Do split-brain cases disprove the existence of an immaterial soul? (Part Two)
|July 20, 2013||Posted by vjtorley under Intelligent Design|
In my last post, I discussed the problem of split-brain cases, which was first raised by KeithS in a post over at The Skeptical Zone titled, Split-brain patients and the dire implications for the soul (June 22, 2013). I began by distinguishing three varieties of dualism (leaving aside property dualism, whose inadequacies from a theistic standpoint have already been ably exposed by Professor William Dembski – see here and here), which I referred to as substance dualism, thought control dualism and formal-final dualism. I then examined the six assumptions used in KeithS’s split-brain argument from the perspective of each of these versions of dualism.
What is a split-brain operation?
Before I go on, I’d like to provide a brief scientific explanation of what a split-brain operation is. The information below is taken from a Web page created by the Psychology Department at Macalester College (bold emphases are mine):
In a normal brain, stimuli entering one hemisphere is rapidly communicated by way of the corpus callosum to the other hemisphere, so the brain functions as a unit. When the corpus callosum of an individual is severed, leaving a split brain, the two hemispheres cannot communicate. In some forms of epilepsy a seizure will start in one hemisphere, triggering a massive discharge of neurons through the corpus callosum and into the second hemisphere. In an effort to prevent such massive seizures in severe epileptics, neurosurgeons can surgically sever the corpus callosum, a procedure called a commissurotomy. If one side of the brain can no longer stimulate the other, the likelihood of severe epileptic seizures is greatly reduced.
Answering KeithS’s questions on split brain patients
In this post, I’d like to discuss and respond to KeithS’s reductio ad absurdum argument. He begins by posing three questions, based on actual cases of split-brain patients, described in the medical literature:
1. In the case of the man who attacked his wife with one arm and defended her with the other, what did the soul want to do? Is the soul guilty of attacking her? Does the soul get credit for defending her?
2. If the right hemisphere knows something that the left hemisphere doesn’t, then does the soul know it? What if it’s the other way around, with the left hemisphere knowing something that the right hemisphere doesn’t?
3. In the case of the patient whose left hemisphere didn’t believe in God but whose right hemisphere did, what did the soul believe? Was the soul a theist or an atheist?
[NOTE: KeithS is alluding here to a case discussed by the neurologist Dr. V. S. Ramachandran in a video lecture in 2006, about a split brain patient who was asked to point to “Yes,” “No” or “I don’t know,” in response to a series of questions, and whose right hemisphere, when shown the question, “Do you believe in God?”, directed the patient to point to “Yes,” while the patient’s left hemisphere, in response to the same question, directed the patient to point to “No.”]
I might add another interesting case which I’ve come across, relating to a patient named Paul S. (whose case history is discussed in detail on a Macalester College Web page on split-brain consciousness), who underwent brain bisection in the 1970s, and whose right hemisphere (unlike that of most split-brain patients) was able to understand not only nouns, but also verbal commands and also questions, after surgery, and respond to these questions in writing, giving simple one-word answers:
Paul’s right hemisphere developed considerable language ability sometime previous to the operation. Although it is uncommon, occasionally the right hemisphere may share substantial neural circuits with, or even dominate, the left hemisphere’s centers for language comprehension and production. The fact that Paul’s right hemisphere was so well developed in its verbal capacity opened a closed door for researchers. For almost all split brain patients, the thoughts and perceptions of the right hemisphere are locked away from expression. Researchers were finally able to interview both hemispheres on their views about friendship, love, hate and aspirations.
Paul’s right hemisphere stated that he wanted to be an automobile racer while his left hemisphere wanted to be a draftsman. Both hemispheres were asked to write whether they liked or disliked a series of items. The study was performed during the Watergate scandal, and one of the items was Richard Nixon. Paul’s right hemisphere expressed “dislike,” while his left expressed “like.”
(Reference: Atkinson, Rita L., Introduction to Psychology, Eleventh Edition , Harcourt Brace College Publishers, Orlando, c. 1993.)
