The brain is not a general-purpose computer

Illustration: María Elena (Mani) Hinojosa

A popular view of the brain is that it works like a computer with a general-purpose global capacity that can centrally handle disparate tasks. It is not so. Numerous neurological disorders belie that view. Here is a list of some of the most illustrative ones.

Capgras syndrome, also known as “impostor syndrome” or “Capgras delusion”. People with this condition will believe that a person whose face they recognize is an impostor. For example, if they see their mother, they’ll recognize her face as indeed being identical to their mother’s face, but will nonetheless deny that the person in front of them is their real mother. Their vision is not at all impaired, that is, their ability to consciously recognize faces is not affected, but brain lesions seem to have severed a connection that produces the emotional arousal that we automatically associate with the different objects and people we see. Our spouse, a car, our home, a random person on the street, a predator, etc., each awaken in us, directly and automatically — that is, in a way not mediated by conscious thought — a particular emotional response.

What is incredible here is that these patients are otherwise perfectly normal. Their reasoning powers are intact. So why can’t they just deduce that if the person in front of them is identical to their mother, then it has to be their mother? Sure, it might take them a bit longer than normal, given that such a realization will not be immediate and effortless, as is the case with the rest of us, but shouldn’t they inevitably reach that conclusion through basic reasoning? That would probably be the case if the brain were really a general-purpose universal computer, but it isn’t, and so they simply can’t infer it.

Maybe there’s actually a rational process behind their bizarre belief. We’re used to feeling a strong emotion whenever we see our mother. If due to brain damage we stop automatically feeling this emotion, we’ll sense that something is off. If we see our mother and don’t feel anything at all, it may not be that crazy to conclude that the person can’t really be our mother. But still… further consideration and evidence, such as other people’s accounts and explanations, should force us to realize that the person must be our mother after all — yet this doesn’t happen. A person with Capgras syndrome has lost his rationality in this narrow, but important, domain.

Mirror agnosia, also known as looking-glass syndrome. A condition in which people confuse the mirror image of an object with the real object. Typically, these are people whose left side of the world “ceases to exist” due to damage to their right hemisphere. Everything on their left side is ignored or neglected. If a mirror is placed on the right side of a patient with mirror agnosia, and he’s asked to grab an object reflected in the mirror, he will try to reach into or behind the mirror, instead of reaching towards his left, where the object should logically be. These patients know that they are looking at a mirror. They’re lucid and intelligent and aren’t otherwise impaired. If the mirror is placed so that an object behind the patient (rather than on his left side) is reflected in it, he will turn back and reach for the object, as would be expected. So they still understand what a mirror does and can normally infer where an object is based on its reflection in the mirror — as long as the object is not on their left side…

Neuroscientist V. S. Ramachandran: “The patient’s belief systems and ability to reason intellectually about such matters have become selectively distorted to accommodate the strange looking-glass world in which they now find themselves trapped. It is remarkable that such a domain-specific tolerance for absurdities can be provoked by the mere use of a mirror.” (Source.)

Inability to understand metaphors. Damage to the left angular gyrus region of the brain can give rise to a curious condition in which patients who are otherwise perfectly lucid are unable to grasp the meaning of metaphors. They can only understand their literal meaning. Given that people affected by this disorder are rational in all other respects, one has to wonder what has happened to their ability to reason in this narrow domain. The only explanation is that many cognitive processes are fractionalized and thus function as independent modules, and not in some sort of holistic way directed by an overarching self who is in control at the center of it all.

Visual agnosia. This is the inability to recognize visually presented objects. As with other neurological disorders, it’s the result of brain damage. Patients can perfectly identify and describe the component parts of a given object, but are nevertheless unable to recognize it. They can’t place it in the right category. They might confuse a carrot with a brush, for example. The elementary sensory functions are intact, that is, this condition is not the result of a deficit in vision (nor in language, memory, intellect, etc.). It is rather a deficit in rationality, and yet another example of it failing in a narrow and specific area.

Anosognosia, the denial of disability. Brain damage can cause hemiplegia — paralysis on one side of the body. Additional damage may cause patients to deny or ignore their paralysis. As in the case of Capgras syndrome, these patients are mentally normal in other respects. This is a particularly astonishing syndrome as regards the generation of irrational beliefs, as it should be blindingly obvious to these patients that half their body is paralyzed — yet, incredibly, they’ll deny it.

It should be clear then, from the syndromes presented, that our brain doesn’t necessarily operate like a general-purpose rational machine. Rather, it could be viewed as an amalgam of disparate modules, each specifically designed for certain defined tasks. If one module fails, its functions aren’t just taken over by another one. Also, there’s no central area of command that oversees and coordinates everything, and that can fill in for a non-performing unit. Our distinct impression that there’s a self (“us”) aware and in control of everything is mostly an illusion.

In the “Tell-Tale Brain”, V. S. Ramachandran makes this very insightful remark: “Anosognosia, far from being just another odd syndrome, gives us fresh insights into the human mind. Each time I see a patient with this disorder, I feel like I am looking at human nature through a magnifying glass.”

Indeed. We’ve seen that outlandish interpretations of reality can result from certain brain disorders, yet we could view such disorders as simply issuing from atypical neurological organizations. They seem perplexing just because they’re different from what we’re used to. What we consider normal would probably seem just as perplexing to an alien. We already know that we’re prone to all kinds of irrational beliefs — no brain damage required. Even in modern industrial societies, people still believe in things for which there isn’t a shred of evidence: astrology, angels, ghosts, miracles, telepathy, reincarnation, etc. At least with education and some mental application we can often realize that such beliefs are not justified. Then there are the well-known psychological biases we’re all subject to, which, again, we can at least identify and sometimes overcome with significant effort. But there may still be things that we’re hardwired not to see or think. Just as a patient with anosognosia is incapable of realizing, despite all evidence, that he or she is paralyzed, we “normal” people probably have misconceptions just as extraordinary, and just as firmly lodged in our brain configuration — blind spots that we may be constitutionally incapable of detecting; and also “anti-blind spots”, that is, notions of reality entrenched in our nature that do not in fact correspond to anything real.

The underlying or ultimate cause of these misconceptions that we’re liable to, is that evolution doesn’t necessarily care that we see reality as it is; all it cares about is that we survive and reproduce, and if that is best accomplished by our distorting reality, and by seeing certain things (both literally and figuratively) or even imagining them, while ignoring others, that’s how we’ll perceive and understand reality.

Interested in natural selection, evolutionary psychology, neuroscience, science in general, human nature, consciousness, philosophy and ethics.

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