Welcome to PsychBoost. This is the Memory Unit. Over the course of the next six videos, we're going to look at two models of memory. We're going to explore different types of long-term memory, find out reasons we forget, and look at problems with eyewitness testimony, and how police can improve eyewitness testimony.
Now, many of the topics in the Memory Unit come from an area of psychology called the cognitive approach. And you might want to watch my videos on the Kongtoor approach either before or after these videos. In this first video we're going to cover the multi-store model, the stores it's made from, the features of each of these stores and how information flows through it, and of course some evaluations of the model. Psychboost.com, over 170 videos to help you with your qualification and Patreon supporters can access bonus resources, tutorial videos and the Discord channel.
Features of the Multistore Model Created by researchers Atkinson and Schiffer in 1968, this is the Multistore Model. It's an information processing model. It's linear, meaning information is moved through in one direction and the stores are passive, meaning they just hold on to information.
The stores are Sensory Register Short-term Memory Long-term Memory I'm going to describe them in detail in a moment but before I start As we go through them keep in mind we need to remember three features of each of these stores. They're coding, capacity and duration. Coding is a format the information is stored in, so in a similar way that your phone's memory will store image and music files differently, the brain is thought to have different ways of coding information. Capacity means how much can those stores hold and duration is how long the information can be held for.
Okay, so I've made those terms clear. We can describe the model. Starting with sensory information. If you consider the five main senses, the information they collect needs to be first detected by sensory neurons, and then received by the brain. The store that directly receives sensory information is called the sensory register.
Now as the five senses are coming from very different sensory organs, we would say the coding is different for each sense impression. We could give the names for each form of coding, so iconic, auditory, haptic, gustatory and olfactory, but in the exam... we can just say the coding of the sensory register is modality specific.
It depends on the sense organ. The capacity of the sensory register is very large, potentially unlimited. It's hard to put an exact number on how big it is, but think of it this way. Your brain needs to detect all of the sensory information you receive in each moment. All of that visual information coming into your eyes and all of the sounds you hear.
Even all of the touch sensations from all across your body. The taste in your mouth and smells are detected by the sensory register. Now I'm not saying you're always consciously aware of those things, but the brain is receiving those sense impressions constantly.
The sensory register has a very short duration. Again this varies between the different stores, but we can use the figure of 250 milliseconds, so a quarter of a second. So the sensory register has a short duration before information is lost. Now of course as I said you're not consciously aware of that massive amount of information coming in.
For that we need to pay attention, maybe to a particular sound or object in our vision. So information moves from the sensory register to the next door, short term memory, through attention. Any information that isn't paid attention to is lost. We say short term memory coding is acoustic, so information in the form of sound. And it feels like that.
If you need to remember a list you may repeat it over and over again. in your head with an inner voice. The capacity of short term memory is 7 items plus or minus 2. So some people have a slightly worse short term memory and some people have a slightly better one.
The duration of short term memory is between 18 and 30 seconds, meaning information that isn't maintained by sub vocal repetition is lost from short term memory after that much time has passed. Information can be passed to the final store by rehearsal. Now this can either be maintenance rehearsal, which is keeping it in short term memory by repeating it again and again and again in a rehearsal loop until it then passes into long term memory, or information can be passed to long term memory in a process called elaborative rehearsal.
And this means by linking the new information to knowledge we already have in long term memory. Information from short term memory that isn't passed into long term memory is of course lost. And this could be due to displacement, Because of the small capacity, new information comes in and displaces what used to be in short term memory, or it could be because of decay. If the information is not rehearsed, it simply disappears over time. The coding in long term memory then is semantic coding.
The memory is stored as part of a set of meaningful connections to other stored information. So as an example, we have a semantic connection between the word wave and the idea of a wave of water or wave in your hand. And recently you may have developed a semantic connection between the word wave and an increase in illness.
Now, I'm going to say both the capacity and duration of long term memory is very large, potentially unlimited. And that's because we haven't found the limit. The oldest people can still record facts from their childhood, and we don't see a point in which brains get completely full up with information and can't fit more in.
But we do forget things. So we could argue that information is lost, but as we'll see in a future video, maybe that information isn't truly lost. Maybe we just lose the ability to access it, and could recall it, if we had the right cue. So that's the multi-store model.
We need to describe the model, the process of information passing through the model, but also the coding capacity and duration of each store. And here they all are in a table. You may want to copy down both the model and this table down and make sure you can recall it from memory.
In the evaluations I want to cover the research that revealed all of these features of the multi-store model of memory and how we could evaluate that research. Research evidence for the multistore model. To start with, just a simple piece of research by Glasner in 1966, showing the primacy recency effect. When participants were asked to recall a list of words, participants tended to remember the first words in the list and the last words in the list, but struggled to remember the middle words.
Now this suggests that long term and short term memory are separate processes, with the first words in the list having moved into long term memory, and the last words in the list. displacing the middle ones and taking their place in short term memory. The first feature of the stores that I'm going to evaluate is the capacity of the sensory register. And this was a study by Spearling. What Spearling did was he flashed a grid of 20 letters onto a screen for a 20th of a second and then got the participants to immediately call one row of letters.
Now because it would take too long to say the middle row or the top row, he used different tones for each row. Let's have a go. So what were the letters?
