New research into human memory shows that it's possible to implant vivid false memories of autobiographical events and then reverse them without damaging a person's memory of true events.

In a study published Monday in Proceedings of the National Academy of Sciences, researchers first implanted false memories in 52 participants over the course of three interviews using suggestive techniques. The interviewers, who were blind to the design of the study, suggested two true and two false events from the participants' childhood, such as getting lost or being involved in a car accident. To make the false memories more plausible, false events were created by the participants' parents. 

The number of participants who believed in false events changed with the amount of suggestion from interviewers. In minimally suggestive conditions, interviewers informed participants that their parents had told the researchers about the events — whether they were true or false. This condition led 27% of people in the study to believe in false events. For massive suggestion, interviewers also verbally reinforced the participants, used guided imagery, and claimed to have a detailed report from parents when participants were suspicious. Under these conditions, 56% of participants believed in events that were completely fabricated. 

Aileen Oeberst, lead author of the study and head of the Department of Media Psychology at the University of Hagen, told The Academic Times that, "Many participants were surprised and shocked" to see how easily they accepted false events as true. The belief in false memories was high compared to previous research, Oeberst noted, likely due to false events that were feasible — earlier studies, for instance, had suggested the memory of a pet dying when the participant never had a pet.

After the initial interviews, two processes were used to reverse false memories. The first is source sensitization, which reminds participants that memories may not always be based on people's own experience but also on other sources, including photographs. The second is false memory sensitization, which raises the possibility of false memories being created in the interview or study itself. 

Unlike previous studies, the two techniques are designed to be used in an everyday setting. The reversal process is "ecologically valid in the sense that it can principally be implemented in the real world," Oeberst said.

Both techniques were successful, as researchers returned the rate of false memories to baseline levels after the three-week trial (at a rate of 15% and 20% for the two suggestion conditions). After one year, only 5% of participants still believed in false memories. They were either consciously aware that the event wasn't true, or had no memory of the false event. Oeberst noted that the low percentage of false memories after one year is likely due to the time participants had to discuss events with their parents.

False memories are relatively easy to suggest and unable to detect, which can be a dangerous combination in the functioning of the legal system. Suggestive interviewing in a courtroom or police station can lead an eyewitness to give a false accusation and directly impact the lives of others. "In forensic settings in particular, this poses a challenge because people may falsely remember events with legal implications that never actually happened," Oeberst said.

False narratives can also occur in a clinical context. A therapist or counselor may suggest that a patient's situation is due to a false event in the past, and that repressing one's thoughts is very common in a clinical setting. Oeberst emphasized that, "You should be careful about what you think you remember and what other people tell you," especially when there is no hard evidence for these events.

Relatedly, in popular culture, Oeberst said that, "In the media, repression is nourished in stories, films, and even documentaries." This widespread idea of repressed memories is based on appealing to people's emotions, not on research, she said. Since popular media has a huge impact on society, this depiction of repression "provides a risk because it makes people susceptible to false memories" on a larger scale. Oeberst has a background in media biases, and her previous research is based on how society constructs collaborative knowledge.

The researchers noted that this study was relatively brief, with an initial process of three weeks and a follow-up interview after one year. In future research, Oeberst wants to "develop a novel way to track false memories, as there is no technique to detect false events" in the brain today. As false memories are so similar to true ones, they can't be pinpointed unless they were implanted in a study environment.

This research provides "hope in principle that you can reverse false memories in eyewitnesses, even if there's an influence in the past," Oeberst said, though further research is needed to minimize false memories during interviews and legal investigations.

The study, "Rich false memories of autobiographical events can be reversed," published March 22 in Proceedings of the National Academy of Sciences, was authored by Aileen Oeberst, University of Hagen and Leibniz-Institut für Wissensmedien; Merle Madita Wachendörfer, Leibniz-Institut für Wissensmedien; Roland Imhoff, Johannes Gutenberg Universität Mainz; and Hartmut Blank, University of Portsmouth.