False memories are fairly easy to plant in many people. It's possible to plant them just by repeatedly asking someone about something that didn't happen:

https://faculty.washington.edu/eloftus/Articles/sciam.htm

Also this:

> “Our findings show that false memories of committing crime with police contact can be surprisingly easy to generate, and can have all the same kinds of complex details as real memories,” says psychological scientist and lead researcher Julia Shaw of the University of Bedfordshire in the UK.

> “All participants need to generate a richly detailed false memory is 3 hours in a friendly interview environment, where the interviewer introduces a few wrong details and uses poor memory-retrieval techniques.”

http://www.psychologicalscience.org/index.php/news/releases/...