 How do you make a film that teaches people about science? I think it's an important question, and I think it's a timely question. Given that, well, video is exploding everywhere on the internet, and there are new initiatives popping up, like Ted Ed. Now, this question, how do you make a film that effectively teaches someone something about science? That was the topic of my PhD. So I'd like to tell you what I found out. I went to the University of Sydney, and I took all the first-year physics students, and I tried to teach them about the basic laws of motion, Newton's first and second laws. So I sent them away to their homes, and I asked them to go online and sit a 26-question multiple-choice test. Here's a sample question, just so you get a feel for what I was asking them. Imagine a basketball player shooting from the free throw line. After he releases the ball, the forces on the ball are A, upwards and constant, B, upwards and decreasing, C, downwards and constant, D, downwards and decreasing, or E, tangent to the path of the ball. I want you to take a minute and think about what you would answer, and think about what you think other people might answer. Then we would get the students to rate their confidence in their answers. How confident are you that this is correct? I should mention that that is not the exact Likert scale that I gave them, but it's, you know, that's the idea across. Then I would randomly assign these students to watch one of several videos about Newton's first and second laws. They lasted about eight to ten minutes. So in a standard exposition video, I would say something like this to them. We would state Newton's laws, and then we would apply it to a real-world example, like a juggler. I can't juggle, so I've got one ball. Anyway, so we would say something like, while the ball is in the air, there's only one force acting on it throughout its flight. It's the force of gravity, it's constant, and it's downwards. We'd actually animate a little arrow on the ball as it goes up and down in slow motion. Okay, so obviously the answer was C, whereas most people usually pick B to that question. Okay, so after watching this video, the students would sit the exact same 26-question test. I wanted to see had they changed their minds about any of those questions. And I also interviewed a couple students to see what did they think about the video. Did they like it? Did they think that they learned something from it? And here's what they told me. Well, they said, Derek, that was a great video. It was clear. These are the most common things they said. It was clear, it was concise, it was easy to understand. Good. And then I looked at their confidence scores. How did that change on average? Well, on average, it improved by about a point. Okay, everything's looking good. But how much did they learn? Well, on the pre-test, they scored six out of 26. And I can tell you there were basically direct answers to at least 14 of those questions. But how much did they pick up? The average on the post-test was 6.3. What happened? They thought they learned, but their scores didn't change. Well, one of the students told me in the video it said, the ball is slowly decreasing in force. They thought there was some upward force in the ball and they thought that was presented to them. I couldn't even correctly remember what was presented five minutes earlier. And I had sat in the room with them and they watched the video. The thing is, in science, students don't know nothing about what we're trying to teach them. They actually know lots of things through their interaction with the world. It just turns out that these things are wrong, scientifically speaking. So when you present something, the student thinks they already know it and they don't really pay up most attention. They don't realize that what's being presented differs from their prior knowledge and they just get more confident in those things that they were thinking beforehand. So actually, a clear expository summary is worse than no instruction at all. I mean that very seriously. So how do you get students to engage? Well, I tried a different approach. I put two people in a video and I got one to voice the common misconceptions. And then the tutor would kind of indicate, okay, that's not quite right, and they would work it out through a social dialogue. But I mean, we would even animate the misconception on the ball without telling anyone it was a misconception. So I had to work that out through the social interaction. So this was the very same setting that the other students watched the exposition video. What did the dialogue students say? Well, no one told me that it was clear. No one told me it was concise. No one said it was easy to understand. In fact, most of the time, they told me it was confusing. Man, maybe this backfired. So how do they go on the post-test? Well, their scores nearly doubled to 11 out of 26. Okay, it's not 26 out of 26, but it's a start. And what was the difference? Well, after the video, I asked students to rate their mental effort. How much mental effort did you expend while watching that video? And the students who watched the dialogue invested significantly more mental effort in engaging with that presentation than students who saw only an expository summary. So to me, there's a really important message there. Depending on how you present, you can change how your audience watches and thereby how much they learn. And I'm now applying this. I've got a YouTube channel. It's called Veritasium. And I've made nearly 100 films, which have been seen over 4.5 million times throughout the world. And you know, you always have to start with the misconceptions. Thank you.