Factors affecting the accuracy of eyewitness testimony Flashcards
What factors affect the accuracy of EWT?
Midsleading information
Anxiety
What are the two types of misleading information?
Leading questions and post event discussion
What is a leading question?
A question, which because of the way it’s phrased, suggests a certain answer
Who provdies research support for leading questions?
Loftus and Palmer
Describe Loftus and Palmer’s study
- 45 students watched film clips of car accidents and were then asked questions about the accident
- they were given a questionnaire
- The critical question (which was a leading question) they were asked was “About how fast were the cars going when they —— each other?”
There were 5 groups - each one was asked the critical question with a different verb:
Smashed, hit, bumped, collided or contacted
What were the findings of Loftus and Palmer’s study?
- the mean estimated speed was caluclated for each group
- the verb contacted resulted in the lowest mean of all the verbs (31.8mph)
- the verb samshed resulted in the highest mean of all the verbs (40.5mph)
- the leading question biased the eyewitness’s recall of the event
Give two readons why leading questions affect EWT
Response bias
substitution explanation
Explain response bias
The wording doesnt have any real effect on their memories it just encourages them to choose a higher speed for the word smashed
Explain substitution explanation
This suggests the wording actually changes the memory. This is supported by a follow up study where the participants were asked if they saw any broken glass (there wasnt any). Those in the smashed condition were more likely to say they had seen glass suggesting the verb altered their memory of the incident
Describe Loftus and Palmer’s experiment 2
150 student participants were shown a short film that showed a multi vehicle car accident and then they were asked questions about it.
The participants were split into 3 groups
They were asked if they could see glass
Those who had the verbed smashed said they could see glass even though there wasnt any
What is post event discussion?
This occurs when there is more than one witness to an event. They may discuss what they have seen with co-witnesses or with other people which may affect the accuracy of each witness’s recall of the event
Who did a key study on post event discussion?
Gabbert et al
Describe Gabbert et al’s study
- studied both younger adults (17-33) and older adults (58-80)
- studied participants in pairs
- each participant watched a video of the same crime (a girl stealing) but filmed from different points of view
- this meant that each participant could see elements in the event that the other could not
- both participants then discussed what they had seen, before individually completing a test if recall
- a control group was also present where there was no post event discussion between the pairs
What were the findings of Gabbert et al’s study?
- in the post event discussion group 71% of the participants mistakenly recalled aspects of the event they did not see, so they picked it up in the discussion
- in the control group with no discussion it was 0%
- therefore, the discussion had lowered the accuracy of their EWTs
Why does post event discussion affect EWT?
Memory contamination
Memory conformity
Describe memory contamination
The discussion causes the EWT to become altered or distorted because they combine (mis)information from other witnesses with their own memories
Describe memory conformity
May go along with other witnesses to win social approval or because we believe the other witnesses are right and we are wrong. Unlike with memory contamination, the actual memory is unchanged
What is anxiety
A state of emotional and physical arousal
It can have both positive and negative effects on the accuracy of EWT
When did anxiety have a negative effect on recall?
Weapon focus
Describe weapon focus
The presence of a weapon leads to anxiety and we focus our attention on the weapon, reducing the witness’s recall for other details of the event
Who did a key study on weapon focus?
Johnson and Scott
Describe Johnson and Scott’s study
- invited participants to a lab where they were told to wait in the reception area. The experiment used an independent groups design, as they took part in one of two conditions:
1) in the low anxiety ‘no weapon’ condition - they overheard a casual conversation from the next room and a man left the lab walking past holding a pen, with his hands covered in grease
2) in the high anxiety ‘weapon’ condition - they overheard a heated exchange and the sound of breaking glass. This was followed by a man running into the reception area holding a bloodied knife
Both groups were then shown 50 photographs and asked to identify the person who had left the laboratory
Describe Johnson and Scott’s findings
- those who had witnessed the man holding a pen = correctly identified the man 49% of the time
- thsoe who had witnessed the man holding a knife = correctly identified the man 33% of the time
What did Loftus claim?
Loftus claimed that the participants who were more exposed to the knife had higher levels of anxiety and were more likely to focus their attention on the weapon and not face the target, a phenomenon known as the weapon focus effect
Who found that anxiety has a positive effect on recall?
Yuille and Cutshall
describe Yuille and Cutshall’s study
- investigated the effect of anxiety in a real life shooting in a gun shop in canada
- the shop owner shot a thief dead
- 21 witnesses were originally interviewed by investigating police and 13 witnesses aged between 15 and 32, agreed to take part in Yuille and Cutshall’s follow up research 4-5 months later
- accuracy was measured by the number of details reported in each account
- these were compared to original policd interviews made at the time of the shooting
- they were also asked how stressed they had felt at the time of the incident on a scale and if they had any emotional problems since
Describe Yuille and Cutshall’s findings
13 witnesses who took part in the follow-up interview were accurate in their eyewitness accounts 5 months later
Those participants who reported the highest level of stress were most accurate approximately 88% compared to 75% of the low stress group
What does the Yerkes-Dodson law explain?
It establishes that performance increases with physiological or mental arousal, but only up to a certain point.
Low anxiety levels will lead to less accurate EWT
As anxiety increases the accuracy of EWT also increases - up to an optimal level i.e. maximum accuracy
However, too much anxiety then starts to lead to less accurate EWTs again
