The idea that Man only uses 10% of the brain’s capacity while 90% remains inaccessible is a widespread myth.
Much of popular culture's output is involved in conveying this idea, such as the TV series Kyle XY, in which the hero finally wakes up by ‘using all of his brain.’ Another example is the film Limitless, where Hollywood actor Bradley Cooper plays the role of a thirty-year-old who becomes a prodigy after taking a pill that boosts his brain capacity. Or Luc Besson's feature film Lucy, where Scarlett Johansson develops exceptional skills through a drug that gives her new powers.
These works all contribute to establish the idea that Man actually has a wealth of unexploited capacities… but this is false!
All areas are used
For several decades now, medical imaging has proved that we use all of our brain capacity. Every region of our brain has a function and its activity never stops (as long as we are alive at least). Even when we are sleeping, it activates itself in order to consolidate memories.
What is true though is that we only use about 10% at a time since it is impossible to use all areas of the brain simultaneously. You will have noticed that you can’t run, eat and read at the same time. One action always predominates over the others. Even when you have the impression of being in full multitasking mode, your brain only activates different areas successively and very quickly.
Thus, when you are reading, the areas devoted to vision, language, understanding, as well as those of judgment activate. If you suddenly get up to go get something, the previously active areas will go to rest, and other areas of your brain will activate.
An unknown origin
So we do use more than 10% of our brain... fortunately! If 90% of our brain capacity was unexploited, the unstimulated neurones would have disappeared a long time ago. Evolution would have shrunk our brain to 10% of its current size.
Moreover, if 90% of our brain was ‘dormant,’ that is to say if we could do without 90% of our brain, the sequelae that cause injuries after accidents or head trauma would not be so disabling.We do not know exactly where this idea came from. Perhaps this myth is a deformation of the fact that neurones represent only 10% of nerve cells, the other 90% being glial cells which are a sort of ‘neural assistants.’ Perhaps this is the consequence of the fact that, for years, scientists did not know the function of the frontal lobes, which occupy a large part of the brain.
Indeed, damage to this area of the brain does not cause any motor or sensory deficit, so doctors wrongly concluded that they were useless. We have since learned that they play a crucial role in reasoning, organisation, decision-making and adaptability… everything that makes Man an evolved being.