A recent IAI News article had the provocative title "Consciousness Came Before Life." Co-authored by Stuart Hameroff, the essay appeals to the authority of physicist Roger Penrose. We get some "quantum consciousness" mumbo jumbo that sounds like just empty hand-waving decorated with lots of physics jargon to try to make it sound impressive. The authors make the unfounded claim that microscopic structures called microtubules appear to be the "memory bank" of a cell, and we have the 100% groundless claim that "observations of extraterrestrial organic matter...provide reason to believe that consciousness came before life." The authors sounds like avid devotees of the physicist Roger Penrose. While Penrose is a very accomplished physicist and cosmologist, there is no reason why anyone should kneel in awe before what Roger Penrose says about consciousness, because a close look at his main work about minds reveals a work with unimpressive scholarship about minds and some very serious errors when talking about brains.
The work I refer to is "The Emperor's New Mind: Concerning Computers, Minds and the Laws of Physics" by physicist Roger Penrose. Penrose spends the first 373 pages of his book talking about physics, math and computing. Finally on page 374 he gets around to discussing human minds and human brains. He starts out by making wrong statements on this topic. He says this:
"Inside our heads is a magnificent structure that somehow controls out actions and somehow evokes an awareness of the world around us. Yet, as Alan Turing once put, it resembles nothing as much as a bowl of cold porridge! It is hard to see how an object of so uncompromising an appearance can achieve the miracles we know it to be capable of."
We get no encouraging signs here. It sounds like just another case of a scientist claiming to know things he does not know. We do not actually know that the brain controls our actions, and do not know that it evokes awareness. On page 379 Penrose makes a series of groundless claims about the brain. He claims without providing any evidence that "plans of action are formulated" in the central cortex. No one has any understanding of any neural mechanism by which a brain could formulate a plan of action.
On the next page Penrose reiterates groundless neuroscientist dogmas about the brain. He makes the incorrect claim that "damage to the hippocampus causes a fearful condition in which no new memories are retained once they have left the subject's attention." That is not true, and we have many cases of people with severe hippocampus damage or loss of one both of the two hippocampus areas, and still good memory ability. See my post "Studies Debunk Hippocampus Myths" for the truth on this matter. Claims like the one Penrose made are based on the case of Patient HM. But as I show in that post, it was not true that this patient could not form new memories, and the literature on that patient shows he did form some new memories after hippocampus damage. And it never makes sense to base a claim that X causes Y because of a single case in which a person has both X and Y. Establishing causal relation requires seeing such a relation in very many patients.
On pages 384 to 385 Penrose speaks approvingly of one of the most groundless deceits of neuroscientists, the claim that split brain operations can lead to two different minds. The evidence on this matter is unequivocal. The two hemispheres of the brain are connected by a set of fibers called the corpus callosum. When such fibers are severed (as is sometimes done to treat severe epilepsy), a person will be left with a single unified mind. This is totally contrary to what is predicted from the theory that your brain makes the mind. Some researchers have made deceptive claims that split brain operations result in two different minds, based on results in oddball special situation perception experiments which do nothing to justify such a claim. Penrose sides with these deceivers, by saying, "I therefore side with those who believe generally that the two sides of a split brain patient can be independently conscious."
To back up his untrue claim that those with split brains have two minds, Penrose offers some ridiculously poor evidence. He refers us to a 1977 paper co-authored by Michael S. Gazzaniga. The paper has the misleading title, "A Divided Mind: Observations on the Conscious Properties of the Separated Hemispheres." The paper refers to a 10-year-old patient PS who had his corpus callosum removed to treat severe seizures, becoming a split-brain patient. In its abstract the paper makes the false claim that the patient has "double conscious processes," a claim not backed up by any observations in it.
