The weirdness of split-brain experiments

January 16, 2020 • 10:15 am

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.)

From Conscious:

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!



91 thoughts on “The weirdness of split-brain experiments

  1. I’m assuming those with the post hoc justifications through “The Interpreter” are quite convinced of their reasoning and don’t have that feeling that they are making stuff up because they feel a need to give an answer?

  2. There are theories by neurologists that our decisions are made in some area if the brain for reasons unknown to our consciousness. Our conscious self then concocts reasons to support those decisions. That is why arguments over issues generally lead nowhere, because we are not even aware of the reasons we believe why we (our conscious we) believe what we believe.

    These experiments support these theories.

    Is Sigmund F. listening. He would be pleased.

  3. Split brain research is very interesting but I don’t see how it says anything about free will regardless of one’s opinion on that subject. A split brain acts somewhat like two separate brains each of which has free will or not, depending on your perspective.

    Of course, a split brain does present some challenges for our justice system. If one side of the brain decides to commit murder, should the whole person be held responsible? Let’s hope we never have to decide that case.

      1. No, not really. Just pointing out that such people do present challenges. We know that there are many bits of knowledge and technologies that are going to challenge society in the coming years. This is just one more.

          1. After thinking about it, I suspect we would dismiss these cases as the split brain person would be mentally incapable of making decisions freely. Their condition is interesting but just one of many mental incapacities so perhaps not so much a challenge for the courts after all.

            1. What of the patient undergoing surgery? He’s not a split brain patient? His brain works like all of our brains.

              1. Clearly that person who is having their brain stimulated artificially is not acting of their own free will. The fact that they invent an explanation for their arm raising says nothing about free will because they clearly don’t have any in this context. It’s just one more form of mental incapacity. Once we start probing and stimulating parts of the brain, there will be literally millions of ways of messing with someone’s brain operation. Once we get into artificial brain enhancement, we will have all kinds of challenges to our legal system.

                It is interesting that such a person invents an explanation for raising their arm, presumably without knowing that they are inventing it. This tells us something about how consciousness and explanation work. It is thought that there are voting mechanisms in the brain where competing thoughts are pitted against each other and the strongest signal wins. Perhaps the brain always requires an explanation for a conscious action and, therefore, one explanation will always win even if it is the wrong one. This seems reasonable to me. If we mess with the signals, there will likely be a failure of some kind.

              2. “Clearly that person who is having their brain stimulated artificially is not acting of their own free will”

                which things exactly were not produced by free will?

                did free will go somewhere? Was it competing with something?

            2. Since your view is that free will is a social construct, what would the brain have to do with that?

              If free will is a property of the brain, clearly then half a brain is half of the free will.

              1. But the arm raising incident kept the response within the context of the moment. He did not respond “waving at the plane that’s overhead.”

    1. If you don’t believe it says anything about free will, can you address Jerry’s two examples which he uses as examples of the lack of free will:

      – the man receiving the suggesting to go for a walk and then creating a post hoc justification for doing so.

      – the patient waving on the table when the brain is stimulated and then giving a post hoc justification for waving.

      1. The brain makes a decision. If that decision is deemed to have been done freely (ie, free will was exercised), society holds that person responsible for their actions. In a split brain patient, that presents some challenges as I’ve pointed out but none of them shed light on the free will discussion we’ve had here.

        The more I think about split brain patients and their responsibility, the more I think we would have to judge them as mentally incapacitated. If one part of the brain can make decisions while only the other part of the brain knows the law, it would be hard to hold such people fully responsible. So it makes sense to say that such a person does not act of their own free will. Although perhaps the particular mental incapacity suffered is interesting and rare, this is the kind of judgement made every day in our courts.

        1. I think what Jerry is getting at is the decision was not made freely because the person was either told to or stimulated to do something and only after did they manufacture a reason for doing it. This suggests that this is how the brain works and it works without the brain willing something independently and instead is only informed after the action happens or makes up the reason after the action happens.

