Transcription
Welcome everybody to this week's cognitive psychology lecture, and our topic will be short-term memory. And we are starting with an introduction into that topic. Okay, so let's, let's have a look.
Now, when we talk about memory, it's important to recognize first that memory consists of several stores, not just of one store. And most know this or have heard of short-term memory and long-term memory, but they are also sensory stores. And we briefly mentioned them already in the attention lecture, and I don't want to go into too much detail today as well. These hold information very, very briefly, just for a couple of 100 milliseconds. So, it's in the visual domain, it's called the iconic store, and in the auditory domain, it's called the echoic store, and or visual and auditory buffer, you may also say. And this is just the, the very first store where, uh, when the information comes in, it's kind of a buffer store to keep it so that following up stores and attention can work on that, can read out that information. It's just a couple of hundred milliseconds, a little bit like when you see something or hear something, the, the echo you have in your mind after that. And they're specific for each sensory modality, and as I said, with the iconic and echoic buffer.
Then we have the shorter memory store, which is the topic for today. And this store holds information in the order of seconds, some would say up to minutes, and it has a limited capacity. We'll look into the details of that today. And then finally, we have the long-term memory, and this holds information about very long periods of time, and it is assumed to happen, sorry, just moved something here, and it is assumed to have an unlimited capacity in principle. And the topic of long-term memory, we will look at in the next week.
Okay, so short-term memory, and there are other terms for that around, synonyms. So, it's also called sometimes primary memory, or active memory, or immediate memory. Some people also call it working memory, but as you will see later, I would say that nowadays there's a slightly different meaning to working memory as compared to short-term memory. Working memory also contains, working memory also contains short-term memory, but has additional elements to it. And the definition for short-term memory would be that short-term memory is the capacity for holding a small amount of information in mind in an active, readily available state for a short period of time. So, this definition already incorporates some of the things we, we said. So, it's a limited amount of information which can be kept in short-term memory. It has, we can store it for a short period of time, limited period of time. And another thing is that it's in an active, readily available state. That means that we have direct access to it, we are conscious of its content, and we can use it, for instance, for mental arithmetics, to do stuff with the information, to work with the information. Okay.
So, there's a lot of research into short-term memory. And when we want to investigate short-term memory, then most people use a very prototypical task, a short-term memory task. And I would like to demonstrate the different stages of such a short-term memory task because these stages also link to the mental functions of our short-term memory system. So, let's have a look.
Usually, in a shorter memory task, where you would present the items, the stimuli, participants are supposed to remember. So, for instance, when we want them to learn a word list, we would present the words. And this links to the first stage of, of the cognitive memory system, and this, this is that the information has to be encoded into short-term memory. And when we present items, we can do that in a many different ways. So, for instance, we can just give the participant a sheet of paper with all items on them, so that they can do this all, they can manage their time by themselves, how long they look at each item, and things like that. Or, in particular, now with computerized presentations, we can present one by one and do it that way. We can manipulate how long we show the items. We can give people a sheet of paper for 15 seconds or a minute. When we present items on the screen, we can do that for half a second or for three seconds each. And we can have an interval between items, and we do that individually, one second an item, one or two seconds break, then a next item. And these parameters all affect how good our memory performance is. So, it's important to keep them in mind that when you think about, okay, I present information to participants and want to test how much they can retain or remember, think about all these factors. Also, in real day life, when you design something where you want to present to students or something else, that this is important, or information, a notification for people.
Then we have the retention interval. That is the, in our memory system, the storage component. So, here the item presentation is encoding. I can have external information, I have to process that to encode it into memory. Now I have to store it and keep it alive in memory. I have to maintain the information. And the parameters for this stage are, first of all, the duration. How long do I have to store? And there are some short-term memory tiles where this explicit retention interval is kept to a zero length, so you present something and you ask for an immediately, immediate recall. But you can also say, okay, try to remember that for 30 seconds. And the next question, and the next two points are related, is rehearsal allowed or, and, and if not, do we prevent rehearsal? What does rehearsal mean? Suppose I tell you, please remember a phone number, uh, 1578, stupid example. And then I tell you for 30 seconds. Then you probably do something like, one, five, seven, eight, one, five, seven, eight, in your mind. That's rehearsal. And we will see later which structures are used for that. And do you allow that rehearsal or not? If you don't allow it, the typical approach to do that is that participants get an additional task during the retention interval. So, I present you the phone number, and then I tell you, please count backwards from 100 in steps of three. So, participants, as soon as they heard the last number, would have to say, start saying out loud, 97, 94, 91, 88, and so forth. And this task is quite challenging. So, and you can use different variations so that, um, just this occupies your system and you can't do the rehearsal. Another option is to just repeatedly say, which is easier to say a word, for instance, the, the, the, the, because it occupies your verbal system so that you can't, um, rehearse the numbers anymore. So, that's the storage element of memory, which we can test or text with the retention interval.