The experimental procedure discussed in the paper is a ridiculous one. The patient PS was given different things to read, some presented on the left side of a barrier, and some presented on the right side. The authors have made the groundless conclusion that the items perceived by the boy on the left side of the barrier represent thought from the left hemisphere, and that items perceived by the boy on the right side of the barrier represent thought from the right hemisphere. The underlying assumption is groundless and preposterous. We have some methodological nonsense in which the young boy is instructed to point to a number between 1 and 7 after being told that 1 is good and 7 is bad. It seems obvious that this bizarre procedure was designed to help parlay direction confusion (such as sometimes occurs with people with split brains) into something that might fool you into thinking split minds were occurring. Words are spoken to the boy, and he is asked to point to one of the numbers. We read that when this was tried in one way, in a way directed toward the right hemisphere, the boy pointed to higher numbers. Laughably, this is presented as evidence of the boy having two minds, one in the hemisphere and one in the right. It is far more likely that is is just a young boy responding in a random or somewhat confused way to very confusing instructions, or simply that the boy had some direction confusion related to his split brain state.
The paper fails to provide any robust evidence of any kind of split mind or split consciousness in patient PS. The procedure is a ridiculous one.
Penrose describes the case like this:
"After the splitting operation, only the left hemisphere could speak but both hemispheres could comprehend speech; later the right hemisphere learned to speak also! Moreover, they appeared to be separately conscious, because they had different likes and desires. For example, the left hemisphere described that its wish was to be be a draughtsman, and the right a racing driver!"
The statements are misleading. It was not a "left hemisphere" that was speaking, but a boy with a single unified mind who was speaking. And it was not a left hemisphere or a right hemisphere that was comprehending speech, but a single unified mind that was doing that. There was no evidence the boy had different likes and desires in different parts of his brains. The anecdote about the boy's career wishes is laughable as evidence. It is extremely common for young boys to give varying answers about what they want to be when they grow up. Ask the average 10-year-old one day what he wants to be when he grows up, and he may say on Monday morning that he wants to be an astronaut, and on Tuesday (or Monday afternoon) that he wants to be a movie star. It wasn't the left hemisphere giving one answer and right hemisphere another, but a boy with a unified mind not giving the same answer when asked a question at different times (something extremely common in both youths and adults).
It is troubling that Penrose appeals to this very poorly designed study and its groundless claims. It suggests that Penrose is willing to accept "hook, line and sinker" the worst type of poorly designed neuroscience research to back up whatever claim he prefers to believe, and also to present such scanty bottom-of-the-barrel evidence as his main evidence for a gigantic claim about minds (the false claim that split brain operations produce two minds). See Appendix A of this post for more on this topic.
On page 392 Penrose gives us more false information about the brain. He describes how nerve signals pass across synaptic junctions, saying, "This curiously exotic mechanism appears to work very efficiently." To the contrary, it was already well known when Penrose wrote his book that synapses transmit nerve signals very inefficiently. Each time a nerve signal passes across the synaptic junction of a chemical synapse, it transmits successfully with a likelihood of only 10% to 50%. See Appendix 2 at the end of this post for science papers backing up that statement. The unreliability of synaptic transmission is one of the main reasons for thinking that the brain cannot be the source of complex human mathematical thinking that can occur with 100% accuracy, and 100% accurate memory recall, such as occurs when an actor playing Hamlet successfully recalls all of his lines.
On page 380 Penrose glibly states that "the reticular formation is responsible for the general state of alertness or awareness in the brain as a whole," and on page 382 he states this:
"The reticular formation, after all, is responsible for the general state of alertness in the brain (Moruzzi and Magoun, 1949). If it is damaged, unconsciousness will result."
The paper he refers to was some experimental paper involving cats not humans, and it established no such claim, nor did it even make any such claim (the word "unconsciousness" does not even appear in the paper). It certainly is not true in general that damage to the reticular formation in humans will always result in unconsciousness. The literature of neuroscience is filled with countless cases of people who had the most severe brain damage and also had well-functioning conscious minds, including cases such as the French civil servant with almost no brain, Lorber's famous cases of people with above-average IQ and very little brain tissue, and other cases discussed here. It sounds as if Penrose has failed to study such cases.
By page 398 Penrose's discussion of the brain is basically finished. He has spent a mere 24 pages talking about brains, and a very thorough scholar of brains will not be impressed by his grasp of the topic. The rest of the book Penrose spends talking about a very wide variety of things such as quantum mechanics, quantum computers, the anthropic principle, and topics such as whether animals are conscious, "what are minds for?" and "what does consciousness do." He discusses insight and creativity, without discussing any neural basis for such things. Penrose wanders all over the map, giving some interesting thoughts here and there.
