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Phenomena that are attributed to poltergeists may in fact be the person's unconscious psychokinetic powers taking effect.
J B Rhine, the forefather of parapsychology, began conducting experiments into telekinesis in his laboratory in 1934. Rhine's first subject was a gambler who claimed to be able to influence a rolling dice, so initially the experiments were carried by rolling dice and trying to influence the outcome. This gave a chance rate of 1 in 6, ie the success rate the subject would expect to get by chance. A score significantly above this would indicate the presence of psychokinesis; Rhine did not expect his subjects to score 100% success rate in his experiments to indicate the existence of psi (psychic ability or phenomena).
However this method of experimentation proved unsatisfactory as it is possible for the subject to affect the results physically as they do have psychical contact with the object they are trying to manipulate. Likewise on a dice with recessed dots, the side depicting the highest number (ie number six) will be lightest and therefore should appear more often. Rhine modified his tests to work with specially-made dice and an automatic dice thrower.
Rhine also found that the more motivated the subject was, the higher the success rate. Likewise subjects tended to perform better during the earlier parts of the tests than later, when they were bored. Rhine noticed a similar tendency with his other ESP tests. This is known as the sheep-goat effect, where subjects who believe in the existence of psi tend to achieve a higher score than chance, while sceptics achieve a significantly lower score than would expect through chance.
Source: pinkfridge