Another explanation for some Mandelas (although probably not the above one) is simply in The Power of Suggetion.
By this I mean that it is very easy to implant an image in someone's mind, merely by suggesting it. (Stop thinking about bananas!)
An example of this comes from this thread. Someone above mentioned that they remembered victorious football teams forming human pyramids when presented with a cup. Now I am not at all a football fan and couldn't be expected to know about such things - but as soon as I read about it up popped an image in my mind of footballers (in those longer shorts they used to wear) forming human pyramids and brandishing a cup. And, yet, apparently this never happened. In my case it wasn't a memory - just a plausible image that had been suggested to me.
Another one. The supposed Mandela about the `lost` picture of Henry VIII brandishing a haunch of venison or chicken leg or whatever. I used to be adamant that I was one of the people that `remembered` that (nonexistent) portrait. And yet I'm now beginning to wonder if I really do. It might have been the case that the idea was suggested to me - and the image being one which fits what we know about that King -my mind duly supplied an image of it.
So it would go like this:
(a) Someone (with a deluded memory) says: `Do you remember when...`.
(b) The other person doesn't, but what the speaker says sounds plausible, so a suitable image is duly supplied in the listeners mind.
(c) This image then gets misattributed to being a `memory`.
(d) And lo! - a Mandela is born! Someone has an apparent `memory` of something which didn't really happen or exist.
(e) Convinced of it, they then go and tell other people about this `memory` - some of whom then have the `memory` likewise implanted in them...and so on it goes.
The psychologist Elizabeth Loftus' famous 'meeting Bugs Bunny at Disneyland' experiment was about that. A minority of participants were successfully induced to 'remember' this impossible event with a little coaxing.
One of Ghislaine Maxwell's attempts at a defence was that her victims had false memories. In this cause she engaged Loftus, whom the journalist John Sweeney called the 'professor of Bugs Bunnyology'.
Sweeney points out that 1. A majority did not believe they'd seen Bugs Bunny at Disneyland and 2. In Loftus' follow-up study her attempts to give participants an unpleasant memory were unsuccessful.
Loftus' research, if it proved anything, appeared to show that how likely people are to falsely remember an incident or image depends on several factors, including how pleasant or important the 'memory' is. Happy though trivial memories of Disneyland can be interfered with whereas traumatic ones are more reliable.
So the false human pyramid and Henry VIII memories stick because they are of relatively unimportant images. Nobody remembers the human pyramid toppling over and causing horrific injuries or a Henry VIII portrait featuring him holding aloft the freshly-severed head of Anne Boleyn.
