Elizabeth Loftus showed subjects a videotape of a car accident. Some subjects were then asked, ‘How fast were the cars going when they smashed into each other?’, others were asked, ‘How fast were the cars going when they hit one another?’ The average speed given by the first group was 41 miles per hour and by the second 34 miles per hour. A week later subjects were asked whether they had noticed any broken glass resulting from the accident. The presence of broken glass was incorrectly reported by twice as many of the first group as of the second: the suggestion that the cars had been travelling fast had made subjects confabulate the occurrence of broken glass.
Excerpt from: Irrationality: The enemy within by Stuart Sutherland