In psychology, the false-consensus effect is a cognitive bias whereby a person tends to overestimate how much other people agree with him or her. There is a tendency for people to assume that their own opinions, beliefs, preferences, values and habits are 'normal' and that others also think the same way that they do. This cognitive bias tends to lead to the perception of a consensus that does not exist, a 'false consensus'. This false consensus is significant because it increases self-esteem. The need to be "normal" and fit in with other people is underlined by a desire to conform and be liked by others in a social environment.
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This also includes believing "Obviously Harry Potter is better, it has more fans! So many people agree with me". or "How can you say Harry Potter is written poorly, a lot of people think it's well written." or "Twilight sucks, just Google "Twilight sucks" for proof"

Yes and no. It depends on my comment weather or not I think lots of people will agree with me. And then there are those comments I think no one will agree with. So I don't really know.

Do I ever? Yes. Specially since I spend so much time obsessing on HP and twilight and visiting their related sites. I just assume everyone's heard of them, has read and/or watched the movies and liked them. I am often taken aback when I meet someone who either doesn't like HP/Twilight or has never heard of them. It doesn't happen often as I don't go out much any more on account of all the time I spend online discussing either series with other like minded individuals...

Nah. I just like what I like, say what I say. Good question, though.

And Harry's expression in the "I'm not sure" choice had me laughing.

Probably, but I've never noticed.

I'm sure there are a ton of people out there (famous authors included) who think that Harry Potter is the worst written piece of literature. Regardless of if its getting good reviews or not, I love HP. When I watched the first one at six, I had no idea that Sorcerer's Stone did so successful in the box office or got amazing critical acclaim. When South Park made fun of Harry Potter (link) I laughed for days! So what if Matt Stone and Trey Parker thinks it sucks. I watched it because I liked it. And to be honest, when I started to really get into recently, I didn't know that it was even close as successful as it.

Same thing goes for Twilight. I was literally the only person in my house who liked Twilight. I watched people bash it on YouTube, TV, and even in my school newspaper (lol, I'm not kidding) but I still thought it was cool. In addition to that, I didn't stop liking Twilight because of other people. I stopped liking Twilight after I watched BDP1 and noticed that it was a very poor movie. I watched the others and noticed how poor those were, too. After all of that, I even read Twilight and couldn't bare to pass page 50. It has nothing to do with what Stephen King says or even HP it's just me growing out of it.

Tough question. Evaluating yourself for flaws is never anyone's strongest point.

I don't think so. Because I've always known Twilight has a lot of fans. I known how Stephenie Meyer draws people in, but I've never been one of them. When I say many people agree with me, the truth is that they do. However, the false-consensus effect can often be over-looked if you're not searching for it, so it is likely I have been affected in the past.

I'm not really so sure :$

Never read any concensus, as I prefer to ignore what's famous and find it out on my own.

Ah on that note, if you count reading twilightsucks as consensus maybe I have but only after I read the book. And have a solid opinion on it.

If you also mean my perception of quality, not popularity.