I am left with the impression of someone who did not very seriously study brains, and someone who did not very seriously study human minds and human mental experiences. I am left with the impression of someone very, very interested in physics and mathematics and computers and the physical universe, but someone not very interested in seriously studying human minds or the vast variety of human mental experiences and relevant medical case histories, someone who is not very interested in making the most detailed study of human brains.
I get a similar impression from Penrose's 1994 book "Shadows of the Mind: The Search for the Missing Science of Consciousness." The human mind, consciousness and mental phenomena (in all its strange variety) has been under the most serious scientific investigation for two hundred years, by a host of investigators such as the researchers of the Society for Psychical Research established in 1882; and people have been getting degrees in psychology for centuries. So what is with the ignorant-sounding reference to "the missing science of consciousness"? Again, we have a book that has its first 300 pages a discussion of physics, computers and mathematics. The discussion of brains and minds only starts around page 348. We have then many pages in which Penrose sounds as if he has no general interest in brains and minds and human mental experiences, but is mainly interested in one of the tiniest structures in a brain, something called microtubules. He has some kind of theory of some quantum something going on in such structures, which he unconvincingly tries to argue has some relevance to consciousness. Again, we get no impression of a very serious scholar of brains or human minds. A serious student of the human mind will delve deeply into the diverse experience accounts and case histories of very many hundreds or thousands of people, but Penrose doesn't sound like he's done any such thing. He gives the impression of someone who is a hundred times happier studying some equation or physics theory than studying the experiences or case histories of human beings. The topic of human minds and human mental experiences is a topic of oceanic depth, and Penrose sounds like he has merely waded his feet in such an ocean.
On page 353 of the work Penrose incorrectly describes the action of synapses, making it sound as if synapses fire with "a strong probability" upon receiving a nerve impulse. The reality (as discussed in Appendix 2 of this post) is that cortical synapses fire with only 10% to 50% likelihood upon receiving such an impulse. This shortfall is of the greatest importance, helping to exclude brains as the source of human thinking and memory recall, which can massively occur with 100% reliability, as when a Hamlet actor correctly recalls all of his lines, or when a math whiz does a very hard math problem correctly in his mind. On the same page Penrose misleadingly suggests brain connection strengths may change in a fraction of a second, which is not true. Changing such connection strengths would require at least minutes, and the sluggish speed of such a process is one reason why brain activity cannot account for the speed of new memory creation, which often occurs instantly.
So I don't understand why the IAI News article (co-authored by Stuart Hameroff) would keep citing Roger Penrose as if he was some very serious scholar of either brains or minds. He seems to be no such thing. Don't get the wrong idea by the use of the word "mind" in the title of two of Penrose's books. Penrose is a very accomplished physicist and cosmologist who seems to have merely done some dilettante dabbling in the study of minds and brains. Hameroff's article is all about promoting a theory (called the Orch OR theory or orchestrated objective reduction theory) that was co-created by Roger Penrose and Stuart Hameroff himself.
We get in the paper only two references to Penrose's work. One is a reference to "The Emperor's New Mind" book discussed above, a book guilty of the serious errors I have discussed. Then we have a reference to a paper co-authored by Roger Penrose and Stuart Hameroff, one entitled "Consciousness in the universe: A review of the ‘Orch OR’ theory."
That paper wanders all over the map without giving any evidence of very serious study of human minds or very serious general study of human brains. It reads just exactly like something someone would write if they were 50 times more interested in physics than human minds.
I can list some problems of the paper:
(1) Near its beginning, the paper states, "Consciousness also implies a sense of self, feelings, choice, control of voluntary behavior, memory, thought, language, and (e.g. when we close our eyes, or meditate) internally-generated images and geometric patterns." No, no such things are implied by the word "consciousness." Consciousness is the noun form of the adjective "conscious." Consciousness merely implies being aware of something. A mind could be conscious without having any memory, thought, language or internally generated images.
