How reliable are pensieve memories?

[zgirnius]

No: HPFGUIDX 157943

Eddie:
> In OotP, "Snape's Worst Memory" may only be how _Snape_ remembered 
the
> event, not necessarily how it actually occurred.  In that particular
> scene, we hear James, Sirius, Remus, and Peter talking about the
> O.W.L. they just took, including reference to Remus being a 
werewolf.
>  Would Snape have actually been able to hear that conversation and
> have it captured in his memory?  Or is these details that Snape has
> "added" after the fact based on information gathered later?

zgirnius:
Pensieve memories are objective, what is shown is what occurred, even 
if the person whose memory it is never noticed. It is what makes them 
so useful. People can take a second look at their own memories and 
see crucial details they overlooked in real time. This was confirmed 
by Rowling in an interview (you are not the first to wonder!)

This is an excerpt from the 7/16/2005 interview Rowling had with 
Melissa Anelli and Emerson Spartz:

> 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.

> ES: I want one of those!

> JKR: Yeah. Otherwise it really would just be like a diary, wouldn't 
it? Confined to what you remember. But the Pensieve recreates a 
moment for you, so you could go into your own memory and relive 
things that you didn't notice the time. It's somewhere in your head, 
which I'm sure it is, in all of our brains. I'm sure if you could 
access it, things that you don't know you remember are all in there 
somewhere.