The case of Paul S. is fully described in an article by Joseph E. LeDoux, Donald H. Wilson and Michael S. Gazzaniga, titled, A Divided Mind: Observations on the Conscious Properties of the Separated Hemispheres (Annals of Neurology 2:417-421, 1977). I’ll quote a few relevant excerpts here:
The question of whether the essence of human consciousness can be represented bilaterally in the split brain patient has so far remained unanswered. The following observations on a new patient, Patient P. S., may help to resolve the issue. For the first time, it has been possible to ask subjective questions of the separated right hemisphere and to witness self-generated answers from this mute half-brain. This opportunity was made possible by the fact that linguistic representation in the right hemisphere of our patient is greater than has been observed in any other split-brain patient. In addition to an extensive capacity for comprehending written and spoken language, the right hemisphere, though unable to generate speech, can express its mental content by arranging letters to spell words …
…The right half-brain spelled “Paul” in response to the question “Who are you!” When requested to spell his favorite girl, the right hemisphere arranged the Scrabble letters to spell “Liz.” The right hemisphere spelled “car” for his favorite hobby. When the right hemisphere was asked to spell his favorite person, the following was generated: “Henry Wi Fozi.” (Henry Winkler is the actor who plays Fonzie.) The right hemisphere generated “Sunday” in response to the question “What is tomorrow?” When asked to describe his mood, the right hemisphere spelled out “good.” Later, in response to the same question, the left spelled “silly.” Finally, the right hemisphere spelled out “automobile race” as the job he would pick. This contrasts with the frequent assertion of the left hemisphere that he will be a “draftsman.” In fact, shortly after the test session, when asked what he would like to do for a living, the left hemisphere said, “Oh, be a draftsman, I guess.” … Finally, it should be noted that on each of these right hemisphere trials the patient was unable to name the lateralized information, thus confirming that the left hemisphere did not have access to the critical information.
It is important to reemphasize that these responses were self generated by the right hemisphere from a set of infinite possibilities. The only aid provided to the right hemisphere was the two complete alphabets from which he could select letters at will…
… Each hemisphere in P. S. has a sense of self, and each possesses its own system for subjectively evaluating current events, planning for future events, setting response priorities, and generating personal responses…
On a day that this boy’s left and right hemispheres equally valued himself, his friends, and other matters, he was calm, tractable, and appealing. On a day when testing indicated that the right and left sides disagreed on these evaluations, the boy became difficult to manage behaviorally.
I therefore propose to add two more questions to KeithS’s list:
4. What did Paul S.’s soul want to be, an automobile racer or a draftsman?
5. Did Paul S.’s soul support or oppose President Richard Nixon?
These are all fair questions, and they deserve straight answers.
Sir John Eccles on split brain cases
I’ll begin by examining what the late Nobel Prize-winning neurophysiologist Sir John Eccles, a modern substance dualist, had to say about split-brain cases.
To begin with, I would invite readers to take a look at this diagram, taken from Eccles’ 1979 Gifford Lectures on The human psyche. As readers can see, the main channel of communication between the (disembodied) conscious self and the brain is via the dominant left hemisphere, but there is also a limited degree of communication with the minor right hemisphere. Next, here is a diagram of communications to and from the brain and within the brain, after the corpus callosum has been severed. Communication from the conscious self to and from the brain is now exclusively via the dominant left hemisphere.
In his 1979 Gifford lectures on The human psyche, Sir John Eccles describes the performance of the two hemispheres of the brain, after a split brain operation:
…[T]he left (speaking) hemisphere has a linguistic ability not greatly impaired. It also carries a good memory of the past linked with a good intellectual performance and with an emotional life not greatly disturbed. However it is deficient in all spatial and constructional tasks. By contrast the right hemisphere has a very limited linguistic ability. It has access to a considerable auditory vocabulary, being able to recognize commands and to relate words presented by hearing or vision to pictorial representations. It was also surprising that the right hemisphere responded to verbs as effectively as to action names. Despite all this display of language comprehension, the right hemisphere is extremely deficient in expression in speech or in writing, which is effectively zero. However, in contrast to the left hemisphere, it is very effective in all spatial and constructive tasks and it is also proficient in global recognition tasks.
After reviewing some investigations by Roger Sperry et al. (1979) on two split-brain patients that were designed to test for aspects of self-consciousness in the right hemisphere, Eccles was forced to acknowledge:
It can hardly be doubted that the right hemisphere has at least a limited self-consciousness.
But then he went on to add:
These tests for the existence of mind and of self-conscious mind [in the right hemisphere – VJT] are at a relatively simple pictorial and emotional level. We can still doubt if the right hemisphere has a full self-conscious existence. For example, does it plan and worry about the future, does it make decisions and judgements based on some value system? These are essential qualifications for personhood as ordinarily understood (Strawson, 1959; Popper and Eccles, 1977, Sects. 31 and 33)…
I would agree with DeWitt’s (1975) interpretation of the situation after commissurotomy:
Both minor and major hemispheres are conscious in that they both, no doubt, have the basic phenomenal awareness of perceptions, sensations, etc. And they both have minds … in that they exhibit elaborated, organised systems of response hierarchies, i.e., intentional behaviour. But in addition I would conjecture that only the major hemisphere has a self; only the language utilising brain is capable of the abstract cognising necessary in order to be aware of itself as a unique being. In a word, only the major hemisphere is aware of itself as a self.
