieved, without some help from the way function has been embodied in actual structures. The reason is simple. Natural Selection is more ingenious than we are.

—F. H. C. Crick, 1985