I work on a variety of topics related to altruism, violence, and peace. At the macro level, I study how the largest mass atrocities in history have ended, and provide the statistical models used by the US Holocaust Memorial Museum in its annual mass atrocity forecasts. In work on Darfur, Syria, and Colombia, I study what influences an individual’s willingness to make peace with former enemies or perpetrators, especially the role of experienced violence. I also (with Dan Posner) use tools from economics and psychology to improve how we measure biases in the altruism and threat-perception people experience towards members of other groups.