THE NUMBER SEVEN—The fact that most people will pick the number seven when asked to choose a number between one and ten is mentioned by Robert-Houdin in his Secrets of Conjuring And Magic, 1868, in a trick titled “The Thoughts of Two Persons Anticipated”, p. 256.

THE NUMBERS 37 AND 68—Albert Cohen seems the first to have explained in print that 68 is most often thought of when asked to choose a number between fifty and one hundred with both digits odd and different, and that 37 is the most frequent choice when thinking of a number between one and fifty with both digits even and different. His explanation occurs in his routine “Mental Marvels” in Hugard's Magic Monthly, Vol. 3 No. 7, Dec. 1945, p. 171.