preconception

/ˌpriːkənˈsɛpʃən/
noun
  1. An opinion or idea formed before having enough knowledge or experience; a prejudice or bias.
    • Her preconception about the city changed completely after she visited it for the first time.
    • Many people have a preconception that learning a new language is impossible after a certain age.
    • The scientist tried to approach the experiment without any preconception about the results.