So, I read this story in high school and this is a part of a bigger story. Technically this is an excerpt. A group of people is locked in a house and they are being observed. Every day they go about their daily routines and they keep on doing it EVERYDAY. One day a guy observes this and wants to find out more about this. So he stays awake one night and finds out that one of the people is going out of the house, which none of them EVER do. SO he follows the man he sees that there is an outhouse and when he goes in that the people in there tell him that he is the first amongst them to get out of the house. when he says that there was another guy who did that too, he was told that that other person was a human but all of the others inside the house including him are Martians.
Thanks in advance. I have been looking for this for almost about a decade.
It's a science fiction story and most probably by Isaac Asimov.