Do you remember when…?

According to a new Israeli-British study, what you remember could depend on peer pressure.

Micah Edelson, a PhD student, and Professor Yadin Dudai at the Weizmann Institute of Science together with scientists from University College London found that comparing memories with other people sometimes changes the stored memory in the brain.

The study, which recently appeared in the journal Science, reveals a unique pattern of brain activity when false memories are formed – one that hints at a connection between our social selves and memory.

Edelson divided volunteers into small groups to watch a TV documentary. Three days later, he individually tested their memories about the program with a questionnaire. They were also asked how confident they were in their answers.

The study’s participants were tested again four days later. This time, they were shown fabricated information for some questions, and were told that all the other members of their group had come up with an answer contradicting their own.

The study showed that 70 percent of the time the subjects changed their answers to fit with the majority.
The researchers wanted to understand if the participants were simply conforming to perceived social demands, or had their memory of the film actually undergone a change?

To find out, the scientists invited the subjects back to the lab to take the memory test once again, telling them that the answers they had previously been fed were not those of their fellow film watchers, but random computer generations. Some of the responses reverted back to the original, correct ones, but close to half remained erroneous, implying that the subjects were relying on false memories implanted in the earlier session.

An analysis of the fMRI data showed differences in brain activity between the persistent false memories and the temporary errors of social compliance.
The scans showed that the amygdala and hippocampus areas of the brains were more active in those who believed false memories over time. The hippocampus affects memory, Edelson said, while the amygdala “probably plays a critical role because it is perfectly situated . . . to mediate between the brain’s emotional-social and memory processing systems.”

The scientists said their research could affect legal cases where eyewitnesses to an event talk to one another about what happened, and through peer pressure a false event is remembered.