Would you give $1000 to stop a child drowning? Almost certainly. Why then are you not giving all the $1000 you can spare to save the lives of the 9 million children who die every year before their fifth birthday? The moral imperative is the same, says the philosopher Peter Singer. I learnt of this moral conundrum at the same time as reading about an experiment of giving. How much would you donate in response after reading this flyer?

“Food shortages in Malawi are affecting more than 3 million children; In Zambia, severe rainfall deficits have resulted in a 42% drop in maize production from 2000. As a result, an estimated 3 million Zambians face hunger; 4 million Angolans—one third of the population—have been forced to flee their homes; More than 11 million people in Ethiopia need immediate food assistance.”

Or what about in response to this flyer with a picture of a young girl?

“Rokia, a 7 year old girl from Mali, Africa, is desperately poor and faces a threat of severe hunger or even starvation. Her life will be changed for the better as a result of your financial gift. With your support, and the support of other caring sponsors, Save the Children will work with Rokia’s family and other members of the community to help feed her, provide her with education, as well as basic medical care and hygiene education.”

You can predict the result. Students were paid $5 to fill out a short survey and were then randomly given the two flyers and asked to make a donation. They gave $1.16 in response to the first flyer and $2.83 in response to the second.

I read of this experiment in Poor Economics: a Radical Rethinking of the Way to Fight Global Poverty by Abhijit V Banerjee and Esther Duflo, two economics professors at the Massachusetts Institute of Technology who run a “poverty lab.” Their thesis is that global poverty will be solved not by large scale, quasi-philosophical debates about aid or markets but by deep understanding of the poor and by experimentation, often using randomised trials. Those who live on under a dollar a day, they write, “have to be sophisticated economists just to survive.”

Banerjee and Duflo conclude from the experiment I’ve described: “the students, it seems, were willing to take some responsibility for helping Rokia, but when faced with the scale of the global problems they felt discouraged.” The authors seem to me to go beyond the evidence in inferring these thoughts, but I’m glad to have some evidence that people respond to human stories better than statistics. But the second flyer also seems to me different from the first in that it describes how the money will be used and tells you that you are a “caring sponsor” and will be part of a larger movement of (implied) “good” people.

This simple experiment is important to those of us trying to generate global action over non-communicable disease. Our usual statistics of the huge numbers of people dying may well be counterproductive. We need human stories and clear information on “solutions.”

There was a second part to the experiment. A second batch of students were told that “people are more likely to donate money to an identifiable victim than when presented with general information” and then shown the same flyers. I find it harder to predict the change that this information might have. What happened was that students gave $1.26 in response to the same flyer (much the same as before) and $1.36 (much less) in response to the second.

This reaction, say Bannerjee and Duflo, is typical: prompted to think again we think that it may all be hopeless. Their book is a response to that sense of hopelessness, arguing that problems of poverty “once properly identified and understood can be solved one at a time.”

PS. If you want to take up Peter Singer’s challenge, visit his website “the life you can save” and take the pledge.

Richard Smith was the editor of the BMJ until 2004 and is director of the United Health Group’s chronic disease initiative.