In this video I cover the second box in the 3-box model, short-term memory, in greater detail. I explain the limited capacity of this store, George Miller’s “Magical Number 7”, and how organizational encoding and chunking may appear to expand this capacity without necessarily increasing the number of “items” being held. This concept of organizing and manipulating information in this store brings us to Alan Baddeley and Graham Hitch’s model of working memory. This model includes 4 main parts; a central executive, the visuospatial sketchpad, the phonological loop, and the episodic buffer (added later). This working memory model accounts for our ability to manipulate incoming information and also draw upon existing long-term memory.
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George Miller – The Magical Number 7 Plus or Minus 2
http://psychclassics.yorku.ca/Miller/
Video Transcript:
Hi, I’m Michael Corayer and this is Psych Exam Review. In this video we’re going to go into more detail on short term memory. So this is the second box in our three box model proposed by Richard Atkinson and Richard Schiffrin.
In the previous video we talked about sensory memory which is all this information coming in from our senses and one of the things that we said about sensory memory is that we can only focus our attention on so much of this information and that means that a limited amount of information is going to be able to move from our sensory memory into our short-term memory.
So one of the first features of short-term memory that’s important is this idea that it has a very limited capacity. There’s only a few things we can have in this short term memory at once. So just how many things can we have in our short-term memory at once? Well based on research by George Miller we have an estimate that we can hold about seven items.
This was described in a paper he wrote called the magical number seven plus or minus two. So the idea here is that if you look at people given different types of tasks involving their short term memory, whether it’s remembering tones or lists of digits or things like that, they can remember about five to nine items and once you get beyond nine items it gets much harder and people start making lots of errors. So this is where we get this magical number plus or minus two and I’ll post a link in the video description where you can read the original paper from George Miller written in 1956.
Now you might think “well I don’t know, the other day I went to a restaurant and the waiter remembered everybody’s order at the table without writing it down and you know we ordered more than seven items, so this doesn’t seem right. How is he able to do that?”
Well the answer is that it depends on how you define items. We can think of items as being single items or we could have groups of items and the waiter is probably grouping things. He’s probably using a technique called organizational encoding. This refers to organizing the information, looking for similarities, things like that, finding some sort of structure to the information in order to reduce the number of items that you’re actually recalling.
So an easy way to demonstrate this would be if I asked you to remember a random list of digits. If I give you 15 digits at once you’d probably find this very difficult, if not impossible to do but here I’m going to give you a list of 15 digits and you probably won’t find it that hard. So if I said “okay remember this number 5 5 5 5 5 4 4 4 4 3 3 3 221” you’d probably have no problem recalling this number, holding it in your short-term memory. Now it’s 15 digits, how are you able to do this? Well you’re organizing the information, you’re looking and seeing that there’s a pattern here and so now you don’t actually have to recall 15 individual items and so you’re probably using a type of organizational encoding called chunking.
This is where you sort of break the information up into chunks and if we look at this we say “ok there were five 5s four 4s three 3s two 2s and one 1”. Now we only have five chunks to remember and there’s a nice pattern to them that makes it even easier. You could say maybe we have six items we have that each chunk and then what the pattern is but the idea is that’s going to be within the capacity of our short-term memory so you’d be able to do this. Whereas if these were 15 totally random numbers and there wasn’t any sort of pattern to them, you’d find this much harder you probably wouldn’t be able to do it.
Alright so this demonstrates that our definition of what exactly we mean by an item can change. So the waiter is probably going to organize this into, there were this many drinks and there were this many entrees and there was one appetizer and there were two desserts or something, and so by sort of thinking about the structure of the order they’re able to recall more than 7 individual items.
Another interesting part of short-term memory is that it’s not just for storage. We have our sensory memory, just like the raw information coming in. There’s a lot of it but we don’t really do much with it, other than we choose to pay attention to certain parts of it. And then we have our long-term memory which has basically an unlimited capacity and we can sort of draw on things from that but it’s in this middle section between these that we’re sort of working with the information that we have. We’re thinking about things, we’re changing them around, manipulating the information and so this brings us to an idea that there’s sort of a distinction between just the short-term storage and a separate process which is referred to as working memory but they’re both sort of happening in this middle ground between our sensory memory and our long-term memory.
So working memory refers the idea that we can actively manipulate this information. We can work with it. This means we have an additional model to take into account within our short-term memory because it’s not just storage, it’s also manipulation.
