So let me show you how quickly our brains can redefine normality, even at the simplest thing the brain does, which is color. I want you to first notice that those two desert scenes are physically the same. One is simply the flipping of the other. Okay? Now I want you to look at that dot between the green and the red. Okay? And I want you to stare at that dot. Don't look anywhere else. And we're going to look at that for about 30 seconds.
And I'll tell you -- don't look anywhere else -- and I'll tell you what's happening inside your head. Your brain is learning. And it's learning that the right side of its visual fieldis 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?
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.
So, what does this mean for context? It means that I can take these two identical squares, and I can put them in light and dark surrounds. And now the one on the dark surround looks lighter than the one on the light surround. 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.