(2) The authors incorrectly state that in "science/materialism" consciousness has "no distinctive role," and follow this with the incorrect assertion that in "dualism/spirituality" consciousness is "outside science." That sounds like the authors have failed to study the history of psychical research. For two hundred years believers in dualism, paranormal phenomena and spiritualism have been intensely pursuing the study of psychic phenomena in a scientific manner, and certainly did not in general maintain that the study of consciousness or minds is "outside science." The literature of such persons providing a scientific basis for the study of minds, psychical phenomena and consciousness is extremely vast, and very often consisted of the most detailed observational accounts following best practices in scientific research.
(3) Section 2.1 of the paper is entitled "Unexplained features of consciousness," but fails to list even a tenth of the unsolved problems in explaining minds. The problems listed are mostly not any of the most serious problems in understanding minds.
(4) A large part of the paper is the groundless speculation that some minute units in the brain called microtubules have some role in computing or "giving rise" to consciousness. No robust evidence is provided for any such speculations. There is no conceivable arrangement of matter that we can say looks like something that could give rise to consciousness. Humans do make computers that can compute, so we do know some of the things that computers have that allow them to compute, such as as (A) hugely complex software systems called operating systems requiring many man-years of labor to create (examples being UNIX, Linux and Windows); (B) many types of application software also requiring much human labor; (C) transistors and CPU units for serially processing instructions. No such things exist in the brain or any of its parts.
(5) The paper attempts to suggest that microtubules in the brain are computing devices. Microtubules in the brain have not the slightest resemblance to any device for computing that humans have constructed, and due to a problem called decoherence (widely discussed in critiques of this theory) we should not expect any type of quantum computing to be possible in microtubules.
(6) When the paper moves over to a very long discussion of the super-speculative "here be dragons" topic of quantum gravity, we get a strong feeling of the authors wandering around lost in the woods and hopelessly off-topic.
Microtubules are tiny cylindrical units inside neurons, and each neuron has many of them. The function of microtubules is known: they serve to provide structural support for a neuron, and also help transport chemicals. Claiming that they also provide consciousness rather reminds me of that classic Saturday Night Live sketch in which someone claims that his floor wax is also a dessert topping. There is not a speck of evidence that microtubules have computed anything, and they have no resemblance to any computing devices made by humans. And if microtubules were to be doing some computing, that would not explain consciousness, because consciousness is not computing.
The Orch OR theory was introduced years ago by Penrose and Hameroff, and it has not attracted much of any appreciable support in the scientific community. What we have in the latest article by Hameroff is something that sounds as bad as what was in a previous article he wrote. For a critique of that article, see my post here, entitled "Saying Consciousness Is a Wave Function Collapse Is Like Saying Your Mind Is a Square Root."
The Orch OR theory relies on exotic physics speculations, speculations about how quantum mechanics might work beyond the way we know it does work. Physicists like to churn out such speculations in great variety, and they come in 1001 varieties; you might even say "they're a dime a dozen." Even if the imagined physics speculations were to be true (which is very unlikely), they would do nothing to explain the human mind.
What goes on in papers such as these is a "bait and switch" trick (a "give us an inch and we'll take a mile" trick) like this:
(1) First, an attempt is made to explain human minds, using the most minimal-sounding word you could use to describe a mind, the mere word "consciousness." The attempt won't sound too outrageous, because the word "consciousness" sounds like a mere thousandth of a human mind.
(2) Then later the authors will try to super-expand 1000 times what they mean by "consciousness," by some language such as the language quoted above, in which the authors claim, "Consciousness also implies a sense of self, feelings, choice, control of voluntary behavior, memory, thought, language, and (e.g. when we close our eyes, or meditate) internally-generated images and geometric patterns."
It's kind of like some employer getting you to agree to a "cut" (when you thought he meant just a hair trim), and then later telling you what he really meant by a cut is an 80% salary cut and a 60% benefits cut.
Microtubules are short-lived structures in neurons. A wikipedia.org article says, "Although most microtubules have a half-life of 5–10 minutes, certain microtubules can remain stable for hours." Things so short-lived are not credible candidates for something that could produce computation in a brain. Claiming that microtubules are computing devices is more implausible than claiming that a bucket of sand is a computing device. Both a bucket of sand and microtubules lack the operating system and application software that would be needed for computing. But at least a bucket of sand is stable.
