Trusting behaviour consists in action that (1) increases one's vulnerability to another whose behaviour is not under one's control, and (2) takes place in a situation where the penalty suffered if the trust is abused would lead one to regret the action. In economic terms this implies that the action would not be taken in the absence of trust because the expected net benefit is lower than if some alternative is chosen. In short, there is no best strategy independent of trust.

Diego Gambetta, Trust - Making and Breaking…, loc. 2503