I’m reading Annaka Harris‘s recent book Conscious: A Brief Guide to the Fundamental Mystery of the Mind, which is a short but very readable and absorbing account of recent work on consciousness, both empirical and philosophical. Although she seems to have a weakness for panpsychism, I’m not yet through with that bit and so will report on it later. (I may post a bit later today on a new Goff piece on panpsychism.)
What I wanted to mention now are two experiments described by Harris that were conducted on “split brain” patients: those unfortunates who, afflicted with terrible epilepsy, undergo a surgical “splitting” of most of the brain (the division of the corpus callosum that connects the brain’s hemispheres). This is done to prevent electrical “storms” that produce epilepsy from spreading throughout the brain. In such operations, depending on what the surgeons do, there may remain some possibility that the brain’s hemispheres could communicate with each other through subcortical structures, but they don’t communicate in some obvious ways (see below). This radical surgery does seem to work pretty well.
The interesting bit to me is how this division of the brain seems to divide consciousness or awareness as well as volition. This is based on some stuff we already knew: for example, that visual information from the left eye goes to the right side of the brain and vice versa, and also that the language center resides on the left side of the brain.
So here’s one experiment about consciousness. You present the word “key” to the subject’s left eye only. That visual information goes to the right side of the split brain. When you ask the subject what word she saw, she says “I saw nothing”, because the ability to formulate language is on the other side of the brain, the left side. This apparently means that the consciousness of having seen the word has been split.
But when the subject is asked to reach through a hole with her left arm (controlled by the right brain) and feel a number of objects, and asked to then pick the object that she’s seen on the screen, she will correctly pick up the key. This seems to mean that the consciousness of having seen the word “key” and picking it out is physically separated from the consciousness of knowing what a key is and identifying it. What’s weirder is when you ask the subject what happened when she picked out the key, she sometimes reports that her right hand acted on its own, without any conscious will to pick up a key. The notion of volition has disappeared from the the left side of the brain.
Well, you can argue about what this means, but this next experiment is even weirder. I’ll just reproduce Annaka’s description. (Matthew Cobb has a description of some of these experiments in his upcoming book on the history of brain research, but I don’t have the book at hand.)
The split-brain literature contains many examples suggesting that two conscious points of view can reside in a single brain. Most of them also topple the typical notion of free will, by exposing a phenomenon generated by the left hemisphere that [Michael] Gazzanaga and his colleague Joseph LeDoux dubbed “the interpreter.” This phenomenon occurs when the right hemisphere takes action based on information it has access to that the left hemisphere doesn’t, and the left hemisphere then gives an instantaneous and false explanation of the split-brain subject’s behavior. For example, when the right hemisphere is given the instruction, “Take a walk” in an experiment, the subject will stand up and begin walking. But when asked why he’s leaving the room, he will give an explanation such as, “Oh, I need to get a drink.” His left hemisphere, the one responsible for speech, is unaware of the command that the right side received, and we have every reason to think that he does in fact believe his thirst was the reason he got up and began walking. As in the example in which experimenters were able to cause a feeling of will in subjects who were in actuality were no in control of their own actions, the phenomenon of “the interpreter” is further confirmation that the feeling we have of executing consciously willed actions, at least in some instances, is sheer illusion. [pp. 59-60]
I talk about those “other experiments” in my lecture on free will. In one of them, doctors are stimulating the brain of a conscious patient undergoing surgery (this is not done as pure science, but as probes during operations on the brain). This causes the patient to raise his arm and wave it. When they asked the guy why he moved his arm, he replied, “Oh, I saw that nurse over there and wanted to wave at her.” Again, in this case the subject confabulates an act of will to account for something he did, suggesting that the idea that “will” made him voluntarily move his arm is an illusion. He was not in any way in control of what he did.
Experiments of this sort are the kind that I use to convince people that “will”, “volition” and “consciousness” are the results of purely physical processes in the brain, and thus that the idea of non-brain stuff is not part of will, dispelling dualism. But most people here aren’t dualists anyway. Still, the experiments also suggest that perhaps the notion of consciousness and of will are things that merely report to us after the fact the deterministic actions of our brain, and are not in any way part of a causal chain. That, at least, is what Annaka thinks. (I think Sam Harris agrees as well.)
Also, it makes you at least think about the truth of panpsychism. Do we really expect to split consciousness by splitting the brain if consciousness is simply a property of the particles of matter that make up the brain (remember, the brain isn’t completely split), or, as some think, not of the particles themselves but of the wave function that encompasses all matter? Answering that question is, for the time being, above my pay grade.
Off to dine with Pinkah!