The question is: Do we use only 10% of our brains?

Let me state this very clearly:

In other words, the statement, "We use only 10% of our brains" is false; it's a myth. We use all of our brain.

The 10% statement may have been started with a misquote of Albert Einstein or the misinterpretation of the work of Pierre Flourens in the 1800's. Maybe it was William James who wrote in 1908: "We are making use of only a small part of our possible mental and physical resources" (from The Energies of Men, p. 12). Perhaps it was the work of Karl Lashley in the 1920's and 1930's that started it. Lashley removed large areas of the cerebral cortex in rats and found that these animals could still relearn specific tasks. We now know that destruction of even small areas of the human brain can have devastating effects on behavior. That is one reason why neurosurgeons must carefully map the brain before removing brain tissue during operations for epilepsy or brain tumors so that essential areas are not damaged.

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Nevertheless, somehow, somewhere, someone started this myth and the popular media keep on repeating this false statement (see the figures). Soon, everyone is believing this lie. I have not been able to track down the exact source of this myth, and I have never seen any scientific data that supports the 10% statement.

 

According to the believers of this myth, if we used more of our brain, then we could perform super memory feats and have other fantastic mental abilities - maybe we could even move objects with a single thought. Again, I do not know of any data that would support any of this.

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What does it mean to use only 10% of your brain? What data was used to come up with the number - 10%? Does this mean that we would be just fine if 90% of our brains was removed? If the average human brain weighs 1,400 grams (about 3 lb) and 90% of it was removed, that would
leave 140 grams (about 0.3 lb) of brain tissue.

That's about the size of a sheep's brain. It is well-known that damage to a relatively small area of the brain, like that caused by a stroke, may cause devastating disabilities. Certain neurological disorders, like Parkinson's Disease, also affect only specific areas of the brain. The damage caused by these conditions is far less than damage to 90% of the brain.
Sheep Brain

Furthermore, from an evolutionary point of view, it is unlikely that larger brains would have developed if there was not an advantage. Certainly there are several pathways that serve similar functions. For example, there are several central pathways that are used for vision. This concept is called "redundancy" and is found throughout the nervous system. Nevertheless, having several pathways for the same function may be a type of "safety mechanism" should one of the pathways fail. Still, functional brain imaging studies show that all parts of the brain function. Even during sleep, the brain is active. The brain is still being "used," it is just in a different active state.

Finally, the saying "Use it or Lose It" seems to apply to the nervous system. During development many new synapses are formed. In fact, some synapses are eliminated later on in development. This period of synaptic development and elimination goes on to "fine tune" the wiring of the nervous system. Many studies have shown that if the input to a particular neural system is eliminated, then neurons in this system will not function properly. This has been shown quite dramatically in the visual system: complete loss of vision will occur if visual information is prevented from stimulating the eyes (and brain) early in development. It seems reasonable to suggest that if 90% of the brain was not used, then many neural pathways would degenerate. However, this does not seem to be the case. On the other hand, the brains of young children are quite adaptable. The function of a damaged brain area in a young brain can be taken over by remaining brain tissue. An incredible example of such recovery is the case of "Brandi," a girl who at the age of 4 years old had a large portion of her brain removed to control seizures. Brandi's miraculous recovery after such surgery would have been impossible for an adult.