Nestling in the shadow of a white horse and a Neolithic long barrow, in a renowned crop circle hotspot, Alton Priors, in Wiltshire, feels like the perfect venue for a spot of water witchery. Prompted by the news that Thames Water and Severn Trent Water use dowsing rods to detect water leaks, I’ve arranged to meet my mum – a geologist and amateur dowser – to investigate the phenomenon for myself.

There are other reasons for picking this particular location. Geologically speaking, Alton Priors lies on the boundary between a chalk escarpment and sandstone, the latter underlain by clay, which means there are numerous springs gushing out of the ground. The local churchyard is also where an acquaintance of my mum once suggested she try dowsing, because “he just had a sense it would work there”. Sure enough, her rods crossed.

My mum isn’t generally prone to magical thinking. An expert on the geology of Wiltshire, and a trained Blue Badge tourist guide, she was first given a pair of dowsing rods when she started taking tour groups around Stonehenge. To her surprise, the rods crossed, piquing her curiosity. Since then, she’s discovered they reliably cross for her over water, trees, ancient henges and barrows, as well as the long axis of churches.

To sceptics, this may sound like a classic case of confirmation bias: the tendency to interpret information in a way that confirms or supports our prior beliefs. If you are expecting a pair of dowsing rods to cross in particular locations, and they do, that’s evidence that dowsing works.

Not so fast, says my mum. There are other locations where she fully expected them to work, and they didn’t, such as iron age hill forts. She doesn’t know why they cross over certain features and not others, but they do – and she strongly suspects water is involved.

Linda Geddes (right) being introduced to dowsing by her mother Isobel in a Wiltshire churchyard. Photograph: Sam Frost/The Guardian

Joining us on this excursion is a photographer, who recounts how a friend recently called out the local water company to fix a leak in his back garden, and the engineer used dowsing to locate the stopcock.

Hearing such anecdotes, I feel open to the possibility that dowsing might be able to detect water – even though my inner sceptic says there’s no logical explanation for it.

My mum hands me a pair of metal rods, and shows me how to hold them, gently but firmly, the long ends pointing forwards. She directs me to a small bridge over a stream, as as I cross, the rods swing towards each other.

Re-engaging my sceptical brain, we continue along a footpath following the stream. I allow my mum to stride off ahead, secretly noting each place where the rods cross, and then I pass her the rods and ask her to retrace our steps. The first time she walks quickly, and the rods don’t cross at all. Then I ask her to do it again, but more slowly; this time, they cross in two of the three locations – but no others. We do it again, and it happens in the same two spots.

Unnerved, but still aware I may be spotting patterns where none exist, we head into the pretty All Saints’ Church. As I walk around the internal perimeter, the rods repeatedly swing out wildly to the sides in two specific locations. My mum tugs at a trapdoor under one of them that I hadn’t noticed before; it conceals a partially buried sarsen stone – the same type used to construct Stonehenge. I later discover that the church may have been built on the site of an earlier sacred place. We find a second trapdoor in the other place identified by the rods, hiding more stones.

Weird as all this seems, there must surely be a logical explanation for it.

According to Prof Chris French, head of the Anomalistic Psychology Research Unit at Goldsmiths, University of London, there is an unseen force at work in dowsing – but it is psychological, rather than some kind of sixth sense.

It’s called the ideomotor effect, a phenomenon whereby suggestions, beliefs or expectations cause unconscious muscular movements that trigger the movement of the rods. “In other words, your mum is moving the dowsing rods herself, without being consciously aware of it,” French says.

My mum doesn’t doubt that unconscious muscle movements are at play, but in her opinion, they’re a subconscious response to subtle cues in the environment, be that some kind of electromagnetism that humans are somehow able to detect, or visual clues.

I feel inclined to agree: assuming my experiences aren’t coincidence or confirmation bias, perhaps my footsteps sounded different over those trapdoors, or I visually registered them, without noticing.

However, this theory holds no water with John Baker, a professional water diviner and archaeological dowser, who claims to not only be able to detect underground water, but to give some idea of the depth, flow and whether it is safe to drink, by consulting his dowsing rods. “I just ask them the question,” he explains.

He says an absence of external cues actually makes dowsing easier, because it allows his unconscious mind to have a good run at the problem: “One of the best jobs I ever did, was on a farm in Kent with four inches of snow on the ground. I had nothing to look at, other than snow and a grey sky, which meant there was nothing to cut into my thinking mind.”

Baker had been called because a large sheep trough at the bottom of a hill was no longer filling with water, and the farmer didn’t know where the supply pipes were. Roughly three-quarters of the way up the hill, his rods identified a pipe which suddenly turned at right angles, and then at right angles again. “The owner said: ‘That’s interesting. There used to be a little pigsty there,’” Baker recalls. “A couple of days later, when they went and dug [the area] up, they found the leak was actually where the bend in the pipe was.”

Back in Alton Priors, I take the dowsing rods out into the churchyard to see if I can identify the place where my mum’s acquaintance had that “feeling”. In one spot, the rods cross with such force, it feels as though a magnet is pulling them together. However, it turns out to be a long way from the place my mum was thinking of. My inner sceptic is relieved – although that experience with the sarsen stones has been unsettling.

Yet, it will take more than anecdotes like mine, or even Baker’s, to convince French.

Possibly, subtle environmental cues could trigger muscle movements that shift the rods, but before he’s willing to take this idea seriously, he would like to see stronger evidence that dowsers can locate the objects they say they can. “The bottom line is that every properly conducted double blind test of dowsing doesn’t support the idea that dowsing really works.”

For instance, when he concealed five bottles of sand and one bottle of water in identical containers, and asked dowsers to find the water bottle – with neither himself or the dowsers knowing the correct answer until the end – they were unable to do so. Other small studies have attempted a similar thing using pipes of running water, with similar results.

“What you will typically find when you talk to dowsers is that they will give you lots of stories about how they found a leak in their neighbour’s pipe, and so on, but there are always other possible explanations,” says French.

“I would want to see evidence that there is something there to be explained before trying to come up with some kind of alternative mechanism that explains it.”

The proverbial gauntlet has been thrown: it is now down to the dowsers to prove they can find it blindfolded.

But Baker doesn’t think he needs to prove anything. His website is filled with testimonials from grateful customers. “I wouldn’t be doing what I do if I wasn’t successful,” he says. “I don’t advertise.”

My mum also shrugs off French’s scepticism. “I was a sceptic too. But dowsing just works,” she says.

If there’s one thing I am confident of, it’s that this debate will run and run. In fact, I can feel it in my waters.