Loftus & Palmer (1974)

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  • Loftus & Palmer (1974)
    • Aim:
      • to investigate whether leading questions influence estimates of speed of a vehicle recalled by eyewitnesses
    • Experiment 1 Procedure:
      • 45 participants shown 7 video clips of different car accidents and asked to judge the speed of the car
      • participants given questionnaire on account of what they'd witnessed, and included one critical question
      • 5 groups of 9: each group had a different critical question "how fast were the cars going when they _ each other?"
        • the verb was either "hit", "smashed", "collided", "bumped" or "contacted"
    • Results (1)
      • smashed gave the highest estimate at 40.8 and contacted gave the lowest at 31.8
    • Conclusion (1)
      • these results could be due to verb altering participants memory, or participants didn't know the answer so relied on the verb to make a judgement
        • to test this, they devised a second experiment. if the verb did alter witness memory it could also alter other details
    • Experiment 2 Procedure
      • 150 participants shown a one minute clip of a multiple car collision
      • they were then asked to give a description of the film and answer a questionnaire which contained one critical question
      • 3 groups of 50: "how fast were the cars going when they smashed/hit each other?" + a control group with no critical question
      • after 1 week the participants returned to answer 10 questions; the main one being "did you see any broken glass?" there was no broken glass in the clip
    • Results (2)
      • smashed condition: 16 yes, 34 no
      • hit condition: 7 yes, 43 no
      • control condition: 6 yes, 44 no
      • this demonstrates the verb did have an effect on recall. leading questions imply a specific response and may alter witness memory of an incident
    • Evaluation
      • critical questions were randomly hidden so participants couldn't guess the aim and display demand characteristics
      • effect confirmed by other studies - Loftus & Zanni: "the" had stronger influence than "a" when asking "did you see _ broken headlight?"
      • has useful applications: police know to avoid leading questions when interviewing. justice system knows witnesses shouldn't be relied upon without corroborating evidence
      • study was conducted in a lab setting so it lacks ecological validity, and thus may not be able to be applied to real life witnesses
      • real witnesses wouldn't be prepared for the incident or recall, these participants were so they could really focus on the films
      • no real consequences for the decision-making of these participants. real witnesses would be more considered in their answers because they may influence decisions

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