Carl Hovland et al. created the Hovland-Yale model which studied the relationship between persuasion and attitude change, the research focused on the communicator, the content of the message and the receiver of the message as they were considered the key features in effective persuasion.
Source factors are influential in terms of persuasion, and it was found that credible experts are a powerful source when it comes to persuasion. This was demonstrated in a study by Insko (1966) who asked students to indicate how much sleep was required to maintain a good health, however their decisions were swayed more when exposed to an opinion of an expert rather than a non-expert. Insko's study shows that expert opinions has more effect on persuasion, due to their credibility and knowledge. The same conclusion was found in another study by Morton and Campbell (2008) who examined the effect of information source on a peer's attitude toward an unfamiliar child with autism and more favourable attitudes were reported towards the child when the information was provided by an expert source like a doctor, rather than a familial source like a parent.
It is also said that the more attractive and popular the source is, the more effective it would be on attitude change. However, Benoit (1987) found that an attractive source didn't produce a significant attitude change in a study that was based on a topic that was of high personal importance of the participants. This shows that the theory that attractive and popular sources are more effective are very limited in terms of studies and evidence that can support this. In terms of source factors, there is more substantial evidence that expert sources are more operative in persuasion and attitude change rather than attractive sources.
The Hovland-Yale model also found that messages were more effective if they created a moderate level of fear rather than a...