“Humans only use 10% of their brain capacity.”

The highest-authority sources (Source 1 - BrainFacts.org/Society for Neuroscience with 0.95 authority score, Source 2 - MIT McGovern Institute with 0.85 authority score) explicitly refute the claim, with neuroscientist Nick Spitzer stating "We use all of our brain" and MIT calling the 10% idea "100 percent a myth." All nine sources unanimously refute the claim, providing converging evidence from fMRI studies, evolutionary arguments, and neurological research that humans use their entire brain, not just 10%.

The evidence directly and uniformly refutes the claim through multiple high-authority neuroscience sources (Sources 1, 2, 4, 5, 6, 7, 8, 9) that explicitly state humans use their entire brain, supported by fMRI data showing widespread neural activation even during simple tasks and sleep. The proponent's argument commits multiple fallacies—appeal to popularity (65% belief rate as evidence of truth), appeal to fiction (movies as evidence), and equivocation (shifting from literal neural usage to metaphorical "potential")—while the opponent correctly traces the logical chain from empirical neuroimaging evidence to the conclusion that the claim is false.

The claim omits overwhelming scientific consensus from neuroscience authorities: Source 1 (BrainFacts.org, authority 0.95) states "We use all of our brain," Source 2 (MIT McGovern Institute, 2024) calls it "100 percent a myth," and Sources 3-9 uniformly cite fMRI evidence showing the entire brain is active during all tasks including sleep. The proponent's rebuttal attempts to reframe the claim as "metaphorical truth about untapped potential," but this is a motte-and-bailey fallacy—the atomic claim makes a specific factual assertion about brain capacity usage (10%), not a vague statement about human potential, and the evidence unequivocally refutes the literal claim as stated.