It’s one of Hollywood’s favourite bits of pseudoscience: human beings use only ten percent of their brain, and awakening the remaining ninety percent, supposedly dormant, allows otherwise ordinary human beings to display extraordinary mental abilities.
In the movie,
Phenomenon (1996), John Travolta gains the ability to predict earthquakes and instantly learns foreign languages. Scarlett Johansson becomes a superpowered martial-arts master in
Lucy (2014). And in
Limitless (2011) Bradley Cooper writes a novel overnight.
This ready-made blueprint for fantasy films is also a favourite among the general public. In a
survey, sixty-five percent of respondents agreed with the statement, “People only use 10 percent of their brain on a daily basis.” But the truth is that we use all of our brain all of the time.
How do we know? For one thing, if we needed only ten percent of our brain, the majority of brain injuries would have no discernible consequences, since the damage would affect parts of the brain that weren’t doing anything to begin with. We also know that natural selection discourages the development of useless anatomical structures. Early humans who devoted scarce physical resources to growing and maintaining huge amounts of excess brain tissue would have been out-competed by those who spent those precious resources on things more necessary for survival and reproductive success. Tougher immune systems, stronger muscles, just about anything that would be more useful than having a head full of inert tissue.
Imaging techniques, such as
positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), allow doctors and scientists to map brain activity in real time. The data clearly shows that large areas of the brain, far more than 10 percent, are used for all sorts of activity, from seemingly simple tasks like resting or looking at pictures to more complex ones like reading or doing mathematics. Scientists have yet to find an area of the brain that doesn’t do anything.
