videos we are going to look at two models of memory, explore different types of long term
memory, find out the reasons we forget, and look at problems with eyewitness testimony
and how police can improve eyewitness testimony. Many of the topics in the memory unit come from an
area of psychology called the cognitive approach. You may want to watch my video on the cognitive
approach either before or after these videos. In this first video we will cover the
multi-store model, the stores it is made from, features of each of those stores
and how information flows through it. And of course some evaluations of the model.
Features of the Multi-store Model
Created by researchers Atkinson and Shiffrin in 1968 this is a multi store model, its an
information processing model. Its liner, meaning information is moved through in one direction
and the stores are passive, meaning they just hold on to information.
The stores are, The sensory register, short term memory and long term memory. I will 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, their coding, capacity and duration.
Coding is the format the information is stored in. In a similar way that
your phone's memory will store image files and music files differently,
the brain is thought to have different ways of coding information. Capacity means how
much can that store hold, and duration is how long the information can be held for.
Ok now 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 received by the brain. The store that directly receives sensory
information is called the sensory register. Now as the five sensors 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, Iconic, Auditory, Haptic, Gustatory, 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, possibly 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 sense information you receive in each moment,
all of that visual information coming into your eyes and all the sound you hear. Even all the
touch sensations from all across your body. The taste in your mouth and smells are detected by the
sensory register. I'm not saying you are 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 very 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 store in 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 duration of short term memory is
between 18 and 30 seconds, meaning information that isn't maintained by subvocal repetition
is lost from short term memory after that much time has passed. The capacity of short
term memory is 7 items plus or minus two, so some people have a slightly worse short term
memory, some people a slightly better one. Information can be passed to the final store
by rehearsal, now this can be either maintenance rehearsal which is keeping it in short term memory
by repeating it again and again in a rehearsal loop until it passes into long term memory,
or information can be passed to long term memory in a process called elaborative rehearsal
and this means linking the new information to knowledge we already have in long term memory.
Information from short term memory that isn't passed to long term memory, is of course lost.
This could be due to displacement, because of the small capacity new information comes in and
replaces 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 waving 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. That is because we
haven't found a limit. The oldest people can still recall 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 will see in a
future video, maybe the information isn't truly lost, but 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. Here they all are in a table,
you may want to copy 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
those features of the multi-store model of memory, and how we could evaluate that research
Hey Sofia, when I was doing my research for the video there was a lot of conflicting research.
Much of it to do with a lack of gender bias in samples. Too much to get into in such a short
vid and at the level of A-level. I don't think you are wrong to take either argument as there will be
research to support your position on this one! Research evidence for the multi-store model.
To start with, just a simple piece of research by Glanzer (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. This suggests long term and short term memory are separate processes
with the first words in the list having moved to long term memory, and the last
words in the list displacing the middle words, 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,
this was a study by Sperling. Spearling flashed a grid of 20 letters
onto a screen for a 20th of a second, then got the participants to immediately recall
one row of letters, because it would take too long to say the middle row or the top
row he used different tones for each row (pause). Let's have a go. (pause)
So what were the letters? (pause) I imagine that was a little too fast,
but spearling 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 all 20 letters
in that moment. This suggests sensory memory has a much larger capacity than short term memory,
and we are only considering here visual or iconic sensory memory.
Moving on from sensory memory, this is a study that demonstrates the coding
of both long term and short term memory. It’s a little complicated but stay with me because
we will be able to evaluate the coding in both long term and short term memory with this one.
Baddeley gave participants word lists to recall, these world lists were either
acoustically similar, acoustically dissimilar, semantically similar or semantically dissimilar.
Baddely had his participants either recall immediately testing short term memory, or
after 20 minutes testing long term memory. Now the results showed the worst recall in the immediate
recall condition was for the acoustically similar words. Baddely argues that this shows short term
memory is coded acoustically, the acoustic similarity of the words causing confusion.
Now students often struggle with the conclusion to this study, it’s a little
counterintuitive to say because short term memory is acoustically coded words that are
acoustically similar are harder to recall. Well to help you try to remember, I will 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 can be more difficult to go in to get the file we want.
Now let me be clear, I'm not saying we have individual files to store our memories.
It's just to help you remember how if a storage system is organised, or
coded in a certain way, if all the items are similar it could be more difficult to recall
those individual items. List A: man, cab,
can, cad, cap, mad, max, mat, cat, map List B: pit, few, cow, pen, sup, bar,
day, hot, rig, bun List C: great, large, big,
huge, broad, long, tall, fat, wide, high List D: good, huge, hot, safe, thin,
deep, strong, foul, old, late
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, or when tested with letters 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 seven items plus or minus two.
This research really shows 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.
Finally for short term memory we have duration. To test this Peterson and Peterson asked
participants to recall trigrams, these are sets of three letters that don't have meaning, so
HFD, or TKU. But Peterson and Peterson used an interference task to stop the participants using
maintenance rehearsal, repeating the trigram to keep it in their head, this was by asking the
participants to count backwards. It was found in this study that the duration of short term memory
was between eighteen and thirty seconds. Moving on to long term memory, we can
use the same Baddeley study again, and we find that recall after twenty minutes, so
when testing long term memory is worse for the list of semantically similar words. The semantic
similarity is causing confusion, suggesting that long term memory is coded semantically.
Now capacity and duration is potentially unlimited, and there is no
way to actually show that, but we can look at two studies that show the capacity and
duration of long term memory is at least very large. Firsty a researcher called wagnaar
created a diary over the course of six years, over that time making more than 2400 entries.
When tested on events there was a 75% recall after 1 year and 45% after 5 years
since making the entry. This suggests the capacity of long term memory is very large.
Bahrick showed old photographs of school friends to participants between the ages of 17
and seventy four. After fifteen years recall was 90%, and even after 48 years recall was
80%. 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 of memory and we want to be able to give overall evaluations of the
multi-store model, and we have a few options. One of the most obvious evaluations
is much of the research 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. There are a few aspects to this,
the lab environment is unusual, not reflecting the places 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 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 have found
about memory under experimental conditions in situations outside of the experiment.
But in the defence 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, 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 observed behaviour.
An interesting point about the large capacity and short duration of the sensory register,
its supported by evolutionary theory, in the wild we would have needed quick reactions for survival,
taking in as much information as possible but only keeping and processing the important information,
holding on to and then processing too much information would slow down reaction speed.
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 are just one thing and
they are just holding on to information. But from research we will see in future videos
there are clearly multiple types of long term memory and short term memory is not unitary,
it has a number of components that are active, they work on information together
passing and processing information between them. And even some basic assumptions of the multi-store
model lack face validity, we clearly have long term memories that are tastes 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 a real exam question on the multi store model. if you are a psych boost
patron at the neuron level and above you can access a tutorial on psych boost .com.
in it I will talk you through a model answer for this question and general tips.for everyone else
don't forget to subscribe so you don't miss the videos released right up to your exams,
and I will see you in the next psych boost video, types of long term memory.