Here is a snip from the above site:
To put it simply, the ideo-motor reflex is the same thing that makes dowsers believe that they are actually divining. Although you BELIEVE that you are not influencing the movement of the yo-yo, you actually ARE, though you are entirely unconscious of it. The only way to prove that you are not physically influencing the yo-yo, would be for you to NOT hold the yo-yo string.
Nobody has ever successfully demonstrated dowsing under controlled conditions ... and nobody ever will ... it is just horsepucky.
But, assay the responses in this thread. It is alarming that science is so ill understood in these times. The dark ages are coming back.
Thanks for the link Bud and for the ONLY reasoned response. Scary!