Many human groups achieve high levels of trust and cooperation, but these achievements are vulnerable to exploitation. Several theorists have suggested that when groups impose costs on their members, these costs can function to limit freeriding, and hence promote trust and cooperation. While a substantial body of experimental research has demonstrated a positive relationship between costs and cooperation in religious groups, to date, this relationship has not held for secular groups. Here we extend this line of research by comparing trust (...) and cooperation among 11 secular groups, including four U.S. Greek fraternities that impose high costs on their members. We find that although fraternities impose greater costs on their members than social clubs, fraternities and social clubs do not significantly differ in their levels of intra-group trust. Moreover, variation in costs does not explain variation in trust among fraternities. We suggest that the lack of an evident relationship between costs and trust in our results is because secular groups, unlike religious groups, lack repeated rituals that are coupled with supernatural ideologies. We conclude by suggesting possible avenues for future research. (shrink)