“It’s the right thing to do.”

In his recent State of the Union address, President Obama urged the Congress to take action on paid sick leave for American workers. Forty-three million workers currently have no paid sick leave, the President noted, forcing many to make “the gut-wrenching choice between a paycheck and a sick kid at home.” Rectify this situation, he told the lawmakers: “It’s the right thing to do.”

“It’s the right thing to do.” This is a familiar refrain by now, six years into Obama’s presidency. If not paid sick leave, it’s health care reform, or the Dream Act, or tax credits for clean energy, or tuition assistance or gay rights. On these and many more issues, the President has again and again used his bully pulpit to justify his policy positions on moral grounds.

He could have done otherwise. He could have justified many of these positions on purely practical grounds, emphasizing the economic benefits of health care reform or immigration reform. And he has made those practical appeals. But in the end, for this President, the most compelling argument is always the moral one: “It’s the right thing to do.”

Is this a good strategy for winning the hearts and minds of the American people? Or are citizens more interested in the bottom line, the costs and benefits of public policy? Strangely, given the importance of public opinion to successful governing, there has been little work done on the impact of how leaders frame and justify their decisions.

Two psychological scientists at Berkeley’s Haas School of Business are trying to change that. Alex Van Zant and Don Moore suspected that moral justifications work better than practical justifications, enhancing support for leaders and their policies. That’s because a leader’s justifications signal something about that leader’s moral character, and leaders of high moral character are seen as more effective and persuasive than leaders of poor character.

Van Zant and Moore tested this idea in a series of experiments. In one, for example, they had volunteers read six policy proposals. Three were public policy ideas, the kind an elected official might propose—a plan to fund a retirement planning agency, for instance. The other three were private sector ideas—a CEO’s proposal to provide healthy meals to all employees. Volunteers were randomly assigned to read either moral or practical justifications for these ideas. So for example, some might read that the retirement agency would allow retirees to live with comfort and dignity—the moral justification—while others read that retirees would not drain public funds—the practical justification. Similarly, the CEO might justify the free meals as a moral imperative to improve workers’ well-being, or as a way to boost productivity.

After the volunteers read these justifications, the scientists asked them how much they supported each policy, and also asked them to rate the leaders on kindness, compassion and caring. The results, described in a forthcoming issue of the journal Psychological Science, were clear: They were much more supportive of policies framed in moral terms than policies framed in practical terms. And importantly, they found that the public support was mediated by the perception that leaders who offer moral justifications are in fact of better moral character. Indeed, in another version of the study, the scientists found that regardless of how a policy was justified, people support policies championed by leaders high in moral character.

Van Zant and Moore ran another version of the study, one that offered an interesting twist on the idea. When leaders renege on policies they have championed—on the campaign trail, for example—such reversals can spark moral outrage. One would expect this from Obama’s failure to close Guantanamo, for example, but the scientists’ results help explain the strangely muted disapproval from the left. They found that people were less outraged when a policy was originally justified on moral grounds, and later abandoned, than when the same policy was justified in practical terms. In other words, moral rhetoric signals the leader’s ethical motives, and this appears to insulate those leaders from outrage even when they renege on their promises.

Follow Wray Herbert’s reporting on psychological science in The Huffington Post and on Twitter at @wrayherbert.