Therapeutic community graduates cluster together in social networks: Evidence for spatial selection as a cooperative mechanism in therapeutic communities

- Therapeutic community residents who graduate receive affirmations from more peers who graduate.
- This effect extends to a network path length of 2.
- Residents who receive more affirmations overall are somewhat less likely to graduate.
- We find no evidence that reciprocity in affirmations predicts graduation.
- These results confirm both theory and laboratory findings on spatial selection in cooperation.