Bounded rationality
We're rational within the limits of mind, information, and time.
What it means
Bounded rationality is the idea that human rationality is constrained by the limits of available information, cognitive capacity, and time, so that people cannot and do not optimize in the way idealized economic agents are assumed to. Instead of computing the best possible solution, they use heuristics and aim for outcomes that are 'good enough,' a strategy Simon called satisficing. The crucial reframing is normative: what looks like irrationality from the standpoint of perfect optimization is often a sensible adaptation to real constraints, and Simon described the mind and its environment as two blades of a scissors that together produce behavior. This sets up a long-running contrast between the 'heuristics and biases' tradition, which emphasizes the systematic errors bounded agents make, and the 'fast and frugal' or ecological-rationality tradition, which emphasizes how simple rules can be remarkably accurate when matched to their environment. It matters because it dethroned the perfectly rational agent at the foundation of economics, opening the door to behavioral economics, and because it reframes the design problem as fitting decisions to real cognitive limits rather than assuming they away.
How satisficing actually works
Satisficing is not a vague gesture at 'good enough'; Simon described it as a specific procedure. You consider alternatives one at a time rather than laying them all out, and you stop the moment one clears an aspiration level set in advance. That threshold is not fixed. When good options keep appearing, you raise the bar; when the search drags, you lower it. This makes the stopping rule, not the comparison, the real object of study, because when you stop determines what you end up with. It also explains why satisficing is not laziness. Setting and updating a threshold economizes on the resource that is usually scarcest, which is attention and time rather than the final quality of the choice, and it lets a decision terminate at all when the options are too many to rank.
Errors or adaptations: the two traditions weighed
The split runs on one empirical question: are the shortcuts of a bounded mind mostly mistakes or mostly good bets? The heuristics-and-biases program measures deviation from logical and statistical norms and finds systematic error. The fast-and-frugal program measures accuracy in real environments and finds that simple rules, such as take-the-best and the recognition heuristic, can match or beat weighted regression models when predicting new cases. The reconciling idea is the bias-variance tradeoff. A simple rule ignores information and so carries bias, but it is stable across samples, whereas a flexible model fits noise and generalizes poorly. Which one wins depends on how much data and structure the environment supplies. That is why both camps can be right at once, each describing the kind of world its evidence was drawn from.
How far the idea reached
Bounded rationality did more than seed behavioral economics. Oliver Williamson built transaction-cost economics on it explicitly: firms exist partly because bounded agents cannot write complete contracts for every contingency. Macroeconomists replaced the all-knowing rational-expectations agent with adaptive learners who update simple forecasting rules as data arrives. In artificial intelligence, Simon's other field, satisficing search underlies heuristic problem-solvers, and Stuart Russell's notion of bounded optimality reframes an agent's goal as the best program given fixed computation rather than the best action given infinite computation. Across these fields the move is identical. Stop treating the constraint as a nuisance to assume away, and fold it into the model, so the analysis asks what a limited processor should do rather than what an unlimited one would do.
What it does not settle
The concept is a research program, not a finished theory, and its looseness is a fair criticism. Naming a bound does not say which heuristic a mind will use, and the strategy-selection problem, how people pick the right rule for a situation, remains partly open. Ariel Rubinstein warned of a deeper trap: many formal models of bounded rationality simply add a cost of thinking and then optimize again, smuggling the unlimited maximizer back in one level up. Used loosely, the term also becomes a label for any behavior an observer happens to dislike, explaining everything and predicting nothing. The discipline the idea demands is to specify the actual bound and the actual rule, then show that the pairing fits the environment it runs in, instead of invoking limits as a blanket excuse.
Examples
A manager picks the first acceptable supplier rather than exhaustively comparing every option.
Nobody views every flat in the city. You see six, take the first that clears your bar on rent, commute and damp, and stop — more searching costs more than the better flat is worth.
A doctor with seven minutes per patient does not work through every possible diagnosis; a few quick questions tuned to what actually walks through that door get it right often enough.
An emergency doctor cannot run every test before acting, so she works from the first diagnosis that fits the main symptoms and revises only if the patient does not improve, rather than ruling out every possibility first.
A recruiter facing three hundred applications does not score them all, but reads until a candidate clears the bar for the role and stops there, treating a good-enough hire found quickly as better than the best hire found too late.
First described in Herbert Simon (1955).
Key references
- Gigerenzer, G., & Brighton, H. (2009). Homo heuristicus: Why biased minds make better inferences. Topics in Cognitive Science, 1(1), 107-143. doi.org/10.1111/j.1756-8765.2008.01006.x
- Kahneman, D. (2003). Maps of bounded rationality: Psychology for behavioral economics. American Economic Review, 93(5), 1449-1475. doi.org/10.1257/000282803322655392
- Gigerenzer, G., & Goldstein, D. G. (1996). Reasoning the fast and frugal way: Models of bounded rationality. Psychological Review, 103(4), 650-669. doi.org/10.1037/0033-295X.103.4.650
- Simon, H. A. (1990). Invariants of human behavior. Annual Review of Psychology, 41, 1-19. doi.org/10.1146/annurev.ps.41.020190.000245
- Simon, H. A. (1956). Rational choice and the structure of the environment. Psychological Review, 63(2), 129-138. doi.org/10.1037/h0042769
- Simon, H. A. (1955). A behavioral model of rational choice. Quarterly Journal of Economics, 69(1), 99-118. doi.org/10.2307/1884852