That's how we know that a smile might mean sadness and a cry might mean happiness, and a stoic, still face might mean that you are angrily plotting the demise of your enemy.
Tako znamo da osmijeh može izražavati tugu, plač može izražavati sreću, a stoičko, mirno lice može odražavati da gnjevno u sebi snujete propast svojih neprijatelja.