How do you know if someone is looking at you because you're in their vicinity vs. they find you attractive?

How do you know if someone is looking at you because you're in their vicinity vs. they find you attractive?

I like to think majority of the time people are just looking at what's in their vicinity. Its a quick look, they turn their eyes fast, and their isn't any emotion on their face.

I feel attraction its longer and you can feel some kind of energy. Or there could be no looking and they're whispering to their friend how cute they think a girl is.

I'm not entirely sure especially since I don't have men staring in my direction much lol.
How do you know if someone is looking at you because you're in their vicinity vs. they find you attractive?
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