Zener cards

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).[1]

Overview

Hubert Pearce with Joseph Banks Rhine.

The Zener cards were a deck made up of five simple symbols. The five different Zener cards are: a hollow circle (one curve), a Greek cross (two lines), three vertical wavy lines (or "waves"), a hollow square (four lines), and a hollow five-pointed star.[2] There are 25 cards in a pack, five of each design.[3]

In a test for ESP, the person conducting the test (the experimenter) picks up a card in a shuffled pack, observes the symbol on the card, and records the answer of the person being tested for extrasensory perception, who would guess which of the five designs is on the card in question. The experimenter continues until all the cards in the pack have been tested. Poor shuffling methods can make the order of cards in the deck easier to predict.[4] The cards could have been marked and manipulated.[5] In his experiments, J. B. Rhine first shuffled the cards by hand but later decided to use a machine for shuffling.[6]

Rhine's experiments with Zener cards were discredited due to the discovery that sensory leakage or cheating could account for all his results such as the subject being able to read the symbols from the back of the cards and being able to see and hear the experimenter to note subtle clues.[7] Terence Hines has written:

The methods the Rhines used to prevent subjects from gaining hints and clues as to the design on the cards were far from adequate. In many experiments, the cards were displayed face up, but hidden behind a small wooden shield. Several ways of obtaining information about the design on the card remain even in the presence of the shield. For instance, the subject may be able sometimes to see the design on the face-up card reflected in the agent’s glasses. Even if the agent isn’t wearing glasses it is possible to see the reflection in his cornea.[8]

Once Rhine took precautions in response to criticisms of his methods, he was unable to find any high-scoring subjects.[9] Due to the methodological problems, parapsychologists no longer utilize card-guessing studies.[10]

During an episode of James Randi's TV show "Exploring Psychic Powers" a psychic was tested on a deck of 250 Zener cards and was only able to predict 50 of them correctly, which is the expected result of random guessing the cards.

Statistics

If the null-hypothesis (no psychic ability) is assumed and each card selected for testing is chosen in a truly random fashion, a user's success ratio is expected to approach 20% (1 hit per 5 trials) as their number of trials increases. The further the observed scenario is from the expected scenario, the more cause for believing the null-hypothesis is not true (the results are not simply due to chance).

References

  1. ↑ "Zener Cards". Glossary of Skepticism & the Paranormal. About.com. Retrieved 2006-12-20.
  2. ↑ Terence Hines. (2003). Pseudoscience and the Paranormal. Prometheus Books. p. 115
  3. ↑ Matt Jarvis, Julia Russell. (2002). Key Ideas in Psychology. Nelson Thornes Ltd. p. 117
  4. ↑ Carroll, Todd (2006-02-17). "Zener ESP Cards". The Skeptic's Dictionary. Retrieved 2006-07-18.
  5. ↑ John Sladek. (1974). The New Apocrypha: A Guide to Strange Sciences and Occult Beliefs. Panther. p. 174 "It's astonishing that playing cards should have been chosen for ESP research at all. They are, after all, the instrument of stage magicians and second-dealing gamblers; they can be marked and manipulated in many traditional ways. At the best of times, card-shuffling is a poor way of getting a random distribution of symbols."
  6. ↑ Massimo Pigliucci. (2010). Nonsense on Stilts: How to Tell Science from Bunk. University of Chicago Press. pp. 80-82
  7. ↑ Jonathan C. Smith. (2009). Pseudoscience and Extraordinary Claims of the Paranormal: A Critical Thinker's Toolkit. Wiley-Blackwell. ISBN 978-1405181228. "Today, researchers discount the first decade of Rhine's work with Zener cards. Stimulus leakage or cheating could account for all his findings. Slight indentations on the backs of cards revealed the symbols embossed on card faces. Subjects could see and hear the experimenter, and note subtle but revealing facial expressions or changes in breathing."
  8. ↑ Terence Hines. (2003). Pseudoscience and the Paranormal. Prometheus Books. pp. 119-120
  9. ↑ Milbourne Christopher. (1970). ESP, Seers & Psychics. Thomas Y. Crowell Company. p. 28
  10. ↑ James Alcock. (2011). Back from the Future: Parapsychology and the Bem Affair. Skeptical Inquirer. "Despite Rhine’s confidence that he had established the reality of extrasensory perception, he had not done so. Methodological problems with his experiments eventually came to light, and as a result parapsychologists no longer run card-guessing studies and rarely even refer to Rhine’s work."
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