In a paragraph of not more than 100 words, say simply what the witnesses thought happened, and what really happened.
A good example of this technique of investigating the reliability of
reports is an experiment reported by S. J. Davey. He was interested in the kind
of phenomena reported during séances and, using quite simple trickery,
which he had planned in advance, he reproduced some of the effects popular
among the mediums of the day. His audiences were asked to write down accounts
of what they had witnessed, and these observations were then compared with what
actually happened. Here is a report written by one witness of such a
séance. On entering the dining-room where the séance was
held, so the report runs, every article of furniture was searched
and Mr Davey turned out his pockets. The door was locked and sealed, the gas
turned out, and they all sat round the table holding hands, including Mr Davey.
A musical box on the table played and floated about. Knockings were heard and
bright lights seen. The head of a woman appeared, came close and
dematerialised. A half-figure of a man was seen a few seconds later. He bowed
and then disappeared through the ceiling with a scraping noise.
Another witness also described the searching of the room, the sealing of the door, and the disposition of the medium and sitters round the table. She alleged that a female head appeared in a strong light and afterwards a bearded man reading a book, who disappeared through the ceiling. All the while Mr Daveys hands were held tightly by the sitters on either side, and when the gas was relit the door was still locked and the seal unbroken.
A third witnesss account was even more sensational. He reported that nothing was prepared beforehand, the séance was quite casual. Having described the locking and sealing of the door, he went on to say that he was touched by a cold, clammy hand and heard various raps. After that he saw a bluish-white light which hovered over the heads of the sitters and gradually developed into an apparition that was frightful in its ugliness, but so distinct that everyone could see it .... The features were distinct ... a kind of hood covered the head, and the whole resembled the head of a mummy. After this an even more wonderful spirit appeared. It began with a streak of light and developed by degrees into a bearded man of Oriental appearance. His eyes were stony and fixed, with a vacant listless expression. At the end of the séance the door was still locked and the seal was intact.
So much for some of the reports. Now for the reality. The séance was not a casual affair at all, but had been carefully rehearsed beforehand. At the beginning, Mr Davey went through the motion of apparently locking the door, but he turned the key back again so that the door was actually left unlocked. The props for the materializations had been stowed away in a cupboard underneath a bookshelf; this was not looked into by the witnesses who searched the room because, just as they were about to do so, Mr Davey diverted their attention by emptying his pockets to show that he had nothing hidden on his person. The phenomena were produced by a confederate who came in by the unlocked door after the lights had been turned out, and while the musical box was playing loudly to drown the noise of his entry. The apparition offrightful ugliness was a mask draped in muslin with a cardboard collar coated with luminous paint. The second spirit was the confederate himself, standing on the back of Mr Daveys chair, his face faintly illuminated by phosphorescent light from the pages of a book he was holding. The rasping noise made when the spirits seemed to disappear through the ceiling was caused accidentally, but interpreted by the witnesses according to their conception of what was happening. When the light was turned on the gummed paper that had been used to seal the door had fallen off, but Mr Davey quickly pressed it back into position and then called the witnesses attention to the fact that it was still intact. Mr Daveys performances were so convincing that some leading investigators, including the biologist A. R. Wallace, F. R. S., refused to believe him when he said that he had no mediumistic powers and it had all been done by trickery. In effect the conjurer was challenged to prove that he was not a medium!
(From Sense and Nonsense in Psychology by H. J. Eysenck)
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