Debunker: 10% of your brain

I admire greatly the life of Carl Sagan. His “Cosmos” series is a wonder, and he dedicated his life to fighting pseudo-science and popularizing science. While I’m not cut out to be a school teacher, I respect those who are (including my sisters-in-law Kelly and Erin). I’ve worked as a trainer, and it has always seemed to me that educating, mentoring and debunking is a very high calling in life.

In the November/December 2003 Skeptical Inquirer, an article written by Carl’s wife, Ann Druyan, gave me a lot to think about:

“Congress cut off federal fnding for SETI years ago. I was with Carl when he went into Senator William Proxmire’s office after Proxmire had given the Golden Fleece Award to the SETI program. Carl sat down with him. I didn’t say a word. I was just a witness. And I just watched Carl. I was inspired by him, by not only the breadth of his knowledge but his patience, his lack of arrogance, his willingness to hear the other person out. Senator Proxmire did a complete turnabout as a result of that meeting.

“And there were other instances of Carl’s remarkable persuasiveness. One was a great story of a so-called “creation scientist” who watched Carl testify at a hearing about creationism in schools. Carl testified for about four hours. It was somewhere in the South, I can’t remember where. And six months later a letter came from the “creation scientist” expert who had also testified that day, saying that he had given up his daytime job and realized the error of what he was doing. It was only because Carl was so patient and so willing to hear the other person out. He did it with such kindness and then, very gently but without compromising, laid out all the things that were wrong with what this guy thought was true. That is a lesson that I wish that all of us in our effort to promote skepticism could learn, because I know that very often the anger that I feel when confronting this kind of thinking makes me want to start cutting off the other person. But to do so is to abandon all hope of changing minds.”

As a former high school and college debater, in my experience Dr. Druyan is right: It’s very hard to convince anyone with harshness, derision, or ridicule.

While I don’t have the training or expertise that Carl had, or the time to put together a site such as Snopes (one of my favorites), or the resources to make a television show such as Penn & Teller’s Showtime series “Bullshit,” or Adam and Jamie’s “Mythbusters,” I will from time to time try to do some debunking of my own here.

To begin, I’d like to discuss a claim that I hear repeated quite often: That we only use 10% of our brains.

Many times, the source of this claim is someone who is trying to sell something that will help you “unlock” the other 90% of your brain, or someone (such as a fortune teller or medium) who claims that they have special powers due to using their whole brain.

In short, there is no science behind this claim. I have three arguments:

  1. MRIs and other brain scans reveal that all of us use almost all of our brains throughout the day. It’s true that at any given moment, not all of the neurons in our brain are firing (and perhaps that’s the source of this claim). But it’s not true that a significant portion of our brains is continuously fallow.
  2. Patients who undergo brain trauma (such as a piercing accident or non-fatal gunshot wound) almost always suffer from some signficant loss of function. When there is brain damage (from, say, years of being a boxer, or a disease) similarly you can witness the effect. If 90% of the brain were not needed, there would be far more cases of strokes, anuerysms, and brain damage having no effect. The myth doesn’t reconcile with the reality we witness.
  3. Simple evolution: Having recently witnessed the birth of my son, I can tell you first-hand that the biggest cause of difficulty during birth is due to the size of the infant’s head going through the birth canal. The birth process would be so much easier if the brain were 90% smaller and the head could be correspondingly reduced in size. Also, think how much of our day-to-day expenditure of calories is solely to keep our heart pumping in order to power the brain with oxygen. Why would there be all this difficulty and energy associated with something that was 90% unused? The selection pressure on having smaller heads and smaller brains would be signficant, because if only 10% was needed, there would be a giant advantage to having a smaller brain. But, the reality is that we succeed by having big brains, and by using all or mostly all of it.

Was that convincing? Hopefully so. Now I see Snopes’ page debunking this claim. Hmm, that’s a pretty good article. Clearly I need to do some homework for my own debunking efforts.

Next time you hear someone make this claim, perhaps now you will gently, and with respect, give them your own counter-arguments. Be proud that you use 100% of your brain!

5 Responses to “Debunker: 10% of your brain”

  1. Dave Zatz Says:

    Ah… this will be an interesting exercise using x% of my brain. I’ve never been on a debate team, but I do like a good argument err thought provoking discussion. Honestly, I have no idea how much of my brain I use (no comments please) and haven’t thought through this topic, but I’ll play devil’s advocate and throw in some counter-points.

    1. While various scans show activity in many (all?) areas of the brain, do the scans indicate the type and quality of that activity? For example, if I were to bench press some weight one could observe several muscles in use… from that could one quantitatively determine the maximum weight I can lift and how good my form could be? I might be lifting 50lbs with sloppy form, but is my capacity 100lbs with good form?