          1. Like Paul, I do not see what this has to do with the question of acting freely. If the brain halves are connected, then when asked “why” the person would simply answer “because you told me to.” But in the split brain case, the responding half is in the dark about the order so it cannot make that answer and, instead, makes something else up. The curious thing to me is why the split brain subject confabulates an answer rather than saying “I don’t know.” It could be simply that when we are asked why we do something, we are expected to give a reason.

            1. I think this is what is the crux – the fact that the mind makes it up. The thing has already happened, but the mind is confident that it was the author of its decision and it gives a reason….this is why the free will part is called into question.

              1. It calls into question the free will of this particular person making this particular decision but doesn’t say anything about free will in general. As I mentioned earlier, I think we have to consider a person with a split brain, or one undergoing artificial stimulation, as a person whose will isn’t free.

              2. So if some people don’t have free will because of brain stimulation or injury, can we not extend that further? If I have an electric stimulation across my brain and it causes me to behave in a certain way (for example when migraines give me depressive spreading I can lose my ability to say words – aphasia) can this no be an example of losing my free will? And if that is the case, where does the loss of free will end?

              3. “It calls into question the free will of this particular person making this particular decision but doesn’t say anything about free will in general. As I mentioned earlier, I think we have to consider a person with a split brain, or one undergoing artificial stimulation, as a person whose will isn’t free.”

                This is special pleading because the subject is conscious and there is no rule given by which free will is suspended in one case and not in another.

              4. Your statements seem to come from the “free will is magic” camp. Free will is a social construct. A person has free will if society says they do. It means the person can make decisions and be held responsible for them. Someone taking part in an experiment involving changes to their brain, or someone who has a split brain, are impaired and not functioning normally. My guess is that society would not hold them responsible for their actions and would say that they don’t have free will. There’s no suspension of the laws of physics involved.

              5. “Free will is a social construct. … A person has free will if society says they do.”

                This sounds like there is no free will process operating inside the person themselves to point at, but just that society likes to make claims that sound good “they have free will” as some broad generalization,.. but if they have free will, where is it? What is it? Does an inebriated person have free will, or only some? Do we have free will in our dreams? If free will turns off when people are unconscious, how does that happen, and how come a loud noise wakes them up?

                “My guess is that society would not hold them responsible for their actions …”

                That part I can understand.

                ” …and would say that they don’t have free will.”

                Again then, where did it go? That’s a pretty straightforward question.

                lastly, semantics :

                “Your statements …”

                the only statement of fact I made was that the argument was special pleading, because it appeared to be special pleading, and we are trained to pick it out. In other comments I made an argument, and asked questions.

                “… seem to come from the “free will is magic” camp””

                you are free to claim that though I don’t know what your point is.

              6. I don’t think free will is something that can “go” anywhere. That sounds like some kind of vitalism which would put it in the “free will is magic” camp.

              7. There is no reason to think a free will decision is involved here, so we cannot conclude anything about free will. The man in the white coat said “Take a walk” and the subject complied. What if the man in the white coat had ordered the subject to “Kill my nurse”? I think then the subject would not have complied, and when asked why he didn’t kill the nurse would have answered “What!?”

              8. But the brain often fills in when memory is lost, similar perhaps to how the visual cortex fills in colors for the blind spot. Amnesia and dementia victims confabulate. It is an interesting phenomenon but I don’t see that tells us anything about free will. In the split brain case, the memory of why the body is walking is there, in the right hemisphere, but the left brain—walking with the right brain—cannot access it, so it makes something up. If we could query the right hemisphere, there would be no puzzle.

                And what about the case where the right brain chooses *not* do something? Would the left brain make up a story why it didn’t kill the nurse, or simply wonder why the hell the questioner is asking the question?

    2. When I do bad things, it’s usually due to a very small portion of my brain. Most of my brain is well behaved.

        1. The side that can do language; the other side can’t talk so it just has to put up with whatever this side of the brain is saying about it.