This corresponds to the situation in real life, where the associates of the patient find no difficulty after the operation in regarding it as the self or person that it was before the operation. The patients themselves would of course concur, but they do have a problem arising from the splitting of the conscious mind. There is the difficulty in controlling the movements emanating from the activity of the right hemisphere with its associated mind. These movements are completely beyond the control of the conscious self or person that is exercised through the left hemisphere. For example they refer to their uncontrollable left hand as their ‘rogue hand’.
It would seem that this interpretation of DeWitt conforms with all the observational data on the commissurotomy subjects, but avoids the extreme philosophical difficulties inherent in the hypothesis of Puccetti that even normally there is a duality of personhood – ‘two persons in one brain’ as he provocatively expresses it.
Eccles died in 1997. More recent studies have shown that both hemispheres of the brain are extensively involved in self-recognition, and that only the right hemisphere possesses the further ability to recognize familiar others (see Lucina Q. Uddin et al., “Split-brain reveals separate but equal self-recognition in the two cerebral hemispheres”, Consciousness and Cognition 14, 2005, pp. 633–640). In an article titled, Self-Awareness and the Left Hemisphere: The Dark Side of Selectively Reviewing the Literature (Cortex, (2007) 43, 1068-1073), Alain Morin argues forcefully that it is a mistake to equate self-recognition (the ability to recognize oneself in a mirror) with self-awareness, which requires a deeper awareness of one’s current emotions, goals, values and thinking patterns. Even the much-vaunted “Theory of Mind” (or the recognition that other minds exist out there in the real world) fails to exhaust self-awareness – as Morin puts it, “It is very likely indeed that one needs first to access one’s own mental self before one can ponder about others’ potentially comparable inner life” (p. 1069). Morin finds that self-awareness is widely distributed across both sides of the brain, but suggests that if anything, it is the left hemisphere (and not the right hemisphere, as argued recently by some authors) which predominates in self-awareness. Elsewhere, Morin argues for the notion of a relation between inner speech and self-awareness, and he concludes: “one must not neglect the role of language (i.e., inner speech) in self-awareness — an activity deeply associated with normal functioning of the left hemisphere.” (Right hemispheric self-awareness: A critical assessment, Consciousness and Cognition 11 (2002) 396–401.)
In another paper, titled, “The split-brain debate revisited: On the importance of language and self-recognition for right hemispheric consciousness” (Journal of Mind and Behavior (2001) 22 (2):107-118), Morin elaborates his argument for the significance of inner speech in self-awareness. Inner speech, he writes, allows us to “incorporate other persons’ potential views of ourselves in our self-talk and gain an objective vision of ourselves which facilitates self-observation” and “address comments to ourselves about ourselves, as others do towards us.” Referring to the mute right hemisphere, he writes: “Certainly it can experience an emotion, but without inner speech I suggest that it might not clearly know that it is experiencing it.” Morin concludes his discussion of split brain cases as follows:
My position is that two unequal streams of consciousness (i.e. self-awareness) emerge out of the transection of the forebrain commissures…. [T]his analysis incorporates empirical evidence (1) regarding the importance of language (inner speech) for self-awareness, and (2) concerning the legitimacy of self-recognition as an operationalization of self-awareness.
Morin adds that in his opinion, the case of Paul S. (discussed above) is “the only convincing case of real full double self-awareness in a split brain patient,” probably owing to the fact that this patient suffered early brain injury in the left hemisphere at the age of two, which led to his language abilities being bilateralzed. Morin regards it as an open question as to whether Paul S. actually has “two independent streams of inner speech – two concurrent but different self-conversations” (p. 531). For my part, I would regard such a claim as doubtful: the extent of Paul S.’s right-hemispheric language abilities amounted to comprehension of simple verbal commands and questions (in oral form), the ability to read single words and the ability to spell single words with Scrabble letters. That’s hardly an argument for the existence of a second independent streams of inner speech in the right brain.
I conclude that Sir John Eccles’ empirical claim that the conscious self is predominantly linked to the left hemisphere of the brain remains a highly defensible position which will probably turn out to be verified over the next few decades, whatever one may think of Eccles’ interactionist substance dualism.
A substance dualist’s answers to five tricky questions on split brain patients
We can now answer the five questions posed above, from the standpoint of Sir John Eccles’ modern version of Descartes’ substance dualism. It is important to note that for Eccles, the terms “self” and “soul” were more or less inter-changeable, as when he wrote: “I am constrained to attribute the uniqueness of the Self or Soul to a supernatural spiritual creation” (Evolution of the Brain: Creation of the Self, Routledge, paperback, 1991, p. 249), and he went on to liken the body and brain to a computer built by genetic coding, while “the Soul or Self is the programmer of the computer” (pp. 249-250).
