In the art of persuasion, does a person’s sex or body type make a difference?
—Randy M. Zeitman, Lansdowne, Pa.

Social psychologist Ros­anna E. Guadagno of the University of Alabama ­replies:

People are more swayed by the opinions and behavior of those who are like them. Specifically, those who are akin in appearance, hobbies or behavior are relatively more persuasive to one another. For instance, a study published in 2005 in the Journal of Consumer Psychology examined the effect of name resemblance on persuasion. Half the participants received a request to participate in a survey from someone who had the same first name as theirs and a close-sounding last name, whereas half received the same request without the name similarity. Letters matched for name similarity recruited nearly twice the number of participants.

So, yes, all else being equal, a skinny man would usually believe another skinny man over a heavier man. Things are seldom equal, however; in our society, skinny people are considered to be more attractive, and attractive people are more persuasive. We witness examples of this effect every time we turn on the television and see good-looking actors endorsing products.
The impact of a person’s sex is more complicated. Overall, men are slightly more swaying than women because we tend to perceive men to have higher credibility and expertise. Yet that is not the situation when the topic is stereotypically feminine (child care, for example).

Other factors are the relationship between persuader and target (whether they are friends, competitors or strangers) and their mode of communication (face to face versus e-mail, for example). My research indicates that when a woman is trying to influence another woman she doesn’t know, a face-to-face conversation works better than e-mail because women typically get to know one another quickly in person. On the other hand, a man trying to plead his case with another man he knows but is not similar to is better off using e-mail, where the focus is on the text and not the persuader.

Finally, across all communication modes, people are usually more successful at winning over members of their own sex. I have found that both men and women are more likely to adopt a more positive attitude about tighter security on campus or taking a comprehensive exam (topics most college students find abhorrent) when the persuader—either a real person or computer-controlled virtual person—matches their gender.

Note: This article was originally printed with the title, "Ask the Brains."

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