And then we have the test phase, and this is the retrieval of information from the storage. So, this is a third phase and the third part of our memory system. And first of all, we can ask, um, do we use recall or recognition? So, what's the difference between the two? Recall, or often also called free recall, means that in the example of word list, you just give participants a blank sheet of paper and a pen, and they should write down the words which you presented before. So, you don't have any help or cue. And this is usually the most difficult variant of, of this retrieval of information. The other one is recognition. And recognition usually works. Let's say you had to learn 10 words, and then in the test phase, you are given 20 words, the 10 words you have learned, and 10 new words you haven't learned. And for each word, you have to say, yes, it was in the list I have learned before, or no, it wasn't in the list I have learned before. And this usually results in a little bit of better performance in the participants because, um, you get this, this cue. You said the word. So, recognizing something is easier than recalling. Another thing you can vary is, suppose you present 10 words, and you can request that they are recalled in the exact order you presented them, or you can say, well, write it down in any order you wish. And of course, in serial order is more difficult. This is more linked than to working memory, usually, because it requires you to also retrieve the sequential information of the words. Is there a time limit? How much time do participants have to, to retrieve the information? And as measures, we can take the accuracy, which is probably the most common one. So, how many percentage of the words, how many percent that they recall correctly? Or, in particular, if we do recognition task at a computer, where they have to say yes, no, yes, no, to each word, we can also take the response times.
Okay, so just to recap that, just to recap that we have three phases in a memory task, which nicely link to the three components of memory system or three functions of memory system. So, that we have to encode, we have to store, and then we have to retrieve to get it out of memory again. Okay.
So, let's have a little demonstration. And for this, and for the other parts as well, in the free and in the short-term memory session, it's a good idea to have a sheet of paper and a pen or something like that because we do some demonstrations. And here we don't, I don't have to wait too long because you can just simply pause the video if you need to get something. Okay, so please get a sheet of paper and a pen. And I will present 12 words for you, each one for two seconds. And your task is to memorize the words as good as you can without writing them down, of course, that will be cheating. We want to test your short-term memory. And when the instruction appears on the screen, then please write down all words when you remember it. And you can use any order, it doesn't need to be in the order of presentation. Okay, so please get ready. And three, two, one, and go.
Okay, now immediately, please write down all the words you can remember. And please pause the video, um, to take your time to write it down. Because for those who didn't do the exercise, I will just continue now with the video. Okay, so if you did that, so you can have a look at how many words you remembered. These were the words in the order of their presentation. And again, you can quickly pause the video to see, um, which ones you remembered and which ones you didn't remember.
Now, one thing to note is, I used to do that as a poll in, in the lecture, which of course now doesn't work. And if you do that, and then people say, how many people did remember fashion? How many people did remember endorse? And so forth, then we notice something. And that is that often, you know, on average, the earlier items are remembered better, and also the later items are remembered better, while those in the middle are more difficult to remember. And this is called the serial position effect, and results in such a U-shaped curve. So, this graph shows on the X-axis the position of the word in the sequence. So, this is word one, word two, word three, and how far up you go, so the first words and the last words, and the middle words. And the Y-axis shows you how many words have been recalled in percentage. So, 50 means half of the words are recalled. And this is just an example to illustrate the effect, which was first discovered by Hermann Ebbinghaus. And this serial position curve indicates that the first words are remembered better, and the last words. And this is called the primacy effect and the recency effect.
Okay, when we keep that in mind for a moment. The primacy effect means that the first words are on average remembered better. And the reason for this could be that the early words can be rehearsed more often. So, you know, the first word, I can't remember the first one, but which it was, let's just say it was fashion, then you see the word, you can start with fashion, fashion, fashion, fashion, fashion. And then the next word comes up, which might be code, then you do fashion, code, fashion, code, fashion, code. So, the later the words, the less you can do rehearsal. And along the same lines for the first word, where you don't have to rehearse anything yet, so far, you can do a deeper processing. So, for the first words, you can, fashion, and let's say the second was code, you can start, oh, fashion and code, they are related. So, maybe I can somehow link them for each other. So, there are arguments which say that the first words may actually already have been transferred and encoded into long-term memory, so that later, when we do have to recall the words, they come from long-term memory, not from short-term memory anymore.
The recency effect is that the last words are just still, still fresh in memory, they're still highly active. And the recency effect can be strongly reduced or even completely abolished if you introduce a retention interval. That means the last word stops, and you don't have to immediately recall, but you have to wait for, let's say, 10 or 15 seconds, and participants have to do a task during that, so that they can't rehearse, like this counting backwards. And then you see that the curve goes down and just is flat towards the end.
Okay, so to summarize our introduction, we have seen that short-term memory is a capacity store which is limited for keeping information active for a short time. And the typical short-term memory task has three stages: the item presentation, then the retention interval where we have to keep it, maintain the information, and then the recall. So, the memory systems have at least three functions which relate to these stages, and this is the encoding of information, the storage maintenance of information, and the retrieval of the information. So, and in a free recall task, as we just have seen, where we have immediate recall, a U-shaped serial position curve is observed. And this is explained by the primacy effect and the recency effect, as you have just seen.
Okay, if you have any questions, please, uh, just post them in the BBL forums for that. Okay, thanks a lot for watching, and I hope to see you soon for the next part.