Imagine your self in a classroom, and the teacher asks a question, the moment he finishes it, you knew the answer is ‘A’. he started to ask your classmates first.
The first answered ‘B’, the second also answered ‘B’, the third also ……., when your turn arrives what will be your answer ?
You guess right, your answer will be ‘B’.
In psychology, this situation is called ‘cognitive dissonance’, it’s when a new external information is in contradiction with our internal ideas, and causes ‘mental discomfort’. and the corollary is doubting your pre-knowledge.