Red-nosed, balloon-making clowns have been a staple of birthday parties and carnivals for ages, to the delight of children around the world.

Well, most children. Let’s face it: Many people, young and old, are actually quite afraid of clowns.

Residents in some Canadian cities have reason to be fearful. This week, there have been sightings of “creepy clowns” in Edmonton, Toronto and Halifax, which has prompted authorities to trigger lockdowns at schools and warn students to keep an eye out.

The sightings may be part of a viral trend that swept into several U.S. cities, where there have been reports of clowns terrorizing children and stalking people in the street.

But why are we so scared of clowns to begin with?

Child and adolescent psychiatrist Steven Schlozman says it has something to do with how clowns are portrayed in popular culture.

“They are supposed to be fun, but they have been part of the horror canon now for awhile, at least 20 years and probably more,” Schlozman told CTV News Channel on Thursday.

He points to films and television shows that have taken the idea of a fun-loving, happy clown and turned it on its head, introducing the maniacal killer character clowns into our thriller lexicon.

From a neuro-biology perspective, Schlozman said clowns also “violate” the rules of pattern recognition.

“We know what a person looks like -- they’ve got two eyes, a nose and a mouth, and so do clowns,” Schlozman said. But with clowns, their facial features are exaggerated and “grotesque.”

In addition, their features are frozen or “stuck,” says Schlozman.

“There’s a permanently painted smile or a permanently painted frown, so you don’t actually know what their motivation is,” he said. “That’s I think what gives people a bit of the willies.”

Schlozman acknowledges some of the fear of clowns is circumstance.

“I think clowns at the circus or a birthday party are not that scary,” Schlozman said. “Clowns in your backyard – that’s a little creepy. I wouldn’t want to see it.”