I see what you mean Gr3tta. I know instantly when I hear, see, feel, and smell the things that others do not hear, see, feel, and smell. I always know that they can not hear, see, feel and smell them. I have learned this through trial and error. Like, "Doesn't it smell like a beautiful meadow filled with fresh lillies in here guys?" And they all usually say, "No, it smells like feet here in this basement." Etc. So I have learned for myself to recognize the difference between my own reality and others'.
I have smelled the smell of Crack-Cocaine Burning like melted plastic in my church many times on Sunday morning. My church is called a "mega-church" by some people on t.v. because it has some thousands of members. It is not likely that someone would be brazen enough to smoke such an illegal drug in a place like this. This gives me the "clue" that others cannot smell this like I can. The beliefs are where the reality check is unhelpful for me. Beliefs are just that. You either believe it, or you don't.