I'm sure its not just me that's very occasionally woken up with not even the impression that you've had a dream that night? Now, I'm not very clever so I hope this makes sense - and maybe its been gone over before - I know that we all have three or so REM cycles every night so that means that even if we don't recall anything we did have dreams.... Could it be that the reason we sometimes have no recall is because the 'dreams' weren't dreams as such but just random images/sounds/junk with no story or narrative etc to bind it all together and therefore there is literally nothing to remember because at best we would only have had split second moments of worthwhile dreams if at all.

I'm sorry if this doesn't make sense, I've been mulling it over he last few days and am finding it hard to put into words, hopefully someone gets it!