This is a general overview of the attempts by scientists and scholars to apply experimental methods to claims of psychic experiences, from spiritualist séances in the second half of the nineteenth century to the statistical methods employed in present-day parapsychology.
The Early Period- The Rhine Era
- Diversifying Methods
- Psychokinesis (PK)
- Contemporary Approaches
- Concluding Observations
- Literature
- Endnotes
The Early Period
The physicist William Crookes, FRS, investigated séances over several years in the early 1870s. One of his subjects was the well-known physical medium Daniel Home, who he brought into his laboratory to try to measure the forces (if any) involved in the production of the physical phenomena – levitations of furniture, musical instruments playing by themselves, and the like – that were being witnessed in Home’s séances. Crookes published a detailed report of his experiments, including measurements of deflections on a balance scale that he attributed to Home’s ‘psychic force’, only to be accused of having allowed himself to be hypnotized, such that he misperceived events and instrument readings, or of being deceived by conjuring tricks. To counter that accusation, in fresh experiments Crookes designed recording equipment to provide an objective record of the forces at work.1
Crookes’s experiments, carried out relatively early in his career, were the most exacting of any conducted with physical mediums. Among his many later achievements in mainstream science was the development of the Crookes tube, a forerunfner of the technology underlying television.
With the establishment of the Society for Psychical Research in 1882 there began a sustained period of investigations, many of them experimental in nature. Edmund Gurney conducted a series of experiments investigating hypnotism and telepathic hypnotism, which he reported in early volumes of the SPR’s Proceedings. This laid the foundation for understanding hypnotism and hypnotic anaesthesia.
Other early experiments toward the end of the nineteenth century investigated ‘thought-transference’, soon to be renamed ‘telepathy’. Among the more noteworthy was a series carried out in Brighton, which was overseen by Eleanor Sidgwick, a mathematician and one of the SPR’s most uncompromising investigators. Subjects were tested under different conditions, primarily using number targets. The results, also published in the Proceedings, revealed that some subjects simply produced chance results, others were well above chance, and one consistently produced exceptional scores. This is an early example of what is called forced-choice testing, where the subject has to choose among a number of possible alternatives, one of which corresponds to a target, such as a number, playing card, or colour.
In Europe the French physiologist Charles Richet (later to win a Nobel Prize) was laying the groundwork for what was to become the most common experimental method used in parapsychology. In 1884, he introduced the use of probability mathematics in card guessing-type experiments to calculate chance expectancy and odds against chance as an explanation for a given result. He later used this method with considerable success in a series of experiments with a special subject under hypnosis.
In the early part of the twentieth century, growing numbers of studies used experimental procedures with statistical evaluations. At Stanford University, John E Coover used a deck of playing cards (with face cards removed) to amass a total of 10,000 trials with over 100 subjects. When the results were published in 1917, Coover claimed that there was no evidence of psychic ability in his data. However years later, a re-examination of his data by Duke University researchers (and others) claimed that Coover had used overly-stringent statistical criteria and had overlooked the possibility of clairvoyance in his control trials. When reanalyzed using more conventional statistical criteria, Coover’s results did yield rather strong evidence of psychic ability.2
During this period psychical researchers were blazing new ground with their methods and analyses, which had few precursors. It was inevitable that mistakes would be made; nevertheless, the self-critical attitude that characterizes the field today was evident from the earliest days. As an example, GNM Tyrrell, who earlier had success testing a gifted subject with playing cards, developed a technique to test the subject’s personal forte, finding objects. The subject pointed to one of five boxes that contained objects. When fellow psychical researcher GW Fisk pointed out that the targets (chosen by the experimenter) were not random, Tyrrell introduced a mechanical commutator to randomize the targets properly, and the subject continued to score significantly.
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