Maybe another way of thinking about that is how connected mentally your date seems to be If he's just making eyes at you, how intellectually engaged is he likely to be, compared to what might be indicated by a long discussion on a myriad of issues? Might he be, in other words, thinking with the wrong head? And if he appears to lose interest the moment the discussion veers toward the intellectual, what does that say about his motives? You're right: smiles can be surprisingly complicated little gestures.