Harvard Health Letter

Ask the doctor: 10% brain myth

Q. Is it true that we use only 10% of our brains?

A. Many parts of the body have some extra capacity built in. You can have an entire lung or kidney removed and get along fine with the one that remains. There's skin, small and large intestine, and bone marrow to spare. If the appendix, thymus, and spleen need to go, so be it. We can do without them if necessary.

But the notion that we use just 10% of our brains, or some other small percentage, isn't true. Brain scans of various kinds have shown we regularly use all of the brain. Some parts are more active at any given time or during a particular activity. Some parts may be less critical for important functions, such as breathing, speaking, understanding, or walking. And the brain is remarkably adaptable, so one part can take over, or compensate, for another. But there is no part of the brain that is known to be unused or completely unnecessary.

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