Friday, June 13, 2008

An anecdote about dowsers being double-blind to their special pleading

For those who are unfamiliar with dowsing, it is:
…the action of a person--called the dowser--using a rod, stick or other device - to locate such things as underground water, hidden metal, buried treasure, oil, lost persons or golf balls, etc.
I already looked at an example of Substitution Richard Dawkins uses in the The Enemies of Reason (part 1). The second thing I want to look at from this documentary is the use of a double blind experiment, and the Special Pleading that follows.

In this clip from The Enemies of Reason part 1 (about 29 minutes into it), we see dowsers explaining why they only picked the correct bottle with water in it 1 time out of 6 (or 2 times at best). There were 6 bottles that had water, out of 36, and they assumed they would identify the correct one better than "chance" (if not 100 percent). When this fails to eventuate, the Special Pleading begins.

Ken Church (one of the Dowsers): How does dowsing work, that’s the number one question. [Surely that’s the number two question, if the answer to the number one question: “Is there any controlled evidence that shows dowsing works”, is “Yes”.] And nobody can answer you. We I reckon… I’m convinced… that something is helping me to dowse. One of the earlier chaps thinks it’s God.
Dawkins (to another dowser - Jim Negus): How do you do it? What’s your principle of dowsing?
Negus: I think the question, and I expect God to respond in a way that I understand… [He goes into some superfluous detail and demonstrates how when he walks forward, the wire bit follows the camera around. This only serves to demonstrate his ignorance of the ideomotor effect and Newton’s first law – inertia.]

Dawkins: Have you done the test yet, in the tent?
Negus: Yes I did.
Dawkins: And what was the result?
Negus: I was going to get six right, 100 percent
Dawkins: Yeah, and what happened?
Negus: One!
Dawkins: So what do you make of that then?
Negus: He’s having his laugh [points skyward], in’t he. He loves a joke. You don’t realise…
Thus we have the Special Pleading.

The next section gets on to explaining how the double blind experiment works. It then shows that all the dowsers tested perform within chance expectation – that is, on average, 1 out of 6 correct (6 bottles filled with water amongst 30 filled with sand, all hidden). The double blind wins again. Chris French, the psychologist running the experiment, goes on to explain that when talking to dowsers, they have many anecdotes of discovering water, or broken pipes, etc. They think it’s a “gift”, however, there are alternative hypotheses worth spinning. For example, could they only pay attention to and remember the times they correctly found water and forget the times they didn’t? I.e., are they counting the hits and forgetting the misses? This is called Observational Selection, or confirmation bias. Unless you write things down, to keep an accurate record, you can’t trust your own memory (I remember reading this somewhere once, or perhaps I heard it on the radio…).

This is the beauty of the double blind experiment; it rules out these biases. If they actually have special water finding powers, beyond random chance and hindsight-confirmation bias, a controlled double blind experiment would conclusively show it.

French goes on to explain that once the subjects are shown they don’t have magical powers, they begin to make excuses – they engage in Special Pleading. This is a common problem of close minded people. Not being prepared to change your mind in spite of evidence means you are guilty of Simple-Minded Certitude. This is a laughable criticism often levelled at skeptics and those accused of “scientism”. Supposedly we don’t believe in alien visitation or homeopathy or dowsing, or whatever, because we are “close minded”. However, it’s the complete opposite. We are perfectly prepared to believe in any of the above, so long as there is credible evidence in favour of it. Chris French is the perfect example of this, as are the scientists who investigated electromagnetic sensitivity. They give these claims “a fair go”.

“Fair go” is not synonymous with “credulous acceptance”, however. Fair go means to listen to the evidence and weigh it up against, or see where it fits in with, scientific orthodoxy. If it doesn’t fit in too well, the evidence would need to be strong. One of the best examples of an open minded person (one prepared to change one’s mind) who gave parapsychology a fair go is Susan Blackmore.

Anyway, back to the dowsing. French goes on to say:
I think that they are completely sincere, and that they’re typically very surprised when we run them through a series of trials and actually say, at the end of the day, “Well your performance is no better than we would expect just on the basis of guess work.” And then what typically happens, they’ll make up all kinds of reasons, some might say excuses, as to why they didn’t pass that particular test.
It then cuts back to Church and another dowser, Karen Fuller
Church: I feel the whole test… is wrong.
Fuller: I’m shocked beyond words that this has happened. But I did say from the outset, couldn’t we just sort out some grey blocks and some scaffold boards, so that I can walk above it, which is what I would routinely do, and I’ve done for forty years. [I wonder if she'd have made the same complaint if she'd correctly identified all six?]

Church: Who knows where, or what bottles, were in what tubs…
Dawkins: That’s the whole point isn’t it? That’s the whole point…
Church: Well, yeah, but, if you understand dowsing like I do, you’ll understand that everything leaves an image.
And there we have it; an extreme example of Special Pleading, “If you understand dowsing like I do…”
I'll leave the last words to Dawkins:

This state of denial is extraordinary. Even when confronted with hard fact these dowsers prefer not to face up to truth but retain their delusion.