Compared to people with no prior knowledge, people with prior knowledge of a subject are to scrutinize messages about that subject and are to change their attitudes about that subject.

The words that comes in the blanks are; more likely; less likely.
People with prior knowledge of a subject are more likely to scrutinize messages about that subject and are less likely to change their attitudes about that subject.
Zakaray L. Tormala and Richard e. Petty, both are professors from different universities, Tormala from Indiana University and Petty from Ohio state university. They both have a recent research in 2002 that is about Source Credibility and Attitude Certainty. According to their when people resist persuasion, they can distinguish this resistance and become more sure of their initial approaches.