Elaboration Likelihood Model of Persuasion.
Petty created the Elaboration Likelihood of Persuasion Model in order to clarify how a convincing message could change the position of the recipient. Cacioppo and Petty proposed that a message was given and received through two different courses of persuasion: the central route and the peripheral route.
The central route tends to work if a person is more knowledgeable of the topic and if they are likely to think about the message expansively. If they are motivated to think about the message and the given message is strong, they are likely to be swayed in agreement to the message. The peripheral route of ELM says that if a person is uninformed of the topic, or if they cannot think of the message at length, they might still be convinced by factors that don't really have to do anything with the message itself. These individuals can be persuaded towards the message in the short term and inadequately.
The first step in the ELM is actually to determine whether or not the message is persuasive. If the message is neutral, for example, it has failed to be persuasive and the recipient will take whatever meaning they want from the argument. So, if we assume that the message is in some way persuasive, the recipient becomes drawn into the next step: motivation. If the receiver is to be motivated to process the message, the message itself must have some bearing to them. Some previous familiarity with the subject matter encourages the recipient to process it. When a person has little relevance to the message, they have no desire to hear about the topic. On the other hand, when a person can relate due to personal experience with information given in the persuasive argument, they are more likely to pay attention to the speaker and comprehend the deeper significance. At this time the receiver might be motivated to process, but the question as to their ability to do so comes into play.