One of Hollywood’s favorite pieces of pseudoscience is this one: humans only use 10% of their brains, and when the other 90%, which is thought to be dormant, is awakened, ordinary people can demonstrate extraordinary mental abilities. John Travolta learns how to predict earthquakes and pick up foreign languages quickly in the 1996 film Phenomenon. In Lucy (2014), Scarlett Johansson transforms into a superpowered martial arts expert. And in Limitless (2011) Bradley Cooper writes a novel overnight.
The general public also loves this pre-made blueprint for fantasy movies. In a survey, the claim that “people only use 10% of their brain on a daily basis” was accepted by 65% of participants. However, the truth is that we constantly employ every part of our brain.
How are we aware? To begin with, most brain injuries would not have any noticeable effects if we only required 10% of our brain, as the damage would only affect areas of the brain that were not functioning in the first place. We also know that natural selection prevents the development of pointless anatomical structures: early humans would have been outcompeted if they had committed their limited physical resources to developing and preserving enormous amounts of extra brain tissue. Instead, they would have been better suited to focus their resources on things more vital to their survival and ability to procreate. It would be more beneficial to have stronger muscles, more resilient immune systems, better-looking hair, or pretty much anything else than a head full of inactive tissue.
These reasonable conclusions have been supported by concrete evidence. Real-time mapping of brain activity is made possible by imaging techniques like functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). The evidence unequivocally demonstrates that a significant portion of the brain—much more than 10%—is dedicated to a wide range of functions, from seemingly straightforward activities like sleeping or staring at pictures to more intricate ones like reading or performing math. To date, scientists have not discovered a part of the brain that is inactive.
So how did we get to think that our brains are only 90% useful? The myth is frequently mistakenly credited to William James, a 19th-century psychologist who postulated that the majority of human mental capacity remains unrealized. However, he never gave a percentage. Albert Einstein, who is notorious for misquoting others, has also been held accountable. In actuality, the self-help sector in America is probably where the idea originated. How to Win Friends and Influence People, Dale Carnegie’s 1936 mega best seller, has one of the earliest mentions in its preface. Since then, motivational gurus, New Age hucksters, and uninspired screenwriters have consistently promoted the notion that we have only scratched the surface of our brains’ potential.
This is obviously bad news for anyone looking to discover the key to suddenly becoming exceptionally intelligent. The good news is that efforts still yield results. There is a lot of evidence to support the idea that practicing difficult mental activities on a regular basis, like reading a novel, playing an instrument, or performing math, can increase brain power.