Tuesday, March 24, 2015

How to create a detailed false memory

Courts today rely to a large extent on eyewitness testimony, both from the person who has been accused as well as from bystanders who happened to be there at the time of the crime. Indeed, if a person confesses to a crime then he is almost certain to be convicted. All this assumes that eyewitness testimonies are generally accurate descriptions of past events, however, there are by now many many studies showing that it is easy to make people believe in things that did not happen. One of my favorite (and funny) examples is a study where participants were led to believe that they had tea with Prince Charles. However, there are also a number of not so funny examples of false memories, such as the memories that led to conviction of many innocent people on charges of child sexual abuse or ritual satanic murders or both.

In a new study published in Psychological Science the authors wanted to create false memories that were more detailed and contained multisensory details, such as smells and feelings, than in previous studies. Most people tend to have more confidence in memories where if they remember how they felt or if they remember a certain smell, than in memories that lack such details.

To instill the false memories each of the 60 participants, aged 18-31, went through three different interviews. In the interviews the naive participants were told about two different events that occurred when they were between 11-14 years old. One of the events had actually happened while the other was made up. The aim of the study was to see if the participants could be led to believe that the false event had actually happened, and to compare the memory of these false events with the memory of the events that had really happened. The false memories were far from mundane and involved criminal acts such as assault. The interviewer used a number of techniques that are common practice for inducing false memories such as…
  • Using incontrovertible evidence (“In the questionnaire, your parents/caregivers said...”)
  • Social pressure (“Most people are able to retrieve lost memories if they try hard enough”
  • Building a good relationship by asking how the students semester, nodding and smiling a lot
  • Using long pauses or asking “what else” to encourage the student to provide additional details. 
The results in this study showed that even with a very conservative measure, 44 of the 60 students had acquired a false memory of their own, serious crime, after the three interviews (in the end they were of course told that the false event had not actually happened). The criteria for saying that they had adopted the false memory included that they said they believed that it had happened and that they had provided a number of details concerning the event beyond what the interviewer had told them. With less strict criteria (e.g. just saying that they had believed that the event had occurred), 54 of the 60 student had adopted the memory. In other words, of the 60 student, only 6 appeared to be at least somewhat immune to the false memory.

Those students who adopted the false memory could provide detailed descriptions of the events such as how anxious they felt. They were also able to describe people who “had been there”, and they reported that they thought about the event outside of the interview situation. In other words, these false memories were rich in details and courts would have had no reason to doubt the validity of these memories. An important lesson from this study is therefore that we cannot trust a memory just because we think we remember the context. As a family man I am also struck by how often it happens that peoples memory contradict each other. “But I told you that you should by xxx”, or “We agreed that xxx”. Clearly, false memories arise outside the laboratory

In conclusion, once again, a study has revealed how error-prone our memory really is. Personally I try to be extremely skeptical with regards to my own memory and I try to never make any certain assertions based on “what I remember”. I think that the court system should probably tune up their skepticism towards eyewitness testimonies a few steps, unless they want to keep sending innocent people to jail.

Shaw J, & Porter S (2015). Constructing Rich False Memories of Committing Crime. Psychological science PMID: 25589599

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