Stupid Cliche Debunked. Again.

I have long believed that if you ever hear anyone say “we only use 10% of our brains,” especially in the process of defending ESP or some similar thing, you can be absolutely certain that you are talking to an ignoramus. Claudia Hammond puts this myth to rest at the BBC:

First of all, it’s important to ask the question – 10% of what? If it is 10% of the regions of the brain to which people are referring, this is the easiest idea to quash. Using a technique called functional magnetic resonance imaging, neuroscientists can place a person inside a scanner and see which parts of the brain are activated when they do or think about something. A simple action like clenching and unclenching your hand or saying a few words requires activity in far more than a tenth of the brain. Even when you think you are doing nothing your brain is doing rather a lot – whether it’s controlling functions like breathing and heart rate, or recalling the items on your to-do list.

But maybe the 10% refers to number of brain cells. Again this doesn’t work. When any nerve cells are going spare they either degenerate and die off or they are colonised by other areas nearby. We simply don’t let our brain cells hang around idly. They’re too valuable for that. In fact our brains are a huge drain on our resources. Keeping brain tissue alive consumes 20% of the oxygen we breathe, according to cognitive neuroscientist Sergio Della Sala

There are two other phenomena that might account for the misunderstanding. Nine-tenths of the cells in the brain are so-called glial cells. These are the support cells, the white matter, which provide physical and nutritional help for the other 10% of cells, the neurons, which make up the grey matter than does the thinking. So perhaps people heard that only 10% of the cells do the hard graft and assumed that we could harness the glial cells too. But these are different kind of cells entirely. There is no way that they could suddenly transform themselves into neurons, giving us extra brain power.

This will not, of course, stop ignorant people from mindlessly repeating that tired old platitude as a fact.

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  • This myth is probably believed by those who use only ten percent of their brains.

  • rowanvt

    The best way to shut those people up is to tell them that we have seen it where someone is using 100% of their brain at one time. We call it grand mal seizures. That usually makes them stop in their tracks and *actually* think for a moment.

  • jamessweet

    I heard that the myth came from a study which estimated that we only use 10% of the brain at any given time. Though that estimate has since been called into question, the idea that we only use a relatively small fraction of our brain at any given time makes perfect sense:

    I only use <10% of my Leatherman multi-tool at any given time. And if I tried to use all of it at once, it wouldn’t unlock some amazing psychic multi-tool powers; it would render the thing nigh useless. Same with our brain: unrestricted activity is the cause of things like epilepsy and hallucinations. The parts that are being used are the ones that are active at any given time, and that number is somewhat less than 100%…

    …though as I alluded to earlier, probably typically more than 10%. So this myth is based on a misinterpretation of a study that turned out to be wrong anyway. It’s double-wrong! Does that cancel out and make it true?

  • dingojack

    Perhaps it’s woo-merchants who only use 10% of their brains. The 10% devoted to scamming people out of their hard-earned cash, that is!

    🙂 Dingo

  • Put to rest? the 10% of your brain thing is that little kid who gets put to bed only to get up and go running through the house a few minutes later.

  • Artor

    The 10% myth dates back to before we had the technology to study the brain effectively. Now that we have the tools to look and know what’s going on in the grey matter, it’s obvious that 10% is bullshit. Like the old canard that bees supposedly aren’t supposed to be able to fly. Obviously they can, but when that myth was spawned, we knew jack shit about aerodynamics. Now we know much more, and can explain how they do it just fine, but the myth still persists.

  • The version of the myth’s origin I heard was that it was the telephone game traced back to Einstein lamenting that humanity wasn’t living up to its potential, and some people probably added in the 10% quantity to make it sound more scientificalified.

  • mck9

    Without disputing the larger point, I must point out that Hammond gets one thing completely wrong: the notion that glia correspond to white matter, and neurons to gray matter.

    White matter contains the nerve fibers connecting different parts of the central nervous system. The fibers are largely covered with myelin, a fatty white insulation produced by oligodendroglia (one type of glia). While the oligodendroglia make up the bulk of white matter, the nerve fibers themselves are inherently neuronal.

    The neuronal cell bodies reside in the gray matter, where the predominant type of glia is the astrocyte. The astrocytes are involved in regulating the level of extracellular potassium, and likely perform other functions that I don’t know about.

