Designed by perceptual psychologist Karl Zener in the 1930s, Zener Cards are playing cards used to conduct experiments for mind reading, extrasensory perception (ESP) and clairvoyance. A pack of 25 cards includes cards illustrated with a circle, a plus sign, three parallel wavy lines, a square and a five-pointed star with five cards of each design.
“In the experiment, the tester will shuffle the pack to randomize distribution, then select a card without showing the person being tested, who then has to name the correct design on the card,” according to Catalog of the Unexplained. “To accurately identify more than fifteen out of twenty-five, the odds are around ninety thousand to one, and identifying above fifteen is even more against the odds.”