when we attribute sensory experiences to 00:06:39 ourselves for instance like the experience of red or the experience of seeing blue the model is external properties and we think of there as being inner properties just like those external properties that somehow we are 00:06:52 um we are seeing immediately

so this is white light passing through a dispersive prison and this is a visible spectrum from about 420 nanometers in the violet through 500 nanometers and 00:00:18 the green 580 yellow 610 and orange and 650 red and some of the slides that have this along the bottom axis so how dependent I'll be in color what do you 00:00:30 think we depend on color a lot a little lots okay

I want to start with a game. Okay? And to win this game, all you have to do is see the reality that's in front of you as it really is, all right? So we have two panels here, of colored dots. And one of those dots is the same in the two panels. And you have to tell me which one. Now, I narrowed it down to the gray one, the green one, and, say, the orange one. 00:00:41 So by a show of hands, we'll start with the easiest one. Show of hands: how many people think it's the gray one? Really? Okay. How many people think it's the green one? And how many people think it's the orange one? Pretty even split. Let's find out what the reality is. Here is the orange one. (Laughter) Here is the green one. And here is the gray one. 00:01:16 (Laughter) So for all of you who saw that, you're complete realists. All right? (Laughter) So this is pretty amazing, isn't it? Because nearly every living system has evolved the ability to detect light in one way or another. So for us, seeing color is one of the simplest things the brain does. And yet, even at this most fundamental level, 00:01:40 context is everything. What I'm going to talk about is not that context is everything, but why context is everything. Because it's answering that question that tells us not only why we see what we do, but who we are as individuals, and who we are as a society.

so here's a straightforward question what color are the strawberries in this photograph the red right wrong those strawberries are gray if you don't 00:00:12 believe me we look for one of the reddest looking patches on this image cut it out now what color is that it's great right but when you put it back on 00:00:25 the image it's red again it's weird right this illusion was created by a Japanese researcher named Akiyoshi Kitaoka and it hinges on something called color constancy it's an incredible visual 00:00:39 phenomenon by which the color of an object appears to stay more or less the same regardless of the lighting conditions under which you see it or the lighting conditions under which your brain thinks you're seeing it

So, if some of you are still feeling a bit too certain, I'd like to do this one. So, if we have the lights down. And what we have here -- Can everyone see 25 purple surfaces on your left, 00:15:03 and 25, call it yellowish, surfaces on your right? So now, what I want to do, I'm going to put the middle nine surfaces here under yellow illumination, by simply putting a filter behind them. Now you can see that changes the light that's coming through there, right? Because now the light is going through a yellowish filter and then a purplish filter. I'm going to do the opposite on the left here. 00:15:31 I'm going to put the middle nine under a purplish light. Now, some of you will have noticed that the consequence is that the light coming through those middle nine on the right, or your left, is exactly the same as the light coming through the middle nine on your right. Agreed? Yes? Okay. So they are physically the same. 00:15:56 Let's pull the covers off. Now remember -- you know that the middle nine are exactly the same. Do they look the sa

let me show you how quickly our brains can redefine normality, even at the simplest thing the brain does, which is color. 00:05:29 So if I could have the lights down up here. I want you to first notice that those two desert scenes are physically the same. One is simply the flipping of the other. Now I want you to look at that dot between the green and the red. And I want you to stare at that dot. Don't look anywhere else. We're going to look at it for about 30 seconds, which is a bit of a killer in an 18-minute talk. (Laughter) But I really want you to learn. 00:05:55 And I'll tell you -- don't look anywhere else -- I'll tell you what's happening in your head. Your brain is learning, and it's learning that the right side of its visual field is under red illumination; the left side of its visual field is under green illumination. That's what it's learning. Okay? Now, when I tell you, I want you to look at the dot between the two desert scenes. So why don't you do that now? (Laughter) 00:06:21 Can I have the lights up again? I take it from your response they don't look the same anymore, right? (Applause) Why? Because your brain is seeing that same information as if the right one is still under red light, and the left one is still under green light. That's your new normal. Okay? So, what does this mean for context? It means I can take two identical squares, put them in light and dark surrounds, and the one on the dark surround looks lighter than on the light surround. 00:06:47 What's significant is not simply the light and dark surrounds that matter. It's what those light and dark surrounds meant for your behavior in the past.