ABSTRACT
Vision is often described as a sensory system that provides with information about three-dimensional objects, based on their two-dimensional retinal projection. 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. The main objective of the psychological theories of vision is to explain how we achieve knowledge of the seen objects, based on the light they reflect or emit. These theories should be distinguished from the philosophical theories and questions of vision. Psychological theories of vision should also be separated from neurophysiological theories, which are more engaged in how vision is implemented on the neuronal level and often focus on more detailed questions.
