Source credibility is "a term commonly used to imply a communicator's positive characteristics that affect the receiver's acceptance of a message." Academic studies of this topic began in the 20th century and were given a special emphasis during World War II, when the US government sought to use propaganda to influence public opinion in support of the war effort. Psychologist Carl Haviland and his colleagues worked at the War Department upon this during the 1940s and then continued experimental studies at Yale University. They built upon the work of researchers in the first half of the 20th century who had developed a Source-Message-Channel-Receiver model of communication and, with Muzafer Sherif, (Muzaffer Şerif Başoğlu) developed this as part of their theories of persuasion and social ju