Presentation on theme: "Yuille and Cutshall (1986) A case study of eyewitness memory of a crime."— Presentation transcript:
Yuille and Cutshall (1986) A case study of eyewitness memory of a crime.
Can the findings of laboratory based EWT studies be generalised to more realistic situations?
Problems With EWT Lab Based Studies Slide sequences and filmed events are not relevant to real work events Lack of seriousness or consequences of actual events There are ethical issues if participants are deceived into thinking an event is real.
Problems With EWT Lab Based Studies Problems with the participants. 41 research articles about EWT from 1974 – 1982 tested students only (according to Brain, 2009). Therefore, field observation are required to help generalise lab study findings.
Background to Yuille and Cutshall, 1986) One spring afternoon in Vancouver, Canada, a thief entered a gun shop, tied up the owner and stole some money and guns. The owner freed himself and picked up a revolver. He went outside to take the car registration number but the thief had not got into the car and he fired two shots at the store owner from a distance of about 6 feet. The owner, after a short pause, fired all 6 shots from his revolver. The thief was killed but the store owner recovered from serious injury. Witnesses viewed the scene from different locations – passing cars, buildings or in the street.
This case was chosen because… There were enough witnesses to compare accounts. The thief was killed and the weapons and money recovered, so there was a lot of forensic evidence to verify the witness accounts. The death of the thief closed the file, so research would not interfere with a police case. There were many visible elements to the scene (car, gun boxes) so eye witness statements could be checked and compared. Witnesses could be asked about elements the police would not have focused on, so previous police questioning would not interfere with or affect the study results.
AIMS To record and evaluate witness accounts. To examine issues raised by laboratory research To look at witness verbatim accounts – their accuracy and the kind of errors made. Loss and distortion of memory takes place over time. The idea was to look at eyewitness interviews immediately after the event, which were conducted by a police officer, and to compare these with interviews carried out by research staff. Misleading questions were incorporated into the research interviews to see how an eyewitness might be affected by distortion.
Participants 21 witnesses interviewed by police. 13 agreed to take part in the research interviews (two had moved from the area, five declined and the other was the victim, who did not want the relive the trauma).
Interview Procedure Police had interviewed the witnesses and recorded the interviews by hand. Each witness had been asked to describe the event and the officer then asked a series of questions. The reports were verbatim (word for word).
4 – 5 months later…………. 13 witnesses interviewed by the researchers – audio taped and transcribed. Research interviews used the same format as police interviews (own account then questions). But TWO misleading questions: 1. “a busted headlight” Vs “the busted headlight”. (There was no broken headlight) 2. “the yellow quarter panel” Vs “a yellow quarter panel”. (Quarter panel was blue)
Interview Procedure Researchers also asked about the degree of stress each witness experienced at the time of the accident. This was a 7 point likert scale, with 1 being perfectly calm and 7 being extremely anxious. They were asked about their emotional state before and after the incident.
Scoring Procedure Research interviews were compared with police interviews by using a scoring technique. Details were divided into ACTION details and DESCRIPTION details of either OBJECTS or PEOPLE. Various reconstructions were set up and evidence was carefully researched so actual details revealed
Results Police Interview Research Interview Action Details392551.5 Person Descriptions 180267 Object Descriptions 77.5238 TOTAL649.501056.5 Total reported classifiable details from 13 witnesses
Results Of the 13 participants, 7 were central witnesses and 6 peripheral witnesses. However, both were equally accurate. In the police interviews 84.56% of the central witnesses were accurate, compared with 70.31% of the peripheral group. The accuracy remained similar and high for most of the witnesses even after 4 – 5 months and errors were relatively rare.
Results Misleading information had little effect (10 said there was no broken headlight or no yellow quarter panel, or said they had not noticed the detail. Stress did not affect memory negatively. Researchers found that witnesses experienced adrenalin more than stress. The stress came later.
Conclusions Eyewitnesses are not inaccurate in their accounts. Y&C suggest they may have investigated flashbulb memories. The fact that those directly involved in the event remembered more might support this and explain the difference in findings from lab studies.
Conclusions Scoring procedures may have undermined the accuracy of the accounts. For example, “he looked like he was in his early 20s’ was scored as incorrect (even though he did look like he was in his early 20s’) because he was 35!
Conclusions The study also shows that just because some details may be wrong (such as the colour of a blanket), it does not necessarily make other details wrong and that the witness testimony should not then be rejected.
Strengths Field study looking at a real incident with real witnesses. Has validity lacking in lab experiments. Researchers took great care with counting details from real incident to make sure that witness testimonies did not alter what ‘really’ happened. This makes finding ‘reliable’.
Weaknesses Problems in generalising from a unique and specific incident. Could be a flashbulb memory, so may be unfair to use these findings to criticise lab experiments. Problems with the scoring (previously discussed). However, as the accounts were found to be largely accurate, emphasising inaccuracies would not have affected the findings in this case. Turning qualitative into quantitative data can always lead to bias and inaccuracy.