 In the simplest model in which such an account exists, agents face a cost of deliberation. The more complex the deliberative calculation, the higher the costs the agent incurs. When the marginal cost of deliberation is sufficiently high, the agent might do better to follow a rule that quickly, and therefore cheaply, identifies a good but not optimal  action.[19]  If the expected benefit from choosing the optimal action (relative to the good action) is less than the cost, it is prudent for the agent to adopt the rule of thumb. More sophisticated accounts of an economic rationale for rule-following rely on more complex models of bounded rationality. 