I thought the eye contact thing was pretty basic ( common )knowledge
I know some guys really struggle to identify female interest but really once you have spent a fair bit of time with women it becomes painstakingly obvious whether they are interested or not
Eye contact is like the female equivalent of cold approach
This.
It gets easier to spot the signs of sexual interest, although at the same time, it really is pretty damn obvious. And as you say, it's basically all in the eyes as far as i'm concerned (at it's most subtle level)
In fact my problem with basically EVERYTHING when it comes to 'game' is that, far from being some super secret powerful stuff that you need to 'learn' and it can force attraction in girls etc, it's actually all so damn obvious! It's just basic stuff that most people already do naturally. e.g - you really don't have any 'edge' over most people. I don't think I ever learnt anything in a PUA book/course that I didn't already know/do! (and i've read and watched a **** tonne!)
My 'results' got tonnes better after reading all of the books etc, but rather than it being due to an increase in 'skill', it was really just because the books and stuff gave me the confidence to actually approach a lot more! And as a result, through numbers game, I was able to find the interested/attracted girls