It’s quite common to hear the claim “Humans only use 10 percent of their brains“. The claim was made in the movie Limitless and most recently, in the movie Lucy starring Scarlett Johansson. The claim is intriguing because it makes one wonder what would be possible if you could access or use all of your brain. But is the claim actually true? Do you really only use 10% of your brain?

The Truth

Unfortunately, the claim is bunk. Our brain, like all of our other organs, have been shaped by natural selection. The human brain is metabolically very expensive to grow and run. The assumption that evolution would have permitted wasting resources on the scale necessary to build and maintain such a massively underutilized organ is beyond belief and simply not logical.

It’s All About Efficiency

In relation to the rest of the body, the brain is a small organ, accounting for 2% of the total weight. At the same time, the brain requires 20% of the blood flow of the heart and an equal amount of available oxygen. From an evolutionary point of view, it’s not plausible that such a demanding organ would only work at 10 percent of its efficiency.

In addition, when we measure the brain’s activity using a wide variety of tests (from EEG to fMRI), there isn’t a single area that does not ‘light up’. Those tests strongly suggest that we use all of our brain.

Where Did The Myth Originate?

The belief that we use only a small part of our brain is unclear. Some believe the roots of the myth began during debates in the early 1800s. The debate was between those who believed that brain function could be localized to particular regions of the brain and those who believed that the brain acted as a whole.

Experiments were done that showed rats were relatively unaffected by removing up to 58% of the cerebral cortex. It is likely that over-interpretation and exaggeration of this data (and others studies like it) led to the belief that only a small portion of the brain is used.



If It’s A Myth, Why Does It Keep Getting Repeated?

The myth has been promoted by the popular media and advertisers looking to sell their products for many years. According to these programs and advertisements, if we buy their products, devices, or programs, we will be able to tap into the brain’s unused powers and enrich our lives.

Another reason this myth keeps being repeated is thanks to self-proclaimed psychics and paranormal pushers. They use it to explain their psychic powers and other “abilities”. Their logic is, “We only use ten percent of our minds. Since scientists don’t know what we do with the other 90%, it must be used for psychic powers!”

The myth has certainly motivated many people to reach for productivity and greater creativity in their lives — definitely not a bad thing. The hope and wonder it embodies helps to explain its longevity. However, like so many other myths that are too good to be true, the reality of it seems to be its least important aspect.



