Factors affecting EWT

• Eyewitness testimony


  Evidence used in court concerning the identity of someone who has committed a crime
• Factors that can influence eyewitness testimony

  • Misleading information
  • Leading questions
  • Post-event discussion
• Leading questions


  Two explanations for their influence:

  1. Response bias explanation: wording of the question has no real effect on the participants memories, but influences how they decide to answer

  2. Substitution explanation: wording of the leading question actually changes the participants memory for the event
• Loftus and Palmer (1974) found that the verb used in a question about the speed of cars in an accident influenced the participants' estimates of the speed
• Loftus and Palmer (1974) also found that the verb used in a question influenced whether participants mistakenly reported seeing broken glass
• Post-event discussion


  Can result in information being added after the event which will also bias the witness's memory
• Memory contamination


  Witnesses become confused about what they witnessed themselves and what they have been told by others
• Memory conformity


  Witnesses may go along with other people for social approval (normative social influence) or because they believe other witnesses have better information than they do (informational social influence)
• Gabbet et al (2003) found that 71% of participants mistakenly recalled aspects of an event that they couldn't have seen, after discussing the event with another participant who had a different perspective
• Research into factors affecting the accuracy of eyewitness testimony has informed police how to effectively interview eyewitnesses to avoid leading questions
• Loftus and Palmers participants watched clips in a lab, which is very different from witnessing real life events (less stressful)
• Foster et al (1994) identified that there are important consequences to eyewitness testimony in real life that can't translate to the research scenario
• Skagerberg and Wright (2008) found participants' memory was distorted through contamination by misleading post-event discussion rather than being altered as a result of memory conformity
• Anxiety


  Psychological and is associated with arousal
• Arousal


  Physiological effects
• Effects of anxiety on the accuracy of eyewitness testimony

  • Negative effect: anxiety creates arousal which prevents paying attention to important cues, so recall is worse
  • Positive effect: the fight or flight response increases alertness and improves memory because we become more aware of cues in the environment
• Yerkes-Dodson law (inverted u)


  Performance increases with arousal (or anxiety) until a certain point and then it decreases
• Deffenbacher (1983) meta-analysis found inconsistent findings of the effect of anxiety on the accuracy of eyewitness testimony, and used the Yerkes Dodson law to explain this
• Weapon focus effect


  In violent crimes where a weapon is involved, anxiety may focus the witness on the weapon rather than other details of the event
• Johnson and Scott (1976) found that participants were less accurate at identifying a person when a weapon was present compared to when no weapon was present
• Pickrel (1998) found eyewitness testimony was less accurate with highly unusual conditions, suggesting weapon focus effect is due to unusualness rather than anxiety
• Christianson and Hubinette (1993) found that people who had been subjected to the greatest anxiety showed more detailed and accurate recall than onlookers, suggesting anxiety has a positive effect on recall