Accuracy of eyewitness testimony

• Reasons for psychologists interest in eye witness testimony

  It involves accuracy of memory. Encoding, schemas, storage and recall
• Loftus and Palmer (1974) 


  Aim - To discover if different questions affect memory
• Loftus and Palmer procedure

  45 students shown 7 films of different tragic accidents

  After each film given questionnaire to describe accident

  One critical question - About how fast were the cars going when they hit eachother
• Loftus and Palmer procedure

  One group given the critical question

  Other 4 groups given the verbs:

  Smashed, collided, bumped, contacted
• Second experiment

  To test if leading questions may bias a participants response or cause information to be altered before it is stored
• Second experiment procedure

  New PP’s divided into 3 groups

  Shown film of car accident

  Asked about speed of car

  Asked to return a week later and given 10 questions involving a critical question
• Second experiment critical question

  Did you see any broken glass?
• Implications of post event discussion?

  Memories can be altered or contaminated by discussing events with others
• Fiona Gabbert (2003)

  71% of witnesses who participated in discussion mistakenly recalled the event
• Conformity effect of post event discussion

  Co witnesses may reach consensus of what happened
• Negative effects of anxiety

  Physiological arousal preventing concentration
• Positive effects of anxiety

  Fight or flight response triggered increasing alertness
• Johnson and Scott (1976)


  Low anxiety condition - heard casual conversation, man walks past with pen and greasy hands

  High anxiety condition - heard heated argument, man walks past with bloody knife
• Findings of Johnson and Scott (1976) 


  From 50 photos

  49% in low anxiety able to pick correct man

  33% in high anxiety able to pick correct man
• Yuitle and Cutshall (1986) 


  Study of real shooting in gun shop

  Interviewed 4-5 months after shooting, compared with police interview at time

  Asked about stress at time on scale of 1-7
• Findings of Yuitle and Cutshall (1986)

  Witnesses accurate in accounts, not much changed within 4-5 months

  Participants with high levels of stress 88% accurate compared to 75%

  Anxiety does not have detrimental effect

  There is an optimal level of anxiety (Yerkes Dodson effect)