Often in economics, we create models of how an idealized economic agent will behave in a particular setting, finding our predictions using constrained maximization of some objective function. However, in doing so we forget the sum total of the cognitive resources it took for us to find such a solution and we marvel when real humans deviate from our models. We forget than an agent may view a situation differently (they do not know the model) or that they lack the resources to find the solution (they cannot solve the model), but both assumptions are implicit in our models and solution techniques. We overlook that agents will often substitute optimization for heuristics, mental rules of thumb that save on costly mental effort. I present three ...