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We’re all familiar with forgetting things. So I've so frequently forgotten, you know,
my wallet, purse or keys, that before I leave the house I go ‘wallet, purse, keys’;
wallet, purse, keys; wallet, purse, keys’. I chant it to myself so that I make sure I've
got each of those items in my bag. We are also, I at least, also frequently forget events
from my past. So someone might say to me ‘oh do you remember going to see the film ‘Finding
Nemo’?’. I don’t really remember it but I nod along and I pretend that I did,
and I'm sure I did see the film so I'm sure that no one’s going to ever tell me that
I was lying. And forgetting is one way that we can be tricked by memory, but it’s not
the only way, and neither is it the way I'm going to talk to you about day. Today I'm
going to talk to you about cases in which we remember rather than forget, but what we
remember is inaccurate in some way. Cases like these are cases in which memories are
distorted. Here is some examples to get you to understand the sorts of cases I'm talking
about.
So Jimmy decides to bake a cake. So he writes himself a shopping list and heads out to the
shop. Unfortunately though he leaves for the shop without the list, okay. Nonetheless as
he’s an optimistic sort he carries on and he thinks ‘I'm going to be able to work
out which ingredients from my list’, so he remains upbeat and he strides round the
shop selecting items. Unfortunately though when he gets home he realises that he’s
got all the items on his list but he’s also bought butter when he really didn’t need
butter. Not as such a sad ending to the story, but still an illustration of a memory distortion.
When he remembers that he’s got butter on his list when he’s in the shop he forms
a memory. There’s some kernel of truth it; he did have bakery items on is list, but the
memories inaccurate because he didn’t really have butter on the list.
Let’s move onto another example. So Nadia is speaking to her mother on skype, okay.
They're having a little chat, a little gossip, and Nadia’s mother tells her that her sister’s
daughter’s started biting other children at nursery. Nadia takes a little bit of glee
in this because she’s ever so slightly mean-spirited towards her sister. But she's interesting
and kind of reassured when her mother says she thinks this is just a phase, not to worry
about the little child, it’s fine, it’s just a phase. And Nadia’s mother says this
because she says ‘well Nadia’s sister herself had bitten other children at nursery
when she was a child’. In fact Nadia’s sister had even bitten Nadia when she was
small. Now initially surprised by this because Nadia’s a few years older than her sister,
and she would expect that if she’d been bitten by her sister she’d remember it.
She nonetheless starts to imagine what this would have been like. So Nadia thinks ‘oh
it would be really terrible if I’d been bitten as child, I must have really hurt me,
I'm surprised I'm not more traumatised’. But after this conversation Nadia doesn’t
think about the biting incident for a while until she speaks to her sister at a later
point. Her sister says ‘oh it’s okay, my daughter’s stopped biting now, she’s
not biting at nursery, you don’t need to worry’. Nadia can’t help herself at this
point, she says ‘oh you know I was never worried because I remember you biting me when
I was small, but you were even smaller, you used to bite me, so I knew it was just a phase
because it was just a phase when it happened to you’. In this case, although Nadia doesn’t
initially remember having been bitten, after she imagines the scenario she becomes convinced
she can remember it. In fact, as it turns out, Nadia had been the biter; when she was
small she used to bite her older brother. So this is a false memory, and because it’s
a false memory it’s a distorted memory – it’s inaccurate. There's some kind of truth there;
there was a biting incident, and she’s been given some information that would be fitting
with the memory being true, but it’s not a true memory, it’s a false memory.
Now for the final example. Dan loves to talk about films, providing detailed examinations
of the plots of films. This is all very interesting and entertaining apart from that he discusses
films with his friends when they’ve only just come out and his friend hasn’t had
the chance yet to see them. So they find out all sorts of plotlines they didn’t want
to know. So because of this tendency Dan becomes a little bit annoying to his friends. They
decide to exact revenge on him. When he starts talking about the latest Bond film, they decide
well this is the chance; this is our chance to trick Dan. So they say that they all agreed
that it was a great film, but they especially liked the bit where the Ben Whishaw character
used a jetpack – this never happened, but you know they're planning to trick him to
get him to make a mistake. And they're really pleased later on when they hear their friend
describing to his colleague how this scene is on film, and he really likes it apart from
the bit with the jetpack. So they're pleased they’ve tricked, and what’s happened is
that Dan has formed a distorted memory. He's formed a memory that has some kind of truth;
he really did see the film, he really did form an opinion about the film, but there
was no jetpack in it, so that wasn’t true.
Now these cases of distorted memory are likely to be less familiar to you than cases of forgetting.
