Groups and group norms work as mediators. For example, one can be strongly disinclined to change to the Democratic Party if their family has voted Republican for a long time. In this case, the person's predisposition to the political party is already set, so they don't perceive information about Democratic Party or change voting behavior because of mass communication. Klapper's third assumption is inter-personal dissemination of mass communication. If someone is already exposed by close friends, which creates predisposition toward something, it will lead to an increase in exposure to mass communication and eventually reinforce the existing opinion. An opinion leader is also a crucial factor to form one's predisposition and can lead someone to be exposed by mass communication. The nature of commercial mass media also leads people to select certain types of media contents.