When I was very young, perhaps around 4, I had a nightmare. In this dream, I would be in a room, and the floor would tilt a little bit and bubbles would start seeping in at the base of the wall. I'm not sure why this was dangerous, but it clearly was. It was something that had happened before, too. When I woke up, I knew that the bubbles had been a dream, but I still believed that it was a dream about something that had really happened before. It took me a long time (months or years) to convince myself that the bubbles were only a dream, and not even a dream I had had more than once.
Until recently, I hadn't often (as best I can recall) had dreams that implanted false memories like that, but lately, I have them all the time. I will dream of something, let's say smurfs, and wake up thinking, "God, I have dreamed of smurfs every day this week! What the hell is with the smurfs!" And then I'll think, "Shit, is this one of those dream memories?" And sooner or later I will realize it is.
Sometimes it has stages. I'll wake up being annoyed that I've dreamt about a smurf revolution all week, then realize almost immediately that, although I've been dreaming about smurfs all week, the revolution part is new, and then realize hours later that I hadn't been dreaming about smurfs at all, up until that point.
Sometimes the dream memories aren't about dreaming. Last night in bed I realized that all week, or all month, or something like that, I had been thinking and fantasizing (while awake) about something like foursquare (the playground game, not the iPhone app). And then I slowly started to question that and to realize that I hadn't even been thinking about that while awake at all, much less more than once. I only dreamed that I was, and had been, doing such a thing.
I'm starting to find the frequency of this experience disturbing. I think it happens several times a week. (And I'm pretty certain that that is not itself a false memory; I clearly remember thinking about this while awake many times over the past year or so.) I like dreaming, but I don't like waking up believing things that are not true. Is this common?