Sam Kean’s new book, The Tale of the Dueling Neurosurgeons: The History of the Human Brain As Revealed by True Stories of Trauma, Madness, and Recovery, is a gold mine of stories about the weird things that our brains can make us do, everything from cortical blindness to alien hand and walking dead syndromes. In people with cortical blindness, the eyes and optic nerves work fine, but the portion of the brain that consciously interprets vision is impaired. The brain has a whole separate set of nerves that process the emotional response to vision, however; people with cortical blindness can therefore smile in response to another person’s smile even though they cannot consciously see it. In alien hand syndrome, a person cannot recognize their own hand—usually the left one—as being part of his or her own body; and in walking dead syndrome, the person cannot recognize the body itself as his or her own.
Perhaps most important, although not the most interesting story in the book, was the experiment that demonstrated that our brain’s conscious decision to do something occurred after the subjects had begun to do the action. That is, the brain’s decision was actually a post-hoc rationalization. This calls into question the entire concept of free will. It appears that we choose to do something only after our subconscious minds have decided to do that thing. Of course, this does not mean we have no conscious control over ourselves. Our conscious minds can prevent us from doing the things we have started to do; that is, however much free will is called into question, self-control is certainly real. As the author says, we may not have free will, but we have free won’t. Also, our conscious minds can create a general pattern of thought that, while it may not control every individual action, certainly influences our general behavior.
The main point of all these fascinating stories is, in the author’s own words: “But if the history of neuroscience proves anything, it’s that any circuit for any mental attribute—up to and including our sense of being alive—can fail, if just the right spots [of the brain] suffer damage…your actions, your desires to act, and your conviction of having acted can all be decoupled and manipulated.”
I have, through reading this book, come to understand myself better. Temporal lobe epilepsy includes the experience of auras that are religious in their effects and intensity—religious delusions. While religion does not consist only of delusion, it has been stimulated by delusion. Famous religious figures, such as the Apostle Paul, Mohammed, and Joan of Arc, and writers such as Dostoevsky to whom religion was of overwhelming importance, showed symptoms of epilepsy. Though I do not have epilepsy, I have some symptoms that suggest my right temporal lobe might be hyperactive in something of the same way as certain epileptics. For example, throughout my life I have had experiences of religious ecstasy. I also have to take an anticonvulsant medication that is prescribed, in higher dosage, to epileptics. And I have a mild case of polygraphia—the compulsion to write everything down, all day every day—that some epileptics also have. Finally, there might be a genetic basis for this; my paternal grandfather was religiously crazy. Somehow just knowing this makes me feel more comfortable inside my skin.
Kean’s book, like the books of Mary Roach, show that the best modern science writing is based on stories and are written to be fun. Filled with fragments and imprecise language, this book would make some science editors howl, but is exactly the kind of book that would make anyone want to learn more about science. This is the kind of science book that I have not yet written myself.