Was Voldemort's piece of soul the reason for Harry being able to resist the Imperius Curse?

Question

And then he heard Mad-Eye Moody's voice, echoing in some distant chamber of his empty brain: Jump onto the desk. . . jump onto the desk. . .
Harry bent his knees obediently, preparing to spring.
Jump onto the desk....
Why, though? Another voice had awoken in the back of his brain.
Stupid thing to do, really, said the voice.
Jump onto the desk....
No, I don't think I will, thanks, said the other voice, a little more firmly. . . no, I don't really want to.
(Goblet of Fire, "CHAPTER FOURTEEN - THE UNFORGIVABLE CURSES")

Having re-read that description of Harry resisting Imperius Curse when Moody made them try it in DADA, it dawned on me: what the heck was that "another voice in the back of his brain"? It sounded very suspiciously like Voldemort's soul piece.

Remember that as per JKR/Dumbledore, plenty of Harry's unusual magical abilities (Parseltongue, etc...) were due to the Voldemort's soul piece that latched on to Harry.

Was this unusual ability to resist Imperius also for the same reason?

I'd prefer a canon answer if available.

Answer 1

I don't believe that it was the 'piece of soul' within Harry which enabled him to resist the Imperius curse.

Supporting reasons:

• From what we read in the books, Harry has a very strong will. A will to survive, a will to do the right thing and a will to be strong¹. Having a strong will is how you counter the Imperius Curse.
• There is no evidence that Voldemort was able to resist the Imperius curse, so why should the piece of his soul within Harry do that?

Lets break it down a bit:

And then he heard Mad-Eye Moody's voice, echoing in some distant chamber of his empty brain: Jump onto the desk. . . jump onto the desk. . .

It seems as though what the Imperius Curse does is it causes the victim's mind to be overcome by the caster's will. Sort of a "shove along, i'm in control here" notion.

Why, though? Another voice had awoken in the back of his brain.
Stupid thing to do, really, said the voice.

Harry's brain hears Moody's voice thinking that the voice belongs to the brain. But when Harry's voice comes in, it seems like it is out-of-place; but that is only because Moody has taken over.

Jump onto the desk....
No, I don't think I will, thanks, said the other voice, a little more firmly. . . no, I don't really want to.

Harry's "voice" or will starts to take over and become stronger, eventually over-powering Moody's.

Note that the same thing happens the other time Harry is put under the Imperius Curse:

“I asked you whether you want me to do that again,” said Voldemort softly. “Answer me! Imperio!”
And Harry felt, for the third time in his life, the sensation that his mind had been wiped of all thought. . . . Ah, it was bliss, not to think, it was as though he were floating, dreaming . . . just answer no . . . say no . . . just answer no. . . .
I will not, said a stronger voice, in the back of his head, I won’t answer. . . . Just answer no. . . .
I won’t do it, I won’t say it. . . .
Just answer no. . .
“I WON’T!”
And these words burst from Harry’s mouth; they echoed through the graveyard, and the dream state was lifted as suddenly as though cold water had been thrown over him — back rushed the aches that the Cruciatus Curse had left all over his body — back rushed the realization of where he was, and what he was facing. . . . .
-Harry Potter and the Goblet of Fire, Chapter Thirty-Four (Priori Incantatum).

Pretty inconclusive; but this is all of the evidence I could dig up.

One thing's for certain: Harry was extremely strong willed, and we know that that seems to be the one thing that someone needs to reject the Imperius Curse.

Answer 2

I don't think it was the horcrux in Harry because, later on in Goblet of Fire, this same voice resisted Voldemort's imperius curse on Harry. If it had been a horcrux, it, most likely, would not have resisted the original soul. Also, this ability (the voice) was something that was supposed to help Harry with occlumency (Snape said so in Order of the Phoenix). But, the voice did not return and Harry failed at occlumency. Dumbledore said at the end of OotP that, because of the connection between Voldemort and Harry (the pieces of each other they both possessed, though the audience did not know it yet) would not allow occlumency to be possible. So, wouldn't it follow that the imperius curse should also not be able to be resisted if the voice in Harry's head was the connection that thwarted occlumency? The horcrux only played a role in occlumency, not the resistance of the imperius curse.