So you might doubt as a result of this whether these sorts of things really occur or whether
they occur very frequently if they do occur. However, psychological studies suggest that
people systematically and predictably make errors of these sorts, and they suggest that
errors of these sorts are part of the operation, the ordinary operation of human memory systems.
So for example, psychologists have undertaken studies using what has become known as the
Deese-Roediger-McDermott paradigm in which they presented participants with words and
then asked them to remember the list of words.
So you’ve been listening for a while, so I'm going to get you to participate if you
want to – you don’t have to. Okay, I'm going to show a list of words now. Now speak
to the person next to you, if you like, if they don’t look too scary, and say all the
words on the list. [talking amongst each other] Right, I've decided you’ve had enough time
now. So put your hand up if you thought the word ‘bread’ was on the list? Okay, a
couple of you. The rest of you really didn’t? No? Okay. As a group you're doing better than
average then it seems because those of you who did think the word ‘bread’ was on
the list committed the sorts of error that very many people do when they're presented
with a list of this sort. When people are presented with a list of this sort, very many
of them recall, falsely recall, having been presented with certain words that they haven't
been presented with. Words that are related to the items on the list but actually weren’t
on the list. So words that weren’t given on the list to a participant, words like in
this example ‘bread’ were falsely reported to have been on the list 40% of the time.
Whilst this isn’t the majority of the time, it’s a very large number of incidents in
which people have the sorts of memory distortion that was described in the shopping list example.
In fact what was found in studies is that items that are in the middle of the list were
recalled at roughly the same rate as the words that actually weren’t on the list but were
related in terms of the meaning to the words that were on the list. These studies have
been replicated numerous times, and it’s been found that this effect lasts over the
course of 24 hours, so people asked 24 hours after they’ve been presented with the list
remember that words were on the list that actually weren’t there. So examples like
this, studies like this, suggest that cases like the shopping list example are likely
to occur in real-life. There's a very close parallel there. What happens in that case
is that someone remembers that a word was on the list that was related to the words
that actually were on the list.
What about the biter example then? In this case, triggered by the discussion with her
mother, Nadia imagines her sister biting her, and as a result of imaging this, Nadia ends
up believing that this event really did occur, that it really did happen to her. Psychological
studies suggest that this sort of phenomenon happens quite frequently. Imaging that an
event kind of has occurred, for example, that you were left in a shop as a small child increases
the likelihood that you will remember that event as having occurred, the event having
happened to you, and in fact increases the chances that you'll have a full-blown recall
of the event. This phenomenon is called imagine inflation. So for example, in one experiment
participants were asked to rate the likelihood that a certain event happened in their past,
that they fell over in a particularly dramatic way. And then they were asked to imagine what
it would have been like if they had fallen over in that dramatic way. Of participants
who initially said that was really unlikely that that event had really happened to them,
after they'd imagined the event happening, 24% of them changed their mind and said that
it was likely that the event did happen. So they went from saying it was really unlikely
to it really being quite plausible. In fact in a recent study, it’s been found that
people who've imagined an event that didn’t happen are just as likely to remember that
event happening as those people who are not asked to imagine but shown a doctored video
of them being there for the event. So this shows, these studies show that it’s highly
likely that cases like Nadia’s will occur in real-life.
So finally let’s consider the film critic example. Is it likely that someone can end
up believing that Ben Whishaw used a jetpack in the Bond film when it never really happened
just because someone later told them that this did happen? Once again, psychological
studies suggest that this sort of thing frequently occurs. Numerous studies show that information
presented to an individual after an event often influences their memory of that event.
And the memories fit with the information that’s presented after the event rather
than the details of the original event. For example, people might be shown a video clip
of a car accident, and then later be given, fed some information about that suggesting
that there was smashed glass at the incident. Later when they're asked to recall the event,
they’ll remember that there was smashed glass when there really wasn’t. There's
been a recent study that’s especially relevant to the film clip example, an example where
people were shown a movie. They were asked afterwards to describe what happened in the
movie. Then a few days later they were asked again what happened in the movie, but this
time they were fed information that was supposedly from other people who’d watched the movie
with them. The information was false, but they're recall, they're description of the
events that happened in the film reflects the false information that’s given to them
supposedly by their peers, rather than what happened in the film itself.
So these psychological studies suggest that not only do we forget things, but we often
remember things that didn’t happen. We form memories that have some kernel of truth, but
are nonetheless inaccurate. In response to these findings we might become sceptical about
the reliability of our memories. We might think that we can’t rely on individual memories
we form or we can’t rely on memory systems more generally. We might think that it’s
actually irrational to trust our memory systems once we understand that they work in this
work. We might think that these studies simply show that we’re tricked by memory.
