Factors affecting accuracy of EWT - Misleading information

• Types of Misleading information

  Leading questions and post event discussion
• What are leading questions?

  A leading questions is one which by its phrasing and wording suggest a particular answer from the respondent.
• What is post event discussion?

  When individuals who witness a crime separately discuss the details/events together before giving their eyewitness accounts
• Leading questions: Loftus and Palmer 1974 Aim


  To investigate the influence of leading questions on the accuracy of EWT.
• Procedure


  45 students watched a video clip of a car accident in a lab settings. Students were split into 5 groups and given a questionnaire which asked them:How fast were the cars going when they x each other?Each group received a different critical verb in their question - smashed/collided/bumped/hit/contacted - acting as a leading question. Researchers recorded the av speed estimated for each group.
• Results


  The critical verb used in the questionnaire influenced the estimated speed given. Higher speeds estimated for 'smashed' (40.8mph) compared to 'bumped' (38.1mph) and 'contacted' (31.8mph).
• Conclusion


  The accuracy of EWT can be significantly reduced by the presence of misleading information in the form of leading questions.
• Loftus and Palmer Study 2 - Aim

  To investigate the influence of leading questions on the accuracy of EWT.
• Procedure for study 2

  150 students were shown a 1 minute film which showd a car driving through the countryside followed by 4 seconds of a traffic accident.Condition 1 -How fast were the cars going when they HIT eachother?Condition 2 -How fast were the cars going when they SMASHED each other?Control -no leading question. 7 days later PPs returned and completed another questionnaire without seeing video. One question asked: Did you see any broken glass?There was no broken glass in the video!!
• Results of study 2


  The majority of PPs reported seeing no broken glass. But, those who received the critical verb 'smashed' were significantly more likely to incorrectly report seeing broken glass than the Hit or Control group.
• Conclusion of study 2

  Misleading information in the form of leading questions results in substitution bias - distorting memory and reducing the accuracy of EWT.
• Low ecological validity

  Loftus procedure lacks mundane realism. E.g. PPs viewed video clips of a car crash, rather than being present at a real-life accident. A video doesn't cause the same emotional anxiety levels as witnessing a real-life accident, also the PPs knew they were taking part in research so would have paid particular attention to the details of the video or may have been less motivated to be accurate in their recall of the information as it was only an experiment. This is alimitationas the findings from Lotus about leading questions have low ecological validity and should be generalized cautiously in the real world.
• Bias sample - Issues with generalisation

  The sample in Loftus study was students who are not representative of the general population. Students may be less experienced drivers and therefore less confident in their ability to estimate speeds. This may have influenced them to be more swayed by the verb in the question. A bias sample means the conclusion about leading questions decreasing the accuracy of EWT cannot be generalised to the wider pop (low pop validity)
• Standardised procedure - YAY

  Strength - lab setting so procedure was standardised. E.g. video clip of car accident and the questionnaire given were kept the same for all PPs. Allowed research to be replicated and through replication assess the reliability of the influence of leading questions of EWT. Upon replication consistent results have been found suggesting the results of Loftus research on leading questions reducing accuracy of EWT are reliable.
• Practical application - YAY

  Her research clearly demonstrates how altering a single verb when questioning a witness can reduce accuracy of EWT. Loftus research has resulted in changes in the ways in which police are trained and how witnesses are interviewed following a crime so as to not bias their responses - development of cognitive interview. Therefore increases accuracy of EWT and saves valuable police resources which has a positive impact on economy.
• Post-event discussion (Gabbert et al 2003)


  AIMTo investigate the influence of post event discussion of the accuracy of EWT.
• Procedure

  60 students from Aberdeen uni and 60 older adults recruited from local community. Paired together and watched a robbery where £10 was stolen from a wallet. But, they had witnessed different versions of the same event and so saw unique details (eg only one perspective saw the girl).Condition 1 -Discuss details of the video together.Condition 2 -not allowed to discuss any details with each other. All PPs then completed a questionnaire, testing their memory of the event.
• Results

  71% (group which discussed the evnt before recalling details) - recalled info they had not seen (from their perspective).

  60% - said that the girl was guilty of stealing £10 , depsite the fact they had not seen her commit a crime from their perspective.
• There was no significant difference between....

