Women often touch a man's arm or shoulder to test if he's attracted to her. She's reading his subconscious reaction to gauge chemistry. Men usually miss these signals because women are better at reading body language.
It's very common for women to kind of break that touch barrier, inappropriate ways, of course. But it's very common for women to break that touch barrier to see if there's chemistry there, to see if you like it or not, because that's going to help her know if you're interested in her. Women naturally are, generally speaking, better at reading body language than men. So much so that women don't even most of the time realize that we're reading body language. And so it will be something she's not thinking, "I'm going to touch your arm. How did you react?" You know, instead it's, "Oh, hey, touch him and see what happens."
