ABSTRACT
Vision is often described as a sensory system that provides us with information about three-dimensional objects, based on their two-dimensional retinal projection. Presumably it has been evolutionarily advantageous to have this kind of a sensory system that functions without an active encounter with seen things. Unlike touch, for example, vision does not place us in too close proximity with predators or other threats, but provides us with information about things of various sizes, colors, and shapes even at great distance. Vision appears to succeed in its task with an apparent ease, but accomplishing the task requires a number of resources and a great deal of complex processing. Indeed it is estimated that from one-third to a half of the cortex is employed in processing visual information. Emphasizing the importance of vision, which is possibly our most important sensory system, a major part of neuroscientic research has focused on discovering the processing that occurs in these areas. Fortunately it can be said that the interdisciplinary eld of vision science has been one of the most successful branches of cognitive science, with the result that a great deal of the anatomical and organizational basis of this processing is nowadays relatively well known. A very short introduction to this empirical knowledge of vision is given in the rst section. This research has been guided by various theoretical approaches to vision. These and the challenges facing the predominant theory of vision are then described in the following two sections. The last section deals with the issues related to unconscious and conscious vision.
