A model based on this analysis predicts a phenomenon that has been taken as evidence for human irrationality—anchoring and adjustment, in which people “anchor” on a first guess and “adjust” it insufficiently (Tversky & Kahneman, 1974). Taking into account the cost of computation reveals that this is exactly what an abstract computa- tional architecture whose elementary operations are the propose and the accept/reject step of the Metropolis-Hastings algorithm should do.