Here's an interesting piece of recent research into the the decision-making influence of the unconscious mind, that uses a parlour game believed by many to allow communication with the dead. Hélène Gauchou, a psychologist at the University of British Columbia turned to the Ouija Board as a means of 'communicating' with the hidden side of our mind:
To keep things simple her team has just one person with their finger on the planchette at a time. But the ideomotor effect is maximised if you believe you are not responsible for any movements - that's why Ouija board sessions are most successful when used by a group. So the subject is told they will be using the board with a partner. The subject is blindfolded and what they don't know is that their so-called partner removes their hands from the planchette when the experiment begins.
The technique worked, at least with 21 out of 27 volunteers tested, reports Gauchou. "The planchette does not move randomly around the board; it moves to yes or no. It seems to move almost magically. None of them felt responsible for the movement." In fact some subjects suspected that their partner was really an actor - but they thought the actor was deliberately moving the planchette, never suspecting they themselves were the only ones touching it.
Goucher's team has not yet used the technique to get new information about the unconscious, but they have established that it seems to work, in principle.
For an excellent history of the Ouija, see Mitch Horowitz's article devoted to the topic in Darklore Volume 1 (Amazon US or Amazon UK), and also check out The Museum of Talking Boards website for a great collection of designs through the past century or so.