I imagine that was a little too fast, but Spieling found that with some practice, the participants were very accurate. Now I'm going to argue that short term memory only has a capacity of between 5 and 9 items. To be able to accurately recall a full row, sensory memory would have to hold onto all 20 letters in that moment. This suggests that sensory memory has a much larger capacity than short term memory, and we're only considering visual or iconic sensory memory. Moving on from sensory memory, this is a study that demonstrates the coding of long term and short term memory.
It's a little complicated but stay with me, because we're going to be able to evaluate the coding in both long term and short term memory with just this one study. Badly Gave's participants were wordless to recall. These word lists were either acoustically similar, acoustically dissimilar, semantically similar, or semantically dissimilar.
Baddeley had his participants either recall immediately, testing short term memory, or after 20 minutes, testing long term memory. The results showed the worst recall in the immediate recall condition was for the acoustically similar words. Baddeley argued that this showed short term memory as coded acoustically.
The acoustic similarity of the words causes confusion. Now, students often struggle with the conclusion of this study. And it's a little counterintuitive to say because short term memory is coded acoustically, words that are acoustically similar are harder to recall.
Well, to help you try and remember, I'll give you a metaphor of a filing cabinet. If it's coded or organised alphabetically, then if we have a bunch of files that are stored across the filing system, when we want to retrieve one, it's easy. But if all the files are similar, it could be more difficult to go in and get the file that we want. Now let me be clear, I'm not saying that we all have individual files to store our memories. It's just to help you remember that if a storage system is organized or coded in a certain way, if all the items are similar, it could be more difficult to recall those individual items.
Moving on to the capacity of short-term memory, we have very old research by Jacobs That showed when asked to recall lists of numbers, people could recall around 9. But when tested with letters, around 7 was the average. Now there was a bit of a range in what could be recalled, some people are a little better, some a little worse. So what we can say is the capacity of short-term memory is 7 items plus or minus 2. Now this research really showed that the capacity of short-term memory is small.
However Miller points out that we can increase the capacity of short-term memory by chunking. This is making small sets or groups of items, effectively reducing the number of items overall. And finally for short-term memory we've got duration.
To test this, Peterson and Peterson asked participants to recall trigrams. Now these are sets of three letters that don't have a meaning, so HFD or TKU. And Peterson and Peterson used an interference task to stop participants just using maintenance rehearsal, so repeating the trigram to keep it in their head. And this was by asking the participants to count backwards. It was found in this study that the duration of short term memory was between 18 and 30 seconds.
Moving on to long term memory, we can use the same badly studied again and we find that recall after 20 minutes, so when testing long term memory, was worse for the list of semantically similar words. This semantic similarity is causing confusion, suggesting that long term memory is coded semantically. Now capacity and duration is potentially unlimited and there's no real way to test that, but we can look at two studies that at least show that capacity and duration of long term memory is. Very large. Firstly a researcher called Wagner who created a diary over the course of 6 years and in that time made more than 2400 entries.
When tested on events there was a 75% recall after 1 year, 45% after 5 years since making the entries. This suggests a capacity of long term memory very large. Baric showed old photographs of school friends to participants between the ages of 17 and 74. After 15 years, recall was 90% and even after 48 years, the recall was 80%. And this does suggest that the duration of long-term memory is very large, potentially unlimited.
Additional evaluations of the multi-store model. Before we finish, we could be expected to evaluate research on the multi-store model and memory and we want to be able to give overall evaluations of the multi-store model itself and we've got a few options. Now one of the most obvious evaluations is much of the research that I have outlined seems like a very artificial way of testing memory.
It's not really like how we use memory in our day to day life. Now there are a few aspects to this. The lab environment itself is unusual, not really reflecting the places that we recall, like school and work.
If we can't apply the findings to those environments, we would say the findings lack ecological validity. The tasks the participants are asked to complete are often not like the tasks that people do in day to day life. So we can say the tasks lack mundane realism.
What I've done here is question the external validity of this research, suggesting we may not be able to apply what we've found about memory under experimental conditions in situations outside of the experiment. But in defense of psychologists, experiments have to be designed to make measurements possible. It may be the only way of scientifically testing the limits of memory.
This is because we are not able to directly observe memory. Psychologists have to make inferences, these are educated guesses about the underlying model based on the behaviour observed in an experiment. This is a problem because those inferences could be wrong.
It could be a completely different process that produces the same observed behaviour. An interesting point about the large capacity and short duration of the sensory register. It's supported by evolutionary theory. In the wild we would need quick reactions for survival. Taking in as much information as possible but only keeping and processing the important information.
Holding onto and then processing too much information would slow down reaction speed, making you lunch. And a criticism of the multi store model is it's a little simplistic. It suggests short term memory and long term memory are unitary and passive stores, meaning they're just one thing and they're just holding onto information. But from research we will see in future videos, they are clearly multiple types of long term memory.
And short term memory isn't unitary, it has a number of components that are active. They work on information together, passing and then processing information between them. And even some basic assumptions of the multistore model lack face validity.
We clearly have long term memories that are of taste and smells. And the capacity of short term memory isn't fixed, it changes over a lifetime and with practice. Have a go at this real exam question on the multi-stuff model.
If you're a psych boost patron at the neuron level and above you can access a tutorial on psychboost.com and in it I'll talk you through a model answer to this question. general tips so don't forget to subscribe so you don't miss the videos released right up to your exams and i'll see you in the next psych boost video types of long-term memory