This paper first appeared in the Winter 2017 issue of the 'Skeptical Adversaria' (the Newsletter of ASKE, the Association for Skeptical Enquiry), pp. 2-3.
In November it was announced that 10 out of the 12 UK water companies had admitted to occasionally using water divining or dowsing to locate leaks or pipes (later communications by the companies indicated that their use of this method was very limited). Media reports informed readers and listeners that the scientific evidence for dowsing indicates that it is no more effective than guesswork, although there were some insistent voices to the contrary.
I have a family interest in dowsing. In 1963, with my parents and brother, I went on a touring holiday in Southern Ireland and we visited 'auntie' Alice (actually my mother's cousin) and 'uncle' Paddy in a village called Bunmahon in County Waterford. They lived in a typical white-walled Irish cottage and although they were poor they had quite a big garden, land being cheap in Ireland in those days. They also had a donkey called Billy. In the middle of their garden uncle Paddy had sunk a well. He had located the source of the water for this well by using his special gift: uncle Paddy was a dowser or water diviner. He demonstrated his ability to us by a taking a forked twig in both hands and positioning it over the well. The twig flipped over. My dad had a go but nothing happened, likewise when I attempted. But I believed in uncle Paddy's special power; at my young age, and when no one was coming up with an alternative explanation, I had no reason to doubt him, and family lore had it that companies had actually paid him to locate water on their premises.
I brought back with me to England two of uncle Paddy's dowsing twigs and for years they remained on our kitchen windowsill. But whenever I had a go with them nothing happened.
Years later a friend showed me two dowsing rods that he had found in the attic of a house he had just moved into. These consisted of two slender metal rods, probably fashioned out of wire coat hangers, each bent at a right angle a few inches from one end. The dowser loosely holds the smaller shaft in each hand with the longer shafts parallel and pointing ahead and walks slowly forward. At some point the rods will swing inwards (or outwards depending on their initial position). To someone using the rods for the first time this comes as a surprise but it has a simple explanation that has nothing to do with the presence of water or water pipes.
If the centre of mass (COM) of each rod is kept below the level of the fulcrum (where the corner of the rod is supported by the hand) the rods will remain in this position. It is therefore best to hold the rods with the COM at or just below this level (this can be accomplished by trial-and-error adjustments at the outset). Movements, deliberate or otherwise, affect the location of the COM of each rod relative to the fulcrum, and if it rises above the level of the fulcrum, gravity will cause the rod two swivel. These influences (which clearly must affect both rods in a similar way, otherwise only one rod would move) include slight movements at joints such as the wrist, elbow and shoulder, tilting movements of the body back and forth, and variations in the evenness of the terrain on which the person is walking that affect body posture. Eventually, the neophyte dowser may discover the actual mechanism triggering the movement of the rods, and the fact that at any time they can create this at will may cause them to lose interest in the whole enterprise. This certainly happened in my case as I pottered around my friend's house, and when I explained it to my friend, he lost interest also. I find it hard to believe that those who practise dowsing have not, at the earliest stages of their careers, realised the simple mechanism behind the movement of the rods (note 1).
None of the above involves ideomotor suggestion, the process whereby a seemingly involuntary movement occurs in response to the idea, suggestion or expectation of that movement. For ideomotor suggestion to operate, the person must have some cognisance of what the relevant physical movement is and when it is required, though one may argue that this knowledge could be at an unconscious level.
Hence the most parsimonious explanations of a positive response from someone familiar with dowsing are that the rods are raised (i) by chance, (ii) deliberately or (iii) under ideomotor influence. Speaking for myself, I believe it can be a combination of all three: when I am attempting to dowse, any sense that the rods are about to swing seems to trigger a voluntary or involuntary response to raise the shafts of the rods and thus create further movement. I find a subtle upward rotation of the wrist to be the best method; with practice, it is barely detectable by observers.
These factors alone may account for a better-than-chance performance in uncontrolled conditions where a dowser has some inkling from the environment where the target, say an underground stream, is likely to be located. In controlled conditions, dowsers typically attain 100 per cent accuracy when they consciously know that they are in the immediate vicinity of the targeted material and chance accuracy when they don't. I understand that in the case of the JREF Challenge, dowsing was the most frequently tested claim and no one was ever awarded the prize. ASKE has taken part in testing one experienced dowser, who was unsuccessful. Controlled studies, including one by GWUP, the German skeptical organisation, have provided no convincing evidence for the effectiveness of dowsing (see the Wikipedia entry for dowsing for a summary of these). So, depending on the circumstances, the phenomenon of dowsing by rods appears to be a combination of random, voluntary and involuntary influences on a simple physical response.
For the best part of 20 years I have been visiting schools during Science Week to talk about 'Science and the Paranormal' and I always do a demonstration of dowsing. The challenge is for the students to explain why the dowsing rods move and thus they learn a little more about force, gravity and, of course, human nature, the most interesting thing being why, for hundreds of year, so many people have believed that they possess this extraordinary ability and why they continue to do so to this day.
As for dear uncle Paddy, maybe he did possess a special gift. But thinking about it a bit more, finding water in Ireland may not be as impressive an accomplishment as all that.
1. I recall many years ago on television the then president of the British Association of Dowsers purportedly showing that movements of his hand were not responsible for the movements of his rod (are you sure you are still talking about dowsing? - Ed). His method was to encase the held part of his rod in a sheath (an empty biro) so there was no direct contact between hand and rod. Surely this man knew that this would have no effect whatsoever on the movement that actually caused his rod to swing, namely the upward rotation of his hand at the wrist and not a horizontal rotation?