So, the perceptual processes that we've discussed so far, causes to see this two dimensional array as a person standing in front of a house. More generally, our perceptual abilities let us segment the world into objects, space into things like people and trees and houses, and let them understand where they stand in relationship to each other. Where they stand in depth, giving rise to three dimensional understanding, out from a two dimensional world. Now, this is just part of the story, and the whole story which we're going to discuss through the end of this lecture, and the next lecture, is how it gets all the way from the world, all the way into long-term memory. This is a complicated diagram, and you don't have to think about it too long. But what's worth knowing is that there are three stages. There's sensory memory, which is basically what you see. What appears to your senses. Then there's working memory, also known as short-term memory, also associated with consciousness. That's what you experience for a brief period of time. Then there's long-term memory, what you carry away with you. If you know your name? If you know the city were born in? If you know my name? It's all long-term memory, it's stuff stored in. What I want to focus on for this lecture, is how things get from sensory memory into working memory, and the answer is attention. When you attend to things, when you focus the spotlight of attention onto things, it causes you to remember them and think about them. Now, it turns out that there are some surprising facts about attention. Attention gets information from sensory memory to working memory to consciousness, but there's lot of things we don't attend to. A lot of what goes on in a world, we're unaware of. Sometimes attention is effortless. Sometimes things just jump out at us, and capture our attention automatically. So, I'll give a demonstration. I'm going to show you a slide, and I want you to tell me when a green X shows up. If you're sitting by yourself just shout, "Got it." We're looking for something green. Go. Now, if you're like most people this was pretty instantaneous. Now, next one, when an O comes up just shout, "Got it." Same deal, you saw it right away. Psychologists say it this is a parallel process because you didn't have to go through each item until you find it, it just popped out at you. But sometimes attention requires work and effort. So, I wanted to tell me when you see a red O. Go. Now I bet it took longer. Some of you by good fortune are incredible mental speed noticed it right away, others are probably still struggling to find it. But, the idea here is that to find a red O requires serial processing, and what this means is you have to effort-fully go item by item, until you find it. Distractions like where's Waldo, which involve looking at sheets of paper where something is hidden, require this search technique, for that red O to get into your mind you have to take the time to search for it. Now, sometimes attention is involuntary, you can't help but attend. The most obvious example is spoken language. So, if I'm sitting next to you, and I'm talking you can't help but listen to what I'm saying. I could be telling you the most boring story in the world, I could be telling it over my phone not to you at all, but if there's no other distractions you can't help but listen, you can't shut your ears. When you could literally sticky fingers in your ears, but barring that my talking will attract your attention, and capture it. Here's another case this is a classic discovery in psychology known as the Stroop effect. It's very simple. We show you a list of colors, and your task is to name the colors. So, you might see this, and you say, "You have to name as fast as possible red, green, blue, black, green, blue and so on." Easy as pie. Now, let's give the colors, let's make the colors words remember, you're not supposed to read the words, just name the colors. Well it's also easy, green, red, blue, black, blue, red, but now and here's what a cool Stroop effect comes in. Imagine the word say different things than the colors. So, imagine you have to do as quickly as possible. Blue, green, red, green, black, slower. It is definitely slower why, because if you know how to read English. You can't help but read English. So, you know you suppose look at the color of letters for the first one which is blue, but you can't help but also read the word red, and red jumps out at you. This just shows how sometimes things out of your control can capture your attention, and derail a mental process. I would just tell you by the way that you can use the Stroop effect to detect Russian spies. So, there's a TV show that Americans, a lovely TV show involving sympathetic Russian spies, and they know Russian. Now, suppose somebody came up to you and said, "I don't speak any Russian, I don't read any Russian. Is there anyway you could find out, whether they did well there is there is the Stroop effect. So, I can give this to you, and say name the colors and if you're not a Russian speaker, you would say, "yellow blue," but if you were Russian speaker it would slow you down, because it so happens according to Google Translate. The first word is the Russian word for blue, and the second word is a Russian word for yellow, and if you read Russian that trip you up. Attention also applies in the real world, now I'll just show you some clips of some everyday demos. This was developed by some lovely experiments done at Cornell about a decade ago. Showing that in everyday life when you're not paying attention to things, you don't notice things. "Excuse me, do you know how get to Trinity church from here. Yeah, you see that church down there. Yes straight through there. Then may keep you. Sorry, which way. See that church that is down there. Yes. Stay on that it reaches on Fifth Broadway, and then you walk down two or three blocks and Trinity church is in over by the. Let me walk with you in that direction. Excuse me do you know where Trinity church is do you. Might be Wall Street in Broadway. Okay. We are down here somewhere aren't we. Yes. Sorry. If you keep going that way all the way and then you go. Thanks very much. That seemed almost too easy, so later on I see how far I can take it. Excuse me do you know where Trinity Church is. Yes. Great. Where are we on here? We are right here. Excuse. Go on. We're on Brooklyn bridge, you want cross over there go down Broadway you will be right there. So, the big themes here for perception, involving the difficulty of perception, and a accessible perception involves educated guesses, about the world, and the theme about attention is, we attend to somethings and not others, and we miss a surprising amount of what happens in the world. In the next lecture, we're going to turn to that the final third of this trilogy and talk about memory.