Source: Attributed in posthumous publications, Einstein and the Poet (1983), p. 31
Spoken on hearing German marchers singing war songs. On p. 474 of Alice Calaprice's The Ultimate Quotable Einstein, she lists "we only use 10 percent of our brain" as a quote "misattributed to Einstein", perhaps this is the source of the misquote? Einstein seems to be speaking metaphorically here, not endorsing the myth http://www.snopes.com/science/stats/10percent.asp that science has shown 90 percent of the neurons in our brain lie dormant. And the myth dates back to before this interview, for example the book Mind Myths: Exploring Popular Assumptions About the Mind and Brain, edited by Sergio Della Salla, has a chapter by Barry L. Beyerstein titled "Whence Cometh the Myth that We Only Use 10% of our Brains?" which shows on p. 11 an advertisement from the 1929 World Almanac containing the line "There is NO LIMIT to what the human brain can accomplish. Scientists and psychologists tell us we use only about TEN PER CENT of our brain power."
Context: What a betrayal of man's dignity. He uses the highest gift, his mind, only ten percent, and his emotions and instincts ninety percent.
