Zener Cards
The Zener cards are a deck of 25 cards (5 symbols × 5 copies) used by parapsychologist J.B. Rhine at Duke University in the 1930s to test alleged extrasensory perception abilities. Designed by psychologist Karl Zener: circle, plus, waves, square, star.
Statistical baseline
With 5 symbols, the expected probability of random hits is 1/5 = 20%. A series of 25 cards has expected mean of 5 correct guesses.