5X5 Episode 48

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5X5 Episode 48
The 10% Brain Myth
1st December 2008

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5X5 47 5X5 49
Skeptical Rogues
S: Steven Novella
R: Rebecca Watson
B: Bob Novella
J: Jay Novella
E: Evan Bernstein
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The 10% Brain Myth[edit]

Voice-over: You're listening to the Skeptics' Guide 5x5, five minutes with five skeptics, with Steve, Jay, Rebecca, Bob and Evan.

S: This is the SGU 5X5 and tonight we're talking about the persistent myth that humans only use about 10% of their brain activity. Sometimes this figure is given as 12%, sometimes it's 10%, but the notion is that the vast majority of our gray matter of our brains are unused and represent un-tapped ability.

J: I looked up the history of this one. I always thought it was something to do with Albert Einstein, and I did find some evidence to that, it's possibly a misquote of Albert Einstein, or a misinterpretation of work done by Pierre Flourens in the 1800s. Also it may have been written by a person named William James who wrote in 1908 "we are making use of only a small part of our possible mental and physical resources."[1]

B: Regardless of the origin of this myth, it's clearly deeply embedded in our culture. You can find it in so many different forms of media. I found a hard drive ad that basically said that "your brain only uses a fraction of its capacity. We think your hard disc should be a bit more efficient than that." So that's part of the reasons why it has endured; the media are constantly referencing this myth. Another reason that I came across is interesting. Why this has endured is that psychics have latched on to this like you wouldn't believe. 'Cos, you know, when people say that it's an obvious conclusion that if you believe that only 10% of your brain is actually being used, then they immediately jump to the belief that 'well, then the other 90% could be responsible for psychic events.'

R: Well, yeah, and the weird thing is though I don't think that this myth is long for this world because advertisers and psychics are still using it, but that's about it, I think. Because if you just do a google search for like "10% of your brain," it's pretty much all skeptical results. So I'm pretty optimistic that this one's on its way out.

E: But at the same time, Rebecca, I mean, we do still see it being used. It has been referenced in recent movies like The 40-Year-Old-Virgin. And I've actually, you know, spoken to some people on the streets kinda just giving them a little test about their basic science knowledge and anytime I mention that, I asked them what they think of the 10% myth and they all seem, well, the majority of them seem to think that there's something to it. So it still has some power and influence in society. There's something that does need to be corrected.

S: There's something strangely appealing about the notion I think, as Bob said. It could be the reservoir of paranormal or ESP or psychic ability, but also just this notion that we could be so much greater than we are. All we have to do is figure out a way to tap into this vast reservoir of ability. So I think that psychology and wishful thinking keeps it going.

Of course there are a number of lines of evidence by which we know with a high degree of certainty that it is not true. First of all, it's based on nothing: there's no reason to believe it is true. But of course through imaging of brain activity, through various ways of assessing brain activity, all of the brain serves some function — every piece of the brain has a function or purpose and is used for some sub-set of tasks that we perform. You can't go in there and take out any significant piece of the brain without causing a deficit, without causing a loss of ability. So let alone 90% of the brain, you know - if this claim were true you could take out huge chunks of brain without causing any problems at all.

R: Yeah, the common joke is that you never hear a doctor say "Well, the bullet did lodge itself in his brain but luckily it was part of the 90% that he doesn't use."

S: (laughs) Right, that never happens.

J: Steve, also doesn't your brain get the freshest blood from your lungs, the most oxygenated blood?

E: It gets about 20% of the entire oxygen of your body, if I'm not mistaken.

S: Yeah, it gets the same blood that the rest of the body gets from the heart, it may be a shorter trip, you know, up to the brain, but as Evan said it's 20% of your metabolic activity, your heart output, everything is going to feed the brain, it's because it's all being used. If we were only using a tiny fraction of it, it wouldn't be the hungriest organ in our body. And also, why would we evolve such a massive brain if most people only used just such a small fraction of it?

E: To make childbirth pleasant.

S: Childbirth had become extremely dangerous. In fact, evolution had to work hugely around just the massive human brain, you know, right - shortening gestation, making infants more dependent upon their parents, and as you say, widening the female pelvis, all just to create this large brain. Where would the selective pressure be if we weren't actually using it? That makes no sense of course.

B: There's also the notion of "use it or lose it" which applies very well to human's developing nervous system. Look at the eyes — there's a window in development, if you do not use your eyes when you are, from say from birth to six months or some time period like that, you will never have good vision. It's, in a sense, use it or lose it really applies because the neurons and the pathways will be co-opted for other uses if it's not being used. So if there's 90% of your brain, all these pathways not being used, not being reinforced and developed, then you could argue that whatever purpose they might have had could never be used because they're not being used.

S: Yeah, they wouldn't develop in the first place. As you say that the brain grows, it organized itself and develops around use - it maps itself to the body and it gets reinforced by use. Like the visual cortex is intended for visual processing; if it doesn't get used for that, it gets co-opted and used for something else. So our understanding of how the brain develops, organizes and functions is dependent upon every piece of the brain being used.

[Note: Jay's source seems to be Neuroscience for Kids. Bless.]

S: SGU 5x5 is a companion podcast to the Skeptics' Guide to the Universe, a weekly science podcast brought to you by the New England Skeptical Society in association with skepchick.org. For more information on this and other episodes, visit our website at www.theskepticsguide.org. Music is provided by Jake Wilson.


  1. William James, 1907, The energies of men
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