Bias in Eyewitness Accounts: The Effects of Question Format, Delay Interval, and Stimulus Presentation

One of three representations of a staged automobile collision was shown to 180 students from introductory psychology classes. We then questioned the students about details of the accident, using either marked or unmarked modifiers. Half the students were questioned immediately after viewing the stimulus material and half after a 20-min delay. The results indicated that estimates of the magnitude of a number of aspects of the collision were significantly greater when unmarked modifiers were used in phrasing the relevant questions. Students who were questioned after the 20-min delay gave significantly greater estimates of monetary damage than the students who answered immediately after viewing the representation. The nature of the stimulus material had inconsistent but significant effects.