Dowsing is a way of being conscious of sensory inputs which are not directly connected to the instinctive brain functions. For example man's sensitivity to magnetism. The organ we assume to be responsible for this sensitivity is the pineal gland . We know that the pineal is contained within the skull, but the pineal lies outside the brain, and has no direct contact with the brain nor does it have direct nerve connections. So the pineal must communicate with the lower brain through subconscious urges, and not rational thought. In the case of dowsing, clearly the brain (not mind) is, in some way, able to alter muscle tension in the shoulders and arms, by way of the ideomotor effect, causing the crossing of angle rods, and the swinging or rotation of the pendulum
Yet the same channels must also be used by other subconscious stimuli for them to be felt. Anyone who has used dowsing tools may find that the same techniques work well for psychic explorations, such as dating artifacts and map dowsing. But, although the manner of bringing the raw impulse through to conscious perception may be the same, this does not mean that the origins are the same. Dowsing may be linked to the magnetic sensitivity of the pineal, but psychic sensations may emanate from quite different organs.
Becker and Marino , 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.'
There are two popular theories to explain dowsing.
The first suggests that dowsing works as a result of natural phenomena. Buried metal, minerals and underground water causes either a magnetic field or a disturbance in the earth’s own magnetic field. It is thought that the dowsing rod is a tool for showing the reaction of the magnetic field in the ground to the natural magnetic field of the body. This theory was investigated scientifically in Logan, Utah, USA, around 30 years ago.
The Second theory is that dowsing works through the arts of the paranormal; an explanation used to account for the ability of some dowsers to find objects which are thought not to produce or influence magnetic fields. As far as field dowsing is concerned, the paranormal theory is probably in error since it has been shown that virtually everything, be it animal, vegetable or mineral, reacts to magnetic fields. However, map dowsing is something else. How does a person dowse a map to successfully locate a target hundreds or thousands of miles away? There are many unanswered questions along the same lines, which are commonly put down to psychic ability or intuition.