Thread:Boxhead:3/@comment-26009950-20150529215116

It depends on force. For example, if you put your hand over your mouth and try, it won't work. (Unless you strongly believe it's by chance then whatevs) I believe it's determined by breath and gravity. The pencils are arrayed in an unfamiliar state, so any slight movement will most likely move them. For example, breath. If you hold your hand Infront of your mouth and say 'Charlie' there is an abnormal amount of breath, but still enough to shift a pencil from a balanced cross arrayed over four quadrants.  