Every memory is a shabby reconstruction.
Think back to an event in your past. A birthday, a night out, a chance meeting. Bring back that memory. It may seem to you that the memory comes to you whole, but it doesn’t. It is merely a flawed reconstruction.
Every time we dredge up a memory we are actually putting it together again like a jigsaw. Some of the pieces are objectively accurate parts from the scene, but much of it is filler. We remember the gist, but most of the details are just made up to fill in the blanks.
And what we use to fill in the blanks is a schema for the situation – a mental representation of what we would typically expect in such a context.
Brewer and Treyens, in 1981, asked students to wait in a particular room for a few minutes before calling them through to take part in an experiment. The room appeared to be a fairly typical office, and the participants were asked afterwards to recall as much as they could about it. They did not know they were going to have to recall what was in the room, so they hadn’t made any effort to memorise it. However, it was clearly an office and so their “office schema” helped them out by telling them what was probably in there. They therefore “remembered” (actually believing they had seen them) items one would find in an average office, even though they had not been present in this case.
When you reconstruct a memory (which is every time you bring something from the past to mind), you are unaware of fact that you are filling in the blanks. The danger is that something which is added may well become a permanent fixture in your memory, and you have no way of knowing that it was never really there.