Other creepy physical features were having bulging eyes, very pale skin, bags under their eyes, a peculiar smile or particularly muscular physique.
Creepy behaviour included standing too close to your friend, laughing at unpredictable times and making it "nearly impossible for your friend to leave the conversation without appearing rude".
Also in the top 15 behavioural traits of creepy people was the person who "relentlessly steered the conversation toward one topic", and someone who dressed too formally for the occasion.
In a total of 44 personal aspects that people found creepy in others, having visible tattoos or not looking a person in the eye when they spoke to you featured, along with the degree to which a person was steering a conversation toward sex.
Other creepy behaviour included touching a friend too frequently, and nodding too frequently.
In studying occupations, the researchers found that professions connected with death, such as taxidermy and funeral directors, or those connected with a fascination for sex, such as sex shop owners were creepy.
Taxi drivers, unemployed people and members of the clergy were also high on the list. But clowns were the creepiest of all.
One final question the researchers made in their survey was "do most creepy people know that they are creepy?"
The majority of people responded with the answer no.
The purpose of the study paper was to psychologically explore the common but unpleasant human experience of "being creeped out", which can make people feel not only uncomfortable but physically cold or chilly.
McAndrew and Koehnke, who work at Knox College in Galesberg, Illinois, also looked at just what factor our "creepiness detector" was warning us about.
"A mugger who points a gun in your face and demands money is certainly threatening and terrifying, [but] most people would not use the word 'creepy' to define this situation," the researchers said.
"It is our belief that creepiness is anxiety aroused by the ambiguity of whether there is something to fear or not.
"In the mugging situation, there is no ambiguity about the presence or nature of threat.
"It is only when we get confronted with uncertainty about threat that we get 'creeped out'."
The researchers found that "creepy" is different to "terrifying", but still is related to the mechanisms humans have developed to protect them from harm at the hands of predators or enemies.
"If you are walking down a dark city street and hear the sound of something moving in the dark alley to your right [and] it turns out that it is just a gust of wind or a stray cat," then your alarm bells have rung for nothing.
But because humans do err on the side of caution by reacting to these factors, we are heightened to respond to people who make us feel uneasy.
"It would be considered rude and embarrassing to run away from an odd person who has done nothing overtly threatening, but, on the other hand, it could be perilous to ignore your intuition and remain in an interaction that is dangerous.
"This ambivalence leaves you frozen in place, wallowing in unease."
Top creepy behavioural traits
1. Standing too close to your friend
2. Having greasy or unkempt hair
3. Licking your lips too frequently
4. Wearing dirty clothes
5. Having a peculiar smile
6. Having bulging eyes or bags under your eyes
7. Dressing oddly or being overdressed for the occasion
8. Having very pale skin
9. Laughing at unpredictable times
10. Having long fingers
11. A person who makes it nearly impossible for your friend to leave the conversation without appearing rude
12. A person who relentlessly steers the conversation toward one topic
Top creepy occupations
1. Clown
2. Taxidermist
3. Sex shop owner
4. Funeral director
5. Taxi driver
6. Unemployed
7. Clergy
8. Janitor
9. Garbage collector
10. Guard
11. Writer
12. Actor