What we have in the writing of Penrose and Hameroff on this topic is a glaring example of one of the most frequently occurring errors of theoretical scientists: the error of requirements underestimation. I gave many examples of requirements underestimation by scientists in my 2015 post "Requirements Underestimation, the Perennial Sin of Theoretical Scientists." The requirements for a man-made computing system are things such as a massive software foundation called an operating system, application software, chips or transistors including something like a CPU, and so forth. No such things are found anywhere in a brain, and the least likely place for them to exist in a brain would be in the short-lived and much-tinier-than-a-neuron units called microtubules. And even if microtubules did computing, that would not explain consciousness, because computing does not mean consciousness. Your computer computes, but it isn't conscious.
The original blunder of Orch OR theory was the error of confusing consciousness and computing. Here are the Cambridge Dictionary's definitions of compute:
(1) to calculate something using mathematics or a calculator (= a device for doing mathematical processes)
(2) to calculate an answer or amount by using a machine
(3) to calculate something
None of these definitions correspond to consciousness or human experience. So someone with a mere theory that microtubules compute can only pass himself off as a consciousness theorist by language trickery in which computation and consciousness are wrongly confused and conflated. We see that at the beginning of a 2003 paper by Penrose and Hameroff, in which they say this: "The most popular scientific view is that consciousness emerged as a property of complex biological computation during the course of evolution." No, computing is calculating something, and that isn't what consciousness is. You can't calculate your way to the state of being aware. And the human mind and its capabilities are something a billion times more complicated than a mere property, which is some simple thing like width, height and depth.
We can understand why such trickery might occur. Humans cannot manufacture any conscious devices, and there is no conceivable way you could arrange matter to look like something we should expect to produce consciousness. So no one can point in anything in the brain, and plausibly say, "That looks like something that would produce consciousness." But humans do make devices that can compute, ranging from a simple abacus to a 1970's Radio Shack calculator to a computer. So a person might be able to point to something in a brain that looks a little like a computing device, and claim that it looks a little like something that might compute. Then the person might engage in equivocation and word trickery to get you to confuse such hypothesized computing with consciousness. We should always cry fowl and "throw a yellow flag" when such trickery occurs, and immediately point out that computing is not consciousness.
After sufficiently studying brains (including their very important physical shortfalls), the most revealing neuroscience case histories, human minds, and human mental experiences in all their strange variety, a person will tend to think, "Neurons cannot explain minds." The right direction to go from such a thought is: look for some reality greater than neurons. Penrose and Hameroff instead went in the wrong direction, claiming to find an answer in something much less than a neuron (microtubules, one of the organelles of a neuron).
We do not need things like the Orch OR theory that are billed as "theories of consciousness." What we need is an adequate explanation for human minds. A human being is not "some consciousness." A human being is a thinking, knowing, believing, loving, questioning, seeing, hearing, creating, imagining, willing, speaking, reading, aspiring, instantly learning, instantly recalling, enjoying, suffering and comprehending unified self, capable of advanced phenomena such as insight, compassion, morality, abstract idea creation, self-introspection, philosophical inquiry and refined spirituality. That amounts to something gigantically more than some mere awareness, and gigantically more than a property.
At the end of Hameroff's IAI article he talks a little chemistry trying to substantiate his 100% groundless claim that "observations of extraterrestrial organic matter...provide reason to believe that consciousness came before life." It boils down to him speculating that somewhere in the Bennu asteroid sample gathered by NASA, there might be the tiniest of ring shapes. The Orch OR theory of Penrose and Hameroff was based on the nonsense of thinking that a hollow cylinder shape (a microtubule) can give rise to consciousness, and now Hameroff is apparently trying to sell us on the similar nonsense of suggesting that ring shapes can give rise to consciousness. Will he think consciousness is arising in the sky the next time he sees three clouds forming a triangle shape?
