Humans only use 10 percent of their brain
Modern brain imaging shows that virtually all regions of the human brain are active at some point during normal daily functioning, and neuroscientists consider the widely repeated claim that people only use 10 percent of their brain capacity to be a myth with no basis in neuroscience.
What we know
The claim that humans use only 10 percent of their brain has circulated in popular culture for over a century, with its precise origin difficult to pin down definitively, though historians of science and neuroscientists who have investigated the myth's history point to several possible contributing sources, including a misinterpretation of early 20th-century neurological research on brain plasticity and reserve capacity, popular self-help writing from figures like Dale Carnegie in the 1930s that referenced supposedly untapped mental potential, and possibly a garbled reference to the finding that glial cells, which support and protect neurons, outnumber neurons in the brain, none of which actually support the specific 10 percent figure that eventually became attached to the myth.
Modern neuroimaging technology, including functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scans, allows researchers to observe brain activity directly during a wide range of tasks, and this body of imaging research consistently shows that virtually all regions of the brain show measurable activity over the course of a day, with different regions becoming more or less active depending on the specific task being performed, but no region remaining permanently dormant or unused. Neurologist and myth researcher Barry Beyerstein, whose work is frequently cited in academic and popular science reviews of the claim, outlined multiple independent lines of evidence against the 10 percent myth, including the observation that brain damage to virtually any region, however small, typically produces some detectable functional deficit, a pattern inconsistent with 90 percent of the brain being expendable or inactive, and evolutionary and metabolic arguments noting that the brain consumes a disproportionately large share, roughly 20 percent, of the body's total energy despite representing only about 2 percent of body weight, an energy cost that would be difficult to evolutionarily justify if the vast majority of that tissue served no active function.
Additional supporting evidence comes from detailed anatomical mapping research conducted over decades, which has associated specific, identifiable functions with essentially all brain regions studied, including areas once considered functionally mysterious or 'silent' in older research, which further investigation eventually associated with specific cognitive or sensory functions rather than confirming any large region as permanently unused. Brain imaging during sleep further undercuts the myth, since substantial brain activity continues even during rest and sleep states, including during memory consolidation and other maintenance processes, meaning there is no extended period, waking or sleeping, during which large portions of the brain sit entirely idle.
Neuroscientists reviewing why the myth persists despite this consistent contrary evidence, including surveys of public belief about the brain conducted by cognitive scientists, note that it offers an appealing and motivating narrative, the idea that untapped human potential is literally sitting dormant and available to be unlocked through the right technique, book, or product, a narrative that has been used commercially to market various self-improvement programs, supplements, and even featured in popular films, reinforcing the myth's persistence in public consciousness despite its complete absence of support within neuroscience. The actual scientific picture, that the brain is a highly efficient organ in which functionally distinct regions are specialized for different tasks and essentially all regions serve identifiable purposes, is considered less appealing as a motivational narrative even though it accurately reflects current understanding of brain function.
Common claims
- Humans only use 10 percent of their brain's total capacity.False, neuroimaging research shows virtually all brain regions are active during normal daily functioning.
- Damage to almost any brain region produces some detectable effect.True, this pattern is inconsistent with large portions of the brain being non-functional.
- The brain uses a disproportionately large share of the body's energy for its size.True, roughly 20 percent of total energy despite about 2 percent of body weight.
- Unlocking the unused 90 percent of the brain can dramatically boost intelligence.False, this premise has no basis since there is no substantial unused brain capacity to unlock.