AND THE ANSWER IS:
From an interview
Anelli, Melissa and Emerson Spartz. "The Leaky Cauldron and MuggleNet interview Joanne Kathleen Rowling: Part Three," The Leaky Cauldron, 16 July 2005
EDINBURGH, SCOTLAND
MA: One of our Leaky “Ask Jo” poll winners is theotherhermit, she's 50 and lives in a small town in the eastern US. I think this was addressed in the sixth book, but, “Do the memories stored in a Pensieve reflect reality or the views of the person they belong to?”
JKR: It’s reality. It’s important that I have got that across, because Slughorn gave Dumbledore this pathetic cut-and-paste memory. He didn't want to give the real thing, and he very obviously patched it up and cobbled it together. So, what you remember is accurate in the Pensieve.
ES: I was dead wrong about that.
JKR: Really?
ES: I thought for sure that it was your interpretation of it. It didn’t make sense to me to be able to examine your own thoughts from a third-person perspective. It almost feels like you'd be cheating because you'd always be able to look at things from someone else's point of view.
MA: So there are things in there that you haven't noticed personally, but you can go and see yourself?
JKR: Yes, and that's the magic of the Pensieve, that's what brings it alive.
-----------------------------------
So Athena's theory was quite correct