Researchers show how memories can be deliberately manipulated, even if they are stored securely
The human memory is fragile. This has both positive and negative side effects. Schoolchildren know that regular repetition is necessary for lasting retention; researchers speak of reactivation. Psychologists have recognized that constant mental reliving of a traumatic experience does not diminish it. On the contrary: the memory stabilizes. Criminologists are aware of the danger that the way a detail is recalled can influence its content.
However, researchers were not aware of how easily memory can be manipulated. In an article published in the u.S. Academy of sciences (pnas), psychologists jason chan and jessica lapaglia of iowa state university now show that memories can be altered whether they initially appear stable or unstable. The scientists first played their subjects an episode of the thriller series "24" .
They then tested some of the study participants on what they had remembered with the help of a quiz consisting of 24 items. The other part of the test persons was allowed to play tetris during this time. Shortly afterwards, the psychologists played an alleged montage of the "24" story from the tape to all the participants. In it, the researchers had omitted eight facts. Eight more facts were changed (for example, the terrorist now used a stun gun instead of a stun gun), while the remaining eight details were correctly reproduced.
Again, the subjects were now given some time before the psychologists checked their memories of the film. The interesting result: when the memory contents had first been reactivated with the first quiz, the test participants remembered the actual details significantly worse after the manipulation than when they had not had to check their knowledge. This was true both for the well-remembered information and for the almost forgotten items. The memory is apparently particularly sensitive during the repetition phase. According to the researchers, this fact had to be taken into account when interviewing witnesses.
First remembering the truth, then telling the lie
The researchers tested the direct temporal relationship in another experiment in which they allowed two days instead of a few minutes to pass between repetition and manipulation. In this case, the manipulation did not prove successful, as expected. However, when the researchers placed the long pause between the learning and repetition phases, which was then quickly followed by the manipulation, the losch effect of the new information reestablished itself.
What content must the manipulation have? The researchers also checked this in the experiment. It turned out that it is not enough to make the repetition phase non-specific. The stimuli must be specific to the information to be repeated. The memory manipulation also proved to be stable, as was shown in a final experiment in which the researchers placed longer time intervals between the individual phases.
To plant a false memory in the mind of the boss or the life stage traveler is nevertheless problematic. Because it is not enough to simply give a new version of the story: you must first remind the person of the truth, and then tell him the lie shortly afterwards. The researchers’ subjects accepted this without grumbling; in real life it was allowed to be more difficult.