Ben Purzycki (Max Planck Institute for Evolutionary Anthropology, Lipsko) and Martin Lang answered this question in a new paper that is out in Cognition. They used freely available cross-cultural data set (goo.gl/qvYzX7) focused on economic games between co-religionists and tested whether people who report their identities to be fused with their religious group are willing to sacrifice more coins to benefit their co-religionists. While identity fusion theory predicts willingness to make extreme sacrifices for the group, Ben and Martin found that it is also predictive in terms of more subtle sacrifices in economic games using money. Data, code, and a preprint are freely available on GitHub (goo.gl/4mg6k2). Stay tuned for another paper using cross-cultural data to test some of the crucial claims in the cultural evolutionary theory of religion!