Do you believe in dowsing, or homeopathy, or that high-cholesterol diets cause heart disease or vaccination causes autism?
Or are you a rationalist, weighing all claims on merits and debunking pseudo-science where it rears its ugly head?
Skeptics quite rightly note the prevalence of confirmation bias amongst those who have strong prior beliefs, Basically we notice the evidence that agrees with our beliefs, and either disregard, or weigh less strongly contradictory evidence.
However, it is often the case that skeptics do precisely the same, and in the process weaken their own arguments.
I was prompted to write this by an article in the Guardian newspaper:
The parents of science blogger, Sally Le Page, had noticed that water engineers were using divining rods to locate pipe leaks. Le Page wrote a scathing critique, ‘In 2017, UK water companies still rely on “magic”’, and followed this by a Freedom of Information Request to water authorities. Although many emphasise their use of high-tech detection including drones and satellite imagery, 10 out of 12 authorities admitted that their engineers may use divining, not as an officially taught method, but in a ‘what works on the ground’ sense.
The Guardian picked up the story and added (in a twist more familiar in their rival The Mail) a “waste of public money” angle.
Crucially Le Page notes that:
“Every properly conducted scientific test of water dowsing has found it no better than chance (e.g. here, here, and here, nicely described here).”
The Guardian quotes this including the links.
Although it would be nice to believe that water diving worked, given the lack of explanation of how it could, I would tend to agree with The Guardian and Le Page in finding this vaguely amusing, although I doubt making serious inroads into the public purse.
However, my natural bent is to play devil’s advocate to any statement, even if I believe it, and also I realised I had no idea on the existence or otherwise of empirical evidence for or against water diving, so followed up the four references provided by Le Page:
- J. Enright. Testing Dowsing: The Failure of the Munich Experiments. Feature. Skeptical Inquirer 23(1), 1999
- J. Enright, Water dowsing: The Scheunen experiments. Naturwissenschaften (1995) 82(8):360–369. DOI: 10.1007/BF01134560
- W Whittaker. Grave Dowsing Reconsidered. Office of the State Archaeologist, University of Iowa, Iowa City, IA 52242. Burials Program: 319–384–0740.
- R. McCarney, et al. “Can Homeopaths Detect Homeopathic Medicines by Dowsing? A Randomized, Double-Blind, Placebo-Controlled Trial.” Journal of the Royal Society of Medicine 95.4 (2002): 189–191..
Let’s start at the end.
Reference [4] is a scientifically refereed article about empirical research, but it is about dowsing for homeopathic remedies, nothing at all about water dowsing. Although some people clearly believe you can dowse for anything, this is irrelevant to the older use for water divining. Interestingly, while the paper concludes that dowsing for homeopathic remedies is ineffective, its review states that , “Scientific experiments into dowsing have yielded mixed results.” So not overwhelmingly skeptical.
Reference [3] is internal report of the University of Iowa in which the only nod to empiricism is (and I quote) “Household Experiments with Dowsing” in particular, “to get a better sense of the sensations of dowsing. I created two simple dowsing rods from two wire coat hangers”. It does, however, include a useful review of dowsing literature, albeit not peer reviewed.
References [1] and [2] are by the same author, Enright, and appear to be part of an academic spat between Enright and Betz. Betz is one of the authors of an article in 1990 that appears (by the discussion, I don’t read German) to support the efficacy of water dowsing.
- Wagner, H., H.-D. Betz, and H. L. König, 1990. Schlußbericht 01 KB8602, Bundesministerium für Forschung und Technologie
Reference 1 is a ‘feature’ in Skeptical Inquirer, so not exactly a mainstream academic publication, but appears largely to reiterate the arguments in reference [2] anyway.
Which brings us to reference [2]. This is an article in a scientific journal that reviews and refutes Wagner, Betz and Konig’s 1990 article.
The 1990 article was itself based on a $250,000 (in 1990, over 1/2 million current value) German Government funded project, which involved 43 dowsers and many hundreds of tests in lab conditions. The paper found that while, by and large the majority of dowsers were ineffective, a few bucked this trend, and were more accurate than chance, and at high levels of statistical significance. The paper concludes that (quoted from [2]), “… a real core of dowser-phenomena can be regarded as empirically proven …”.
Enright’s critique in reference [2] is that Wagner, et al. cherry picked the positive data (a sadly common problem) and offers an alternative analysis of the data that reveals no effect of dowsing. In other words, Enright claims that Wagner, et al. mistakenly came to their conclusion despite the actual data being contrary to it. This would not be the first academic paper I have encountered where the abstract, introduction and conclusion run completely counter to the actual data and results within!
Arguably Le Page should have referenced the original Wagner, et al. study as well as the refutation. However, I do understand the rhetorical problem in this as in many areas (certainly similar problems in climate change denial and anti-vac literature), where if you ‘give an inch, they take a mile’; by admitting alternative evidence, however, weak, your opponent will leap upon that and say “there I told you so”.
Assuming Enright’s critique of Wagner, et al. is sound, and it seemed so, end of story.
… except …
Reference [1] it also mentions two other parts to the story: Betz and others publish a rebuttal, ‘Dowsing reviewed — the effect persists’, to Enright’s critique [2] and then Enright publishes a counter rebuttal ‘Dowsers lost in a Barn’. Furthermore, as part of this ongoing discussion and independent researcher, Ertel re-examined the data, and agreed with Wagner, et al.’s positive interpretation.
I must admit that at this point my interest started to flag (only so much dowsing in a day), and the next step would clearly be to check the stats in detail myself … maybe another day. However, I did read the initial page or so of each discussion.
Betz et al’s rebuttal begins, “We reply to a recent critique by Enright … The results of his treatment lead him to conclude that our entire research outcome can reasonably be attributed to chance and if reason prevails our study should be considered as the last major study of this sort that will ever be undertaken.”. However, they do not accept Enright’s conclusion, and they so continue to a more detailed statistical analysis arguing that their more statistically complex analysis is more accurate than Enright’s simpler methods.
Enright’s response to this starts, “ Very simple graphs of the Scheunen experimental results (plots of dowsers’ choices vs. water-pipe locations), when thoughtfully considered, clearly demonstrate that dowsers with their various kinds of witching sticks usually lost their way completely, when seeking a hidden pipe in a barn (Figs. 1 to 4 in [3]). Attempts to discredit that graphically obvious conclusion [1,2] demonstrate that statisticians who search through data, armed with various fancy tests rather than divining rods, can also lose their bearings.”
In other words, “why believe the mathematics when I’ve got a picture”.
On the face of it, it appears that Enright has given up on scientific argument, and that the largest scientific study created positive, albeit contested, evidence for dowsing. If this were any conventional topic, where I had no strong prior belief or evidence, I would conclude, based on these references, that the case for water divining is, if not conclusively proven, at least substantially strong.
Of course it could be that Le Page knows of a vast body of literature that does unequivocally demonstrate that water divining is ineffective, but she just happened to choose bad examples to cite (rhetorically I am “giving an inch” here!). Certainly doing quick web searches myself, I found no sign of strong confirmatory experiments except Wagner, et al. However, the actual evidence offered is at best weak and arguably contradictory to the argument it aims to support.
In conclusion, I am still skeptical about water divining, but after reading the limited evidence provided by the Guardian and Le Page, if anything I look more positively on water diving than I did before!
Bad arguments weaken the case.