Marcel Cairo pointed me to a poorly written Web essay on the ganzfeld experiments, which appears on a site called Mind Hacks.
The article begins by claiming that "some of the positive findings may be due to experimenters unconsciously prompting the participants as they gave their answers." I immediately knew this was wrong, because the ganzfeld experiments are double-blind; the experimenters do not know what the correct answer is, and therefore cannot prompt the participants to provide it. This fact is so basic to ganzfeld research that no one who is unaware of it can be said to know anything at all about the subject.
Of course, a lack of knowledge is no obstacle to the author of the piece, who continues,
Taken as a whole, these sorts of experiments show a weak but positive evidence for extra-sensory perception (ESP), but it's not clear whether this isn't just due to a tendency for some negative trials not being reported.
Wrong and wrong. "Taken as a whole," the ganzfeld tests show extremely strong evidence for ESP, with odds against chance (as calculated by Dean Radin) of a trillion to one. The author is apparently confused by the fact that the ESP faculty itself seems to be relatively weak in most people; but given the very large number of trials that have been carried out, the cumulative evidence is very powerful. Again: 1,000,000,000,000 to 1.
And contrary to the article's assertion, it is clear that this result cannot be explained by the "file-drawer effect," i.e., a refusal of researchers to publish negative or neutral findings. This issue was exhaustively debated and disposed of long ago; even Ray Hyman, the most vocal and knowledgeable skeptic to criticize the ganzfeld tests, has conceded as much. (Mind Hacks supports its assertion by linking to an article on PK studies, which have nothing to do with the ganzfeld tests. The point of the PK article is that the individual studies were small and therefore allegedly subject to the file-drawer effect. This is itself dubious at best, but in any event the ganzfeld studies, which have involved thousands of trials, are not small.)
The article goes on,
... some of the positive findings may be due to this subtle prompting which is known as the Clever Hans effect, after a horse who was thought to be able to do amazing calculations, until it was later discovered that he was simply clopping his hoof until his trainer responded in a positive way.
Amazingly, this is also wrong, although I admit that most people who've heard of Clever Hans have received this explanation. Actually, while one skeptical investigator did conclude that the horse was receiving unconscious suggestions from his trainer, further study by other researchers ruled out this possibility. For one thing, Hans (along with other horses) was found to give correct answers even when his trainer was not present, and even when the calculations were too complex to be done on the fly by the researchers themselves. The case of the "counting horse" remains a mystery, as Scott Rogo has documented.
The article concludes with a backhanded compliment:
It sometimes strikes me as ironic that some scientists consider academic parapsychologists to be unscientific when they do often some of the most carefully designed studies in the literature.
The fact that these studies typically find no evidence of ESP doesn't mean they're not doing science, and in fact, they're provided some of the best evidence against airy fairy notions of 'psychic powers'.
But it's the author himself who is guilty of "airy notions" - something that an addendum to the article makes clear. It seems that neuroscientist Christian Jarrett pointed out some of the errors in the piece, most important of which was the claim that the experimenter could have guided the test subjects to the right conclusions.
Jarrett writes:
The observed interaction effect occurred during the review phase, where the researcher goes through the images the receiver spoke out loud earlier as the the 'sender' watched the video clip. This is prior to the receiver's attempt to choose the correct video clip from a few distractors ...
Remember too that these were double blind experiments, so it is not a case of the experimenters directing the receivers towards the correct imagery.
Mind Hacks says this "puts a different spin on it." Why, yes, it does - inasmuch as getting the facts right gives a "different spin" than getting them wrong.
http://michaelprescott.typepad.com/mich ... -work.html
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