I think the first 90 pages of this short book could have been omitted, or at least some guidance provided for short cutting sections. The first 90 pages are not very original except I did appreciate the story of H.D. who had had non functional eyes since the age of three. When cataracts were removed she did not experience what she had hoped. Humphrey supposes that her experience was more like blindsight. I wonder if her new sight would be functional if her livelihood depended on it.
I have one quibble with Humphrey’s story of Helen, the monkey, whose visual cortex had been removed. I thought that Visual area V3 of the cortex specialized in edge detection. Was Helen’s V3 intact? Surely edge detection is necessary in early stages of the evolution of sight. Indeed edge detection may be much more important to the unconscious blindsight than to the conscious qualia. If Helen’s visual cortex was gone, including V3, how do the older blindsight functions serve their ends? Ramachandran’s ideas on blindsight in “A Brief Tour of Human Consciousness” suffers from the same problem. I think a functional diagram is needed.
There are some ideas past page 90 that are new to me. I think Humphrey has a good hypothesis. The evolutionary perspective is very fruitful here. I would place visual qualia as a new brain addition that allows us to reason about what we see rather than merely react reflexively to it. Ultimately it allows us to describe what we see to others and this is obviously adaptive.
We are told that the frog’s eye does not report pixels to its brain. I think it is good that our eyes do.