Misleading & PED

• Eyewitness testimony


  Legal term for evidence supplied by people who witness a specific event, like a crime, based on memory.
• Leading questions

  Using words to imply (sometimes wrongly) that something has happened so the witness gives a false testimony.
• Post event discussion

  Discussion after an event which causes memories to be permanently altered.
• Loftus and Palmer: Leading questions causing response bias- Aim


  To investigate how information in the form of a question, provided to a witness after an event will influence memory of that event.
• Loftus and Palmer: Leading questions causing response bias- Procedure

  An opportunity sample o 45 American students took part in a lab experiment in which there were 5 conditions (independent measures design). They were shown a film of an accident involving a number of cars and were then asked o describe the event as if they were eyewitnesses.
• Loftus and Palmer: Leading questions causing response bias- Question

  'How fast was the car travelling when it... with the other car?'

  • Hit
  • Smashed
  • Collided
  • Bumped
  • Contacted
• Loftus and Palmer: Leading questions causing response bias- Findings

  How the question was phrased influenced he participant's speed estimates.

  When the verb 'smashed' was used, participants estimated that the cars were travelling much faster than when the verb 'contacted' was used.
• Loftus and Palmer: Leading questions causing response bias- Conclusions


  Response bias: The different speed estimates occurred because the critical word influences/biases a person's response.

  OR

  Memory is altered: The critical word changes a person's memory so they actually 'see' the accident differently, i.e. more or less severe.
• Loftus and Palmer: 2nd experiment, PED and MI- Procedure

  150 student participants were shown a short film that showed a multi-vehicle car accident and then they were asked questions about it. They were split into 3 groups of 50 participants.
• Loftus and Palmer: 2nd experiment, PED and MI- Groups

  One group: How fast were the cars travelling when hey hit each other?

  Second group: How fast were the cars travelling when they smashed into each other?

  Third group: Not asked about speed of vehicles, CONTROL GROUP.
• Loftus and Palmer: 2nd experiment, PED and MI

  Purpose of the control group is to show how many people would jus t say yes.
• Loftus and Palmer: 2nd experiment, PED and MI- 1 week later

  All participants returned a week later and were asked: Did you see any broken glass?

  There was no broken glass in the video.
• Loftus and Palmer: 2nd experiment, PED and MI- Results

  Finding 1: 'Smashed' group said car was travelling faster, therefore findings in the first study are reliable.

  Finding 2: More likely to think they had seen broken glass in the smashed condition (16 people said they saw glass in 'smashed' condition compared to 6 in control and 7 in 'hit' group).
• Loftus and Palmer: 2nd experiment, PED and MI- Conclusion

  We are affected by leading questions. The way a question is asked/worded can alter an event. This suggests it isn't jus response bias, you can actually alter someone's memory.
• Gabbert et al (2003): PED and false memories- Procedure

  Participants watched a video of a girl stealing money from a wallet. They were then allocated to two conditions: a control group (alone), and an experimental group (tested in pairs- co-witness). The co-witness group were told that they all watched the same video but they actually saw different perspectives of the same crime. Only one person in the pair saw the crime actually happen. The ppts in the co-witness group then discussed the crime together. All ppts were completed a questionnaire to test their memory of the event.
• Gabbert et al (2003): PED and false memories- Findings

  71% of witnesses recalled events/ information they hadn't seen in the co-witness group.

  60% said that the girl was guilty despite the fact that they didn't see her commit a crime.
• Gabbert et al (2003): PED and false memories- Conclusion

  These results highlight the issue of post event discussion and the powerful effect this can have on the accuracy of eyewitness testimony.