During Priori Incantatem, How Did Cedric, Bertha, Lily, and James Know So Much Info?

Question

In Goblet of Fire, Harry's and Voldemort's wands connect due to their twin cores, forcing Priori Incantatem to occur. Voldemort's wand spits out spectral figures of his last five victims. Later, after Harry is safe with Dumbledore again, Dumbledore explains that these spectral figures are not ghosts.

‘No spell can reawaken the dead,’ said Dumbledore heavily. ‘All that would have happened is a kind of reverse echo. A shadow of the living Cedric would have emerged from the wand ... am I correct, Harry?’

‘He spoke to me,’ Harry said. He was suddenly shaking again. ‘The ... the ghost Cedric, or whatever he was, spoke.’

‘An echo,’ said Dumbledore, ‘which retained Cedric’s appearance and character. I am guessing other such forms appeared ... less recent victims of Voldemort’s wand ...’

‘An old man,’ Harry said, his throat still constricted. ‘Bertha Jorkins. And ...’

‘Your parents?’ said Dumbledore quietly.

‘Yes,’ said Harry.

_{Goblet of Fire - pages 605-606 - Bloomsbury - chapter 36, The Parting of the Ways}

Using Dumbledore's explanation, it seems these smokey figures should have emerged from Voldemort's wand, perhaps parroted back a few of the last sentences they said before dying, and then simply dissipated. The multiple definitions of 'echo' at Dictionary.com are not particularly helpful in working out a plausible definition of 'echo' that would explain these spectral figures.

I'm trying to figure out how these "echoes" could have possibly interacted in a sentient manner with Harry and had as much information as they did.

None of the figures who appeared knew that Harry's and Voldemort's wands had twin cores; they couldn't have anticipated Priori Incantatem. Bertha Jorkins calls Harry by name, even though she has never met Harry before. Lily tells Harry to "hold on", that James is on his way, and that James has been waiting to see Harry -- how could James's echo even know that Harry would even be there before James was out of the wand? James says, ‘[Y]ou must get to the Portkey, it will return you to Hogwarts ... do you understand, Harry?’ How did James's echo know about the Portkey at all, much less where it would transport Harry?

How were these echoes able to communicate effectively with Harry if they were not sentient ghosts? And how did they have so much information about Harry and what was going on at the moment of Priori Incantatem (i.e. like the Portkey)?

Answer 1

I'm trying to figure out how these "echoes" could have possibly interacted in a sentient manner with Harry and had as much information as they did.

Well,

'All that would have happened is a kind of reverse echo. A shadow of the living Cedric'

Even if they're not strictly ghosts, it doesn't mean that those echoes do not have a sentient property as the ghosts do. Dumbledore's description sounds a lot like a ghost.

None of the figures who appeared knew that Harry's and Voldemort's wands had twin cores; they couldn't have anticipated Priori Incantatem.

Oh, but they realized that their wands had twin cores because they saw the Priori Incantatem acting at the moment. But hey, this Priori Incantatem stuff sounds like a rather complex and advanced topic...

... So perhaps, no one knew about Priori Incantatem, but it was not necessary at all: They just saw an epic ray of energy and all they had to do was think: "What happens if Harry releases? Err... Voldy would toast him.... OH GOD HARRY DON'T RELEASE IT"

Bertha Jorkins calls Harry by name, even though she has never met Harry before.

That doesn't surprise me at all: He is Harry Potter. The damn boy who lived. The popular dude. How many characters had not met Harry, but immediately realized it was him just from the scar?

Lily tells Harry to "hold on", that James is on his way, and that James has been waiting to see Harry -- how could James's echo even know that Harry would even be there before James was out of the wand?

No, James didn't know. But Lily did (because she was already there). And she told Harry. Lily realized that people was "coming back to life". It would be rather easy to assume that James was about to pop up. And it wouldn't surprise me that Lily tells Harry that James is waiting to see him (I think these words were purely to calm down Harry).

how could James's echo even know that Harry would even be there before James was out of the wand? James says, ‘[Y]ou must get to the Portkey, it will return you to Hogwarts ... do you understand, Harry?’ How did James's echo know about the Portkey at all, much less where it would transport Harry?

Alright, I think I got a bit of an idea here - hopefully it is logical:

Let us begin with the veil in the Department of Mysteries. I think we agree that you can hear dead people there. So we got this: dead people can, as a minimum, talk. With whom? Well, it seems like with other dead people.

So when Cedric dies, he goes to the world of the death. If dead people can talk, who would Cedric attempt to talk with first? Well, given the situation, probably Harry's parents: he would try to explain them what happened, and the danger Harry might be on. The most important thing he would tell Harry's parents would be "I was sent to a graveyard, along with Harry, through a Portkey... it was a trap! They killed me immediately. I'm not sure how is Harry." - so now Harry's parents are aware of what is going on AND that there is a Portkey involved.

When James comes, he comes already knowing about the Portkey.

... wait! Didn't Dumbledore say that they were just echoes? Shouldn't they know as much as they did before dying, and nothing more? I think that's false. If that was true, they wouldn't know they are dead - instead, they would be surprised, saying something like "How did I get here?!" because, if they were echoes, they would know all they did before dying except the fact that they died. So, when Dumbledore says they're echoes, I think he did mean to say something beyond the usual definition of echo: almost like a ghost.

Okay, maybe they are not sentient ghosts. But they are sentient something.

Answer 2

My understanding was that the "echoes" that emerged from Voldemort's wand in the graveyard scene in Goblet were much the same as those summoned by the Resurrection Stone in the Forest in Hallows. They were sentient, able to interact meaningfully with Harry, and knew what was happening (not to mention some of what was about to happen) just like those in Goblet. The difference was that they were selected by virtue of being victims of that particular wand rather than being emotionally connected to the holder of the Stone.

Edited to correct a stupid error on my part which has little bearing on the underlying point but distracts from it.