Consider this: If you're supporting your own genuine opinion, you might have your own carefully chosen perspective that is slightly different from the question's wording. You only select the answer because it's the closest one of the options, not because it's exactly your answer. So, you may be inclined, then, to say things that are related but don't fit the question exactly. If you're confabulating to support a random opinion, though, what do you have to go by but the wording? The opinion is directing your thoughts then, leading your thoughts to fit the opinion. You aren't trying to cram pre-existing thoughts into an opinion box to make it fit your view.
Or looking at it another way:
When expressing your point of view, the important thing is to express what you feel, regardless of whether it fits the exact question.
When supporting "your" point because you don't want to look like an idiot in front of a researcher, the objective is to support it as precisely as possible, not to express anything.
As for whether your interpretation of that selection is correct: it's past my bed time and I'm getting drowsy, so someone else should answer that part instead.
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).