Hameroff tells us that he hopes to expose some of the dirt-and-tiny-rocks Bennu sample to anesthetic gas in hopes of supporting his theory, stating, "If we find such signs of life in a sample, we will expose them to anesthetic gas to see if they are inhibited proportional to anesthetic potency in blocking consciousness in animals and humans." The idea of applying such a medicinal gas to the lifeless dirt of the Bennu sample in hopes of clarifying the origin of consciousness sounds like as silly an idea as I've heard all year, as silly as the idea of injecting a flu vaccine into your backyard's dirt. We recently got a 73-page report on the Bennu sample, and from a biology standpoint, it's a bust. The report fails to even mention amino acids, the simplest components of proteins. There's not even a mention of glycine, the simplest amino acid. The Bennu sample is as dead as a doornail.
Appendix 1: In the video here we see a split-brain patient who seems like a pretty normal person, not at all someone with “two minds." And at the beginning of the video here the same patient says that after such a split-brain operation “you don't notice it” and that you don't feel any different than you did before – hardly what someone would say if the operation had produced “two minds” in someone. And the video here about a person with a split brain from birth shows us what is clearly someone with one mind, not two. In the video here we have a long interview with a girl who had a split brain operation (a functional hemispherectomy) that disconnected the two hemispheres of her brain. She is obviously a single unified mind, not two minds in a single body.
A scientific study published in 2017 set the record straight on split-brain patients. The research was done at the University of Amsterdam by Yair Pinto. A press release entitled “Split Brain Does Not Lead to Split Consciousness” stated, “The researchers behind the study, led by UvA psychologist Yair Pinto, have found strong evidence showing that despite being characterised by little to no communication between the right and left brain hemispheres, split brain does not cause two independent conscious perceivers in one brain.”
The press release states the following: “According to Pinto, the results present clear evidence for unity of consciousness in split-brain patients.” The paper states, “These findings suggest that severing the cortical connections between hemispheres splits visual perception, but does not create two independent conscious perceivers within one brain.” The recent article here in Psychology Today describes the bizarre experiment that was used to make the groundless claim that split-brain patients have two minds. It was some experiment based only on visual perception, using some strange experimental setup unlike anyone normally encounters. The article shreds to pieces claims that results from such an experiment show that split-brain patients have two minds:
"Not so fast. There are several reasons to question the conclusions Sperry, Gazzaniga, and others sought to draw. First, both split-brain patients and people closest to them report that no major changes in the person have occurred after the surgery. When you communicate with the patient, you never get the sense that the there are now different people living in the patient's head.
This would be very puzzling if the mind was really split. Currently, you are the only conscious person in your neocortex. You consciously perceive your entire visual field, and you control your whole body. However, if your mind splits, this would dramatically change. You would become two people: 'lefty' and 'righty.' 'Lefty' would only see what is in the right visual field and control the right side of the body while 'righty' would see what’s in the left visual field and control the left side of the body. Both 'lefty' and 'righty' would be half-blind and half-paralyzed. It would seem to each of them that another person is in charge of half of the body.
Yet, patients never indicate that it feels as though someone else is controlling half of the body. The patients’ loved ones don’t report noticing a dramatic change in the person after the surgery either. Could we all — patients themselves, their family members, and neutral observers — miss the signs that a single person has been replaced by two people? If you suddenly lost control of half of your body, could you fail to notice? Could you fail to notice if the two halves of your spouse’s or child’s body are controlled by two different minds?"
Nowadays split-brain operations for epilepsy are called by the name of functional hemispherectomy. You can search for advisory medical pages talking about functional hemispherectomy, and none of them will mention anything about single minds being turned into two minds. The paper "Long-Term Outcomes of Hemispheric Disconnection in Pediatric Patients with Intractable Epilepsy" studied 12 children who had these "split brain" operations, and tells us "none had additional motor or cognitive deficits after surgery," which would not be true if any of them suddenly became bodies with two minds. Nowhere in the medical literature reviewing the effects of functional hemispherectomies (split-brain operations) will you read anyone listing a "two mind" effect as being a result of such an operation.
A 2020 paper states this about split-brain patientis: " Apart from a number of anecdotal incidents in the subacute phase following the surgery, these patients seem to behave in a socially ordinary manner and they report feeling unchanged after the operation (Bogen, Fisher, & Vogel, 1965; Pinto et al., 2017a; R. W. Sperry, 1968; R. Sperry, 1984)."
