Zener Cards are a set of cards used in experiments to test psychic abilities, particularly extrasensory perception (ESP). Created in the 1930s by psychologist Karl Zener, the deck typically consists of 25 cards, each featuring one of five symbols: a circle, cross, waves, square, or star. The cards are often used in controlled tests where one person tries to guess the symbol on a card held by another person. The goal is to determine if individuals can perceive information beyond normal sensory channels, contributing to research in psychology and parapsychology.