d. People who nod their heads up and down express greater agreement with a persuasive message than those who nod their heads side to side.
Petty and Cacioppo (1986a, 1986b) state that there are two "routes" to persuasion:
central and peripheral. The central route to persuasion consists of thoughtful consideration of the arguments (ideas, content) of the message.
Central processing has two prerequisites: It can only occur when the receiver has both the motivation and the ability to think about the message and its topic. If the listener doesn't care about the topic of the persuasive message, he or she will almost certainly lack the motivation to do central processing. On the other hand, if the listener is distracted or has trouble understanding the message, he or she will lack the ability to do central processing.
The peripheral route to persuasion occurs when the listener decides whether to agree with the message based on other cues besides the strength of the arguments or ideas in the message. A listener may decide to agree with a message because the source appears to be an expert, or is attractive.
Receiver notices that a message has many arguments -- but lacks the ability or motivation to think about them individually.