NARRATOR: OK. Clear your mind, because I'm about to show you a series of six numbers, which I want you to try and remember. Ready? Here it is. All right. Now what were those six numbers? Most of you should be able to say 490375. 

Easy, you say. But what your body just had to do to make that happen was anything but. First your, visual system had to detect and process that information. That process is called encoding. Next, that information is stored inside your brain-- storage-- and finally, when asked you to, you had to bring that information back out. Retrieval. 

These three steps are the basic process of memory. We're going to have a look at that in a bit more detail, starting with encoding. So that's the process of putting information into a form that will make sense with your personal storage system. So for most of us, those six numbers were pretty easy. But say it asks you to remember something like this. How would you do it? 

Well, numbers are easily encoded. This would probably have to be processed as a series of shapes, or something, and that's how your brain would have to make sense of it to try and store it. This, by the way, is Arabic for psychology, which, according to Google Translate, is pronounced [ARABIC]. 

Or say I asked you to remember this. Your visual system would be taking this image, storing it somewhere in your brain. But for some of us, we might actually be encoding this, maybe subconsciously in words, "blue fish," for example. The next step is storage, which is when this encoded information is stored in your memory, and finally, retrieval, which is the process of getting that information back. 

The example of a computer is often used as being analogous to memory. You've got encoding when you're sort of typing the information in, storage in the hard disk, and finally, retrieval when you're getting the information back out again. While that analogy is helpful, there are a couple of differences. 

For starters, memory in the brain is spread out across many cells in many different regions. Not as well organized as a hard drive. And secondly, memory in the brain is nowhere near as precise as in a hard drive. Human memories, for example, can easily change over time. 

OK. Let's delve further into this. In 1968, Atkinson and Shiffrin proposed a three-storage model of understanding memory. Those three storage places were sensory memory, short-term memory, and long-term memory. All of these interact with each other and are working at the same time. 

In the form of a diagram, the multi-store model of memory looks something like this. Let's take a little moment to make sense of this. So environmental input first gets registered by our sensors, and then it goes into short-term memory. Now, this can stay here if we do things like rehearsing, or strategies to try and retrieve it, or it might go into long-term memory. 

Whatever the case, before it can be retrieved, it needs to go back into this sort of short-term working memory space, and then it can come out as a response. We're going to be looking more at these sections in the next lesson. But for now, we're going to focus on sensory memory, starting with a little demonstration. 

In a moment, I'm going to show you three words really quickly, and I want you to try and remember what those words are. Ready, set, go. Now, what were those three words? Most of you should be able to recall "boy," "paper," and "orange." 

But here's the thing. There is no way you could have read those three words in the time they were actually shown on the screen. In other words, you were reading them after they had disappeared. What's going on? 

Well, according to the multi-store model of memory, you were using sensory memory, or memory within the sense organ. So this is a store for incoming, really, really short, fleeting, sensory information. This store is able to hold information, really, just for a fraction of a second to several seconds, and doesn't actually enter awareness until you pay attention to it. If attention is not given, it'll just fade and decay, and it'll be as if you never knew those things at all. 

It's a bit like the dash cam in a car. These devices are always recording whenever the car is driving. But obviously, it can't store every single video ever. Instead, it just keeps the most recent few hours or so, which, unless you choose to download, you'll never see it. 

We're going to have a look at two types of sensory memory. And they are iconic and echoic memory. Iconic memory comes from the Greek word "icon," meaning image. And this is a sensory register for the fleeting storage of visual information. 

It lasts about 0.3 of a second, and explains, for example, why, when a sparkler is being waved around in the dark, we can see a bit of an afterimage, like the trail which it came from. Iconic memory also explains the floppy pencil illusion, which I'm sure a bunch of you have tried yourself. 

In fact, it even explains why it looks like this animated hand is moving. You're, of course, just looking at a video on a screen, which is displaying to you 30 different pictures every second. But altogether, because of iconic memory, it looks like fluid, smooth movement. 

All right. Take this scenario. You're daydreaming in class when the teacher suddenly calls out your name and says, what did I just say? Now, you have literally no idea, because you were not listening. 

But suddenly, you get this vague sense of a number. And the thing is, if you hadn't been forced to try and think about it, you never would have remembered "page 53." The reason why you were able to do that is because of another sensory register called echoic memory-- just like iconic memory, but this time for hearing. 

Another difference is that this one lasts longer than iconic memory. It's thought that we can store about 3 to 4 seconds of hearing information-- long enough, for example, to let us process full sentences, even if they're spoken really quickly. So if a full, long, complicated sentence is spoken really quickly, just like this one, you might be processing the first half of that sentence, but fortunately, the second half is held in echoic memory until we're ready for it. 

Sensory memory, like iconic and echoic memory, are so important because they prevent us from being overwhelmed by the huge amounts of incoming sensory information. It means that we can filter what we want to pay attention to. So we might be taking everything in, but we really only register it if we want or need to. 

The rapid decay of sensory information is also an advantage, because it means that it can always receive new incoming information. But it's still held there long enough to allow the brain to decide if it does want to transfer it to short-term memory. All this means that we perceive the world around us as smooth-- as ongoing and continuous. 

That concludes this little introduction to how memory works. I hope you remember it in more than just 3 or 4 seconds. But I will see you in the next one. 

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