by Liam Skoda

Created on: January 30, 2009

The misconception that humans use only 10% of our brains has persisted for years without any scientific basis. The brain is easily the least understood of human organs, due to an unfathomable complexity that rivals any object in the known universe. This, combined with the philosophical debate over mind and consciousness has lead to the idea that neuroscientists know very little about the workings of the brain. Perhaps this is where the myth began; if it was proposed that only 10% of the brain is understood, it is a short leap to the misconception that 90% of the brain is unused.

Regardless of how it began, the myth has entrenched itself in our society for a number of reasons. The mystery that surrounds the brain is important for such a skeptical claim to be accepted. Like the widespread myth that nails and hair keep growing after death, the combination of such a shocking idea and ignorance of the underlying science leads not only to acceptance but repetition of this shocking "fact". Finally, there are other motives to repeat the idea, which range from harmless encouragement to learn new things to seriously flawed arguments for psychic abilities.

Of course, none of this refutes the original idea, but that simply requires a basic understanding of science and some common sense. If humans only use 10% of our brains, that implies that the other 90% is unnecessary for our daily lives. Does that mean we could lose it without any problems? If 90% of your brain was destroyed, the result would almost certainly be death, or some kind of vegetative state. Lesions that destroy far smaller fractions of the brain can have devastating consequences. Neuroscience illustrates how different parts of the brain have unique functional significance. In Parkinson's disease, damage to a tiny segment of brain in the substantia nigra is enough to cause life-altering disability. In reality we use 100% of our brains, but it's worth considering the alternative: what if we only used 10%? Would the other 90% even exist?

The answer is obvious if you look at evolution. The brain evolved over millions of years, building on simple origins to become more and more complex, and with each step forward there was an advantage gained that allowed the developments to be passed on. From this point it should be clear that it is ridiculous to suppose that over the course of evolution the fully functional brain grew by a factor of 900% to its current size for no reason. But suppose it did. It could be argued

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