It's the latter (using things like click through rates). I'm not sure if any one blog sums up their methods, but they write about this topic a lot. In one post I read, they specifically mention that having a high quality camera correlates with their attractiveness ratings and so do different types of poses. So "attractiveness" might be better thought of as popularity, not beauty (though, that's the approximation).

okcupid is now very similar to tinder in that users can rate each other on a 0-1 scale. (It used to be 1-5).

The rating algorithm is probably a lot like pagerank. Ratings by users that are rated highly matter more.

The potential signals are:

* swipes yes or no

* messages received

* length of conversations

* number of unmatches/blocks received