OK, I'm going to try to perform a trick right from my computer (note I came up with this myself after some inspiration.) OK, so just try out the following:
If you place a pendulum (find a moderately heavy object hanging from a string or make your own) over a male's hand, then it will swing in a straight line. If you do the same to a female's hand then it will swing in a circle.
Now that's the whole trick.
