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The Definition of "Double Blind" PDF Print E-mail
Swift
Written by James Randi   

We have had several requests from potential prize applicants who believe that they have the power to dowse, and who need general guidelines for how to conduct a double-blind test before they actually make application. We recognize that not everyone will know what a double-blind test is, so here is a general description.

The term "double-blind" refers to the condition under which neither the subject of the experiment – in this case, the dowser – nor the experimenter, knows the answer that is being sought. As one example, I recall that we tested a very enthusiastic dowser – Mike Guska – who actually came to the JREF headquarters in Fort Lauderdale. He claimed that he could detect gold. When we suggested that the gold sample he had brought with him – a genuine gold nugget – should be concealed in one of ten opaque, numbered, and sealed Styrofoam cups, he agreed that that would be an adequate test. 

Before we began, I had him "scan" the entire floor space of our library, where the test was to take place. This was for him to determine whether or not there were any distractions present that might mislead him or give him a false reading. Indeed, he found two spots where he said there were anomalies, and these were plainly marked off as not suitable to be included in the test area. (It is of interest to note that other dowsers, given the same opportunity, have also determined such spots – but no two dowsers have ever located the same spots!) We then placed the Styrofoam cups, uncovered, at various points in the room. By randomly selecting a numbered ball from an opaque bag, we arrived at a number between one and ten, and openly placed the gold nugget he had brought with him, into that cup. He was then asked to scan the area with his dowsing stick to determine if it would be attracted to the gold sample. It apparently was, to his satisfaction. We repeated this "baseline" demonstration 10 times, and it was always successful.

We had now determined that his dowsing method should work under the circumstances established.

Now, we were ready to perform the double-blind test. Both the dowser – the subject – and I – the experimenter – stepped out of the room while another person, continuously videotaped, went through the randomization process, placed the gold sample in the selected cup, and sealed it with a lid. Then, she left the room and called out to us to proceed.

Both of us reentered the room, and the subject walked about with his dowsing rod, finally selecting the one in which he believed the gold had been enclosed. We entered that guess on a list, and both signed the entry. Then we left the room together and called out to the other party to reenter the room and repeat the process.

Understand, the only person who knew the location of the “target” was the person who had randomly placed it in position, and that person was out of the room, and unseen.  That constitutes a “double-blind” test.

This resulted in 20 guesses being made, each guess being recorded and signed.

The dowser was then asked to estimate what his success rate had been; he thought that his results would show at least 90% correct. In actuality, the result was what we had expected, and have expected, in all the years that we have been testing dowsers: he obtained two correct results out of the 20 tries, exactly what would be expected by chance alone.

I think you will see from this, what a double-blind test really means. If you wish to try this yourself, use a similar method of randomization, have a second or third person involved who will not be present during the actual dowsing procedure so that no inadvertent clues can be given, and do not make excuses for failures.

We have recommended that dowsers – in particular – should always do this double-blind procedure, to determine if they actually can do what they believe they can do. In almost every single case, they have replied that they "don't need to do that," because they're absolutely convinced that they have the power. In the one case where the dowser said that he had performed a double-blind procedure in advance, he admitted later that he had not. There are no more convinced – self-deluded – claimants for the JREF prize, than the dowsers, and they are by far the largest percentage of those who apply.

For that reason, we sincerely and strongly urge potential applicants to apply double-blind procedures before applying.

(I should add that Mr. Guska had brought with him several coins he believed to be gold. He even demonstrated that his dowsing rod reacted to them, strongly. In actuality, these were U.S. Sacagawea dollar coins, which are made of manganese brass – no trace of gold, at all.)

As an indication of how naïve dowsers can be, Mr. Guska also complained that his dowsing rod had been distracted by the gold stamping and gold edges of a set of the Encyclopaedia Britannica on a library shelf. We pointed out to him that this had not affected his “open” trials, but only the “blinded” trials, and that this, too was not real gold, yet he insisted that there was probably some gold hidden behind the library walls…

We did not pursue this possibility…

 

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