Psychologists implant false beliefs to understand how human memory fails

A recent study published in Applied Cognitive Psychology provides evidence that the types of false memories people form depend on how believable an event is and how often they are told it occurred. The findings suggest that highly plausible events are much more likely to generate false beliefs, but only when people are led to believe the event happened just once. These insights help clarify how suggestion can distort human memory in everyday situations and legal settings.

To understand the new study, it helps to distinguish between false beliefs and false memories. A false belief occurs when a person is confident that a specific event happened to them, even if they cannot visualize it. A false memory goes a step further and involves vivid, sensory details of an event that never actually took place, making it feel like a genuine recollection.

While memory is generally reliable, it is not perfect. It is reconstructive, meaning it tends to be malleable and prone to errors. When people are exposed to suggestive questions or misleading information, they can sometimes adopt false beliefs or false memories.

The new study was authored by Mara Georgiana Moldoveanu of Maastricht University, Babeș-Bolyai University and KU Leuven; Ahmad Shahvaroughi of KU Leuven; Ivan Mangiulli of KU Leuven and the University of Bari Aldo Moro; Javad Hatami of the University of Tehran; and Henry Otgaar of Maastricht University and KU Leuven.

The researchers sought to address a specific gap in memory research regarding event frequency. Past work suggested that telling someone an event happened repeatedly did not significantly change their likelihood of forming a false memory compared to telling them it happened only once. But no previous study had looked at how this suggested frequency interacts with the plausibility of the event itself.

Understanding this interaction has practical importance for legal and therapeutic environments. In real life, witnesses or victims are sometimes suggestively interviewed about repeated past abuses or highly implausible situations, such as ritualistic events. The researchers wanted to see if false memories for repeated or unlikely events could be reliably generated in a laboratory setting to better understand these real-world scenarios.

“Suggestion-based false beliefs and memories elicited are not just lab curiosities; real-world cases of false accusations or wrongful convictions sometimes involve suggestive therapy or interviews in which single, but also repeated abuse is sometimes suggested,” the researchers told PsyPost.

“So far, we are still investigating whether false memories for repeated events can be reliably elicited in the laboratory. Abuse reports may also involve less plausible events, such as satanic rituals. Such real-life cases ultimately represent the actual inspiration for this study and line of research, which is really aimed to be practically relevant besides interesting.”

To explore this, the researchers used a technique known as a blind implantation paradigm. In one of the typical memory paradigms, scientists often had to contact a participant’s parents to verify childhood events. The blind implantation method avoids this by relying entirely on the individual’s own initial answers to establish a baseline of what they believe to be true or false.

Initially, 855 participants from Western Europe, Romania, and Iran completed an online survey. In this first survey, participants read a list of 20 childhood events and indicated whether they had experienced them. Two of these items were critical events designed for the experiment.

One was a high-plausibility event, which was losing a toy as a child. The other was a low-plausibility event, which was almost drowning in the ocean. The scientists filtered the group to find people who stated they had never experienced the two critical events.

One week later, 103 of these eligible participants completed a follow-up survey. This final sample had an average age of 33.7 years, and 62.1 percent identified as women. In the second phase, the researchers presented each participant with a personalized list of five events.

Four were true events the participant had actually experienced, and one was the false critical event they had previously denied experiencing. The participants were randomly assigned to different groups where the false event was either highly plausible or less plausible.

Additionally, the researchers altered the suggested frequency of the false event. They told some participants the event happened once, while they told others it happened repeatedly during their childhood.

The final breakdown included 25 people in the highly plausible single group, 26 in the highly plausible repeated group, 30 in the low plausible single group, and 22 in the low plausible repeated group. The scientists asked the participants to rate their belief that the event occurred and their actual recollection of the event on an eight-point scale.

Next, the researchers instructed the participants to vividly imagine the event. The participants were asked to visualize the details, such as where it took place and who was there, and write down their thoughts. After this imagination exercise, the participants rated their belief and recollection a second time.

The data revealed a distinct interaction between event plausibility and suggested frequency for false beliefs. When the scientists suggested the event happened only once, the highly plausible event generated much higher false belief ratings than the low-plausibility event. Up to 52 percent of people in the highly plausible, single-occurrence group developed a false belief.

