Just asking if someone experienced a fictitious event can create false memory of it.
It seems that merely being asked about something can, in some cases, lead to memories of having experienced that thing.
Psychologists Miriam Lommen and colleagues studied 249 Dutch soldiers were deployed for a four month tour of duty in Afghanistan. As part of a study into PTSD, they were given an interview at the end of the deployment asking them about their exposure to various stressful events that had occurred. However, one of the things discussed was made up – a missile attack on their base on New Year’s Eve.
Eight of the soldiers reported remembering this event right there in the interview. The other 241 correctly said they didn’t recall it, but seven months later, when they did a follow-up questionnaire about their experiences in the field, 26% said they did remember the non-existent New Year’s Eve bombardment (this question had been added to an existing PTSD scale.)
Susceptibility to the misinformation was correlated with having a lower IQ, and with PTSD symptom severity.