Musicals. Our DS, 20 mos., loves music. Music on TV will stop him in his tracks. When dialog starts, he moves on to something else.
Tonight we went to friends' house for their movie night. The Debaters is what they were watching. DS wasn't in the room much, as their daughter took him to play in the other room. But when he was in the room, he enjoyed clapping after the debaters finished talking, and after a scene where there was arguing. I think he is cued by the music that something dramatic has ended and it's time to clap.