Gibson's Rejection of the Retinal Image 2

If the retinal image is not transmitted to the brain as a whole, the only alternative has seemed to be that it is transmitted to the brain element by element, that is, by signals in the fibers of the optic nerve. There would then be an element-to-element correspondence between image and brain analogous to the point-to-point correspondence between object and image. This seems to avoid the fallacy of the little man in the brain who looks at an image, but it entails all the difficulties of what I have called the sensation-based theories of perception. The correspondence between the spots of light on the retina and the spots of sensation in the brain can only be a correspondence of intensity to brightness and of wavelength to color. If so, the brain is faced with the tremendous task of constructing a phenomenal environment out of spots differing in brightness and color. If these are what is seen directly, what is given for perception, if these are the data of sense, then the fact of perception is almost miraculous. (Gibson, 1979, p. 60-1).

From Kandel, Schwarz, & Jessell, 2000.

But, neuroscientists have found many retinotopic maps.  Dozens, right?  So, far from this consequence being an embarrassment, it has been amply confirmed.

"There would then be an element-to-element correspondence between image and brain analogous to the point-to-point correspondence between object and image,"

So, what's the problem?

The correspondence between the spots of light on the retina and the spots of sensation in the brain can only be a correspondence of intensity to brightness and of wavelength to color.

"can only be"?  No, simply wrong.  That's the beauty of non-demonstrative inference.  You can begin with data on intensity and wavelength and up with lots of new things.  So, you might begin with intensity and wavelength and get oriented line detectors, motion sensitive detectors, face sensitive cells, and cells (such as mirror neurons) that are sensitive to grasping.  (In fairness to Gibson, most of the relevant single cell work was just getting up steam near the end of Gibson's career.  Hubel and Wiesel started in the early 1960's, right?  Most, I guess, has been done since 1979.)

If so, the brain is faced with the tremendous task of constructing a phenomenal environment out of spots differing in brightness and color.

Absolutely.  So?

If these are what is seen directly, what is given for perception, if these are the data of sense, then the fact of perception is almost miraculous.

While the sense datum theorists, among others, might have held that what is directly seen are spots of brightness and color, cognitivists typically do not.  But, the fact of perception does seem almost miraculous, if there is no computation in the brain.