1. In the case of the man who attacked his wife with one arm and defended her with the other, he attacked her with his left hand (which is controlled by the right hemisphere) while simultaneously trying to protect her with his right arm (which is controlled by the left hemisphere). Since the conscious self interfaces with the brain only via the dominant left hemisphere after a split-brain operation, what the man’s soul wanted to do was to defend his wife – an act for which he gets credit. The man is not morally responsible for what his rogue left hand does, as it is controlled by the right hemisphere, which is no longer controlled by the conscious self.
Indeed, Eccles famously suggested in The Self and its Brain (Berlin: Springer International, 1977, p. 329) that a homicide committed by the left hand of a split brain patient (which is controlled by the right hemisphere) would be manslaughter rather than murder!
2. If the right hemisphere knows something that the left hemisphere doesn’t, then the conscious self (or soul) doesn’t know it. But if If the left hemisphere knows something that the right hemisphere doesn’t, then the conscious self knows it.
3. In the case of the patient whose left hemisphere didn’t believe in God but whose right hemisphere did, the patient’s soul, I am sorry to say, didn’t believe in God. In the case described by Dr. Ramachandran, all the patient had to do was point to “Yes” or “No”, when asked, “Do you believe in God?” But that behavior is not enough to warrant the attribution of a belief to someone, in the way in which that word is properly applied to rational beings. A belief is pre-eminently something which you may be called upon to justify, and state your reasons for. The patient’s right hemisphere couldn’t say why it believed in God; nor could it defend its point of view against objections. Hence it could hardly be said to have a belief in the proper sense of the word. It may have had a residual belief in God from early childhood, when people are unable to vocalize the grounds for their beliefs, but since the patient, as an adult, came to consciously reject that belief, then the patient’s soul, or conscious self, will be held liable for this rejection and judged accordingly.
4. Paul S.’s soul or conscious self wanted to be a draftsman, since that is the answer given by his left hemisphere.
5. Paul S.’s soul supported President Richard Nixon, since his left hemisphere expressed a liking for the man.
How would a thought control dualist answer these five questions?
One of the main differences between substance dualism and thought control dualism is that the former identifies the soul with the highest part of a human being – the conscious self – whereas the latter regards the soul as a hierarchical structure which informs the body at multiple levels, the highest of which (rational thought) is immaterial. In other words, thought control dualism, like Professor Edward Feser’s formal-final dualism, is hylemorphic: it regards the soul as the essential form of the body.
What that means is that according to thought control dualism. my lower mental states (e.g. sensations, desires) are just as much “mine” as my higher mental states (e.g. acts of reasoning, understanding and will). However, I am only morally culpable for those states which are subject to rational control.
1. In the case of the man who attacked his wife with his left hand (which is controlled by the right hemisphere) while simultaneously trying to protect her with his right arm (which is controlled by the left hemisphere), what his soul wanted to do on a rational level was to protect his wife. However, on a sub-rational level, he may well have had some feelings of hostility towards his wife. These feelings would also be attributable to his soul, but because the movement of his left hand was no longer subject to reason, he would not be morally culpable for attacking his wife with his left hand, as it is controlled by the right hemisphere.
A thought control dualist would agree with Eccles’ contention that a homicide committed by the left hand of a split brain patient (which is controlled by the right hemisphere) could not be called murder.
2. If the right hemisphere knows something that the left hemisphere doesn’t, then a thought control dualist would say that the soul does know it, but not in a manner which is amenable to reason and critical thinking. (It would be interesting to see what happened if the right hemisphere of a split brain patient was exposed to someone dressed up as a ghost. How, I wonder, would the patient react? My guess is that unless the patient was previously skeptical of ghosts, it would be impossible to convince the right hemisphere that what it had seen was not a ghost.)
What the dominant left hemisphere knows, on the other hand, is amenable to critical thinking and reflection. Such knowledge belongs to the highest faculties of the soul.
3. In the case of the patient whose left hemisphere didn’t believe in God but whose right hemisphere did, a thought control dualist would say that the soul retained, at some level, a habit of belief (derived from childhood, perhaps) in God. However, such a belief is no longer amenable to reason in the split brain patient. By contrast, the belief expressed by the patient’s left hemisphere is a belief that the patient could justify and give reasons for, if asked to do so. Thus it counts as a bona fide belief.