So how does this manipulation process work? Well, a model proposed by Alan Baddeley and Graham Hitch says that there’s a few parts to this process. First we have this idea of a central executive and the central executive is sort of like the decision maker. It decides what to do with the information and in doing that it draws on some different tools. So what are the tools that the central executive can use?
Well one of these tools they refer to as the visuo-spatial sketchpad. This is sort of a fancy way of saying a mental image that you sort of create in your mind. You sort of bring it up on this mental sketch pad. So if I were to ask you to describe your bedroom to me, you’d probably bring up a mental image of it and then you’d use that, you’d sort of look at it you, direct your attention to this mental image and you’d tell me about what you’re seeing in your mind, describe your bedroom to me based on what you have in this visuospatial sketchpad.
Now another tool you might draw on, if I asked you a different type of question, would be, you might draw on the phonological loop. So what’s the phonological loop? Well if I asked you to tell me, how many syllables are there in phonological loop? How are you going to answer that question? Well you’re not going to bring up a mental image, what you’re probably gonna do is you’re gonna mentally loop this sound, pho-no-lo-gi-cal loop, right? You’ll say six syllables, you’re probably going to count on your fingers while you do this.
So what that’s doing is it’s showing that there’s a different type of process you’re using to manipulate that information. You’re sort of mentally repeating the sound of it rather than bringing up a mental image so that means it’s a different tool that your central executive can call upon. And you probably use this phonological loop in a technique called rehearsal and this is the idea that, let’s say I ask you to remember a phone number, what you’re going to do is you’re going to probably mentally repeat the sound of that number over and over again.
That’s called rehearsal and essentially you can think of rehearsal as re-inputting the information back into your sensory memory, sort of creating this sort of loop between ok it’s in my short-term memory but I know it’s only going to be there for a short amount of time but if I mentally repeat it then I sort of get to start the process over again. It’s like I just, it’s as if you’ve heard the number again even though you might not have to actually say it.
You don’t have to actually hear it but you mentally hear it again and you repeat the number and then you get to the end. Okay i’m going to start forgetting it, I remember it just long enough to repeat it again and then just long enough to repeat it again and hopefully in the meantime I either dial it or find a place to write it down. So I’m repeating it, repeating it, I know you don’t really have to remember phone numbers anymore. When I was a kid you had to do this much more often. Now you just type it into your cell phone but you’re sort of repeating this process over and over again right? That’s this technique called rehearsal and it relies on this phonological loop.
What you probably also know about this is as soon as that attention gets distracted, right, that’s a fundamental part of this loop is you have to be paying attention to it as soon as somebody asks you a question or if somebody starts saying other numbers, you’re going to immediately lose it. Either because your attention got distracted or because they started introducing sounds of numbers into this loop and that sort of made it impossible for you to continue doing this.
Now later Baddeley introduced another possible tool that this central executive can call on and this is an idea called the, what is it called, the episodic buffer. This is just the idea that we must also have some tool that helps to integrate these other parts right? So you have the visuospatial sketchpad and you have the phonological loop, you’ve got sights and sounds but you also have a way to put them all together.
So when I tell you a story, you’re probably creating some mental images for some parts of the story but there’s also, you’re hearing the sounds that I’m using and you might sort of be mentally repeating some of them, certain words that I use to keep track of the story and so you’re integrating these into a chronology that makes sense, right? It’s almost like a movie scene, right? So this is sort of another tool that must have to exist in order to make that process happen.
You don’t have this disjointed like, there were mental images and there were sounds and you know, you find a way to put them together and in an order that sort of makes sense into an episode, sort of a narrative that you can follow. So that’s another proposed part of this working memory system. Ok so that’s the idea that short-term memory is not just a storage facility, it’s also this manipulation process, this working memory.
Now exactly how these two relate to one another is still sort of up for debate and people argue about “should we consider, is there really a difference between short-term memory and working memory” or things like that but that’s beyond the scope of an introductory course.
But the important thing to remember, no matter how exactly these parts integrate with one another we sort of have to agree that there is this space between our sensory memory of information coming in and our long-term storage. There is this short 30 second section of time where we’re able to manipulate information and work with it, we have some recall for it, we’re kind of storing it but not really compared to long-term storage but there’s definitely this sort of gap between those two boxes.
Ok so I hope you found this helpful, if so, please like the video and subscribe to the channel for more.
Thanks for watching!