  4. A friend of mine took Elizabeth Crosby’s neuroanatomy class at Michigan. She told me of a split brain study reported by Crosby. The male, split brain patient was shown an attractive woman only in the right eye and he identified it without emotion as a woman. When the same image was projected into the left eye, he did not know what it was, but wanted to see it again.
    This was cited to show specialization of the hemispheres, but nothing to do with free will.

    1. I think the free will component Jerry references is that thoughts arise in the brain instead of being the product of something consciously willed in the brain – the example being how the person was told to “take a walk” and then gave a post hoc reason for taking that walk, having not consciously realized it had been suggested to him.

      1. “thoughts arise in the brain instead of being the product of something consciously willed in the brain”

        The second thing here is what trips up those who believe in woo-ish explanations of free will. They experience making a decision as some kind of instantaneous spark in their stream of conscious, but if one thinks carefully about how decisions must be made in the brain, one realizes that it must be a multi-stage process regardless of how we consciously experience it. These experiments bring the stages into the light which is bound to shake the woo-meisters to their core.

  5. Some other fascinating observations:
    One researcher reported that when you give a peanut to a split-brain monkey, the result can sometimes be a tug-of-war between the two hands.

    If you give a split-brain monkey a matching task, where either hand can press images on a screen that match information presented on that side of the screen, she can perform that task at a blazing speed. Much faster than a whole-brained monkey. I may be getting details about the task wrong, but that was the gist of it.

  6. Forensic Files told the grisly story of Peter Porco’s death – he attacked with an ax by his son, then went about his business unaware that he was injured because of the nature of the injury (but he did die):


    No grisly photos, but a grisly description! It’s amazing what he was able to do despite bleeding out from head injuries.

    1. Yeesh! There are also those stories of people in car crashes that receive brain injuries, going about their business unaware. I’m thinking specifically about the fellow that hit a moose and totalled his car then carried on driving the wreck of a car all bloodied having not realized anything had happened and having no memory of the incident.

      The quote at the top is so Newfoundland: “Then I realized, it’s Steve Bromley from Conche … I used to buy my codfish from him”

  7. I started Annaka Harris’s book and found it quite good…until I got to the part about panpsychism. Then I couldn’t force myself to go any farther. If you find light beyond that tunnel, I’d be delighted to hear of it, and may go back to pick up where I left off.

    1. “…until I got to the part about panpsychism.”

      Agreed. Why this dalliance with panpsychism, one wonders? Harris mainly touts its simplicity as scientifically virtuous (67-9), but simplicity on its own doesn’t get us very far. She may not have sufficiently considered the explanatory potential of neuroscientific hypotheses concerning consciousness, to which she gives short shrift in this volume. She leaves unexplored (perhaps to keep the book brief and accessible to the general reader) some of the major empirically-motivated explanatory contenders, for instance those of Thomas Metzinger (self-model theory of subjectivity), Jesse Prinz (attended intermediate representations), Giulio Tononi (integrated information theory) Stanislas Dehaene and Bernard Baars (global workspace), and Andy Clark (predictive coding). Panpsychist speculation about experience being the intrinsic character or nature of physical reality (if such a nature even exists) seems empirically bereft and premature compared to such work.

      1. Agreed. I haven’t read Harris’s book but I suspect the fundamental mistake she’s making, along with all the other panpsychists and their variants, is in thinking that consciousness is some sort of magic that needs a magical explanation. After they make that mistake, it comes down to which particular brand of woo they choose to explain it away.

        1. Panpsychists like Goff (and Chalmers on alternate Tuesdays) take themselves to be naturalists, not woo-ists, but are way too comfortable in their armchairs. Philosophy disconnected from science ain’t much use when it comes to empirical questions like the nature of consciousness.

          1. Goff for sure but I’m not sure Chalmers is a really into woo. He does think experience needs to be explained to the extent that he’s dedicated his philosophical career to it. While I agree with him that experience represents a different kind of knowledge than that revealed by scientific study, I simply put it down to experience’s unique vantage point and see no reason to explain it further. We can learn everything there is to know about how a bat works but still not know what it is like to be a bat.

