So, what happens to information after we perceive it? So, if I show you a bowl of fruit, and then I take it away, and I ask you how many apples were in that bowl. Would you be able to answer it. Would you be able to tell me how many plums, or how many oranges? The only way you would be able to know that is if you had access to it. If it was stored somehow in your memory. So, in this video, we're gonna talk about how information goes from being perceived and taken in, in particular by our visual system and how that information does or does not make it into our memory as something that we can then access later. Here's a very simple depiction of how this whole process works. We have our senses, we have our eyes, our ears, our nose, our mouth, our sense of touch, and information about the outside world is available to us through our senses. Some of the information that's available is perceived and made available for thinking and for commitment to memory, and the process of remembering actually takes place in two stages. We have short-term memory, where we store information for a short period of time on the order of seconds, and we have long-term memory where we store information for as the name implies much longer-term for duration's of minutes, to years, to decades. What we know is that, for information to be transferred from our senses to our consciousness through the process of perception, it requires attention. We have to be paying attention to that particular sense at that particular time, and we know that as a result of this, a very small amount of what is available to our senses is actually perceived or actually something that we become conscious of. Whatever is perceived is available for thought, but initially, it's only available for a few seconds and a lot of what is available at a lot of what is transferred through the process of perception into our short-term memory is actually lost. If it's not committed to long-term memory, it's lost and we don't have access to it later, and we know that a relatively small amount of information is learned or committed to long-term memory from short-term memory. So, the vast majority of the information that's available to us through our senses, is essentially lost in a very small amount of that is transferred to long-term memory and available for us later. In this lecture, we'll be focusing mostly on short-term memory and how that works and in future lectures, we'll focus on long-term memory as well. So, I want to do an experiment with you now to give you an intuition about how short-term memory works and what I want you to do is for the next few seconds, I want you to pay close attention to the screen. How many apples did you see? So, the answer was three and I'm guessing that most of you got that answer right, and we'll talk about why that task was not very difficult in just a minute. But before we do that, I want to do the second phase of the experiment, and I want you to pay attention to the screen again. How many chickens plus ducks did you see? I'm guessing that that was a much more difficult task. The answer was six. But why was it a more difficult task? Well, you've probably recognized that there was a difference in the number of objects that were shown. There were a much smaller number of fruit that were shown in the first example than there were animals in the second example, and what this illustrates is that, short-term memory has limited capacity. In fact, research has shown that the number is somewhere in the single digits. The original research back in the 1950s came up with what is referred to as the magic number of seven plus or minus two items. Meaning that most people can hold about seven items, in this case, fruit or animals in their short-term memory and depending on individual differences that number can be a little bit higher, a little bit lower. Subsequent research has put that number a little bit lower. Maybe it's more like four plus or minus one, but the point is it's limited and it's a fairly small number of things that you can hold in your short-term memory without committing them to long-term memory, and information that is not retained or learned or committed to long-term memory, is lost. You don't have access to that information later. In this process of committing information to long-term memory is what we call learning. So, in the first example with the fruit, there were only six items, and that six items falls within that magic number of seven plus or minus two. So, for many people, it was probably possible for you, even though you didn't know what I was going to ask you, to just play back through the sequence of fruit that you had just seen and count the number of apples that were in that sequence. In the second example, I showed you 13 items, and so by the time we got to item number 13, the first five or six items had been lost to your short-term memory. So, if you didn't have a rule or a heuristic for keeping track of how many cats you would see in how many ducks you would see and so on and so forth, you wouldn't have access to the information about how many ducks and how many chickens you had seen because you wouldn't be able to play back all 13 of those items. So, the key takeaway, is that short-term memory is limited. Whether it's limited to seven items or four items or nine or five, it doesn't really matter what the exact number is. But we can use this information about how short-term memory works to come up with some principles for how we might design interfaces that work better for people. So, some of those principles might include, keep lists of options short. Because if users have to read through a long list of options by the time they get to the end, they will have forgotten what was at the beginning of that list. Also, in cases where you're going to present users with lots of information and lots of options, you should consider giving them tools to reduce the number of options that they have to compare or they have to decide between at any particular time, so that they can use their short-term memory effectively. Finally, don't expect users to remember stuff from one screen to the next. If the information is not visible and you don't have a strong reason to believe that they would have memorized it or committed to long-term memory, they're not going to have access to that information when you ask them for it later. So, one of our principles is keeping lists of options short wherever possible, and to illustrate that, let's look at this example. This is a website that sells music equipment, musical instruments recording, and so on and so forth. If I look at the list of options and let's say, I'm looking at recording equipment. I see a long list of options. Pro Tools, recorders, microphones, headphones, and so on and so forth, and if I don't know exactly what I'm looking for and I don't know exactly what category it would be in, by the time I've read to the bottom of this list, especially if there's lots of unfamiliar terms, I've forgotten what's at the beginning and I might have to go through this list multiple times to decide where it is that I need to go next, and if it was a shorter list, it would be a much easier task because I'd be able to keep all of those options in mind when choosing where to go next. Another principle that we discussed is when presenting users with lots of options, give users tools to reduce the number of options that they have to think about at any one time, and for an illustration of this, I'm looking at the new egg website, Newegg sells computer, equipment, and hardware and things like that and I'm looking at different graphics or video cards. This is something that I did recently with my kids when I was helping them build gaming PCs. So, that's why I'm familiar with this. There's a bewildering number of options and I've just reduced this and facts to the set of graphics cards that are that are recommended for gaming and it's pretty overwhelming. So, what this website has done and many other websites offer features like this as well, is it's given me the option to pick a subset of these items to compare against each other. So, I might pick this one and this one and this one, and compare them. Now, I only have three items that I need to compare with each other and it's much easier what I'm looking at a particular feature, let's say I'm looking at a clock speed or I'm looking at memory size, or I'm looking at price, I can compare those very easily because the number of options fits within my short-term memory and I can make reason about them without having to do something that's more difficult cognitively, like memorize the different details of each of these items. Because of the limits of short-term memory, we can't expect users to remember information from one screen to the next if that information isn't available when they need it. So, as an example, here's a website that I often use for ordering pizza. When I use this website on my mobile phone, and I click checkout right here, it takes me to this screen where it asks me if I would like to add a tip, and I would like to add a tip for the driver who's going to deliver my pizza. Usually, I like to do that as a percentage of the total amount that the bill is going to be. However, I can't see what the amount was, and if I didn't commit it to memory earlier, I'm not going to know how to calculate the tip on this screen. It will be much more effective if that information, the bill was made available to me on the tip screens, so that I would know how much to tip or perhaps even suggestions about how much to tip would be helpful as well. So, we've just talked about the limits of short-term memory and from that, derived a set of principles that we could use for designing more effective interfaces. So, first we need to keep lists of options short especially when users may not know exactly what they're looking for. Where we do need to present lots of options to users, we need to give them tools for reducing the number of options especially when comparing among those options. Finally, we can't expect users to remember stuff that they've seen on previous screens or in other interactions with systems that we're designing when they're engaging in subsequent interactions. If the information is important for a task that they're performing, we need to make sure that that information is available and visible at the time that they're performing the task. We can't count on them to remember it from having seen it before.