The second important fact that we need to keep in mind, and I mentioned before, is that attention plays a really big role on visual perception. So, there are a number of facts. First, we only retain a very small portion of the information that is entering our eye, but what is retained in our memory and what is processed by our visual processing system is very highly dependent on what we are attending to. What we are attending to in turn, depends on the task, on what we are trying to accomplish, which of course, is very relevant for visualization design. Because when we are designing a visualization, we are typically designing a visualization to help people accomplish some communication task. So, that's very important. Here, I want to introduce a new concept. The concept of inattentional blindness. What is an inattentional blindness? Well, it's a concept introduced by vision scientists when they started noticing the idea that related to how powerful attention is in visual perception. The idea is the following: it's very easy to be blind to very big changes if we do not attend to the visual information that changes. So, maybe this is still a little bit vague. In order to make it more concrete, I want to show you an example in a video. This is a video reproducing a classic experiment in vision science. What is the experiment about? Well, it's one among many different experiments that have being developed or examples that have been developed to show the problem or the effect of inattentional blindness. In this video, you're going to see a person asking some information to another person and then these two persons are temporarily interrupted by two guys coming over with a painting or something else. So, they are temporarily blocking the view, and without this person noticing it, the person who is asking for information is changing. Sometimes the new person showing up is very different and despite that, most people don't recognize the difference. They don't notice it. So, let's watch the video first, and then I have a few more comments on inattentional blindness. Excuse me. I'm looking for the Skyline. Then, we break the two up, walking through them holding a large sheet of wood. Now watch as I replace Vin. You might think people would notice the switch, but almost half the time they didn't. Of course, that means more than half the time they did. We only tried the experiment nine times, and by no means was it good science. But we were surprised four people didn't notice the switch. In Simon's original experiment, seven out of 15 people didn't either. So, what determines whether or not you can figure out the switch? When you look at another person, you encode what's relevant for what you're doing right then, in that case, giving directions, and you don't pay attention to the details that are irrelevant, say what color their shirt is or exactly how tall they are. As long as you are able to make sense of the meaning of the scene and roughly the main categories of that person, say their height, their age, what race they are, what sex they are, as long as those important things don't change, the meaning of the scene really hasn't changed and you're not going to notice that anything is different. Scientists have documented inattentional change blindness since the 1970s. While they allow you to focus your attention, this failure to see every detail can prove costly. Drivers often cause accidents because they overlook quick changes to their environments, such as pedestrians or cyclists. Faulty memories can wreck havoc during eyewitness testimony. The goal of vision isn't to build a photograph or a complete model of the world in your mind, the goal of vision is to make sense of the meaning of the world around you. Being aware of our limitations can help us adapt and compensate for them, allowing us to do things that prevent the really negative consequences that can happen due to failures of awareness. For example, Simon thinks that people might be willing to put away their cell phone when driving if they just understood the limits to their attention. Juries might realize that eyewitness testimony is far from ideal, and the next time you and a friend are fighting about the details at a past event, it's likely you're both wrong. Now, that's something to remember. Okay. So, I hope the concept of inattentional blindness is now a little clearer. Before we move on, I want to ask you a question. Did you notice any difference between this video and the previous video? I guess you didn't. You want to try? Is there anything different in the new video? Well, in this video, I'm wearing a watch, but in the previous video, I'm not wearing a watch. Maybe you should go back and check. I'm pretty sure that most of you didn't actually notice, until I ask. So, this is another example of inattentional blindness. You won't notice the difference until you have a reason to attend to the information that is needed in order to perceive the difference. I want to conclude with a couple of quotes again. So, the first one that I really like is the idea that the world is its own memory. What does it mean? Well, it means that most of the information that we need to carry out a task or solve a given problem is not in our hand, is in the world. But the way cognition and visual perception work is that we can look for this information when is needed. So, there is another quote that I want to give you. This is from Collin Ware's book, and the book is called "Visual Thinking for Design", a fantastic book. The quote is, "It's more accurate to say that we are conscious of the field of information to which we have rapid access rather than we are immediately conscious of the world." Once again, I think this is a really important concept to keep in mind. So, why is this important for visualization design? I think there are a couple of important ideas here. The first one is that when we design a visual representation, we have to guide the attention of the viewer in a way that is useful to achieving the goal that we want people to be able to achieve. So, the more explicit you are in how you are directing attention through your design, the better your design is going to be. If you just don't care and don't even think about it, it's likely that you're going to have problems with your design. In turn, as a visualization designer, you have to be aware of how your choices as a designer are going to affect attention. So, if you inadvertently attract attention of the viewer to pieces of information that are not important for achieving the goal that you want your viewers to achieve, then you are in trouble. So, in summary, it's very important in visualization design to be mindful of the effect of attention and how your design actually affects attention.
