Loftus and Palmer 1974

Loftus and Palmer 1974

1. Aim

   • To investigate how information supplied after an event, influences a witness's memory for that event.

2. Method

   • Two laboratory experiments/ both examples of independent measures design
     • IV - The verb used DV -Participants speed estimate
     • IV - The verb used DV -If they saw glass or not

3. First Experiment

   • 45 students of the University of Washington.
     • Each shown seven film-clips of traffic accidents
       • Ranged from 5 to 30 seconds long.
         • students were asked to write an account of the accident they had just seen
   • 5 Conditions
     • Bumped
       • 38.1
     • Hit
       • 34.0
     • Collided
       • 39.3
     • Smashed
       • 40.8
     • Contacted
       • 31.8
   • Explanations
     • Results could be due to a distortion in the memory of the participant. The memory of how fast the cars were travelling could have been distorted by the verbal label which had been used to characterise the intensity of the crash.
     • Results could be due to response-bias factors, in which case the participant is not sure of the exact speed and therefore adjusts his or her estimate to fit in with the expectations of the questioner.

4. Second Experiment

   • To provide additional insights into the origin of the different speed estimates.
   • 150 student participants viewed a short (one minute) film which contained a 4 second scene of a multiple car accident, and were then questioned about it.
     • 3 conditions (IV)
       • Hit
         • Yes: 7 Hit: 43
       • Smashed
         • Yes:16 No:34
       • Not interrogated
         • Yes: 6 No:44
     • One week later, the participants returned and, without viewing the film again, they answered a series of questions about the accident. The critical question was 'Did you see any broken glass?' (There wasn't any)
   • Explanations
     • They argue that two kinds of information go into a person's memory of an event.
       • The first is the information obtained from perceiving an event (e.g. witnessing a video of a car accident),
       • The second is the other information supplied to us after the event (e.g. the question containing hit or smashed).

5. Evaluation

   • Strengths
     • Experiments allow for precise control of variables.
       • Control is intended to allow us to conclude that it is the IV, and nothing else, which is influencing the DV.
         • For example the researchers were able to control the age of the participants, the use of video and the location of the experiment.
   • Limitations
     • The experiment was not typical of real life situations. The experiments carried out by Loftus are artificial in the sense that they are different from how people would normally witness events.
       • For example, when the participants were giving their estimates of speed, they did not have any personal involvement in the judgement and had not taken part in the event.
     • Use of students as participants.
       • Students are not representative of the general population