There is also something powerful in the concept of an ‘airport idea’. On the surface, it links with Dan’s plea for what students should do if they me… - David Franklin

So Trump was 29% likely to win. What does 29% mean?” he asks. This is an odd question for many: they’re doing a Master’s degree at Harvard, and they’re being asked what a percentage means. The question is aiming at the gut reaction of the brain to the number. Inevitably, students think it might be a trick question. Dan waits a while, and when no-one raises their hands, he breaks away from the example to tell a story: “You know, when I first started teaching, I was terrified of silence. I thought, ‘oh my god, I’ve got to do something, they’re not saying anything’.” The class laughs: he has eased the tension created by the silence. “The more I taught, the more I realised that silences are important in a class – they give time for people to think. These days, I’m not afraid of silence at all.” After a few seconds, a woman puts up her hand. “Well, obviously, I knew that it meant there was some chance that he would win. But it was still a shock that the 29% happened.

Now – those who got it right. On the count of three, I’d like you to sit down if you’d seen the question before. 1, 2, 3!” Everyone who was standing sits down. This gets a huge laugh. The students who got the answer wrong suddenly feel much better about their mistake: in a Harvard class, not a single person got it right unless they had seen it before.

But everyone who guessed in this way went low, rather than high. It suggests that there is some form of systemic bias in play.