I recently read Michael Gazzaniga’s book, ‘Who’s in Charge: Free Will and the Science of the Brain‘. Gazzaniga, working with Roger Sperry, performed some of the famous split-brain patient experiments. The results of these experiments had implications for our understandings of consciousness, the self, and free will.
In patients with certain types of severe epileptic seizures, who have not responded to other treatments, an operation may be performed to cut the corpus callosum, the neural fibers that connect the two hemispheres of the brain. This operation often improves the seizure symptoms, usually with only minimal effect on the person’s cognitive abilities. They are generally able to function well afterward.
Animals tests had previously established that when an animal’s brain hemispheres were separated, they lost the ability to communicate between the hemispheres. However, the apparent functionality of split-brain patients caused uncertainty about whether or not this applied to humans, at least until split brain patient experiments.
It was already well known that the left hemisphere of the brain controls the right side of the body, and the right hemisphere controls the left side. Furthermore, the left hemisphere perceives the things in the right field of vision while the right hemisphere perceives things in the left field.
Using these facts, scientists were able to isolate communications with each hemisphere in these patients, by controlling what they saw in each field of vision and asking them to do things with each side of their body.
When the right hemisphere was shown an image, the left hemisphere knew nothing about it, and vice versa. When asked to make choices with their hands based on what they had been shown, each hemisphere could only do so with the side of the body they controlled. In other words, it was demonstrated that these patients had two separate consciousnesses.
When it appeared as though the hemispheres in a patient could communicate, it turned out to be a situation either where the corpus callosum hadn’t actually been entirely cut, or where one side was able to signal the other, either by body movements or by saying something aloud. In the latter situation, adjusting the experiment made the apparent ability to communicate disappear.
Bizarrely, the split brain patients were completely unaware of this situation. Yet they were able to function normally. Language is usually controlled by the left hemisphere, so it was the one that usually answered any questions. In situations where the left hemisphere should have been confused, it confabulated a reason on the spot to explain what the right hemisphere had done. Instead of merely admitting ignorance of why the right hemisphere had done something, it made up a reason for why it did it.
For example, a patient was shown images and asked to select associated words from a list. In one case, the right hemisphere was shown a picture of a snow field and understandably selected “shovel” as the associated word. The left hemisphere was shown a picture of a chicken and selected “chicken foot”, again understandably. When the patient was asked why they chose “shovel”, the language controlling left hemisphere, which had seen the chicken but not the snow, instead of saying they didn’t know why they had selected “shovel”, said that the shovel would be needed to clean the chicken coop.
The implications of these experiments are important. While there’s no way to know for sure, the ability of the split brain patients to continue functioning normally means that what they are doing is probably not that different from what happens in normal healthy humans, albeit with more internal communication. It means that brain processing is not controlled in any central area. It functions more like a cluster of independent modules that coordinate their actions.
So why do we have this strong feeling of unity? Of being one self? The answer of course is consciousness. Consciousness is often called an illusion, but I think a better phrase is that it’s not what it appears to be. Consciousness is not a controlling entity. Gazzaniga refers to it as the interpreter. It was the interpreter that quickly rationalized the other hemisphere’s choice. The interpreter essentially concocted a story after the fact to explain what was done.
The strong implication is that this is what it always does. It rationalizes decisions that have already been made. It explains actions that have already been taken. But it doesn’t initiate them.
Gazzaniga relates all of this in his book but offers an important caution about reading too much into its implications. Yes, it appears that the conscious self is not in control. But the conscious self is not the whole self. The brain, with all of its modules, including all its unconscious components, makes up the self. Just because we now have insights into the components of the self doesn’t mean that the self isn’t there. And just because the conscious self isn’t in control doesn’t mean that the whole self isn’t.
In many ways, this view of consciousness melds well with the Attention Schema Theory of consciousness put forth by Michael Graziano. Graziano believes that consciousness does have at least some control, but I think a better term would be “causal influence”. Consciousness or awareness, aggregates, summarizes, and models some of the information in the brain, and then makes that information available to the whole brain system. In so doing, it provides information that the brain uses in its decision making.
Consciousness then is a feedback mechanism, an analyzer. In some ways, it’s like a dictionary, which gives the appearance of defining words, when in reality the lexicographers who compile it simply report how the words are used in society. Or it’s like the news media in a society, which reports back to that society of what’s going on within it. Such an account is always incomplete and often inaccurate, but what does get included in our “public consciousness” influences the decisions that society makes.
I’m excited by this growing scientific understanding of consciousness. Is any of it getting at “the hard problem”? I think it depends on how you define that problem. But what is clear is that we know a lot more about it today than we did fifty years ago, and that we’ll probably know a lot more in coming years.
- UCSB’s Michael Gazzaniga Named 2015 William James Fellow (independent.com)
- Who’s in Charge – Us? (blog-thebrain.org)
- Learning From A Brain Divided (stimulatingsynapses.wordpress.com)
- Right vs. Left Brain (soccer1523.wordpress.com)