Factors affecting the accuracy of EWT

• Eyewitness testimony


  Persuasive but flawed memory recall subjected to interpretation by person reporting it.

  
• Loftus and Palmer (1974) - Leading questions

  - Students watched clips of car accidents and were then given questions - one of which was a leading question (different people were given slightly different questions).

  - The verb 'contacted' resulted in a mean estimate speed of 31.8 mph.

  - The verb 'smashed' was 40.5 mph.
• Leading question


  Questions asked in a way that suggest you have a preferred answer
• Misleading information


  Supplying information that may lead a witness' memory for a crime to be altered
• Why do leading questions affect EWT?

  Response-bias explanation

  - Wording of the question doesn't effect the memory but influences how they decide to answer.

  
  

  Substitution explanation

  - Wording a leading question changes the participants memory.

  - This was demonstrated as by hearing the word 'smashed' they thought they saw broken glass.
• Post-event discussion


  A conversation between co-witnesses or an interviewer and an eyewitness after a crime has taken place which may contaminate a witness' memory for the event

  
• Gabbert et al (2003) Post-event discussion


  - Each participant watched a video of the same crime, but from different angles

  - Participants then discussed what they had seen, before individually completing a recall test.

  - 71% of participants incorrectly recalled aspects of the event they couldn't have seen.
• Why does post-event discussion effect EWT?

  Memory contamination

  - When co-witnesses' discuss it with each other, their eyewitness testimonies may become altered or distorted.

  - This is because they combine information from other witnesses with their own memories.

  
  

  Memory conformity

  - Witnesses often go along with each other, either to win social approval or because they believe the other witnesses are right and they are wrong.

  - The actual memory is unchanged.
• Strengths of misleading information research

  Real-world application

  - Leading questions can have such a distorting effect on memory that police officers need to be very careful about how they phrase their questions when interviewing eyewitness.
• Limitations of misleading information research

  Evidence against substitution

  - Sutherland and Hayne showed participants a video clip.

  - Their recall was more accurate when asked misleading questions.

  
  

  Evidence challenging memory conformity

  - Skagerberg and Wright showed their participants film clips.

  - There were 2 versions.

  - Participants discussed the clips in pairs, each person having seen the other clip.

  - Reported a blend of the 2 clips.
• Anxiety


  The condition of feeling uneasy or worried about what may happen

  
• Johnson and Scott (1976)


  - They led participants to believe they were going to be part of a lab study.

  - While seated in a waiting room participants heard an argument next door.

  - In the 'low anxiety' condition a man walked though the door carrying a greasy pen.

  - In the 'high anxiety' group saw a man with a bloody knife.

  - 49% of the 'low anxiety' group identified the man and 33% of the 'high anxiety' group identified the man.

  
• Yuille and Cutshall (1986)


  - 13 witnesses to a real life shooting which involved the owner of a gun store in Canada and an armed thief in which the store owner was wounded and the thief was shot dead were interviewed.

  - Witnesses were at different distances from the shooting when it took place.

  - High levels of stress reported more accurately.

  
• Yerkes-Dodson Law


  The principle that performance increases with arousal only up to a point, beyond which performance decreases

  
• Limitations of the effect of anxiety

  Unusualness not anxiety

  - Johnson and Scott may not have been testing anxiety.

  - The reason participants focused on the weapon may have been out of surprise not anxiety.
• Strengths of the effect of anxiety

  Support for negative effects

  - Valentine and Mesout (2009)

  - Visitors to a horror labyrinth divided into low/high anxiety based on a heart monitor.

  - Asked to describe an individual encountered in the labyrinth

  - Low anxiety - high accuracy of EWT, anxiety has a negative effect on recall

  
  

  Support for positive effects

  - Christianson and Hubinette (1993)

  - Questioned 110 witnesses who had, in total, witnessed 22 real bank robberies.

  - NOT STAGED.

  - Some were onlookers, others were employees who were directly threatened.

  - Victims were more accurate - could remember even after 15 months.

  People are good at remembering highly stressful events if they actually occur than in controlled conditions.