Just call

Do you ever call on the river just to see what your opponent has?

Not talking bluff catching or anything like that. Like really say "i missed--no way I win this hand--but I just want to see WTF you played like that?"

obviously a -EV move lol but I do it....probably too often. I feel like it can give you an edge..esp when they flip over something marginal and you're like wow...that's how he played THAT? this guy's dead. lol;

If they take a weird line in the hand and the river bet is small, ya I'll call just to see wtf they were up to.

I do this from time to time if Im really curious about someones hand. It honestly has helped me a lot lets you know how that player likes to play hands.