The memory of two great mental calculators: Charcot and Binet's neglected 1893 experiments

French neurologist Jean Martin Charcot (1825-1893) and French psychologist Alfred Binet (1857-1911) are almost unknown as investigators who conducted original and fascinating studies in the area of memory. In a series of 1893 experiments, they compared the performance of two expert mental calculators, Jacques Inaudi and Périclès Diamandi, in tasks that consisted of recalling digits. Inspired by Ribot's psychological work (1881), they believed in the existence of not one type of memory but several partial, special, and local memories, each devoted to a particular domain. In all arithmetical prodigies, memory for digits is abnormally developed compared with other memories. Inaudi was considered to be an auditory memory-based mental calculator; when memorizing digits, he did not rely onthe appearance of the items or create visual imagery of any kind. Rather, he remembered digits principally by their sounds. Inaudi's methods of calculation and memorization were original and different from those used by Diamandi, who was a typical visual memory-based mental calculator. The experiments presented in the 1893 article were among the first scientific demonstrations of the importance to psychology of studying different types of memory. The present work gives a translation of this pioneering experimental article on expert calculators by Charcot and Binet, instructive for the comprehension of normal memory.