Yes, and they also have to do it within very short periods of time. As you can often see, it's harder to maintain a dialogue when the interpretation lags four or five seconds behind.
So, on the one hand, interpreters have to consider the emotion, as Mr. Ball noted. That's the Canadian interpretation model, and it's a good one. And, on the other hand, they have to do the work quite quickly to facilitate a real-time discussion.