He wasn't so deep into his own mind that he didn't hear the sound of someone (rather large) come into the dining hall. Ubbe simply didn't expect to look up and see the person have horns. So, that earned him the right to stare while he nods at both questions. The Viking takes the beer and mutters his thanks.

It's in the following moments that Ubbe says something that would have come out of his father's mouth, because Ragnar didn't care much for manners. He gestures vaguely up at the horns.

"Were you born with those?"