      2. Bunge writes in _The Myth of Simplicity_ : “Simplicity isn’t simple.” Someone appealing to simplicity as an intellectual or similar virtue should be asked: “In virtue of what? What sort of simplicity? (Ontological, epistemic, semantic, computational, etc.?)

    2. I will keep reading, as I have only a chapter to go. It’s a short book. I’m still puzzled as to why, given that she’s critical and rational, she so readily buys into panpsychism. She doesn’t buy into it nearly as heavily as Philip Goff, and she does have her doubts, but she considers it a pretty plausible hypothesis rather than an speculative and unevidenced guess.

  8. The notion of volition has disappeared from the the left side of the brain.

    My take is that the left brain must retain some concept of volition in order to be able to say “I didn’t cause that.” I interpret this to mean that the left brain is denying responsibility for actions controlled by the right motor cortex (e.g. those carried out by the left hand). If we could interrogate the right brain, I predict it would similarly deny responsibility for actions controlled by the left motor cortex. So the notion of volition hasn’t vanished; it’s just been split into two quasi-independent volitions (as we would expect from having two quasi-independent brains in one body).

    But the experiments also suggest that perhaps the notion of consciousness and of will are things that merely report to us the deterministic actions of our brain post facto, and are not in any way part of a causal chain.

    If we can talk about them, then they must be part of the causal chain that determines what we talk about. If they can be part of that causal chain, they can in principle be part of other causal chains controlling other kinds of behavior. And there are sound evolutionary reasons to think such complex mental phenomena must have some causal effect on behavior, or natural selection would be unable to build and conserve them.

  9. The split brain experiments, and multiple personalities can also be explained with memory. Again, examine memory to explain various states of dreaming, mental problems, drug hallucinations, consciousness, free will, even religion and philosophy. Sure it is simplistic, but to me explains decently the big stuff. Now just get the details as to how the brain stores or restores that lifetime of experiences. Like where is memory? Must be in multiple places?

  10. “. . .if consciousness is simply a property of the particles of matter that make up the brain. . .or, as some think, not of the particles themselves but of the wave function that encompasses all matter?”

    I’ve pretty convinced that the former (panpsychism) is a dead end. Is there a name for the latter (which I assume is a reference to what Bernardo Kastrup espouses)?

    I too have started Annaka Harris’s book.

  11. If I can simplify for my brain. When split brain subjects are asked to perform a function, the other half having no input to the action when asked why, will give a coherent answer to make sense of their world. Regardless of its being true.

    Subliminal. How your Unconscious Mind Rules your Behaviour
    Past… Hey there. Yes: You, Sexy. Buy this book now. You know you want it.
    by Leonard Mlodinow and a collaborator of Stephen Hawkings had some very interesting case studies.
    Foe sure, one book of many available on brain studies out there.
    This super organ does a lot of filling in and padding out automatically to paste and stick a seemless world together.
    This has inklings to me to cast more layers of shadows to fall on free will.

    1. Don’t we all have lots of split personalities, depending on the situation. Sometimes for discretion, we should. What is so wrong with being an atheist but going to church on Sunday because of fantastic sacred music. Of course, down deep I do not think that I am a hypocrite, since my mind has been changed because of scientific evidence. And hurray for the split brain that is half democratic, half republican, so that when they sit on the fence, and get new evidence, can actually change their mind, and get rid of some politician. This is also the essence of doubt in science … that we should sit on the fence until the evidence swings us to a better point of view.

      1. I see nothing hypocritical whatever in enjoying sacred music. Heck, I used to sing in a church choir. They didn’t ask and I didn’t tell. Great sacred music like Bach’s Mass in B Minor was written expressly to invoke numinous awe in the human mind. There is no harm in enjoying it without the need to believe.

        1. Indeed! I think my favorite piece of music, bar none, is Verdi’s Requiem.

          Verdi was also pretty much a non-believer.

