I think you may have a point here.
The first girl I ever tied up for sex was a tough bitch in public, but when we were kissing I noticed that she got hotter if I held her wrists. So I started pinning them behind her or out to the sides and she couldn't get enough of it... After I first tied her up she said "How did you know I wanted that?" and I said "You told me."
But with more experience I've learnt to spot the signs without getting that close, even if my "asdic" is intuitive and I mostly don't know what's clueing me in. I remember once when I was in a new counselling group and we were doing the round of introductions, and as one girl spoke up I felt the buzz and thought "Her, eh?" I didn't do anything about it, because it's very bad form to hit on your counselling partners; but I was open about my own tastes with the group, and months later she phoned me because she'd been getting overwhelming masochistic fantasies and I was the only person she knew who wouldn't think she was sick. I was glad to be able to help, but I also had a smug little feeling of "I knew that!"