1. Dowsing What’s Dowsing?
Dowsing is a method used by people to locate water, oil, minerals, etc.
Traditionally uses a forked stick
Now often uses a pendulum or dowsing rod
Rods are held loosely in the hand
When over water, the rods cross, or uncross, or move

2. Success of Dowsing
How can we explain the high rate of success of dowsing?
Underwater rivers are, in fact, extremely rare
However, ground water is extremely common
In many areas, more common than not
It is possible that dowsers are unconsciously moving it themselves
It is difficult to hold objects like this absolutely still

3. The Ideomotor Effect (1)
The body moves – often unintentionally
Even thinking about moving has an effect
If I shout at you, your muscles would tense involuntarily
Your body reacts without planning to
Your body prepares for any motion you will actually do
Think of even the simplest motion – standing up from the chair
Shift your feet back to put them under your center of mass
Shift your upper body forward to balance yourself
Flex muscles to bend joints at hips and knees
If you think about moving, your body will make small motions that give it away
Magicians use this to do common tricks
Leave the room
Let the audience hide something
Magician reenters
Someone will give it away with an involuntary motion of their eyes
Or muscle tension when the magician is close

4. The Ideomotor Effect (2)
Poker players know that people involuntarily give away what they are thinking
“Poker Face” is hard for most people
If the dowser knows where to look, he can “detect” it there
The motion of the dowser guiding the rods can easily be too subtle to notice
The dowser is not necessarily cheating
The motion can be entirely due to the ideomotor effect

5. Ouija Boards
Ouija boards are (or were) a popular form of entertainment
Supposedly information coming from the beyond
You place your hands on the “planchette” and ask questions
It points to the answers
Doubtless caused by the ideomotor effect

6. How to Not Test Dowsing Put a dowser in a natural environment
Have them select a spot
Dig until you find water
Of course, water exists naturally lots of places, if you dig far enough
There are also clues that you can use to get an idea where water can be found that don’t require dowsing rods
Lower elevation
Plants
Combined with the ideomotor effect, a dowser could get a very high success rate
Again, this does not mean that dowsers are intentionally cheating

7. How to Test Dowsing
The easiest way to test dowsing is to simply fill a bunch of jugs with water and leave others empty (or put sand in them) and let dowsers try to detect which have water
The dowsers cannot be allowed to touch the jugs
Ideally, any experimenter participating should also not know which jugs have water in them
To avoid giving it away via the ideomotor effect
This test has been done many times
Always a catastrophic failure