  12. The results of those split-brain experiements are wild, even unsettling. But in another sense, it doesn’t seem surprising that when you break up the coherency of the brain that causes consciousness, you break up the coherency of consciousness. A brain fundamentally altered in that way does weird things for consciousness is what you’d expect on a materialist paradigm (even if you don’t know exactly the details of how, before-hand).

    “But the experiments also suggest that perhaps the notion of consciousness and of will are things that merely report to us the deterministic actions of our brain post facto, and are not in any way part of a causal chain. That, at least, what Annaka thinks.”

    It’s interesting to think about consciousness as not being part of the causal chain (and that idea seems to have some real problems when you run it through). But a beef I have is where many people – especially those in the no-free-will camp – infer from those and similar experiments that our consciousness is merely “making up a story” in a routine fashion, mimicking the “false stories” that occur sometimes in the split brain experiments cited here.

    In other words the implication is that we can not know or access the “real reasons” we think or believe anything in that any story we become conscious of is likely false.

    That seems to me a very poorly justified gratuitous leap from the evidence. It’s like leaping from experiments with optical illusions to “everything we see is false, to that degree.”

    How would this apply to any of the countless real-world instances of human deliberation?

    If you ask a mathematician how he arrived at a sum, he can give you the complicated equation and math he reasoned with to get there. If his conscious report is wrong about his path of reason, if it’s merely some inaccurate “story” the conscious mind tells, what possibly COULD the “real” story be that would explain it? His coffee was cold? An argument with the wife this morning?

    If you ask NASA engineers “why does the mars probe have the form it does and how did you get it to mars?” they will give you a reasoned account – experiments, inferences from the experiments, learning over time, the math, the engineering, etc. These are the reasons they are conscious of having and can consciously convey to you. And the reasons they give will have very tight explanatory power in terms of the facts they are explaining, AND have predictive power for the actions of the NASA scientists in designing the next probe.

    So if someone wishes to present the hypothesis that the conscious account is false, a fantasy concocted whereas there is some different, real story for how the NASA engineers reasoned towards their feat, what could it possibly be? It would have to be an even better explanatory fit with the facts needing explanation, and have as good or better explanatory power. But this is never what we ever get. We only get these gratuitous propositions “Well, in this highly artificial experiment we managed to fool the brain to give a false conscious story…so that must be how it all works in every situation where people are reasoning!”

    1. I suspect our consciousness is “making up stories” when we report on our own thinking. It is well known and, as far as I know, completely uncontroversial that consciousness has access to only part of what goes on in our brains. We all know this from the limits to our own introspection. For example, when we make a mistake we guess at why we did it in order to avoid making it in future. We are always making up stories. We hope they are correct most of the time but have no way of being sure they are. If someone is messing with our brains, it reduces the accuracy.

      It seems to me an incredible evolutionary advantage to be able to reflect on our own thinking. Obviously we would only realize this advantage if the stories we tell ourselves and others are accurate most of the time. However, there’s no way to be sure they are accurate.

      1. Agreed, Paul.

        However, there’s no way to be sure they are accurate.

        True, but in the context that we don’t have assurance of anything. So we go with the best models.

        For much of what we say/think consciously it seems the best model/theory is the general accuracy of our conscious account. Because, as I said, it seems to be a good explanatory model, and doesn’t yet seem to have reliable alternatives.

        1. Well, we do value photographic evidence over that of an individual’s report of their experience. We also take the collective reporting of multiple witnesses over that of a single witness or the perpetrator’s own account. We know that human consciousness is not 100% reliable even if deliberate lying is not involved. Our consciousness makes up stories that are our own version of truth. It does the best it can with what it has: an imperfect function operating on imperfect data.

  13. But the experiments also suggest that perhaps the notion of consciousness and of will are things that merely report to us the deterministic actions of our brain post facto, and are not in any way part of a causal chain. That, at least, what Annaka thinks.

    I think so too. Those post facto explanations are tuned by culture and must fit within societal norms. If they don’t, you’re crazy.

