Recently a journalist contacted me with three or four questions about dowsing. I’ve written about dowsing several times, and last year I wrote a CFI blog about a conversation I had with a dowser. Here’s a transcript of the interview:

1) Why do you believe dowsing is fraudulent? Do you think dowsers are purposefully fraudulent or just deluded?

I don’t believe dowsing per se is fraudulent–that is, for the most part it’s not a scam, hoax, or intentional deception. Instead it’s a form of self-deception that often convinces others. There’s no intent to deceive, it’s more of a mistake or misunderstanding. I’ve met many dowsers over the years and without exception they have been credible, down-to-earth people. They seem sincere because they are sincere: they really believe they have this power, and have convinced themselves over and over with their results. In this way they often convince other people, especially those who haven’t researched skeptical or science-based explanations.

As for its origins, in her book Divining the Future: Prognostication From Astrology to Zoomancy, Eva Shaw writes, “In 1556, De Re Metallica, a book on metallurgy and mining written by George [sic] Agricola, discussed dowsing as an acceptable method of locating rich mineral sources.” This reference to De Re Metallica is widely cited among dowsers as proof of its validity. However it seems that the dowsing advocates didn’t actually read the book because it says exactly the opposite of what they claim: Instead of endorsing dowsing, Agricola states that those seeking minerals “should not make use of an enchanted twig, because if he is prudent and skilled in the natural signs, he understands that a forked stick is of no use to him.” So even 400 years ago, dowsing was recognized as not being useful.

2) How can you empirically disprove dowsing?

There are various ways to scientifically test dowsing abilities. I have done it several times myself, and read studies done by others. The easiest is to get 20 identical 5-gallon opaque plastic buckets and (with the dowser out of sight or at another location) place a sealed gallon jug of water under one of the buckets (being careful of course not to leave any traces that might reveal where it is). The buckets should be placed 2-3 meters apart (or at whatever interval the dowser claims they can discriminate water from non-water). Have the dowser come out to the field or lot and find the water. You can do a similar experiment hiding valuables on sandy beaches in grids as well.

Of course there’s a 5% (1 in 20) chance that the water will be found simply by random chance, so if you repeat the test 20 times that should give enough of a sample size to see whether there’s a real effect or not. If the dowser truly can find water, presumably they should be accurate at least 80% to 90% of the time. A dowser once proudly noted (partway through the trials) that so far he had successfully found water at a significantly higher rate than would be expected by random chance, at 20% instead of 5%. I pointed out that performing better than random chance was a pretty low bar and asked him if he would be eager to hire a doctor, architect, or mechanic who–like him–was wrong 80% of the time.

In my experience the dowsers are surprised by their failure, and often make excuses or find reasons to explain away their results. Sometimes they complain that “skeptical” thoughts somehow block their powers…

3) How do you explain apparently successful dowsers?

The problem is that dowsers fail to demonstrate their ability in scientifically controlled experiments and tests. It also depends on what you’re looking for and where. In fact it can be difficult to disprove a dower’s claim for the same reason: if they claim water will be found in a spot at a certain depth, they can always insist that the water is there-just that they were a bit off on the depth: It’s 50 meters, not 20 meters like they thought. In order to prove or disprove that, of course, you’d need to dig another 30 meters (possibly a difficult and expensive proposition).

And if they find water, does that mean that dowsing works? Not necessarily. In most places on Earth there’s water somewhere below the surface-maybe a few inches, maybe a few meters or more. So any dowser who says “If you dig here you’ll find water” is statistically very likely to be correct-and would be just as correct if he or she chose a spot 10 meters away in any direction, or 10 miles away.

There’s also the issue of what psychologists call “confirmation bias,” also known as “remembering the hits and forgetting the misses.” People generally tend to better remember their successes than their failures, or they rationalize away their failures (“I was having an off day,” or “The sun was too hot,” etc.). Unless dowsers keep careful track of all their claims-both correct and wrong- it can be easy to misremember their success rate.

Of course when dowsers are wrong they simply point out that no one is 100% accurate all the time–doctors, mechanics, scientists, and others make mistakes, and this is of course true. But the problem with that comparison is that doctors and mechanics can reliably prove their skills most of the time; this is not true with dowsers, and in fact there is no known scientific mechanism by which a forked branch, pendulum, or two L-shaped rods could possibly “detect” water.

Keep in mind that dowsers claim to be able to find a great many “hidden” objects, including missing keys, water, oil, gold, and even ghosts! This raises the interesting question of how dowsers could know what the rods are reacting to: Is it a vein of gold 20 meters below the earth, a reservoir of water 100 meters below the earth, oil shale 200 meters down, or the dead spirit of someone who died at that spot in 1973? There’s no way to know. British Petroleum and other multinational oil companies spend billions of dollars (and pounds) trying to locate offshore oil fields through expensive, difficult, and time-consuming sampling, computer models, and so on.

In fact late last year (September 2015) the Royal Dutch Shell Corporation abandoned its drilling in the Alaskan waters after spending $7 billion searching fruitlessly for oil. Why would they do that if all they need is to have a dowser on hand to point them directly where to drill? Any dowser who could reliably and successfully do what they claim could easily become a multi-millionaire consulting agent.

Why doesn’t it happen? Ask the dowsers…