“Humans only use 10% of their brain.”

The widespread notion that humans only use a small fraction of their brain, often cited as 10%, is a persistent neuroscientific myth. This misconception likely originated from a misinterpretation of early 20th-century research and statements by prominent figures. For instance, Harvard psychologists William James and Boris Sidis explored "reserve energy" and the idea that people only meet a fraction of their full mental potential. James himself stated that "we are making use of only a small part of our possible mental and physical resources," which was later misinterpreted as a literal claim about brain activity and popularized with the specific 10% figure, even appearing in the 1929 World Almanac. The myth has also been falsely attributed to Albert Einstein.

Modern neuroscience unequivocally debunks this idea. Advanced brain imaging techniques, such as fMRI and PET scans, demonstrate that virtually all parts of the brain are active throughout the day, even during sleep or simple tasks. If only 10% of the brain were in use, damage to other areas would not impair performance, yet even slight damage to small brain regions can have profound effects. Furthermore, the human brain consumes approximately 20% of the body's energy despite making up only about 2% of its mass, an evolutionary expense that would be highly improbable if most of it remained unused.

People commonly believe this myth because it offers an appealing thought: the possibility of unlocking vast, untapped potential for greater intelligence or extraordinary abilities. This captivating idea has been further fueled by popular culture, appearing in self-help movements and blockbuster movies that dramatize characters gaining superhuman powers by accessing more of their brain. However, the brain is incredibly efficient, with different regions working together in a complex, interconnected network (Review), constantly engaged in various cognitive and physiological tasks.