Sometimes, it is true, we may think we believe that something is true because we consciously avow it, but at a subconscious level, we intuitively recognize that what we consciously declare is mistaken. (I know a man who once told me of two ex-Catholics he knew, who publicly denied the faith, but who re-expressed a belief in it after they’d had a few beers!) In a person with a normally functioning brain, reason and intuition doubtless have lots of little tussles of this sort, and they usually manage to resolve them eventually. The truly sad thing about the split brain patient is that this kind of resolution cannot take place. In the case of the left-brain atheist discussed by KeithS, the patient’s right brain may know on an intuitive level that there is a God, but the bridge between intuition and reason has been severed. God, being merciful, will take the patient’s impairment into account.
4. Paul S.’s soul wanted to be a draftsman on a rational level, but on a more primitive, feeling-based level, his soul wanted to be an automobile racer.
5. Paul S.’s soul liked President Richard Nixon on a rational level, but disliked him on an intuitive level.
How would a formal-final dualist answer the above five questions?
The principal difference between thought control dualism and form-final dualism is that on the former account, the soul can interact with the brain and initiate neural processes, while on the latter account, the soul does not make neurons in the brain move: the soul explains the “what” and the “why” of a voluntary human action, but not the “how.” Thus thought control dualism, like substance dualism, would attempt to identify locations in the brain which are still capable of interacting with the rational soul (whose choices, like its acts of understanding, are disembodied acts), whereas formal-final dualism, which rejects such an interactionist account, would attempt to identify those actions performed by split-brain patients which still manifest rationality (and hence are morally praiseworthy or blameworthy), on an operational level – i.e. by performing relevant tests, such as carefully probing the patient’s stated reasons for his/her actions.
Bearing this in mind, we can answer the five questions above from the perspective of the formal-final dualist, as follows:
1. In the case of the man who attacked his wife with his left hand (which is controlled by the right hemisphere) while simultaneously trying to protect her with his right arm (which is controlled by the left hemisphere), both acts are attributable to different levels of the soul, as each human being embodies a psychic hierarchy. However, the action that should be counted as rational (and hence morally evaluable) is the one that the man himself can give a reason for, both before and after performing the act (this last condition is vitally important, in order to prevent confabulation, where patients make up reasons to cover their embarrassment over sudden bodily movements of theirs which they are unable to explain).
2. If one hemisphere knows something that the other hemisphere doesn’t, then a formal-final dualist would say that the soul knows it, but not in a manner which is fully integrated with the entire body. Recall that for a formal-final dualist, the soul is essentially the form of the body. If the form is badly damaged, in a way that affects cognitive functions, then the patient’s awareness may be localized, rather than spread over the global brain.
3. In the case of the patient whose left hemisphere didn’t believe in God but whose right hemisphere did, a formal-final dualist would try to ascertain which stated belief was properly integrated into the patient’s life. For example, if the patient made a habit of praying every night and going to church on Sundays, then that would be a good reason to take seriously the right hemisphere’s avowal that it still believed in God, notwithstanding the left hemisphere’s professed atheism. Deeds speak louder than words.
4. There may be different levels of the soul on which Paul S.’s soul wants to be a draftsman and an automobile racer, but the one that deserves to be called most authentically Paul S.’s wish is the one which he doggedly pursues over a period of several years, as people do when undertaking long-term rational plans.
5. Regarding President Nixon, it’s very hard for a formal-final dualist to ascertain what a split brain patient’s feelings were towards a politician, unless that patient had devoted a fair bit of time towards getting Nixon elected – or alternatively, ejected from office. In the absence of such rational, goal-oriented behavior, a formal-final dualist might be inclined to reject both hemispheres’ professed likes and dislikes as mere preferences, as opposed to rational choices. Of course, if Paul S. was able to say why he liked Nixon, than that kind of behavior would count as evidence, but only if it cohered with the rest of his political views. Since Paul S. was only eleven when Le Doux, Wilson and Gazzaniga wrote their famous article about him in 1977, some skepticism is warranted. (His views now would of course count as evidence, as well.)
In this post, I have tried to answer KeithS’s questions about split brain patients from the perspective of three distinct varieties of dualism. I shall leave it there, and let readers judge for themselves between these versions of dualism. What I have attempted to show, however, is that split brain patients do not pose an insoluble problem – or even a particularly pressing one – for believers in an immaterial soul.
Readers wanting to learn more about the history of how Christian and other dualistic philosophers tackled the problem of split brain patients may like to consult Minds Divided: Science, Spirituality, and the Split Brain in American Thought by Stephen E. Wald (ProQuest LLC, ISBN-13: 2940032034322, eISBN-13: 9780549633204), some of which can be viewed online here).