In the last presentation we talked about some of the things that affect the encoding
stage of memory. What about the next step: the storage stage? To what extent can we hold
on to our memories of events? Well, let’s examine some data on the sort of high impact
traumatic event that should be very hard to forget: having a car crash.
Even a minor damage only car crash ought to be hard to forget due to the expense and inconvenience
caused, let alone a crash in which people are hurt or killed. But it so happens that
Geoff Maycock and Julia Lester of the Transport Research Laboratory in the UK found that drivers
appear to forget about 30% of the car crashes they’ve been involved in per year. That’s
incredible on the face of it. How could people possibly forget something like that? We’re
not even talking about details like the colour of the car you crashed in or whose fault it
is. We’re talking about people forgetting that the entire event ever took place.
So, the first message about memory storage is that it seems that people are surprisingly
likely to forget things that we really wouldn’t expect them to forget. So aside from forgetting,
what else can happen to memories during the storage phase? It turns out that it is startling
easy to modify memories both deliberately and otherwise by introducing misinformation.
That is, stored memories can be interfered with. In the real world, this might well happen
just by accident. For example, listening to an inaccurate report of the crime in the media
or chatting with another eyewitness who has misremembered the original event.
One thing that memory researchers are very aware of is the extent to which memory is
vulnerable to tampering. In a typical experiment, people are shown a video of a crime. They
then read a written account of the crime, such as might appear in a newspaper article,
or they talk to someone who has also seen the crime. So half of the participants might
be fed false information via the follow up account. For example, in the original the
criminal might be clean shaven, but in the newspaper account it might be inferred that
they had a moustache. Then they are asked to recall the crime, and the people who have
been fed the false information often end up incorporating it into their report. For example
recalling that the criminal had a moustache when in fact he didn’t. In a study from
2013, by Harmut Blank and colleagues from the University of Portsmouth, participants
watched a two minute video clip of a crime captured on CCTV, in which four men rob a
jewellery store, where one of them has a gun.
Then participants discussed the crime with another participant who was actually a plant
who had been briefed to give misinformation. An example of the misinformation they introduced
was to identify the wrong person as holding that gun. The following week, participants
returned and were asked to recall details of the crime. Even when they were told that
the information from the other witness might be incorrect and that they should ignore it,
they often still incorporated the false information into their account of the crime.
Maybe it would be different if the situation was more stressful and personal? Well, in
another recent study, Charles Morgan of Yale University and colleagues, found that military
personnel who were subject to a highly stressful prisoner of war camp simulation which involved
them being aggressively interrogated, they identified the wrong person as being their
interrogator after being shown misinformation – in this case a photograph.
Psychologists have been investigating the details of the misinformation effect for decades.
The sort of questions they’ve been looking at include things like: under what circumstances
is misinformation most likely to affect memory? What type of person is most susceptible to
misinformation? What actually happens to the original memory when the misinformation supplants
it? As we’ve seen, even when you tell people that the misinformation is incorrect, they
often still can’t ignore it – it becomes part of their memory. That is, in a real crime
case, even telling eyewitnesses that a media report of a crime is inaccurate might not
help prevent their memory of the crime from being contaminated.
We could have an entire course just looking at the misinformation effect – it’s a
complex and fascinating topic all on its own. Here’s another excerpt from that interview
with Elizabeth Loftus, which was conducted by my colleague, Matt Thompson. And here’s
her take on false memories.
Is it possible to implant a false memory, make somebody believe something happened when
it never actually happened?
Absolutely. I mean, in my own work, for example, we’ve changed people’s memories for the
details of events that they did experience. We’ve made people, for example, believe
that a car went through a stop sign instead of a yield sign, or a guy running from the
scene had curly hair instead of straight hair. That’s really easy to do. But you can go
further with people. You can plant entirely false memories, whole memories, into the minds
of people for things that didn’t happen.
Wow. So surely that has implications for people testifying in court, like witnesses saying,
“Yes, that was the guy that committed the crime,” or, “Yes, the car went through
the stop sign and hit the other car.” Does your research have implications for the courtroom?
Well, it does because, you know, most of the time little errors that we make in memory
don’t matter very much. I mean, it doesn’t really matter if I tell you that I had a hamburger
for lunch instead of chicken, but when it comes to the legal world, now very precise
memory matters, and so memory evidence is precious. It needs to be preserved. It needs
to be protected. Unfortunately, a lot of times, it’s not, and people or circumstances get
in there and contaminate those memory traces and lead to travesties of justice.
So, we’ve given some examples of problems at encoding and problems during storage. Now
let’s now turn our attention to memory retrieval. As an example of what might bias this aspect,
let’s look at another case of false memory. It turns out that you don’t even need misinformation
in order to create false memories. Let’s look at some of Elizabeth Loftus’s own research
to illustrate this. She conducted an experiment with John Palmer when she was at the University
of Washington, and this experiment involved showing people films of car crashes and asked
them how fast the vehicles in the film were going.
Some participants were asked how fast the cars were going when they HIT each other.
Others were asked how fast the cars were going when they SMASHED into each other. One week
later, the group who had the word “smashed” in their question, not only gave faster speed
estimates, they were more likely to remember there being glass at the scene – even though
there wasn’t any. That is, even in a situation where, crucially, there is no factually incorrect
information being introduced, we are still getting a false memory. So, overall, the picture
of eyewitness memory that the research is painting does not appear promising. Memory
appears to be much more fragile and vulnerable to distortion than people expect, and these
distortions can occur at numerous points in the memory process for a wide range of reasons.
So, the issue now becomes, what can we do about this? Are there any techniques that we can
use to improve eyewitnesses’ memory? That’s the question we’ll look at next.