Jake and Samira were longtime friends who started dating several months ago. However, they have begun to question each other's actions and motives after becoming romantically involved. Jake gets jealous when Samira talks to other men, accusing her of flirting. On the other hand, Samira becomes suspicious whenever Jake goes out without her and assumes he is being unfaithful. This has led to frequent arguments and tension in their relationship.Which characteristic did this couple lack as their friendship became a romantic relationship?