    2. In most cases brain trauma does severely impact a person’s performance, but frequently those skills (swallowing or walking for example) can be relearned/reacquired to an extent (or even completely) through other parts of the brain indicating it is possible to lose a portion of one’s brain and still function.

    3. I have an appendix that I don’t need 100% of the time and evolution hasn’t taken care of it… yet. I also have wisdom teeth and hair on my toes which haven’t done me much good.


  2. Stephen Says:

    All right, challenge accepted! I should argue first that those making the claim that only 10% of the brain is used should have the burden of proof, since it seems to counter one’s default assumption that there is a purpose for the brain being the size that it is. I took enough philosophy courses to know that I’m never going to “prove” anything. A sufficiently motivated devil’s advocate can keep spreading doubt forever.

    For the specific points:

    1. On the surface, your argument here doesn’t seem to contradict my point that scans show that 100% of the brain is used. You seem to be arguing that perhaps 90% of your brain is only getting a little bit of use, and the other 10% is doing the heavy thinking. That’s certainly possible, but I’d say that any use is enough to refute the claim that 90% is unused.

    2. You’re absolutely correct, but I think the relearning/reacquiring actually proves that the whole brain is being used — because while the brain is flexible, there is certainly a period of therapy and training that indicates that a loss has taken place and that something that was in use is now damaged.

    3. You’re right that appendices and toe hair and wisdom teeth have little or no use, but there’s no selection pressure to evolve them away, since there’s no evolutionary advantage to getting rid of them. For the brain, in contrast, there is much more of a selection pressure to evolve a smaller brain due to the tremendous energy that brains use up and due to the significant dangers a big head poses during birth.

  3. Ed Says:

    you make some great points. i dont know who it was that originally said this or what exactly was said but i imagine what they probably meant was if we could channel all the various sections of the brain and focus them on one task we could do amazing things with all that brain power. this sounds like nonsense to me because it appears each section of the brain has been designated a specific function atleast according to what ive cannot use the cerebellum to process language nor can you breathe with your heart or pump blood with your lungs.even if you could somehow use these parts of the brain for something other their intended purpose it seems like you would likely lose the ability that they were originally intended to provide, like breathing..people have this absurd need to believe the snake oil salesman rather than the scientist probably because fact can be less entertaining than fantasy but in the end they are just an ignorant ass with useless snake oil.
    dont question its usefullness though because ” the snake oil guy said it was good shit and thats that!”people who believe in this crap(10%of the brain/psychic mediums) will argue their point with rightous fervor and when its all said and done the dumb will remain dumb and willfully coerced by people like john edward and sylvia brown.

  4. Ed Says:

    oh yeah and there are adults who actually believe david blaine has magical/telekinetic powers because he uses 20% more of his brain than everyone else. LOL!!!!!!!!

  5. Jon Says:

    Oh yummy. This is an interesting conversation. I’m going to try to debunk and not debunk all at the same time, so bare with me. Apparently people are misunderstanding this whole 10% of the brain thing.

    1) Fact: Human beings use 100% of their BRAIN. The brain is used for functionality (i.e. breathing, walking, using your arm, etc.). It can also be said that when a person is sleeping, resting or watching TV, that portions of the brain are not fully active. They are still functioning, but at a lesser rate, because the need to move is not a constant during the resting period(s). If you didn’t use 100% of your brain, you would not be able to carry on with your day to day life. Might as well be a vegatable…

    2) Fact: Human beings use less than 100% of their MIND. This is where many get confused. We’re talking about the MIND, not the BRAIN. Potentially, if you were an absolute genius and could do anything and everything, then yes, you could possibly be using 100% of your mind, or close to it. However, most people are not so. I’m not saying that everyone only uses 10%. Maybe we use more than that but I wouldn’t say too much more. As an example, while a child ages, they use a large amount of their mind (i.e., learning, creating, daydreaming, etc.). If this child were using 100% of it mind, then it might not be able to learn or remember new things/ideas. Now, as the child becomes an adult, he relinquishes some of that learning capability that he had. Why? He’s learned then basics, most the intermediate and probably dabbled in the advanced knowledges. He may still learn and try new things, but it will never be like his original growing experiences. He’ll probably get a job that doesn’t require a lot of new ideas or thinking. Therefore, just another robot that pushes pencils or a worker that continues to hammer nails. The mind itself, as far as anyone can tell is nearly limitless. Now, I’m not going to contribute to the so-called psychics and illusionists, but you do have to wonder….. If we’re only using 10%-40% of our mind, then what’s the rest for? Or has it shut down because the initial learning period is over?

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