    There are at least two other types of glia: microglia (macrophages that respond to infection or other damage) and Schwann cells (which produce myelin in the peripheral nervous system).

  • jamessweet

    Okay, so now we have a whole bunch of meta-myths about where the original myth started. I want to know the truth about the falsehood, damnit! 😀

  • Well, I often only use 10% of my brain for dealing with the KKKristianist fuckwads who can ONLY use 10% of their brain (and that use is mostly amygdalian in nature). My body uses the rest without my permission–the fucker. It’s like, “You aren’t smart enough to breathe on your own, or hear, see, listen, touch, feel, learn, eat, shit, fuck and care about others.”. Ah, hell, it’s prolly right, but it still pisses me off!

  • cham826

    Interesting, so saying you only use 10% of your brain is like saying you only use10% of a table because you only use the top.

  • cottonnero

    #11: Or like saying you only use 10% of your house because you’re in only one of its ten rooms right now.

    Which is probably why I leave the TV on in the other room.

  • blehdude

    that’s why I always say bullshit by default. whether it’s god or somebody saying they can dunk, i’m skeptical. most of the time i let it go because i don’t care.

  • Okay, so now we have a whole bunch of meta-myths about where the original myth started. I want to know the truth about the falsehood, damnit! 😀

    The earliest reference I’ve been able to find is the foreword of How to Win Friends and Influence People,” which in turn appears to derive from research at Harvard at the end of the 19th century. Psychologists William James and Boris Sidis held that most people could have a much higher measured IQ if only they received proper childhood education, nutrition, etc., and thus that people were using only a small part of the potential of their brains. Lowell Thomas, who was many things but not a scientist, added a sciency-sounding 10% and a poor phrasing when he wrote a foreword for Dale Carnegie’s enormously popular self-help book, and the rest is source amnesia.

  • Midnight Rambler

    jamessweet – I suspect that it’s resulted from the conflation of several of them, with the one Dalillama cites being reinforced by the white matter/gray matter issue. When the former says “We only use 10% of our brains!” and the latter says “gray matter is where the actual neurons are and thought occurs, and it only makes up 10% of the brain”, people who hear both think that the first one is right even though it’s not like white matter is useless or we can expand “thought” to it.

  • grumpyoldfart

    I’ve been explaining the falsity of that myth for decades and so far I have convinced no-one.

  • Happens I looked into this a few weeks ago. While the idea was around, it really took off in the mid-1960s under the influence of the so-called human potential movement. Two guys who founded Esalen were pushing it, but it became a beloved falsehood throughout the broader movement.

    You can see a steep rise in published mentions beginning in the mid-1960s.

  • doubtthat

    Well, that 10% landed a dude on the fucking moon, and all the 100%ers seem to be able to do is bend spoons and ask your dead relatives where they hid the casserole recipe.

    Arguably that 90% is ignored for good reason.

  • Amphiox

    It’s not like those 90% glial cells are sitting around doing nothing. They’re doing important metabolic work to support the functioning of the neurons. Without them the neurons would rapidly fry/short circuit/starve/degenerate etc.

  • godlesspanther

    I think it was Cheech and Chong — maybe it was the Freak Brothers:

    Since we only use 10% of our brains, why not blow the other 90% out with drugs?

  • andrewlephong

    This 10% myth gets even more annoying when you’re told that Albert Einstein or Thomas Edison were able to use 11% or even *gasp* a whopping 12% of their brains!

  • dingojack

    mck9 – are Schwann cells developmentally related to oligodendroglia?

    With idle curiosity,


  • valhar2000

    Okay, so what’s worse: 10% of the brain stories, or fake Founding Father quotes?

  • Dunc

    Ever hear about the guy who got shot in the head without suffering any ill effects, because the bullet passed through part of the 90% of his brain he didn’t use? Nope, me neither…

  • mck9

    dingojack @ 22:

    No. Schwann cells are derived from neural crest cells that have migrated to the periphery. I’m a little hazy on oligodendroglia but they’re not from the neural crest; they spend their entire lives within the central nervous system.

    The other main difference is that one Schwann cell wraps itself around one nerve fiber (i.e. axon), while an oligodendroglial cell puts out multiple extensions that wrap around multiple different axons.

    PZ could give you a more authoritative answer.

  • dingojack

    Interesting, since they have similar kinds of functions. I might just ask PZ about that.

    Thanks, Dingo