The Democratic Peace : An experimental test of a causal relation and of underlying mechanisms

Democracies go to war with each other less frequently than dictatorships do with each other. This isan established empirical regularity. However, it is not clear whether there is a causal link betweendemocracy and peace. We use laboratory experiments to study whether there is a causal impact. We study the bellicosity of democracies compared with two types of dictatorships, inclusive andexclusive, where each society is composed of three members. We also analyze how bellicositydepends on the presence of the possibility of deliberation between the members of a society. Neither the ‘voting’ nor ‘inclusion’ aspect of democracy nor ‘deliberation’ in isolation has a positive causal impact on peace. However, when all three are combined, there is evidence that their combination produces less bellicosity than some kinds of dictatorship. It is the addition of deliberation that makes the crucial distinguishing difference for democracy in our experiment