One common experiment used in parapsychology to test claims of ESP involves the use of a set of 25 cards called Zener cards. They were designed in the early 1930s by the perceptual psychologist Karl Zener and his colleague, the renowned parapsychologist J.B. Rhine, at Duke University. The purpose of Zener cards is to test a person's psychic abilities, specifically their capacity for telepathy, clairvoyance, and precognition.

The deck consists of five simple and distinct symbols, making them easily recognisable and unambiguous to avoid confusion during ESP tests. The symbols are a circle, a plus sign, three wavy lines, a square, and a star, with each symbol appearing on five cards in a deck.

While these symbols themselves do not inherently represent specific meanings, their design follows a sequence. The circle is one solid shape, the plus sign is made out of two lines, there are three wavy lines, a square with...