For centuries, psychics, clairvoyants, and other psuedo-scientific charlatans have touted their own extraordinary perceptive powers by saying that ordinary people only use 10% of their brains.
This is a great hook because it makes the rest of us think that if we just tapped into the other 90% of our brains, we too could do amazing things. But, alas, most of us are already using all of the resources our brains have to offer.
Evidence for the Health Claim
No medical evidence supports the theory that we use only a small portion of our brains.
One plausible explanation for the continuation of this unfounded assumption could be that scientists still only have an incomplete understanding of the human brain. So while we may know that most people use the majority of their brain on a daily basis; we can’t claim to know how each part of the brain actually works.
Because neurologists have studied brain activity in people as they perform a wide variety of tasks, we do know that simple, menial activities only require us to engage a small portion of our brains. In these cases, therefore, there may be some truth to the 10% theory.
By way of comparison, think of your kitchen as your brain. When you cook dinner for a group of people, you probably use the majority of the space and appliances that you have. When you make toast, however, you use far fewer resources. So, in mental “toast” cases, we often have no need to use the bulk of our brains.
Proponents of the 10% theory sometimes hold it up as evidence that we don’t use our brains efficiently. They point to scientific research showing that many parts of the brain can, and do, perform similar or even identical tasks. However, brain researchers argue that these redundancies are necessary to prevent lapses in function. For example, if one pathway of your brain doesn’t get the message from your eyes that the traffic light has turned red, another pathway can take over and send a message to your foot to step on the brake. So, while redundancies exist, they are beneficial, even essential, for our survival.
Evidence Against the Health Claim
Abundant evidence from clinical neurology indicates that most people use the majority of their brains while both awake and asleep. Brain imaging has shown that more than 60% of our brain is active during REM, or rapid eye movement, sleep when we are dreaming.
Positron emission tomography (PET) scans of brain activity show that widespread areas of the brain "light up" during even routine activities, indicating a high percentage of our brains are active during almost any cognitive task. Also, while studies sometimes show areas of the brain where neurons are not firing, neurologists point out that these neurons may in fact be busy receiving signals from other neurons; so it is possible that areas of the brain that appear to be inactive, are in fact, working—they are just on the receiving end.
Neurologists have used electrical stimulation (with local anesthetic) on live human brains and found no dormant areas in the brain—areas which might be expected if only a small portion of the brain is being used. Also, in extensive studies of stroke and head injury victims, it is apparent that damage to even a small portion of the brain results in measurable deficits—cognitive, physical, or both—regardless of which part of the brain is damaged.
It is also difficult to explain why we would have evolved such a massive brain if we only utilize such a small percentage of its volume. Large brains require large heads to house them, which increases the risks associated with childbirth. If we derive no advantage from having such oversized brains, then why has nature left us with all that excess brain mass, which consumes a lot of wasted energy and predisposes us to unnecessary harm?
It is exciting to think that we can expand our minds by tapping into unused portions of our brains. However, researchers have yet to discover any large areas of inactivity. Although at times it may seem that some of us can’t possibly be using more than a tiny fraction of our mental capacities, it takes far more than 10% for humans to be human. Consider it a compliment—you are using your whole brain.