You know that feeling when you walk into a dimly lit parking garage and notice there’s someone walking behind you?  You’re not exactly scared, you’re not nervous, you’re just a little bit… creeped out?

Well, it turns out that "creeped out" feeling could actually have a scientific explanation: A new study from Knox College finds that feeling is how we respond to moments when we're unsure if something is really a threat.

"I started to notice how frequently people referenced the concept of 'creepiness' or being 'creeped out' in everyday conversation…" lead researcher Francis T. McAndrew told Revelist. "I heard very similar responses from almost everyone, so I decided to look into the scientific literature to see what we knew about this."

McAndrew, a psychology professor, surveyed 1,341 people to determine exactly what makes someone creepy.

First up: gender. A whopping 95% of people think men are more likely to be creepy than women. That's probably because men are more likely to be perceived as a threat, hence setting off our creep response.

Women also rated "steering a conversation towards sex" as creepy more often than men did, proving what women have known for decades: Repeatedly bringing up sex in a casual conversation is a terrible way to pick up chicks.

The nature of an interaction also plays a big role in whether someone is deemed creepy or not. Not looking your partner in the eye, asking for a picture with your partner, and digging into other peoples’ personal life are all definitively creepy. Also creepy: Staring at people before you start talking to them. Don’t do it.

Creepiness can also be determined in part by occupation. Participants rated death- and sex-related fields (such as taxidermists and sex-shop owners) as highly creepy. The researchers think a perceived fascination with death or unusual sexual behavior sets off our creepiness radar. But the most creepy profession of all? Clowns. No scientific explanation for that one.

The researchers conclude that all of these factors prove one thing: unpredictability equals creepiness.

"Anything that makes the person unusual also makes them less predictable, and hence the potential for more creepiness," McAndrew told Revelist.

So when people exert weird behaviors like bringing up sex all the time or working at a taxidermy shop it signals that they could possibly be a threat. The creeped-out sensation is just your body saying, "I don't know if this blood-spattered clown staring at you is a threat, but I'm letting you know just in case."

So the next time a dude creeps you out, thank him. He just reminded you that your evolutionary threat detector is working just fine.