Aim: To investigate the effect of leading questions on eyewitness testimony (EWT)
Participants: 45 undergraduate students from the University of Washington, USA for Experiment 1; 150 participants from the same university for Experiment 2
Procedure: Two lab experiments which used an independent measures design for both Experiment 1 and Experiment 2
- Experiment 1: Participants were shown seven film clips of traffic accidents. After each film they filled in a questionnaire based on what they had witnessed about the accident – the questionnaire included several ‘filler’ questions and a critical question
- The critical question (independent variable) was: ‘About how fast were the cars going when they smashed/hit/bumped/collided/contacted each other?’ Each participant was in one of the five conditions i.e. each participant was asked only one of the critical questions containing only one of the five verbs. Participants had to estimate the speed in miles per hour
- Experiment 2: 150 participants divided into three groups of 50 each. All participants watched a one-minute film of a multiple-car accident. They then answered some questions about the film
- The critical question was, ‘How fast were the cars going when they hit/smashed each other?’ Each participant was randomly allocated to either the ‘smashed’, ‘hit’ or control condition. The control group were not asked any questions about the speed of the cars
The participants were asked to return a week later. They were asked several questions about the accident in the film. The critical question was, ‘Did you see any broken glass?’ with the response being ‘yes’ or ‘no’. There was not, in fact, any broken glass in the film
Results:
Experiment 1: Participants in the ‘smashed’ condition estimated the highest speed out of all the five conditions at 40.8 mph; participants in the ‘contacted’ condition estimated the lowest speed out of all the five conditions at 31.8 mph
Experiment 2: 43 participants in the ‘Smashed’ condition reported having seen broken glass as opposed to 7 participants reporting seeing broken glass in the ‘Hit’ condition
Conclusion: Leading questions may lead to unreliable EWT by providing information after the event
Evaluation of Loftus & Palmer (1974)
Strengths
- This research has huge implications for the ways in which EWTs should be questioned hence it has great application to the wider world
- The standardised procedure and control of variables make this study easy to replicate which increases its reliability
Weaknesses
- Watching recorded footage of a traffic accident is not the same as experiencing the event in real life so the study lacks ecological validity
- The participants might have been prone to response bias - i.e. the emotive quality of the words may have prompted the participants to think that a higher or lower speed estimate was expected of them (e.g. ‘smashed’ sounds like it should be given a high estimate)
Key terms:
- Eyewitness testimony
- Information after the event
- Response bias