Oliver Sacks is no stranger to regular readers of The New Yorker, and over the years, I have eagerly devoured each new account of strange and bizarre human behavior. In his most recent book, The Mind’s Eye, Sacks focuses on afflictions and conditions related to sight and communication, but particularly those that arise from injury or atrophy of parts of the brain. It is a compendium of case histories laced with references to scientific studies, all filtered through Sacks’ engaging and endearing personal observations.
The overall theme is visual imagery or what is it that one sees in the mind. If you are blind from birth or become blind, what kind of images, or not, do you have in your mind’s eye? How does the age of blindness affect this and is it the same for everyone? Not so from these case histories. And how is it that one may lose the ability to read (Lilian Kallir), but still be able to identify letters and to write?
If one loses the ability to speak (aphasia), does that mean one also loses all ability to communicate? Pat, with a severe case of aphasia, eventually developed a rich lexicon of gestures that enable her to make her wishes known and to have some semblance of a social life within the confines of the hospital.
Sacks posits the question why, since writing came late in human evolution, “all human beings have this built-in facility for reading.” For Alfred Russel Wallace, this potential for something that wasn’t immediately useful must have been implanted by God. “Darwin, understandably, was horrified by this idea and wrote to Wallace, ‘I hope you have not murdered too completely your own and my child.’” Darwin’s view was much more flexible and took into account that biological structures might find different uses from those they had evolved from.
There is a growing understanding of the plasticity of the human brain: evidence that certain functions associated with seeing and language can be pinpointed to particular regions of the brain and a recognition that the brain can adapt and some areas can take on new tasks to make up for deficiencies in another area. But at least one task, face recognition, seems to be an exception and persists throughout one’s life.
The inability to recognize faces, face blindness or prosopagnosia, is usually congenital, runs in families, and is an unsettling handicap. It was not conclusively identified until the mid- 20th century. Sacks himself suffers from this and from an inability to recognize and remember places. If he met you this morning, he would probably not know you this afternoon so you would need to re-introduce yourself.
Upon reading this, I have been pondering my own capacity for visual imagery. I am an avid reader, a word person, so to what extent do I see images in my mind’s eye? What characteristics of color or imagery do my dreams have? The Mind’s Eye is a worthwhile exploration of some of the human brain’s amazing capabilities.