The Largest Controlled Test Ever Run

Dowsing has been tested more thoroughly under controlled conditions than almost any other psi claim, and the results are unambiguous. The most extensive study was commissioned by the German government and conducted in Munich in 1987 and 1988 by physicists Wagner, Betz, and Koenig, involving more than five hundred dowsers across more than ten thousand double-blind trials, in which dowsers attempted to detect a concealed water pipe from inside a windowless mobile wagon. The final report to the funding agency concluded that dowsers, as a group, performed no better than chance; a small subset of individual dowsers showed results that looked statistically unusual in a first pass, but subsequent independent statistical review found these did not hold up as evidence of a real effect once proper analysis was applied.

Separately, the James Randi Educational Foundation's long-running Million Dollar Paranormal Challenge tested dowsing applicants directly: over a thousand people applied to demonstrate a paranormal ability including dowsing under agreed test conditions between the challenge's creation and its closure in 2015, and none succeeded. Dowsing remains in occasional practical use, but as a claim of extrasensory detection it has been tested at scale and has not withstood the test.