Social science research seeks to improve the world we live in. Yet, there is little information on how much political leaders actually value this research when making policy decisions. In this VoxDev talk, Diana Moreira of the University of California, Davis discusses an innovative experiment which took place in more than 2,000 municipalities in Brazil and sheds new light on this topic. The findings suggest that Brazilian mayors not only change their beliefs after evidence briefings, but are also more likely to introduce related policies in their municipalities.