The idea that memories are not as reliable as we think they are is disconcerting, but it's pretty well-established. Various studies have shown that participants can be persuaded to create false childhood memories—of being lost in a shopping mall or hospitalized, or even highly implausible scenarios like having tea with Prince Charles.

The creation of false memories has obvious implications for the legal system, as it gives us reasons to distrust both eyewitness accounts and confessions. It’s therefore important to know exactly what kinds of false memories can be created, what influences the creation of a false memory, and whether false recollections can be distinguished from real ones.

A recent paper in Psychological Science found that 71 percent of participants exposed to certain interview techniques developed false memories of having committed a crime as a teenager. In reality, none of these people had experienced contact with the police during the age bracket in question.

After establishing a pool of potential participants, the researchers sent out questionnaires to the caregivers of these individuals. They eliminated any participants who had been involved in some way with an assault or theft, or had other police contact between the ages of 11 and 14. They also asked the caregivers to describe in detail a highly emotional event that the participant had experienced at this age. The caregivers were asked not to discuss the content of the questionnaire with the participants.

The 60 eligible participants were divided into two groups: one that would be given false memories of committing an assault, theft, or assault with a weapon, and another that would be provided with false memories of another emotional event—an injury, an attack by a dog, or the loss of a large sum of money. In the first of three interviews with each participant, the interviewer presented the true memory that had been provided by the caregiver. Once the interviewer’s credibility and knowledge of the participant’s background had been established, the false memory was presented.

For both kinds of memory, the interviewer gave the participant “cues”, such as their age at the time, people who had been involved, and the time of year. Participants were then asked to recall the details of what had happened. No participants recalled the false event the first time it was mentioned—which would have rung alarm bells—but were reassured that people could often uncover memories like these through effort.

A number of tactics were used to induce the false memory. Social pressure was applied to encourage recall of details, the interviewer attempted to build a rapport with the participants, and the participants were told that their caregivers had corroborated the facts. They were also encouraged to use visualization techniques to “uncover” the memory.

In each of the three interviews, participants were asked to provide as many details as they could for both events. After the final interview, they were informed that the second memory was false, and asked whether they had really believed the events had occurred. They were also asked to rate how surprised they were to find out that it was false. Only participants who answered that they had genuinely believed the false memory, and who could give more than ten details of the event, were classified as having a true false memory. Of the participants in the group with criminal false stories, 71 percent developed a "true" false memory. The group with non-criminal false stories was not significantly different, with 77 percent of participants classified as having a false memory. The details participants provided for their false memories did not differ significantly in either quality or quantity from their true memories.

This study is only a beginning, and there is still a great deal of work to be done. There are a number of factors that couldn’t be controlled for but which may have influenced the results. For instance, the researchers suggest that, since only one interviewer was involved, her individual characteristics may have influenced the results, raising the question of whether only certain kinds of interviewers can achieve these effects. It isn’t clear whether participants were fully honest about having believed in the false memory, since they could have just been trying to cooperate; the results could also have been affected by the fact that there were no negative consequences to telling the false story.

This study also did not distinguish which of the persuasion tactics actually had an effect, since the only goal was to establish that the creation of criminal false memories was possible. Controlling for different techniques to see which are responsible for creating the memories will be important work.

Finally, not mentioned by the researchers is the question of the age at which the false memory is said to have occurred. People may be inclined to develop false memories of events during childhood or adolescence because of a folk-psychology belief that our memories of growing up can be faulty. Alternatively, they may be inclined to develop a false memory of events long ago that they may have forgotten, but less likely to do so for a more recent event. These factors may determine the extent to which these findings are important for the legal system.

Psychological Science, 2015. DOI: 10.1177/0956797614562862 (About DOIs).