Solomon Shereshevsky could recite entire speeches, word for word, after hearing them once. In minutes, he memorized complex math formulas, passages in foreign languages and tables consisting of 50 numbers or nonsense syllables. The traces of these sequences were so durably etched in his brain that he could reproduce them years later, according to Russian psychologist Alexander R. Luria, who wrote about the man he called, simply, “S” in The Mind of a Mnemonist.