...As to why people might fear clowns, Radford suggested that the heavy, mask-like makeup could cause unease because it obscures a clown's true expressions.
"There's something inherently menacing about a masked stranger," Radford said.
Clowns also have qualities that can appear suspiciously otherworldly, Radford told Live Science. They can cram 20 of their friends into a tiny car. They can unfurl endless scarves or squirt water from floral boutonnieres. So it's no wonder that children, or even adults, in a clown's audience might be inclined to connect the figures to the supernatural.
And for some people, the unpredictability of clowns makes them frightening, said Kristin Kunkle, a clinical psychologist at the Columbia University Clinic for Anxiety and Related Disorders.
"They pull things out of their sleeves. They blow up balloons and then pop them," Kunkle said. "They do things that bring on a rush of emotion that some people might be excited about and some people might find overwhelming."
It probably hasn't helped that in recent decades, a number of horror movies and TV shows have prominently featured gleefully diabolical clowns, such as the costumed alien invaders in "Killer Klowns from Outer Space" (1988), Pennywise from "It" (1990), Killjoy from the ongoing "Killjoy" film series (launched in 2000), and Captain Spaulding from "House of 1000 Corpses" (2003) and "The Devil's Rejects" (2005).
Batman's villainous nemesis the Joker is another murderous example of a man whose clown makeup and maniacal grin accompany heinous crimes and evil deeds...