In comparison, only 10 percent of those in the low-plausibility, single-occurrence group formed a false belief. This suggests that plausibility plays a major role in shaping beliefs when an event is presented as an isolated incident. This difference vanished when the researchers suggested the event happened repeatedly.

In the repeated conditions, the plausibility of the event did not have a statistically significant effect on how strongly people believed it happened. The rate of false belief was 38.5 percent for the highly plausible repeated group and 22.7 percent for the low-plausibility repeated group. The lowest rate of false belief, at 9.1 percent, appeared before the imagination exercise in the group given the low-plausibility event that supposedly happened repeatedly.

The researchers suspect this interaction might relate to script theory, which involves a person’s general knowledge of how typical events unfold. When an event is described as happening repeatedly, it might activate existing knowledge about routine events, making it feel familiar regardless of its actual plausibility. On the other hand, if a person lacks vivid memories of a supposedly repeated event, they might reject the suggestion entirely.

When looking at false memories, which require actual sensory recollection, the overall rates were lower than those of false beliefs. Before the imagination exercise, false memory ratings did not differ significantly based on the plausibility of the event or the suggested frequency. False memory rates hovered between 9.1 percent and 16 percent across the different experimental groups.

After the participants were asked to imagine the event, an interaction emerged, but neither plausibility nor frequency alone showed a strong, independent effect on forming detailed false memories. These findings provide evidence that false beliefs are easier to implant when an event seems likely and is framed as an isolated incident.

The results highlight “that memory is not a recording video camera; it is generally reliable, but also malleable and prone to errors such as false beliefs (confidence that an event happened) and memories (vivid details that feel real),” the researchers said. “These could have real consequences in everyday life, but more so in legal contexts.”

“That does not mean we should distrust our memory and memories! It just means we have to consider context (e.g., suggestive questions) and factors such as event plausibility or suggested frequency when evaluating our memories, especially in court settings.”

“This study is a single investigation of the (interactive) effects of plausibility and suggested frequency on false beliefs and false memories,” the researchers added. “Are the obtained effects large enough for clear field implications? In false memory research, even a single detail change in testimony, such as believing the suspect had a red car, can have practical consequences, such as starting a criminal investigation.”

“We found practically relevant effects (e.g., for plausibility), but this meets only one criterion for field use, such as expert witness reports; generalizability (across ages, paradigms) and replicability (direct repeats) are still needed for confidence. Thus, the study advances the field, but requires cumulative evidence.”

As with any study, there are a few limitations to consider with this research. The final sample size of 103 participants was smaller than the researchers originally planned, which means the study might not have had enough statistical power to detect smaller effects. Some participants might also have genuinely experienced the critical events but forgotten them during the first survey, meaning they reported a true recovered memory rather than a newly implanted false one.

Future research will need to replicate these findings with larger groups to ensure they apply broadly across different populations. The scientists also plan to use events where the absolute truth is known to better separate false memories from forgotten true memories. Identifying the boundary conditions of false memory formation remains an ongoing project that requires cumulative evidence before being firmly applied in courtroom settings.

“This line of research is part of a broader scientific community studying false memories,” the researchers explained. “The main goals are to identify factors that influence false belief and false memory formation, and to develop ways to reduce false beliefs and memories and their potentially harmful consequences.”

“Another important aspect of this work is determining when the findings can be confidently applied in real-world settings, for example, in the courtroom. This specific project is also connected to research on self-deception, which may represent a form of motivated false belief. Several labs and researchers are investigating these timely topics.”

“For our work and that of our colleagues, you can visit our publications page here: https://celleuven.wixsite.com/home/publications. You might also want to explore research from groups at universities such as the University of Chicago, Cornell University, University College Dublin, Amsterdam University, etc., that are doing work on (false) memory and belief.”

The study, “The Effect of Plausibility and Suggested Event Frequency on the Implantation of False Beliefs and Memories,” was authored by Mara Georgiana Moldoveanu, Ahmad Shahvaroughi, Ivan Mangiulli, Javad Hatami, and Henry Otgaar.