Pendulums and mysticism. What's it all about Alfie?

The other day I was at a birthday party where a friend of the family grabbed a pendulum that was in the living room and started holding it and allowing it to move in some direction. Her daughter, who was present, is pregnant and does not know the of the baby yet. I thought it was a game but they really believe that they could get answers by the motion of the pendulum. Several people did this and they saw movement in the pendulum and believed that this circular movement meant that the baby is going to be a girl. I was the only one who held the pendulum and it stood completely still. The mother grabbed it out of my hand. I am curious what that means to someone who believes in this kind of mysticism. Anybody know?