By definition, an irrational fear of clowns is known as coulrophobia, with the prefix “coulro” coming from the ancient Greek word for “one who goes on stilts.” Symptoms of coulrophobia can include sweating, nausea, feelings of dread, fast heartbeat, crying or screaming, and anger at being placed in a situation where a clown is present.

According to Rami Nader, a psychologist and director of the North Shore Stress and Anxiety Clinic in North Vancouver, B.C., the psychological roots of the phobia may be traced to the fact that clowns are basically wearing disguises (albeit funny ones) while displaying artificial emotions (even silly ones) that perhaps hide their true feelings.

“You can’t really tell who they are,” he says. “You can’t really see their face. You don’t really know what that all means behind the mask.”