Imagination inflation can lead to false memories

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 were asked "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 the feeling of knowing and be mistaken for true. This is one reason that political or advertising claims that are not factual but are repeated can gain traction with the public, particularly if they have emotional resonance. Something you once heard that you hear 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