Social image, observer identity, and crowding up

People behave more pro-socially when observed by others. We develop a theoretical model incorporating social distance between agent and observer and test its predictions in a field experiment with 670 high-school students. The experiment manipulated the observer's identity (friend, acquaintance, or none) and capped personal rewards. Observability increased effort, and personal rewards enhanced above-threshold effort when effort was observable. Among young adolescents, these effects were stronger when observed by an acquaintance rather than a friend. While partly exploratory, our findings suggest a positive correlation between social distance and social-image effects.