Tribal self preservation instinct. Works when identifying outsiders.

I think maybe they give off some sort of smell.
I know exactly what you’re talking about.

Sometimes I’ll look at someone and it will remind me of someone you might see in a true crime documentary about murderers or something.

Sometimes, for me, also, it will be the way a person acts. It might be something friendly, for example, I was telling someone before about how I took my daughter to the mall when she was a baby, in the baby carriage, and some guy held the door open for us. Of course I said thank you but it was just creepy because he looked creepy.

For me, I think it’s their eyes. They look at me a smidge too long but not as if they’re interested in what I’m saying. Or rather than looking at me when I’m speaking I can tell their interest is on other people around us in a distracted way. Or they look at the wrong places on me, you know.

With the eyes, I think there’s also some sort of inner voice that tells us something is a little off.

Then, of course, there’s the people who should be clanging alarm bells in our heads and we’re oblivious – like with charming serial killers.

Intuition.

They smell like BS !

To me it’s the certain way that they act. I often find myself creeped out by people who are overly friendly and talkative upon first meeting. You know, the kind that immediately acts like you are their best friend and asks for personal information and demands to be friends, things like that. Those people give me the impression that they want something from me and are trying to lure me in. And oftentimes I’m correct. This also works with people my friends are involved with.

People that try to sell me something and act like they don’t understand, “I’m not interested”.

People have the ability to read and project from subtle clues, yes.

Such skills can develop both consciously and subconsciously.

Different people develop such abilities to different degrees and in different ways, and about different types of signs and different types of people.

One way is from experience, and yes, can be from particular bad experiences with some people.

There are many different types of signs that can be picked up on.

There are a lot of things that can cause us to feel creeped out – the way I a person pronounces words, body language, how a person walks, resting facial expression, etc.

I agree with @Mimishu1995 to a degree. Coming in hot with personal questions is sus.
I think there are a lot of people who do mean us harm, and our instincts/bodies/brain can sometimes tell. It’s saved my life a few times as a younger person out partying with strangers.

The creepy person has physical features that scared us or creeped us out when we were kids.

OTOH there are some people we like and trust immediately. Isiah Pacheco comes to mind.

Pheromones or their equivalent. Some low-level chemical reaction.

^^^ What he so succinctly said!

@Dutchess_III

“OTOH there are some people we like and trust immediately. Isiah Pacheco comes to mind.”

I agree, and anyone who wears a red jersey with a gold helmet is a total creep! ;-0

Very interesting question. I brought up an experience I had with a person we encounter frequently and my husband recognized who I was describing right away. He noticed feeling the same way about this stranger. He is a person we don’t know, but see frequently at Jazz festivals we attend.

I have met people who make my skin crawl only later to get to know them and end up being perfectly comfortable around them. The reverse is sometimes true. Psychopaths can be quite likeable and charming at first. Usually my first instincts turn out to be correct though. I’m not sure why, I suppose it is deeply seated instinct.

It’s mostly bias. Bias informed by experience, but bias nonetheless.

It’s all of the things you mentioned, except psychic ability, which is probably not real. Our experiences craft a complex web of metrics for judging other people quickly, because to judge every person correctly takes too much effort.

It’s usually something about their eyes that makes me feel someone can’t be trusted. I I feel this way very seldom but when I do I avoid the person as much as possible.

Some possibilities:

Pheromones.

Experience and knowledge we have acquired over the years that clues us in.

Warnings from our parents or other people that makes us hypervigilant.