Trust game

What it means

The trust game, also called the investment game, is an economic game designed to measure trust and trustworthiness: a first mover (the investor) can send any portion of an endowment to a second mover (the trustee), the amount sent is multiplied by the experimenter on the way, and the trustee then decides how much, if any, to return. Self-interested rationality predicts that the trustee, facing no enforcement, will return nothing, so the investor, anticipating this, should send nothing — yet investors reliably send substantial sums and trustees reliably return enough to reward the trust, far exceeding the selfish equilibrium. The amount sent operationalizes trust (a willingness to be vulnerable in expectation of reciprocation), while the amount returned operationalizes trustworthiness and reciprocity, separating two constructs that are often conflated. The game has been used to study the neuroscience and hormonal correlates of trust, individual and cultural differences, and the effects of reputation and repeated interaction. It matters because trust is the lubricant of economic and social exchange, and the game provides a clean, incentivized measure of it that consistently reveals people to be more trusting and trustworthy than narrow self-interest would predict.