    1. I don’t think they can validly claim that consciousness and will are always post-factual. Take the example of a student who chooses to study tonight for an exam tomorrow. (1) He consciously sets an intent to study. (2) His studying primes his neural pathways related to the subject matter so that when he sees a question on the test, the answer will be retrieved to conscious awareness where he can “report it” by writing his answer on the exam.

      This is literally a conscious choice to alter the neural pathways of ones own brain. And it presents a clear case of top-down causation.

  14. “doctors are stimulating the brain of a conscious patient undergoing surgery (this is not done as pure science,”

    Is there more to this example, published perhaps? Because I am wondering if the patient has cognitive problems to begin with, or if the surgery itself is affecting the observations. Though it is a suggestive example, I think it is difficult to make a firm conclusion about free will from it.

    1. Originally this was again in the context of epilepsy. Pioneered in the 1940s and 1950s by W. Penfield and his colleagues in Montreal. The idea is to remove a small amount of brain tissue that seems especially involved in the production or maintenance of otherwise untreatable seizures. Needless to say one doesn’t want to remove anything else important, so one literally probes the brain to find what’s where.

      (I am just reporting textbook presentations, of course, here.)

  15. FYI. “Tales from both sides of the brain: a life in neuroscience” by Michael S. Gazzaniga offers a deeper dive into this issue. Thanks.

  16. About the patient whose arm was raised and confabulates the reason:

    I think it is interesting to ask if the patient or their doctors could have done otherwise. The answer is no.

    1. In Gazzaniga’s “Who’s in Charge?”, one of the things that happens after the two hemispheres are split is that the patient will move his head slightly to supply the missing data that used to come through the corpus callosum. Even without the split brain, a person with one eye would need to move his head to see everything he needs to see.

  17. I first learned about confabulation when reading about hypnosis. The subject is given a post-hypnotic suggestion, perhaps to take off his shoe when he hears the word “shark”, and then told to forget it. When triggered, the subject takes off his shoe, and if we ask why, he’ll make up some reason.

    We should keep in mind though, that Gazzaniga’s interpreter is not always making up a story. Every child, more than once, has been asked “Why did you do that?” And that causes us to stop and think of how to explain our actions to ourselves and to others. So we are motivated to construct an explanation that is consistent with who we are and how we usually think about our choices and our actions.

    The prospect of being asked “Why did you do that?” may also cause us to think twice before doing something questionable. And in this case the thought process may call a halt to the action we were considering, if we can’t justify it to ourselves and others.

    So, conscious thought does have a role to play in behavior, that is sometimes up front of the behavior rather than lagging behind.

    By the way, I’d recommend Gazzaniga’s “Who’s In Charge? Free Will and the Science of the Brain”. He covers a lot of split-brain experiments and actually was involved with them.

    For a reasonable theory of consciousness, I’d recommend Michael Graziano’s “Consciousness and the Social Brain”. He describes conscious awareness as a data set that tracks the brain’s attention mechanism. He locates a center of awareness in the brain, and describes a condition called the “Hemispatial Neglect Syndrome”. After an injury to the awareness processing area, some patients are no longer aware of objects on one side of their field of vision. Their sensory apparatus is fully functioning, but their awareness of that sensory input is missing.

    1. Every child, more than once, has been asked “Why did you do that?” And that causes us to stop and think of how to explain our actions to ourselves and to others. So we are motivated to construct an explanation that is consistent with who we are and how we usually think about our choices and our actions.

      Yes! We are conditioned to provide that explanation and in many cases (especially for children), when asked “why did you do that” a response of “I don’t know” is socially unacceptable, even though that is often the correct answer.

      1. It certainly could be the correct answer but I suspect it more often represents an attempt to avoid a proper answer, as in:

        “Why did you steal that cookie?”

        “I don’t know.”

        Of course, the asker is also being disingenuous in this case.

        1. But there are so many possible answers to “why did you steal that cookie?” and the ‘correct’ answer depends on culture.

          Military culture: “because I was weak.”
          Fundamentalist culture: “because Satan overpowered me.”
          Moralist culture: “because I was immoral.”
          Anarchist culture: “because I was hungry.”

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