Some witnesses to crimes who are struggling to recall them are instructed to let their minds roam freely, to generate whatever comes to mind, even if it is a guess. However, the act of guessing about possible events causes people to provide their own misinformation, which, if left uncorrected, they may later come to retrieve as memories.
Suppose the police interview a witness shortly after a crime, showing pictures of possible suspects. Time passes, but eventually the police nab a suspect, one whose picture has been viewed by the witness. If the witness is now asked to view a lineup, he may mistakenly remember one of the suspects whose photo he saw as having been present at the crime.
We cannot remember every aspect of an event, so we remember those elements that have the greatest emotional significance for us, and we fill in the gaps with details of our own that are consistent with our narrative but maybe wrong.
Imagination inflation refers to the tendency of people who, when asked to imagine an event vividly, will sometimes begin to believe, when asked about it later, that the event actually occurred. Adults who ask "Did you ever break a window with your hand?" Were more likely on a later life inventory to report that they believe this event occurred during their lifetimes. It seems that asking the question led them to imagine the event, and the act of having imagined it had the effect, later, of making them more likely to think it had occurred (relative to other group answer the question not having previously imagined it occurring).
Accounts that sound familiar can create a feeling the feeling of knowing and be mistaken for true. This is one reason that political or advertising claims that are not factual but repeated can gain traction with the public, particularly if they have emotional resonance. Something you once heard that you hurt again heard it again later carries a warmth of familiarity that can be mistaken for memory, a shred of something you once knew and cannot quite place but are inclined to believe. In the world propaganda, this is called "the big lie" technique-even a big lie told repeatedly can come to be accepted as truth.
Peter C. Brown and Henry L. Roediger III, Make It Stick: The Science of Successful Learning