Guybrush

I don't think there's anything telepathic about stuff like this. When you meet someone, the unconscious part of your brain is processing all kinds of information about this person, interpreting the way they look, the way their facial expression changes, the way they stand or hold their arms, what they say and how they say it and so on .. A lot of stuff which you get by "normal" sensory input.

I think what you call a gut feeling is simply based on stuff like that. To judge how someone's going to react to you, whether or not they can be trusted, and so on would be highly important to our fitness as social animals and highly adaptive. So, we should be good at it and there are telltale signs that give you that information without the need of a sixth sense.

edit :

Also, there's psychology involved here like association. Your fond memories of your grandmother and other experiences with elderly may make you more friendly inclined to old ladies for example.

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Something Completely Different

djchameleon

Just to add a little more to this, I also think while the brain is accessing for information about those minor details it is also attempting to match those things to traits of a person that you disliked in your past that also shared the same traits and that's where the whole gut feeling comes from.

I have come to notice that I come across the same type of people but they are just in different "shells". The way that they end up conducting themselves are very similar to people that I have met in my past.

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Fame, fortune, power, titties. People say these are the most crucial things in life, but you can have a pocket full o' gold and it doesn't mean sh*t if you don't have someone to share that gold with. Seems simple. Yet it's an important lesson to learn. Even lone wolves run in packs sometimes.