Observational evidence that economic reciprocity pervades self-organized food co-operatives

Evolutionary scientists argue that prosociality has been central to human eco- logical success. Theoretical models and behavioral experiments have found that prosociality, and cooperation in particular, is conditional and context dependent, that individuals vary in their propensity to cooperate, and that reciprocity sta- bilizes these behaviors within groups. Experimental findings have had limited validation with observations of behavior in natural settings, especially in organiza- tional contexts. Here, we report in situ measurements of collective action where reciprocity is abundant in organizations embedded in a cash economy. We study small ‘food clubs’ where members share bulk purchases and are considered to be heavily dependent on cooperation. We take advantage high-resolution data of economic interactions for 1,528 individuals across 35 clubs over a combined 107 years of operation. We develop a network method to detect different directional and temporal forms of economic reciprocity, and statistically classify individual behavioral types akin to those in experiments. We find abundant direct reciprocity, supplemented by indirect reciprocity, and that members of most clubs can be identified as consistent reciprocators. This study provides initial observational evidence that economic reciprocity may be more abundant in real-world settings, sharpening the findings of the behavioral study of cooperation and contributing to the more naturalistic study of reciprocity and prosociality.