IN business, everyone knows that if you want to persuade people to make a deal with you, you have to focus on what they value, not what you do. If you’re trying to sell your car, you emphasize the features of the sale that appeal to the buyer (the reliability and reasonable price of the vehicle), not the ones that appeal to you (the influx of cash).

This rule of salesmanship, as we demonstrated in a series of experiments detailed in a recent article in the journal Personality and Social Psychology Bulletin, also applies in political debate — i.e., you should frame your position in terms of the moral values of the person you’re trying to convince. But when it comes to politics, this turns out to be hard to do. We found that people struggled to set aside their reasons for taking a political position and failed to consider how someone with different values might come to support that same position.

In one study, we presented liberals and conservatives with one of two messages in support of same-sex marriage. One message emphasized the need for equal rights for same-sex couples. This is the sort of fairness-based message that liberals typically advance for same-sex marriage. It is framed in terms of a value — equality — that research has shown resonates more strongly among liberals than conservatives. The other message was designed to appeal to values of patriotism and group loyalty, which have been shown to resonate more with conservatives. (It argued that “same-sex couples are proud and patriotic Americans” who “contribute to the American economy and society.”)

Liberals showed the same support for same-sex marriage regardless of which message they encountered. But conservatives supported same-sex marriage significantly more if they read the patriotism message rather than the fairness one.