Is Your Brain Goofing Off? - The Wall Street Journal

The origin of the tale is murky but might be rooted in an outdated theory about the structure of the brain that was repeated in a bestselling self-help book more than 80 years ago.

Today, the trope is still trotted out in cartoons, books and movies.

In the 2014 thriller “Lucy,” a scientist repeats the 10% claim while speculating about the promise of accessing a larger portion of the mind.