But now I'm going to try and convince you that we understand the explanations that are
given of a phenomena like the DRM allusion – that’s the word list allusion – imagine
inflation, and the post event information effect – that’s the final one – it becomes
clear that these errors are the result of our memory systems working in a way that increases
rather than decreases the likelihood of us getting true beliefs overall. So rather than
just being cases where we’re tricked by memory, these are also cases where we demonstrate
tricks of our memory. So I'm going to go through the examples again and show you how each of
these cases can be interpreted as cases in which our memory systems are doing the sorts
of things that are likely to lead to true beliefs.
So the DRM cases – this is the word list case – how does this show signs that our
memory systems are working in such a way that we’re likely to produce true beliefs? We
they’ve been two explanations of this sort of phenomena. The first explanation is that
when people falsely recall words, so when the few of you who admitted to falsely recalling
the word ‘bread’, when you falsely recall words like this, what you're doing is displaying
how your memory systems lead you to think of concepts that are related to the concepts
that you're currently thinking about. So if you're thinking of items related to bread,
then as a result of thinking of those items you think of bread itself.
Now it’s clear that this tendency could be really beneficial for people who want to
make correct predictions about what they're likely to find in their environment. So I'm
going to get you to do a bit more imaging now, again. So imagine you're in the jungle.
Can you see yourself there? You're surrounded by jungle related items – trees, and other
things that you find in the jungle. As a result of seeing those items you automatically think
of other items that are found in a jungle, including snakes – so you think of snakes.
If there are snakes in the jungle, then it’s going to be really beneficial for you to be
prepared to see snakes, and so for you to see items related to the jungle and think
of other related items such as snakes. This will enable you to predict what you're going
to encounter in your environment. So if this allusion, the word list allusion, is just
showing that we ordinarily make associations of this sort, that we think about concepts
that are related to the concepts that we’re currently encountering like concepts of tree
and leaves and the rest of this, we think related items like snake, then it could well
be a sign that our memory systems are working in a positive way. What's happening is that
we've got these memory systems that help us make predictions about our environment, and
these manifest in this particular case in this way that we end up thinking that a word
was on the list when it wasn’t.
So in this case, this particular tendency of our minds, leads us to error because we
end up thinking that we remember seeing a word on the list when we really don’t, and
we really just think of it, we just think of the concept. But it can nonetheless be
the result of a system that helps us to think well in very many situations. So that’s
explanation one of the phenomenon, but it’s not the only explanation out there on the
market.
There is another explanation, and this is that people only remember the gist, information
about the list. So rather than recalling specific details about the items on the list, what
they do is they recall just the gist of the list which in this case might well be something
like items related to bread. So there can be various advantages to not remembering the
details of the list but rather remembering the gist, like items related to bread. So
you have the relevant information stored away to you, so you have relevant information,
and in this case it just, you know, they were bakery items out there that I need to be thinking
about. But you don’t take up that much space in your memory storage capacity. So that’s
one advantage. So you’ve got the relevant information there, these items are related
to bread, but you're not taking up too much storage capacity in your memory.
But there could be another advantage which is that what you're doing then is you're recalling
abstract information. You're not recalling just the details of each item on the list,
you're recalling something abstract from that, so these are bread related items or bakery
related items. So to understand how it might be an advantage to be recalling information
in an abstract from rather than the details, I'm going to give you another example but
actually I'm going to return to Jimmy and his list.
So imagine that Jimmy starts wondering ‘oh is it really worth going outside in the rain
to buy these items for the cake’. There are two ways we could think about this. He
could think is it worth going out to buy eggs and flour and baking powder and sugar. He
might think individually none of those items are that interesting and worth him going out
in the rain. But he might think in another way. He might think is it worth going out
and getting these items I need to bake my cake. Those are two different ways of thinking
about it. If he ends up thinking about it in terms of the more abstract description,
so he ends up thinking about is it worth going out and buying the ingredients for my cake,
then maybe he's more likely to make the correct decision in this case which is of course to
go out and buy those items and make that delicious cake. Unfortunately, thinking about the items
in this way, in this abstract way, rather than remembering the details of each individual
item on the list leads him to make an error. He ends up buying butter, but in many cases
it could be that actually he’s more likely to make the correct choice and form an accurate
judgement about the situation if he remembers the situation in this way.
So what about imagination inflation? This was illustrated by the Nadia example. How
can this be considered to be the result of our memory systems operating in a way that
makes us likely to get true beliefs rather than make errors overall? Well some psychologists
argue that memory actually exists to allow us to imagine what might happen in the future.
