Is there a mental disorder in which a person believes they are sexually aroused by certain things but actually are not?
i dont think this question can even begin to be answered with out more information. the only thing that i can think of is that you are speaking of a fetish. what certain things (example) and why do they think that they are not aroused?
Pyrophilia (pie-row-phee-lee-a) is a disorder of the mind where an individual becomes sexually aroused by the acts of creating fires or watching fires. It is very different from pyromania because of the sexual nature. Pyromaniacs do not become sexually aroused by their crimes, whereas pyrophiliacs do. The cause is unknown but the treatment consists of cognative behaviourial therapy with a psychiatrist or a clinical psychologist.