Turning a Parlour Claim into a Laboratory Protocol

What Rhine did that his predecessors had not was reduce the claim to something a clerk could score. The instrument was a deck of twenty-five cards designed by his Duke colleague Karl Zener, five each of five symbols, so that a run through the deck had an expected score of exactly five hits by chance and any subject's performance could be stated as a departure from that number in standard deviations.

Where the Society for Psychical Research had spent fifty years arguing about the credibility of witnesses to single dramatic events, Rhine argued about arithmetic accumulated over hundreds of thousands of low-stakes guesses, which meant the dispute could in principle be settled rather than merely continued. He also separated the conditions carefully: a subject guessing a card nobody had looked at was tested for clairvoyance, a subject guessing a card an agent was watching for telepathy, and a subject guessing the order a deck would take after shuffling for precognition, and he treated these as distinct claims requiring distinct designs. The vocabulary followed the method. His 1934 monograph made extra-sensory perception and its abbreviation ESP ordinary English, and he took the German term parapsychology as the name for the whole enterprise in preference to psychical research, precisely because it sounded like a laboratory discipline rather than a seance. Whether the effect he reported was real remains contested; that he changed what counted as an argument about it is not.