They argue this in part because the areas of the brain that are responsible for remembering
are also those that are responsible for imagination, at least there's some overlap but not precisely
the same brain regions. So it’s argued that memory is structured in such a way as to facilitate
use being able to imagine the future. So what happens when we remember something is that
we remember it in such a way that it will be useful for us to imagine something in the
future. So we store away in the future. So we store away pieces of information, fragments
of information rather than whole episodes.
For example, I might meet my sister in the park. As a result of this I might store away
pieces of information; I met someone in the park, I met my sister. Then at a later point
I might meet my brother at a bowling alley, so I store away; I met my brother, I met someone
at the bowling alley. Then when I remember one of these events at a later point, I will
recombine the pieces of information I've stored away to form an accurate picture of what has
happened. I might do so correctly and remember meeting my sister at the park or I might recombine
the pieces of information in a way that is not correct and falsely recall meeting my
brother in the park. However, I might be doing something a bit more interesting and instead
thinking about meeting my brother or my sister, but it probably wasn’t great anyway, probably
fine – don’t know, may be meeting your brother or sister is amazing, either way fine.
Instead today I am imagining meeting David Bowie in the park. So because the systems
responsible for remembering the same ones that are responsible for imagining, it’s
likely the information about your imagination of this event, meeting David Bowie in the
park, will be stored in the same systems as the information about the memories. So when
I remember an event at a later point, I might actually, because the systems are storing
the pieces of information about memory and the same ones that are storing information
about what I've imagined, I might end up recombining these pieces of information such that I remember
meeting David Bowie at a bowling alley. You might think at this point, Kathy what you’ve
got to do is realise this is very unlikely and change your memory. But there might be
a more plausible example where something similar had happened. You recombine pieces of information
stored away in your imagination and stored in your memory in such a way that you form
a full belief that something happened when you really only imagined it.
So there are costs of memories working in this way, but there are also distinct advantages.
It’s incredibly important that we’re able to imagine what happen in the future so that
we’re able to make predictions and decisions. One good way to do this is to draw on past
experience, but the future is never exactly like the past. So it’s useful to be able
to combine different pieces of information about the past in various different ways to
imagine the future. And sometimes it’s going to be useful to imagine scenarios that haven't
happened in the past. So it’s going to be useful to use your imaginations and your memories,
combine these together to try and construct a picture of what might happen in the future.
So if this is right, then the structure of memory and the way it’s so closely tied
in with imagination might be crucial and important to allowing us to make accurate predictions
and decisions about the future.
So let’s move onto the final example then. So in this example what we found was that
you had an individual who’s given information after an event, and they combine this information
with the information that they have about the event itself, and they form a distorted
memory of the event. How might this be viewed to be the result of a system operating in
such a way that it’s likely to increase our chances of getting true beliefs? Well
the argument goes as follows.
I've just noted memory functions to support imagination and prediction of future events.
A memory system would be most effective if it’s able to incorporate the most recent
evidence that an individual has available to them. And sometimes information relevant
to your understanding of a particular event doesn’t become available to you until significantly
after the event occurs. The post event information effect – this is where the individual takes
information given to them about the film and they incorporate it with the information that
they had about the film – this illustrates that we are able to do this. We’re able
to update our memories with the most recent information that’s been given to us. This
capacity is likely to be especially useful when we’re trying to make predictions about
other people and their behaviours. So you might remember an episode in which you interacted
with a person. So you talked with David Bowie or you probably didn’t in the past. So you
have some information stored away about that episode. But later you might find out information
about that past event or about that individual that it would be important and useful for
you to be able to draw on and integrate with your information about that episode. So if
you want a proper picture of that individual, their reliability, what they're like, then
it’s useful for you to not only draw on the information that you gain from meeting
them, but also on any information that their friends or someone else that you meet might
tell you about them at a later point.
So what happens it seems is that people’s memory systems work in such a way that they
take the information about the past event and the new information, they integrate them
together, and they recall events in a false way, but in a way that reflects the sum total
of the information available to the individual at the point where they're doing the remembering.
So we have the most up to date impression of individuals to use to make predictions
and explanations about them.
Now errors follow in terms of the accuracy of our impressions of events that have happened
in the past because our impressions of those events are changed in light of information
we obtain after the event. But nonetheless it seems as if these errors are just a sign
of the operation of the system that’s quite dynamic. That actually enables us to make
the best use of all of the information available to us including information that is gained
after an event.
So conclusion. When we notice memory distortions we shouldn’t automatically conclude that
they're signs of irrationality, and we shouldn’t immediately assume that we should adopt a
sceptical position towards all of our memories and worry that they're ever reliable. Memory
distortions are signs that we’re tricked by our memories, but they're also signs of
tricks of our memories, signs that our memory systems are operating in ways that are likely
to improve our chances of getting true beliefs overall.