There’s a simple explanation for how the Ouija board works: it’s not ghosts, but how you feel about them.

You remember the Ouija board, right? If you went to sleepovers as a kid, you might have played with one. You gathered around with a few friends, put your fingers on the pointer, and asked a question. The pointer seemed to move of its own accord as it spelled out answers to your questions. Maybe you thought it was a fun game, or that you were actually speaking to the dead. Maybe you thought more sinister forces were making it move, or simply someone else sitting around the table.

It’s widely accepted by scientists that the Ouija board works through the ideomotor effect. The people whose hands hover over the little pointer that glides around the board are actually moving it to spell out the answers, even if they don’t mean to. Ideomotor movements are unconscious gestures we make in response to strong ideas or emotions. Though there are different theories of the ideomotor effect, expectation and imagination play a key role—anticipating an action, whether that’s performing it or resisting it.

The Ouija board, from its design to the myths surrounding it, practically hums with the desire for movement. We have this idea of the pointer swooping around the board. Maybe we think of it because we want it to happen, or because we’re afraid it will. Those thoughts prime our hands unconsciously, almost irresistibly, to make that first twitch. Once the movement begins, the excitement and drama build up—Who’s moving it? I’m not; are you?—making us all the more susceptible to ideomotor movements and all the more unaware that we’re making them.