Wikipedia
Zener cards
Zener cards are cards used to conduct experiments for extrasensory perception (ESP), most often clairvoyance. Perceptual psychologist Karl Zener (1903–1964) designed the cards in the early 1930s for experiments conducted with his colleague, parapsychologist J. B. Rhine (1895–1980).
Usage examples of "zener cards".
As for more mundane tests, we have a rather sophisticated Zener cards machine, and other similar devices based broadly on the work of J.