Zener Cards

There are five designs of Zener Card: Circle, Cross, Wavy Lines, Square and Star.

There are two main types of experiment for which Zener Cards are used: precognition and telepathy.

In a precognition experiment, the cards are shuffled and the subject tries to predict each card before it is put aside. In this sort of test the experimenter has as little knowledge of the next card in the deck as the subject.

For a telepathy experiment, the experimenter draws a card and thinks of it. The subject then tries to ascertain the design. In this case, since the experimenter knows the nature of the card, it is important to design the experiment to rule out subconscious clues being inadvertently passed between the two. Another complexity with this sort of experiment is determining the extent to which a particularly good (or bad) result is attributable to the sender or the receiver.

When performing these experiments it is vital that the subject is not told the results as each card is turned. Otherwise knowledge of which cards have and have not been used would allow more accurate guessing of those remaining. It would be the Zener equivalent of "card counting".

It is also necessary to have a good knowledge of statistics when analysing the results of these experiments for possible evidence of parapsychology or psi powers. Chance guessing would suggest five "hits" in a test. Therefore a result of eight hits might seem impressive. In fact it would not be statistically significant on a single test. Such a result would only become significant if repeated over many runs.

An unfortunate drawback of the early Zener Cards was that they were printed with a picture of Duke University on the back. As a result the cards were "one way" - not symmetrical in design. This feature can be used by mind magicans (mentalists) to perform apparent psychic feats. Modern Zener Cards usually have a geometric design, but even some of those you can buy on the market today still have a one-way back.