Persuasion - Neurobiology of Persuasion

Neurobiology of Persuasion

Attitudes and persuasion are among the central issues of social behavior. One of the classic questions is when are attitudes a predictor of behavior. Previous research suggested that selective activation of left prefrontal cortex might increase the likelihood that an attitude would predict a relevant behavior. Using lateral attentional manipulation, this was supported.

An earlier article showed that EEG measures of anterior prefrontal asymmetry might be a predictor of persuasion. Research participants were presented with arguments that favored and arguments that opposed the attitudes they already held. Those whose brain was more active in left prefrontal areas said that they paid the most attention to statements with which they agreed while those with a more active right prefrontal area said that they paid attention to statements that disagreed. This is an example of defensive repression, the avoidance or forgetting of unpleasant information. Research has shown that the trait of defensive repression is related to relative left prefrontal activation. In addition, when pleasant or unpleasant words, probably analogous to agreement or disagreement, were seen incidental to the main task, an fMRI scan showed preferential left prefrontal activation to the pleasant words.

One way therefore to increase persuasion would seem to be to selectively activate the right prefrontal cortex. This is easily done by monaural stimulation to the contralateral ear. The effect apparently depends on selective attention rather than merely the source of stimulation. This manipulation had the expected outcome: more persuasion for messages coming from the left.