A famous probability puzzle is discussed involving goats and game shows with German psychologist Gerd Gigerenzer. Is he right to suggest in his new book 'Risk Savvy' that we really don't understand risk and uncertainty? And More or Less listeners weigh in on a problem from last week’s programme - how old will you be before you're guaranteed to celebrate a major, round-number birthday (like 40 or 50) on a weekend?