I have seen dowsing work in finding graves, even the sex of the individual buried in a grave, so I know that there is something to it.
At the same time, I also know that in some cases the results can be influenced by the dowser.
I believe that what Dr. Clark did with the synchrometer was very similar because the synchrometer on its own is not effective. It is manipulated by the operator to provide suggestive results.
The same problems exist for muscle testing. Not saying that it does not work, because I believe that it does, but that it is subjective and therefore the results are influenced by the operator.
There needs to be an instrument developed that works on its own without subjective influence.