[He flinches when she apologizes. Maybe that's not the reaction she was expecting, but it's the one she gets. The more she talks, the more frustrated he gets and he's not even sure exactly /why/ it frustrates him, but it does.

He faces her sharply.]

Stop it! No one asked you to apologize for something you couldn't control. It was an experiment-- and I don't need you thanking me, either. [Even if he was the one who entered the trial...]