How We Think with our Eyes and See with our Brains

While it is common to understand the function of the eyes to be like a camera, and the function of the brain to be like a computer, this is an oversimplification so profound as to render it misleading and ultimately wrong. The... [ view full abstract ]

While it is common to understand the function of the eyes to be like a camera, and the function of the brain to be like a computer, this is an oversimplification so profound as to render it misleading and ultimately wrong.
The starting point of this discussion is that the retina, which is located within the eye, is actually a part of the brain. The photosensitive cells of the retina are neurons which are the same type of cell as in the brain proper. As a part of the brain they could be expected to perform some of the kinds of processing functions that are normally ascribed to the brain and, in fact they do. There are several types of cell within the retina, not all of which are photo-sensitive. These are the cells which perform processing functions within the retina itself.
The two primary types of photo-sensitive neuron within the retina, the rods and the cones, each has a discrete a different function. Similarly, the rods and the cones serve as primary data feeds to two different areas of our consciousness. The rods serve as hazard identifiers and provide a significant input via the unconscious (preconscious) mind. The cones, with their higher level of acuity and full color capability serve to give detail and greater information via our conscious mind. A third, and newly discovered type of retinal neuron, the Intrinsically Photosensitive Retinal Ganglion Cell (IPRGC) has an additional and significant role in our ability to identify hazards.
Seeing with our brains goes far beyond the functions of the retina and is, in fact, quite independent from the processing and sensing that occurs in the retina. Seeing with our brains is, in large part, a function of what we expect to see and what we know. The research done in the mid-1970’s by Professor Harry Hurt of the University of Southern California on the subject of motorcycle accidents provides the underlying data that supports this conclusion. Dr. Hurt’s research showed that if people were looking for automobiles they would not see motorcycles and consequently pull directly into the path of an oncoming motorcycle.