The Misinformation Effect

Memory is often imagined as a recording that can be played back unchanged. A pair of experiments published in 1974 by the psychologists Elizabeth Loftus and John Palmer challenged that picture.

In the first, university students watched short films of traffic accidents and then answered questions about them. The key question asked how fast the cars had been going when they "hit" each other. For different groups, however, the verb was replaced with "smashed," "collided," "bumped," or "contacted." The films were the same for everyone, yet the estimates were not. Participants who heard "smashed" gave the highest speeds, and those who heard "contacted" gave the lowest, roughly nine miles per hour slower.

A skeptic could explain this result without any change to memory. Uncertain of the speed, participants may simply have taken a hint from the wording when choosing a number. The second experiment was designed with that objection in mind. New participants watched a film and were divided into three groups. The first was asked the speed question with "smashed," the second with "hit," and the third was not asked about speed at all. A week later, all three groups returned and were asked whether they had seen any broken glass. The film contained none. Yet participants who had heard "smashed" reported glass more than twice as often as those who had heard "hit."

Loftus went on to study this phenomenon for decades, and it became known as the misinformation effect. Information that arrives after an event can be absorbed into the memory of the event itself.