ESP Cards (often called 'Zener Cards) were designed in the 1930s by perceptual psychologist Karl Zener for his colleague J.B. Rhine. Rhine used these cards extensively for experiments in extrasensory perception (ESP), including telepathy, clairvoyance, and precognition.
Five symbols were chosen for the cards (Circle, Cross, Wavy Lines, Square, and Star). This simplified the procedures and statistical analysis of card-guessing experiments, which previously had typically used ordinary playing cards. The five ESP designs have the advantage of being easily recognized, clearly different from each other, and fairly equal in size, emphasis, and response preference
A standard deck consists of 25 ESP cards, five of each symbol. To test for ESP, the cards must be well shuffled by the experimenter. The participant then attempts to guess each card as it is selected from the deck. By chance, five correct guesses are expected from 25 cards. For more information on different card guessing procedures and analyses, see our Advanced ESP Test.