They did this on showtimes Bulls*** show with Penn and Teller. They were able to show that people using are moving the cursor but unaware of it. They did this by blind folding them and flipping the board upside down. They would ask yes or no questions, the cursor would move but to where the users last saw the yes or no, which at that time were on the ther side of the board. Questions with spelling involved obviouslly did not happen when they were blindfolded.
http://www.youtube.com/watch?v=eG4wTZuT3wM
http://www.youtube.com/watch?v=eG4wTZuT3wM