When some people think of clowns, they picture brightly coloured hair, big smiles, and lots of laughs.
Others find clowns creepy with evil intentions hiding behind a cheerful, gruesome mask. The intense fear of clowns is called coulrophobia.
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At the forefront of modern-day clowns are Joseph Grimaldi and Jean-Gaspard Deburau who excelled at making people laugh, but in real life, Grimaldi died as a penniless alcoholic and Deburau murdered a boy in the street.
They were not unusual. John Wayne Gacy, a professional clown, turned out to be a notorious serial killer. He used to say "A clown can get away with anything." Since then, the perception of the clown seems to have taken a turn.
People may also feel uncomfortable with clowns because the painted-on and exaggerated face pose a false expression, and that breeds distrust.
Sigmund Freud called this disconnect "uncanny". This "uncanny valley" is something computer animators and robot creators have difficulty with.
In the age of artificial intelligence, there is a growing number of devices that communicate with us. We give them names like "Siri" and "Alexa" and don't find them threatening - until they are given a face.
Evolving technology can create robots that look like people, but it is also at this point where people start to object. Once you can make eye contact with a machine, it starts to look like a horror movie.
Laughter, a positive, contagious and heartwarming expression can be scary sometimes. This phenomenon is due to our fears, which stem from a misalignment in what we see and what our expectations were.
If laughter sounds sinister, out of context or out of tune with what is happening (like a person laughing while seeing people dying in an accident) it sends a red flag to the mind, signalling that something is not right or that the person is not to be trusted.