Nov 17 2010

Reviving the 10% Brain Myth

If you do a Google search on “10% brain” all of the relevant hits on the first page are discussing the fact that the notion that humans use only 10% of their brains is a myth. I took this myth down myself 12 years ago. It is a fun myth to debunk, and it a good hook for the discussion of brain function and anatomy and all the ways in which we know that we use more than 10% of our brains.

The Mythbusters even took this one on this season – and found that during specific tasks about 30-40% of brain capacity was used. I have some quibbles about how they approached the question, but they did provide some useful information, and certainly busted the myth.

But I was recently pointed to this article by Neil Slade. Yes – it has all the markings of a crank site, but it’s a crank site that is selling something, and I think that is the underlying context. Slade wants to sell you products that will “supercharge” your frontal lobes.

That has always been the appeal of the 10% myth – the notion that the brain has vast untapped resources can be used to sell all kinds of neuropseudoscience. Purveyors of brain boosting nonsense don’t want their favorite sales pitch taken away simply because of some pesky science.

Aside from a fun edition of  “name that logical fallacy,” Slade provides some new bad arguments to dissect. He writes:

“Such a statement as “We use all of our brain all of the time” or “It’s a myth that we only use 10% of our brain” are both misleading and unhelpful uninspiring skeptical crumbs with barely a grain of truth-As well as not even being accurate statements regarding usage of the human brain.”

Slade employs a lot of logical fallacies – starting with this straw man. Who ever said we use “all of our brain all of the time?” I have never read this statement before. The quotation marks imply that this is a direct quote, or at least a representative paraphrase – but I challenge Slade to provide a reference that anyone has ever made this claim before. This is what I had to say:

“Modern techniques to measure the blood flow to each part of the brain, the consumption of glucose, and the electrical activity of the brain, demonstrate that the entire brain has a certain baseline metabolic rate in the quiet awake state. When specific mental tasks are undertaken certain parts of the brain will kick into high gear and increase their metabolic functioning.”

No one claims that the entire brain is working at maximal capacity all the time, or even at any time. A certain amount of the brain is working just to be conscious, and then different parts of the brain, collaborating in different networks, will become active during specific tasks. But you cannot do a complex mathematical problem, compose a poem, engage in abstract reasoning, listen to music, identify an odor, and examine a complex visual puzzle all at the same time. But that’s what it would take for most of your brain to be active at one moment.

This also points out that the “10% of the brain” claim has always been very vague, and I often encounter understandable confusion as to what, exactly, it means. Does it refer to the percentage of the brain that we use at any one moment, the percentage of the brain that we use ever, the percentage of our theoretical brain capacity, or of our intellectual potential? Slade does not address this ambiguity, and in fact seems to exploit it by floating from one interpretation to another.

The first two interpretations are easiest to quantify. I have already dispensed with the first question, how much do we use at any one moment. The Mythbusters were addressing this question in their segment, and came up with the answer that during active mental tasks we use about 30-40%, which is quite a bit.

In my previous article I primarily addressed the second interpretation – how much of our brains do we use ever. It is my impression that most people use this interpretation. The implication being that the rest of the brain is “dormant” in some way, and if it can be tapped into then we could vastly increase our brain power, or perhaps overcome a disability or heal from an injury like a stroke. I have had more than one patient or family invoke the 10% myth in this context.

There are multiple lines of evidence to suggest that we utilize (at different times) most if not all of our brains. The brain uses up a great deal of resources (in blood flow, oxygen, and glucose). In evolved at great expense to be larger in order to provide greater cognitive power – there would have been a tremendous evolutionary pressure to use this large and hungry organ efficiently and not greatly expand it only to use 10%. Damage to any part of the brain causes deficits (some more than others). Diffuse damage or disease of the brain reduces mental ability. And various techniques of brain mapping (fMRI, PET, EEG, etc) all show that every part of the brain is active at one time or another.

