Human cooperation declines in punctuated steps

What the study found: Human cooperation can decline in punctuated steps over time, even when conditions are otherwise favourable. In this study of group lending in Sierra Leone, cooperation started high, then gradually fell, with sharp rebounds when loans were restarted.
Why the authors say this matters: The authors conclude that these findings have direct implications for preventing behavioural decline in cooperative programmes and institutions. They suggest that long-term cooperation is affected by time-varying departures from rational behaviour, not only by strategic behaviour or learning.
What the researchers tested: The researchers analysed a natural social dilemma in the field: group lending with joint liability in Sierra Leone, where all members lose access to future credit if the group loan is not repaid in full. They tracked cooperative dynamics over five years using 47,931 group payments from 7,108 borrowers and supplemented this with semi-structured interviews from a two-stage cluster sample.
What worked and what didn't: The study reports a statistically robust pattern of punctuated decline driven by behavioural mechanisms. Cooperation rates declined because group members' cooperative motivation and effort fell; when loans were restarted, clients were resensitized to their cooperative responsibilities and cooperation rebounded, although each later restart was followed by a faster decline.
What to keep in mind: The summary describes one field setting, a specific lending structure, and a five-year observation window. The abstract does not describe additional limitations beyond this scope.

Key points

• Cooperation in group lending declined over time in a punctuated pattern.
• The decline was linked to decreases in cooperative motivation and effort.
• Restarting loans produced sharp rebounds in cooperation.
• Each later restart was followed by a more rapid subsequent decline.
• The study used five years of data from 47,931 group payments by 7,108 borrowers.