Loftus and Palmer (1974)
Aim: To see if phrasing a question would affect estimates of speed, applying these findings to the idea of leading questions in court.
Procedure: 45 students were put into group. They had to watch a film of a traffic accident, 7 films were shown and the films lastes for 5-30 seconds. After every film the PPs had to fill in a questionnaire. First they were required to give an account of the accident, and then to answer specific questions. The critical question was the one asking about the speed of the vehicles. 9 PPs were asked 'about how fast were the cars going when they hit each other?' and equal numbers of the rest were asked the same question, but with the word 'hit' being replaced with either 'smashed', 'bumped', or contacted. The same procedure was followed for each film.
Results: 4 of the 7 films shown weres staged crashes so the speed of the cars was known by experimenters. One was 20mph, two were 30mph and the other was 40mph.
The average speed estimated, according to the words used in the question were:
Word used Mean speed estimated (MPH)