The common trend is for each individual dowser to build up a belief system that 'works' and then use this foundation for further conjecture.
Physical dowsing is a way of being conscious of sensory inputs which are not directly connected to the more cerebral brain functions. Take as an example man's sensitivity to magnetism. The organ most likely to be responsible is the pineal gland (at puberty the outer layer hardens and becomes magnetically sensitive). Yet, although contained within the skull, the pineal lies outside the brain and has no more direct contact with the brain than your big toe; in fact less, as there are no direct nerve connections. So the pineal must communicate with the lower brain, which means the sensations rise up not as 'rational thoughts' but as subconscious 'urges', 'moods' or whatever other work one wants to use to describe such diffuse impressions. In the case of dowsing, clearly the subconscious brain is, in some way, able to alter muscle tension in the shoulders and arms, giving the characteristic 'flick' to a 'V' rod, the crossing of angle rods, or the change in rotation of pendulum.
Physical dowsing may, for instance, be linked to the magnetic sensitivity of the pineal, whereas 'psychic' sensations have emanated from quite different organs.
There is a widespread tendency for us to perceive the novel and 'unknown' in terms of our own cultural contexts. Dan Wilson was perhaps the first to explore in print the idea that our psychic capacities tune in to highly specific forms. To act as a 'handle' for his ideas Wilson adopted the term 'Display Theory (DT) which he described as ' the idea that psychic (or 'second-seen') phenomena such as energy lines and auras are not things in their own right but explanatory constructs within the mind of the perceiver.
To understand the problem we have with energy dowsing consider the fact that, within the "neural network" of the brain, there is only information: input and output. At this level we have almost no way of linking information with the original source of that information. Ideas and images and metaphors - meta- of information - are, at this level, indistinguishable from sensory information: they are all equally "real". any kind of pattern can easily become a "preferred pathway", a pseudo-cause of the dowsing effect. (I suspect, very strongly, that this is usually, rather than occasionally, the case with most so-called "energy dowsing" that happens today.)' (author's emphasis)
What is not necessarily in dispute is that there is 'something there' - whatever this so-called 'Earth energy' may be. Maybe it is something 'subtle' and intangible in any other way (a 'consciousness field', if you like). For my money it could just as easily be the Earth's natural electromagnetic field being distorted by each and every object - and person - on the planet. Any attempt to make sense of such a complex and every-varying phenomena would be, to borrow a taoist metaphor, like trying to catch a moving stream in a bucket.
He cites various scientists, such as Becker and Marina, who state that not all information gathered by the usual senses is 'processed at the conscious level, and there is no physiological principle that would preclude the subliminal detection of EMFs (electromagnetic fields) by the nervous system.)
The dowsing or water-diving reflex - the twitch of the arm muscles that indicates a field-change - is only one of the human responses behind which lies this 'webwork of forces' of which animals and plants are, as it were, initiated and active presences. It is like a great collective mind, which we call Unconscious, for the reason that we are for the main part unconscious of it. We are capable of more, far more.
- Trubshaw Bob, Dowsing - the good, the bad and the muddled, EDGE, http://www.indigogroup.co.uk/edge/dowsing.htm