Measuring Indirect Reciprocity: Whose Back Do We Scratch?

This paper presents an experimental investigation of strong indirect reciprocity. We examine both generalized indirect reciprocity (if A helps B then B helps C) and social indirect reciprocity (if A helps B then C helps A), in a setting where reciprocal behavior cannot be explained by strategic motivations. We also consider a treatment for direct reciprocity, as a benchmark, and use a variant of the strategy method to control for di®erences in ¯rst movers' actions across treatments. We ¯nd evidence of strong reciprocity within each treatment, both for strategies and decisions. Generalized indirect reciprocity is found to be signi¯cantly stronger than social indirect reciprocity and, interestingly, direct reciprocity. This ¯nd- ing is interpreted as re°ecting the relevance of ¯rst movers' motivation for second movers' reciprocal behavior.