Change blindness is the phenomenon whereby people fail to notice changes in scenery and whatnot if they're not directed to pay attention to it. There are countless videos online demonstrating this effect (one of my favorites here, by Richard Wiseman).
One of the most audacious and famous experiments is known informally as "the door study": an experimenter asks a passerby for directions, but is interrupted by a pair of construction workers carrying an unhinged door, concealing another person whom replaces the experimenter as the door passes. Incredibly, the person giving directions rarely notices they are now talking to a completely different person. This effect was reproduced by Derren Brown on British TV (here's an amateur re-enactment).
Subsequently a pair of Swedish researchers familiar with some sleight-of-hand magic conceived a new twist on this line of research, arguably even more audacious: have participants make a choice and quietly swap that choice with something else. People not only fail to notice the change, but confabulate reasons why they had preferred the counterfeit choice (video here). They called their new paradigm "Choice Blindness".
Just recently the same Swedish researchers published a new study that is even more shocking. Rather than demonstrating choice blindness by having participants choose between two photographs, they demonstrated the same effect with moral propositions. Participants completed a survey asking them to agree or disagree with statements such as "large scale governmental surveillance of e-mail and Internet traffic ought to be forbidden as a means to combat international crime and terrorism". When they reviewed their copy of the survey their responses had been covertly changed, but 69% failed to notice at least one of two changes, and when asked to explain their answers 53% argued in favor of what they falsely believed was their original choice, when they had previously indicated the opposite moral position (study here, video here).
An alternate explanation:
Maybe the years of public schooling that most of us receive cause us to trust papers so much, that if we see something written down on a paper, we feel uncomfortable opposing it. If you're threatened with punishment for not regurgitating what is on an authority's papers daily for that many years of your life, you're bound to be classically conditioned to behave as if you agree with papers.
So maybe what's going on is this:
You fill out a scientist's paper.
The paper tells you your point of view. It looks authoritative because it's in writing.
You feel uncomfortable disagreeing with the authority's paper. School taught you this was bad.
Now the authority wants you to support the opinion they think is yours.
You feel uncomfortable with the idea of failing to show the authority that you can support the opinion on the paper. (A teacher would not have approved - and you'd look stupid.)
You might want to tell the authority that it's not your opinion, but they have evidence that you believe it - it's in writing.
You behave according to your conditioning by agreeing with the paper, and do as expected by supporting what the researcher thinks your point of view is.
I think this might just be an external behavior meant to maintain approval of an authority, not evidence that they've truly changed their minds.
I wonder what would happen if the study were re-done in a really casual way with say, crayon-scrawled questions on scraps of napkins instead of authoritative looking papers.
Also, I wonder how much embarrassment it caused when they seemed to fill out the answers all wrong and how embarrassment might have influenced these people's behavior. Imagine you're filling out a paper (reminiscent of taking a test in school) but you filled out the answers all wrong. Horrified by the huge number of mistakes you made, might you try to hide it by pretending you meant to fill them out that way?
It seems to me that this hypothesis is more of a mechanism for choice blindness than an alternate explanation- we already know that human beings will change their minds (and forget they've done so) in order to please authority.
(There's nonfictional evidence for this, but I need to run, so I'll just mention that we've always been at war with Oceania.)