New research from Cornell University sheds light on the types of statistical and narrative evidence that are most effective at persuading people to pay attention to global issues.

Study co-authors Adam Levine, associate professor of government, and Yanna Krupnikov of Stony Brook University wanted to understand what makes people care about social and economic problems they may not necessarily face in their daily lives, and whether that concern is a function of how the problems are described.

The team looked at several types of evidence showing that a problem exists. For example, statistics can describe the magnitude of the problem or they can be phrased in percentage terms -- such as the percentage of people facing a problem. They designed a series of studies to test which type of evidence increased people's engagement, either by making a donation, paying attention to an email or stating a concern.

The research was conducted in collaboration with a nonprofit in Ithaca, New York, that strives to increase access to affordable health care, including funding for a free clinic.

In the studies, likely new donors received solicitations by mail, members of the organization received a solicitation email, and study participants unaffiliated with the organization took a survey gauging their interest in access to affordable health care.

The messaging used in solicitations included combinations of high percentages, low percentages, case studies and raw numbers to describe the magnitude of the uninsured who can't afford health care.

For example, the potential donors received either a standard letter, one saying 57 percent of uninsured people couldn't afford the care they need, or one describing how a real uninsured person benefited from the nonprofit's services.

Across the board, the percentage-based evidence and human interest evidence tended to drive engagement, but talking about the overall magnitude of the problem didn't.

"When you talk about the millions of children who are starving, or the millions of refugees who are seeking out a better life, it fails to have this emotional connection that tends to then motivate people to pay more attention and to become engaged," Levine said.

The study offers a model of what a meaningful collaboration between researchers and practitioners can look like.

"Pull at people's emotional heartstrings," Levine said. "You can do it with certain forms of statistical evidence. You can do it with sympathetic case studies. And that will move behavior and move attitudes."