See also this scientific paper "The Myth of Dual Consciousness in the Split Brain." The actual facts about split-brain surgery are related here by a surgeon who has performed such an operation. He states this about split-brain patients:
"After the surgery they are unaffected in everyday life, except for the diminished seizures. They are one person after the surgery, as they were before."
The surgeon states: "In a rational scientific community in which evidence and reason held sway, split-brain surgery would be hailed as compelling evidence for dualism and the immateriality of the intellect and will."
Physician Michael Egnor states the following about Sperry's research:
"The neuroscientist Roger Sperry studied scores of split-brain patients. He found, surprisingly, that in ordinary life the patients showed little effect. Each patient was still one person. The intellect and will – the capacity to have abstract thought and to choose – remained unified. Only by meticulous testing could Sperry find any differences: their perceptions were altered by the surgery. Sensations – elicited by touch or vision – could be presented to one hemisphere of the brain, and not be experienced in the other hemisphere. Speech production is associated with the left hemisphere of the brain; patients could not name an object presented to the right hemisphere (via the left visual field). Yet they could point to the object with their left hand (which is controlled by the right hemisphere). The most remarkable result of Sperry’s Nobel Prize–winning work was that the person’s intellect and will – what we might call the soul – remained undivided. The brain can be cut in half, but the intellect and will cannot. The intellect and will are metaphysically simple."
Equivalent to a split-brain patient, Patient H.W. is a man born without any corpus callosum, the bundle of fibers that connect the two hemispheres of the brain. Instead of him having two minds in a single body, Patient H.W. led a normal life, and performed very well on a wide variety of tests of intellectual and psychological function. An article on the man is entitled "This Elderly Man Was Born With His Brain Hemispheres Disconnected. Did It Affect His Life? Hardly." The relevant scientific paper is here, and its title describes the man as one with "minimal neuropsychological impairment."
Making a generalization about people born without a corpus callosum connecting the two sides of the brain (equivalent to split-brain patients), a scientific paper states this:
"The major anatomic feature of Primary AgCC is the absence of the corpus callosum....Primary AgCC has surprisingly limited impact on general cognitive ability. Although the full-scale IQ may be lower than expected based on family history, scores frequently remain within the average range."
We hear no mention of any "two minds in one body" effect. Another paper states this:
"In the 37 adult cases of agenesis of the
corpus callosum, 19 (51%) had some degree of
intellectual impairment, with the remainder
being judged to have a normal IQ. Of those
with learning difficulties, two thirds had a mild
impairment, and one third had a moderate or
severe problem."
You can find papers on the condition of being born with no corpus callosum by searching on Google Scholar for papers having the phrase "agenesis of the corpus callosum." You will not find any discussion of "two minds in one body" in such papers about split-brain equivalent patients, which helps show that the claim of such an effect is groundless.
Appendix 2: A scientific paper tells us, “Neuronal variability (both in and across trials) can exhibit statistical characteristics (such as the mean and variance) that match those of random processes.” Another scientific paper tells us that “Neural activity in the mammalian brain is notoriously variable/noisy over time.” Another paper tells us, "We have confirmed that synaptic transmission at excitatory synapses is generally quite unreliable, with failure rates usually in excess of 0.5 [50%]." A paper tells us that there are two problems in synaptic transmission: (1) the low likelihood of a signal transmitting across a synapse, and (2) a randomness in the strength of the signal that is transmitted if such a signal transmission occurs. As the paper puts it (using more technical language than I just used):
"The probability of vesicle release is known to be generally low (0.1 to 0.4) from in vitro studies in some vertebrate and invertebrate systems (Stevens, 1994). This unreliability is further compounded by the trial-to-trial variability in the amplitude of the post-synaptic response to a vesicular release."
The 2010 paper "The low synaptic release probability in vivo" by Borst is devoted to the topic of what is the chance that a synapse will transmit a signal that it receives. It tells us, "A precise estimate of the in vivo release probability is difficult," but that "it can be expected to be closer to 0.1 than to the previous estimates of around 0.5."
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