What Does the Trust Game Measure?

The ubiquitous “Trust Game” of Berg, Dickhaut, and McCabe is the dominant experimental paradigm for the study of trust and trustworthiness in experimental economics, social psychology, and neuroscience of the last two decades. This elegant framework, promising a quantifiable behavioral measure of trust and trustworthiness, is at the center of a strikingly broad range of research programs. This paper brings Trust Game research into conversation with literature in the philosophy of trust to show that widespread adoption of the Trust Game marks an unnoticed yet fundamental shift in how trust is understood in social science. In the classic BDM trust game, the second mover’s motive for returning money is indeterminate. This means that we are not entitled to interpret the return of money as an indication of trustworthiness. The paper concludes with positive suggestions for empirical researchers who aim to nuance and deepen our understanding of trust and trustworthiness.