There is no theoretical reason or direct evidence that any part of our brain is dormant, waiting to be tapped into by some technique that you can buy for just 5 easy payments of $19.95. In fact brain physiology is such that unused portions of the brain are either used by another function or they atrophy away. For example, if the eyes fail to develop or are damaged at a young age, the visual cortex will be taken over by other functions. Every bit will get used.

Slade, however, grossly misinterprets neuroanatomy to make the “dormant” claim, writing:

“Russian neurosurgeon Alexandre Luria proved that the 1/3 bulk of the frontal lobes are mostly dormant. He did this by performing ablation experiments on persons. He gave physiological and psychological tests before, cut our parts and whole frontal lobes, the (sic) retested after. His conclusion: removal of part or all of  frontal lobes causes no major change in brain function, (some change in mood alteration).”

Slade has butchered the fine work of Alexander Luria who made many contributions to neuropsychology. In Luria’s work he describes how the frontal lobes are involved in regulating behavior – they are not dormant. Yes, you can damage parts of the frontal lobes (not including the motor cortex, speech areas, or frontal eye fields that are part of the frontal lobes) without causes specific functional deficits. But neither can you dismiss the deficits that are created as “some change in mood alteration.”

The frontal lobes are involved with the highest order of cognitive function – ambition, planning, problem solving, self-control, social interaction, etc. Luria’s research contributed to our understanding of the incredibly important functions of the frontal lobes – the opposite of showing that they are “dormant.” (It’s also rather absurd to cite a 40 year old paper and ignore all the neuroscience of the last 40 years showing the many functions of the frontal lobes.)

Another point Slade misinterprets is that the higher cognitive functions of the frontal lobes are bilaterally redundant – meaning that each side (left and right) can function on its own. Therefore, damage to one side or the other causes minimal deficits because the remaining side can handle the function. It’s like losing one kidney – the other one will get the job done by itself. That does not mean that the kidneys are “dormant”. But damage both sides of the frontal lobes, and you have severe deficits to personality and behavior (ever hear of a frontal lobotomy?).

Slade also butchers what happens with hydrocephalus – an expansion of the fluid-filled cavities within the brain:

“In England John Lorber did autopsies on hydrocephalics. The illness causes all but the 1/6th inch layer of brain tissue to be dissolved by acidic spinal fluid.”

Wrong. Hopelessly, pathetically wrong. Spinal fluid does not dissolve brain tissue (we all have spinal fluid in and around our brains – so that would be a problem). In hydrocephalus the spinal fluid pushes the brain outward and compresses it. The brain is highly compressible, and remarkably can still function even under such conditions, especially if the compression is slow enough. What is amazing is that the brain can be compressed in children to a thin rim and still largely function (although certainly not normally). But Slade misinterprets this as 90% of the brain being “dissolved” and yet there being no deficits.

That’s all Slade has – grossly misinterpreting neuroscience. He also personally attacks skeptics, just to add another logical fallacy to his repertoire. And he confuses the various possible interpretations of “brain function” I listed above. After confusing brain activity at any one time, to the amount of brain that is ever active vs dormant, he then seamlessly moves on to “brain potential.”

Brain potential is a hard thing to quantify, and Slade seems happy to exploit this ambiguity. He claims the brain has “infinite” potential, but that is nonsensical, even for a sales pitch. I don’t care how empowering he thinks such a view is – it is not informative or meaningful.

I do think that human potential is enormous and most people do not come close to achieving their potential, but that’s just part of the human condition. You can always do more, learn more, experience more. Human potential is open ended, but not infinite.

But I don’t think that is what anybody means when they invoke the “10% of the brain” myth – they are not talking about the fuzzy concept of “human potential.”

Slade incorporates terrible logic, sloppy thinking, misrepresentation of neuroscience and the skeptical position, and poor definition of terms to promote a long-discredited myth. While I can’t know his motives and true beliefs, the reader can make reasonable inferences from the fact that he is also selling dubious brain boosting products.

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