Gibson's Rejection of the Retinal Image 1

But this success makes it tempting to believe that the image on the retina falls on a kind of screen and is itself something intended to be looked at, that is, a picture. It leads to one of the most seductive fallacies in the history of psychology-that the retinal image is something to be seen. I call this the "little man in the brain" theory of the retinal image (Gibson, 1966b, p. 226), which conceives the eye as a camera at the end of a nerve cable that transmits the image to the brain. Then there has to be a little man, a homunculus, seated in the brain who looks at this physiological image. The little man would have to have an eye to see it with, of course, a little eye with a little retinal image connected to a little brain, and so we have explained nothing by this theory. We are in fact worse off than before, since we are confronted with the paradox of an infinite series of little men, each within the other and each looking at the brain of the next bigger man. (Gibson, 1979, p. 60).

Now, no one likes the little homunculus for psychological theorizing (even if they are ok for the Men in Black).  But the homunculus hypothesis can be avoided consonant with accepting retinal image processing.  Let an image be a set of (oversimplifying) luminance values.  This can be processed by something other than a homunculus.  It might be processed by a computer.  Bitmap images can be manipulated by computers without supposing that there must be a little CPU inside the CPU.  That was one of the virtues of the computational theory of mind: It shows how one can avoid having to invoke a homunculus to do image processing.  So, Gibson seems to be mistaken in thinking that a retinal image leads to (in the sense of requires, at least) a homunculus.