All right. I'm going to start out with a challenge for you. I'm going to show you a series of shapes, and I want you to count the number of yellow stars that you see. Also, count the number of red X's that pop up on the screen, so that's two separate numbers, one for how many yellow stars you see and one for how many red X's come up on the screen. All right. So that was probably a challenging task because you had to count two different things and I kept talking to you while you were trying to do that. That's an example of divided attention, which we'll talk about in just a second. But first, you probably want to see how you did. So let me show you everything you just saw. All right, this is everything that popped up on your screen. There were 15 yellow stars and 13 red X's, and also one smiley face. Don't worry it if you didn't see this guy. We'll talk about that later. But now that you have a good example of how limited a resource your attention is, let's talk more about it. When you're paying attention to something, that means that you're concentrating on it at the exclusion of the other stimuli in the environment. A lot of times, though, we try to divide our attention and do multiple things at once. So maybe you watch TV while studying, or try to count yellow stars while trying to count red X's. The thing is, as you just saw, attention is a limited resource, and we can't split it all that well when it comes to complicated stimuli. So if you're trying to do two things at once, you usually end up switching between those tasks rather than doing them simultaneously, even if you're switching so fast you can barely tell. So think back to when you had to count the yellow stars and the red X's. You couldn't really do that at the same time. You had to kind of flip back and forth. When you switch, or if you do just intend to focus on one thing at a time, you're exercising your selective attention. You can think of selective attention like a flashlight beam on some aspect of your environment. You can move the flashlight around, depending on what you want to focus on, but at any given moment, it's illuminating one particular area of interest, and everything else is just kind of dimmer. So the question is, what causes your flashlight beam to swing around and focus on one thing or another? There are two types of cues that can direct our attention, exogenous and endogenous. Exogenous cues are external to any goals we might have, meaning we don't have to tell ourselves to look for them in order for them to capture our attention. They include things like bright colors or loud noises, because you can be in the middle of a gripping conversation and have every intention on focusing on it, but a loud noise will still cause your focus to shift. And with salient visual cues, the ones that really stand out, this is called the pop-out effect. Something just pops out at us, like a yellow circle amidst a bunch of green circles. Endogenous cues, on the other hand, are more internalized and higher order, meaning they involve the internal knowledge to understand the cue in the first place, and the intention to follow it. Take an arrow, for example. If you didn't know what an arrow meant, then you wouldn't know to follow it. It's just some random lines on a piece of paper. But because you have the internal knowledge of what an arrow is, you can carry out an intention to look where it's pointing. One really good example of selective attention is the cocktail party effect, which you've probably experienced yourself multiple times. And this is your ability to attend to one voice even amidst many others. And it most commonly occurs when you hear your own name amid those voices. So, for example, picture the last time you had a big family dinner, and you're at one end of the table talking with someone, and then Grandma down at the other end of the table says your name. And even though you haven't been listening to grandma's conversation, you instantly swing your flashlight beam of attention down to hear what she's saying about you. And if you had to guess what type of cue your name was in that situation, endogenous or exogenous, what would you say? If you said endogenous, then that's right. Because it was the meaning of your name that drew your attention to when Grandma said it. All right. So now we know that different cues draw our attention to certain stimuli, whether we want them to or not. But what happens to all the stuff we're not paying attention to? Scarily enough, we experience something called an inattentional blindness, which means that we're not consciously aware of things that happen in our visual field when our attention is directed elsewhere within that field. So think back to that smiley face from our demo in the beginning. Because you were focused on yellow stars and red X's, you might have missed the smiley face, especially because he kind of blended in with the yellow stars. And that's a minor example, but inattentional blindness happens in more important situations too. For example, can you say exactly where the nearest fire extinguisher is? If you're like most people, you probably go by this every day when you're going to your home or office or wherever you are, but very few people actually pay attention to where things like fire extinguishers are, even though they're bright red and they can be necessary for our survival. Usually your attention is directed elsewhere, so you fail to notice the fire extinguisher. Closely related to inattentional blindness is change blindness, which is when we fail to notice changes in the environment. Now be careful, because the difference between change blindness and inattentional blindness is subtle but important. Inattentional blindness means that you miss something right in front of you, while change blindness means that you fail to notice a difference between a previous state and a current state, like when you don't notice when your mom gets a haircut or you get back to your room and don't notice that furniture or books are in a different place. And this is actually very common as well, so don't feel bad if it happens to you. In fact, there's one really good example when a researcher stopped people on a busy street and asked for directions. And part way through when the people were giving their directions, a large bookcase was carried between them and the researcher, and he swapped places with a different person. And almost no one noticed. And very few people even noticed when the new person was a different race or gender. So it was just a great example of our limited attention and our ability to focus on one thing to the exclusion of everything else.