You begin by removing a small piece of paper from a cloth bag and handing the bag to a helper. You explain that you'd like their help in an experiment involving free will. Your helper removes three wooden disks from the inside of the bag. Each disk has a simple geometric shape on one side. The helper mixes up the disks and then places them face down on the table.
The helper now chooses one disk for himself, one for the performer, and one to be put back in the bag. The choices are always up to the helper and they may change their mind before they commit to the selections.
You now ask one final question to the helper, "Did you feel every choice you made was of your own free will?" The helper responds, "Yes." The helper now opens the piece of paper which has been on display before ANY choices were made and it explains with complete accuracy where each of the symbols is now located!
A terribly unnerving reminder that the choices we make may not always be our own!