 Now let's go back to this distinction between system one and system two. Now earlier on you gave us a few examples that come effortlessly to us. So two plus two equals sort of appears and recognizing an angry face just sort of happens. But there are groups of people that we call experts who can do some pretty amazing feats effortlessly, tasks that you and I would find difficult as novices. So for example, chess experts can identify and remember just thousands of chess moves and they can quickly decide what the next move is. Way better than novices. Radiologists, medical examiners can put two mammograms, two breast screens side by side on the screen and just in the blink of an eye can tell you whether a person has cancer or not. There's another example that you and I have worked on for fingerprint experts. So again, if you put two fingerprints side by side on the screen to a fingerprint expert, they can in a blink of an eye tell you whether those prints came from the same person or two different people. Right, so I mean it's this idea of expertise which I think is really quite interesting from a systems perspective. So when you're talking about chess experts or diagnosticians, these things which were system two is now system one. So when the diagnostician, the radiologist is looking at a breast scan, they can tell as you said within 250 milliseconds whether the scan is normal or abnormal. Now obviously that didn't happen overnight. They can't just look at it without knowing anything about a breast scan and so they need to know what they're looking for but after they've accumulated thousands of experiences with that particular class of materials, then it becomes a system one process, then it feels like it's just birth equipment, like it's just happening to them. So that's kind of hallmark of expertise. Now we talked earlier about pupil dilation. Well the same thing actually happens. Imagine, so going back to the example that I provided before in terms of driving. Now the same thing happens when you're learning how to drive for the first time. If I were to measure the pupil dilation of a novice driver, imagine all of the things that they have to pay attention to when you're learning how to drive. Particularly if it's a manual transmission, the friction point of the clutch, you have where the pedestrians are, where your indicators are, everything else. They're paying attention to a million things at once and if I were to measure the pupil size of the novice driver, they'd be like saucers, wouldn't they? But as you learn how to drive, these things just get easier and easier. As you accumulate hours at the wheel, eventually after 10 or 20 years of driving, you're eating a sandwich, you're carrying on a conversation, you're talking on the phone, you're swerving between traffic, watching, but it's like breathing. It feels like an extension of you, if anything. It's truly a System 1 process. If you were to measure the size of the pupils of the expert driver, they'd be just tiny by comparison to the novice driver. I think that's a really nice example of, again, the difference between System 1 and System 2 and how that develops as you develop expertise. Another really good example is faces. We're all experts with faces and if we were to show people upright faces, you have all of these sort of tasks that you can instantly recognize whether it's male, whether it's female, even who the person is and that's only because we have experience with upright faces that we've experienced our entire lives. But if we turn the faces upside down, then it's a completely different story. People are not good at recognizing upside down faces, so much so that there's a whole bunch of different demonstrations that I think are really quite impressive. But this is only because we're not experts with upside down faces, only upright faces. But I asked Danny Kahneman about this idea of expertise and you may have heard the number 10,000 hours, so it takes 10,000 hours to become an expert. So I asked him about this idea of expertise and how to turn novices into experts more quickly and here's what he had to say.