I believe, based on the notions of persuasion dialogue and negotiation dialogue that are common in the literature of non monotonic reasoning, that a notion of "persuasion" is essentially based on the "evaluation" of the arguments. Fundamentally, this is possible ONLY when agents involved in the discussion have positive and negative PREJUDICES. A prejudice is something that an agent believes true but cannot prove the truth of.

In other terms, a person would be convinced of something different form her original opinion, that is changed due to the dialogue, because one of the following facts occurs:

1) The discussant presents NEW FACTS, that the agent who is further persuaded did not know before. The introduction of these facts provides a consequence that was not believed before (and the new evidence shows that this is the case);

2) The agent presents a rule (a way of deriving things from facts) that proves a prejudice of the other agent.

An example of the first case can be a situation in which I have no prejudice about X, and a discussant provides a proof for X, based on a new fact that is introduced, and there rest of the proof is just under my control.

An example of the latter would occur when I believe not X, but have no proof of my thesis (for instance I cannot prove -X, or, more weakly, I can assert that there is no proof for X in my set of rules and facts). The discussant shows me how to prove X.

This is, in my opinion, the situation of persuasion dialogue.

Dear Temitope,

In my research with human persuasive argumentation, I have seen much promise in study of facial-expressions / muscle-movements in and around the eyes.

Regards,

Bob Skiles

Persuasive argumentation is not a simple one, it is based on fiction, myth, lie, seduction. But many times it has success in convincing process!