Eyewitnesses are trusted to give evidence in court
that can result in convictions. But how accurate is eyewitness testimony,
and what are the factors that make eyewitness testimony more, or less accurate?
This video will cover the effects of misleading information,
post event discussion and anxiety to examine how accurate eyewitness testimony really is.
# Misleading information.
Before jumping into misleading information I need to give you a little background information on the
ideas of this guy, Bartlett. Bartett argued that memories are not accurate snapshots of the past
that are carefully stored away in our mind. No, Bartlett argued our memories are reconstructive.
Bartlett developed an idea called a schema, these are packages of information that we
use to understand the world around us. Now schemas are a really important part
of psychology, and come up again and again in this course, for a more detailed explanation
of schemas, jump over to my cognitive psychology video, maybe after this one
When applied to memory we would say that schemas reflect our attitudes and stereotypes,
and we use schemas to construct our memories. This is a problem for eyewitness testimony.
If memory is reconstructive then it's not accurate, in its reconstruction
it is changed and will produce errors, false memories that Bartlett called confabulations.
This explains how misleading information influences memory,
this can include leading questions. The words I use to ask a question can imply a certain
response, and this influences the memory that someone reports. There are two possibilities,
one that the actual memory does change, it replaces the old memory completely,
we would call this substitution bias. But there is a second possibility, the memory doesn't actually
change, but there is an emotional pressure that alters your response. We call that response bias.
Before we come to the research I want to quickly define post-event discussion,
this is the contamination of eyewitness testimony with another witness's memory, reducing accuracy.
When witnesses discuss what they have seen we find that their testimony alters to match the
accounts of the other witnesses, this is called memory conformity.
Watch this clip.
How fast were the cars traveling when they smashed into each other?
Ok, what about how I asked that question could we say is leading? Of course the word smashed.
A researcher called Loftus showed traffic accident clips like that to participants,
and asked how fast were the cars going when they hit each other,
changing the verb hit into smashed, collided, bumped and contacted.
The results showed the more extreme the verb the faster the participant guessed the car was
travelling. Contacted was the slowest speed at 31.8 mph, and smashed the fasted at 40.5
Now this does suggest that misleading information in the form of leading questions
can influence the recall of eyewitness testimony. In a second study one week after being asked if
the cars smashed or hit each other participants were invited back and
completed a follow up questionnaire, one of the questions was did you see any broken glass.
More than twice as many participants said they had seen broken glass in the smashed condition.
Now as it had been a week since the first part of the study, and it's likely the
participant may not even remember that the word smashed or hit was originally used,
I would argue this is a real change in the memory, so substitution bias, not just response bias.
Now I’ve already described post-event discussion, that witnesses change their recall to be
in line with other witnesses. And here is an interesting research study showing the effect.
Gabbert showed videos of the same crime to pairs of participants. But each member of the pair was
shown a different video, showing the crime from separate perspectives. Now if they were allowed
to discuss what they had seen with the other witness, when interviewed later alone 71% of
participants would include items they hadn't seen in their video, but had heard in their discussion.
This is a demonstration of memory conformity that witnesses will change their recall to
match other witnesses. # Anxiety
Another factor that affects eyewitness testimony is anxiety.
A quick definition of anxiety is it's a mental state of arousal, you tense up and
feel overly cautious. There are biological factors too like an increased heart rate.
Now it seems a fair point that anxiety may have a role to play in the accuracy of eyewitness
testimony, which is important as in many situations that use eyewitness testimony
witnesses are recalling anxious situations like violent crimes.
But none of the lab based research we have looked at so far
makes the participants anxious. So maybe those studies lack validity.
There are a few suggestions of how anxiety affects recall. Some psychologists argue
anxiety decreases recall, people are so anxious they become distracted, not paying attention
so they can accurately recall later. An aspect of this theory is the weapon focus effect, the
eyewitness is so focused on the gun or the knife that they don't look at the face of the criminal.
On the other hand there are psychologists who argue that high levels of anxiety actually
increase recall. The anxiety makes the witness more alert to the situation around them, as well
as the stronger emotion making a stronger memory. But there is a third theory that brings
both of these two opposite ideas together, the Yerks-Dodson law of arousal. This theory
suggests that with very low anxiety recall is low because the witness isn't paying attention,
as anxiety increases the witness becomes more aware and focused so recall improves.
But at a certain point the witness becomes too anxious and stressed, and in that panic
loses concentration, resulting in less accurate eyewitness testimony. As you can see we can draw
a graph to represent the accuracy of eyewitness testimony with low medium and high anxiety.
The classic research on anxiety and eyewitness testimony was conducted by Johnson and Scott.
In this study unaware or we can call them naive participants sat outside a lab waiting to take
part in a study. But little did they know the study was about to start. The participants either
heard a conversion about equipment failure and a man walking out with greasy hands and a pen,
or a hostile conversation, breaking glass and furniture being knocked over,
a man walked out this time with a knife and his hand covered in blood.
When asked to identify the man from fifty photographs 49% of participants
could identify the man with the pen. But only 33% could identify the man with the knife.
Well this study did cause anxiety, and the results suggest that the anxiety caused by
the knife resulted in weapon focus and less accurate eyewitness testimony.
Now we could criticise this as still being a lab study, but we see a similar effect in
a field study by Peters who showed that recall was worse for identifying a nurse
who gave an injection to the participant than for a researcher in the room. This suggests
weapon focus for the syringe reduced accuracy. But there is counter evidence, thirteen witnesses
to a real life deadly shooting were interviewed by researchers Yuille and Cutshall four months
after the event. The researchers found recall to be highly accurate, the participants managed to
resist leading questions and high levels of stress didn't seem to impact the accuracy of eyewitness
recall. Some of the most accurate recall was from the people who would have been most stressed
as they were closest to the shooting. Additional Evaluations
We can finish by exploring a range of additional evaluations.
Firstly there have been real world applications of research on the limitations
of eyewitness testimony, in particular the development of the cognitive interview.
The cognitive interview is the subject of the next memory video.
But all of the lab based eye witness studies can be criticised as having low validity
because of the lack of consequences. Incorrect eyewitness testimony in a courtroom when under
oath can lead to wrongful convictions, and this may lead to more accurate eyewitness testimony.
Lab studies also suffer from demand characteristics,
with participants' memories not actually changing but perhaps picking up on the
language used and guessing a response that they think that the researcher wants to hear,
this could be a problem especially in research looking at leading questions.
And finally much of the research investigating anxiety could be unethical.
Researchers have a duty not to harm participants and to gain informed consent,
research like jhonstone and scott needs to break both of these guidelines and asking participants
to recall the details of a murder they have witnessed could be a traumatic experience.
have a go at this a real exam question on factors affecting eyewitness testimony. 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, improving the accuracy of eyewitness testimony