  The 2 age groups - suggesting both were equally influenced. Post-event discussion can result in memory conformity where witnesses may provide inaccurate details of the event.
• Results have low ecological validity

  The procedure lacks mundane realism. PPs knew they were taking part in an experiment so are more likely to have paid close attention to details of the event in the video. Ina real-world crime scene witnesses are often surprised by a crime unfolding and experience some levels of anxiety which can influence their memory, this reduces the ecological validity of the results. The findings cannot be generalised to real world instances of exposure to misleading info from other witnesses.
• Population validity - YAY

  Tested 2 different populations and found little difference between these 2 conditions. Results have high population validity and allow for generalisations to be made to the target population. Allowing us to conclude that post-event discussion affects younger and older adults in a similar way.
• Standardised procedure - YAY

  Using lab experiment means standardisation. The length of the videos, perspectives, interval tasks and questionnaires to assess recall were kept the same for all PPs. Standardising the procedure in this way allows replication of the research. Upon replication, consistent results have been obtained highlighting the reliability of findings about post-event discussion on memory.
• Practical application


  Findings show how the accuracy of EWT is reduced when witnesses are allowed to discuss events of the crime after it has occurred or are exposed to repeat interviewing by police. Therefore, the police are now aware of the importance of isolating witnesses and preventing discussion from taking place until after interview to prevent memory conformity. This has economic benefits as it saves valuable police resources such as time and money from being wasted pursuing wrong lines of enquiry from faulty EWT.
• Yerkes Dodson Law 1908

  Deffenbacher 1983 reviewed 21 studies and found that the stress performance relationship followed an inverted U function proposed by theYerkes Dodson Curve.Theinverted u theory.The accuracy of EWT depends on the levl of anxiety experienced. Accuracy is impaired by too little or too much anxiety.Accuracy increases as anxiety levels increase- up to a certain point. After which accuracy declines. Accuracy is optimal when a moderate level of anxiety is experienced.
• Inverted u theory diagram

  
• Johnson and Scott - Weapon focus - Procedure

  HIGH ANXIETY REDUCES ACCURACY OF EWT.Invited PPs to a lab where they were told to wait in reception. A receptionist who was seated nearby, left to run-an errand, leaving PP alone.independent group design-PPs were then exposed to one of 2 conditions.1)No weapon condition - PPs overheard a convo in lab about equipment failure. Thereafter, an individual left lab and walks by the PP holding a pen with his hands covered in grease -low anxiety.2)Weapon condition - PPs overheard a heated exchange and the sound of breaking glass and crashing chairs. This was followed by an individual running into the reception area, holding a bloody letter opener -high anxiety.Both groups shown 50 photos and ask to identify the person who had left the lab. PPs were informed that the suspect may, or may not be present in the photographs.
• Results


  Those who'd seen the man holding a pen correctly identified the target 49% of the time, compared to those who had witness the man holding a knife - high anxiety. Loftus argued that PPs who were exposed to the knife had higher levels of anxiety and were more likely to focus their attention to the weapon and not the face of target.
• Christianson and Hubinette 1993

  HIGH ANXIETY INCREASES ACCURACYInterviewed 58 witnesses of actual bank robberies in Sweden 4-15 months after the crime. Bank tellers (high anxiety) and bystander (low anxiety). All witnesses showed good recall ( 75%). The most accurate recall was provided by the bank tellers (high anxiety). Suggesting high anxiety levels do not impair EWT.high ecological validity.
• Lacking ecological validity - johnson and scott


  Although PPs were waiting in the reception area outside the lab, they may have anticipated that something was going to happen, which could have affected the accuracy of their judgements. Furthermore, results from real life case studies reuse the findings of Loftus and suggest that her results do not represent real-life cases of extremem anxiety.
• Ethical issues of johnson and scott

  PPs were deceived about the nature of the study and so could not give informed consent. Furthermore, those who had experienced the weapon condition will have suffered from psychological harm. However, the benefits of the research to our understanding of the weapon effect outweighed any temporary harm to the PPs who were promptly debriefed after the study and given the right to withdraw.
• Supporting research - Valentine 2009


  Opportunity sample of 56 visitors to the London dungeon. They wore a heart rate monitor throughout their visit. When they were in the dungeon, a 'scary person' stepped out in from of them inducing anxiety. Afterward given a questionnaire to self-report their anxiety. They were shown a 9-person line up and asked to identify the scary person. They were told that the scary person may or may not be in the line up and were asked to say if they couldn't identify the person. They also noted their confidence, as a %, that the person they selected was the scary person. High state anxiety was associated with reporting fewer of the target person, more incorrect details and making fewer correct identifications from a line-up. High state anxiety reduces accuracy of EWT.