Bounded rationality
Herbert Simon's idea that people with limited time, information and processing ability settle for a satisfactory and sufficient choice — they 'satisfice' — instead of finding the optimal one.
In plain language
Finance theory pictures an investor who reads everything, weighs every choice and picks the best one. Real people are not like that. When they have to decide, most have limited time and limited information. They also have a limited ability to handle complex information.
Faced with many choices, people get confused. So they settle for one that looks good enough. They pick it after a quick look, using thumb rules. It may not be the best choice. It may be sub-optimal.
The workbook's word for this is satisficing. It joins "satisfactory" and "sufficient". The opposite is optimising, or maximising, which means always seeking the best.
The key point is this: bounded rationality is not irrational decision-making. It is rational decision-making within limits. It sits between two things. One is full rationality, where you use all information to reach the best answer. The other is intuition, which draws on experience.
How it works
Credited to Nobel laureate Herbert Simon (1978) (Chapter 14, section 14.2.1).
The three limits: (i) time, (ii) information, (iii) ability to comprehend complex information.
The three steps of decision-making under bounded rationality:
- Process only the information that is manageable, not all information.
- Apply rules of thumb or quick approaches while processing.
- Select the solution that is satisfactory and sufficient — the satisficing solution.
Where it sits:
| Rationality | Bounded rationality | Intuition |
|---|---|---|
| All available information processed | Manageable information, thumb rules | Experience |
| Optimal solution | Satisficing solution | — |
The workbook presents it as the first of two answers to "how do individuals make decisions?" — the second is prospect theory.
A worked example
Illustrative figures. Priya, a 30-year-old software engineer, has ₹6 lakh to invest and one free weekend to decide.
The optimising approach would compare every equity scheme, PMS strategy and debt option on return, risk, cost and tax — hundreds of products.
What she actually does:
- Manageable information only: she looks at the top 10 flexi-cap schemes on one comparison website.
- Thumb rules: "at least a 5-year record" and "expense ratio below 1%". Four schemes survive.
- Satisficing: she splits the money equally across the first two that also appear in a friend's portfolio — ₹3 lakh each.
Is this irrational? No. Given two days and no training, it is a reasonable decision that is satisfactory and sufficient. It may not be the optimum: a scheme outside her top-10 list might have suited her better. That gap between the satisficing choice and the optimal one is exactly what bounded rationality describes.
Why NISM asks about it
Chapter 14 (Behavioural Finance), section 14.2.1, sets out bounded rationality as the first way individuals actually make decisions, before prospect theory in section 14.2.2. Expect conceptual questions: who is credited (Herbert Simon, 1978), what satisficing means, the three steps, and whether bounded rationality is irrational (it is not).
Common exam traps
- Not irrational. It is rational decision-making under boundary conditions — the workbook stresses this.
- Satisficing = satisfactory + sufficient, not "satisfying". The outcome is possibly sub-optimal.
- Herbert Simon (1978) — not Kahneman (prospect theory, 1979) and not Thaler (mental accounting).
- It sits between rationality and intuition. A question that places it beyond intuition, or identical to full rationality, is wrong.
- Only manageable information is processed — not all available information. "Processes all information with thumb rules" mixes up the steps.
Where this is taught
- Series XXI-B · Chapter 14: Behavioural Financeintroduced here
- Series X-B · Chapter 16: Basics of Behavioral Financeintroduced here
Related terms
- Anchoring biasA cognitive error in which people rely too heavily on an initial piece of information — a purchase price, a past high, a first quote — and judge everything afterwards against it.
- Behavioural financeThe study of how psychology shapes the decisions of market participants, individually and in groups, and how those decisions show up as gaps and anomalies in financial markets.
- Prospect theoryKahneman and Tversky's 1979 theory of choice under risk: outcomes are judged as gains or losses from a reference point, and losses hurt more than equal gains please.
- Mental accountingA cognitive error in which people treat equal sums of money differently depending on where they came from or what they are earmarked for, instead of treating all money as interchangeable.
- NudgeA small, low-cost change in how a choice is presented — not a mandate or a financial incentive — that steers investors toward a better decision by working with a behavioural bias instead of against it.
- Standard financeThe traditional view of finance built on rational, self-interested investors with full information — the baseline set of assumptions that behavioural finance was developed to challenge.