Bounded Rationality vs Prospect Theory
Bounded Rationality and Prospect Theory are two Behavioral Economics concepts in AP Economics that students often mix up. Bounded rationality is the idea that people make reasonable decisions within the limits of their information, time, and mental capacity. Prospect theory describes how people choose among risky options based on perceived gains and losses relative to a reference point, not final wealth. Here is how they compare side by side.
Rather than optimizing perfectly, people 'satisfice', they pick a good-enough option given real constraints. The concept, from Herbert Simon, explains why actual choices fall short of the textbook rational ideal.
Developed by Kahneman and Tversky, it shows people weight losses more than gains (loss aversion) and overweight small probabilities. It explains many real choices that expected-utility theory cannot.
Bounded Rationality vs Prospect Theory: Broken Process or Rebuilt Preferences
| Bounded Rationality | Prospect Theory | |
|---|---|---|
| What it replaces in the standard model | The process of deciding | The thing being valued |
| Does the chooser still maximize? | No, search stops once an aspiration level is met | Yes, but over gains and losses instead of final wealth |
| Core machinery | Limited information, limited time, a stopping rule | A reference point, steeper losses, distorted probabilities |
| What predicts the choice | The aspiration level and the order options arrive in | Where each outcome sits relative to the reference point |
| Risk is | One more thing that is costly to work out | The centerpiece of the model |
| Removes the effect if you change it | Make comparison instant and free | Move the reference point |
| Companion idea in the same tradition | Satisficing | Loss aversion |
Prospect theory still maximizes something, bounded rationality has stopped maximizing
Both models reject the textbook chooser who ranks every option by the expected utility of final wealth, and each rejects a different half of that picture. Bounded rationality attacks the process. The person never surveys the full option set, cannot compute the whole ranking, and quits as soon as something clears an aspiration level. Prospect theory keeps the machinery of maximization intact and rebuilds what is being maximized, replacing utility of final wealth with a value function defined over gains and losses measured from a reference point, with losses carrying more weight than gains of equal size. A prospect theory chooser is therefore still optimizing. A satisficing chooser has abandoned optimizing altogether. Put both on one scene and the division of labor shows. Someone is reselling a bike they paid 180 dollars for. Bounded rationality answers the search question: holding an aspiration of 120 dollars, they take the first offer at or above 120 and take down the listing, even though a buyer willing to pay 145 would have called the next week. Prospect theory answers a different question about the same sale, since 120 dollars lands as a 60 dollar loss against the 180 dollar reference point, which is why the seller feels cheated at a price they set themselves.
Two frames with identical final outcomes tell you which model is running
Build the test as a matched pair. In the first frame you are handed 200 dollars, then choose between a further 100 dollars for certain and a coin flip paying a further 200 dollars or nothing. In the second frame you are handed 400 dollars, then choose between giving back 100 dollars for certain and a coin flip that takes back 200 dollars or nothing. Line up the outcomes and the two frames are the same problem: the certain branch leaves 300 dollars either way, and the gamble leaves 400 or 200 on a fair coin either way, an expected value of 300. Prospect theory predicts a reversal. Gains are valued along a concave stretch of the value function, so the certain 100 dollar gain wins in the first frame, while losses are valued along a convex stretch, so the gamble wins in the second. Bounded rationality predicts no reversal at all, because the computing burden is identical in both frames, two options and one multiplication each, and a person satisficing on an aspiration of 300 dollars takes the certain branch in both. Observe the reversal and the reference point is doing the work, not the limits on calculation.
Frequently asked questions
Is prospect theory a type of bounded rationality?
Prospect theory belongs to a separate strand of behavioral economics rather than sitting inside bounded rationality. Bounded rationality, from Herbert Simon, says the process of deciding is limited by information, time and computing power. Prospect theory, from Daniel Kahneman and Amos Tversky, keeps a full comparison of options but changes what is compared, valuing outcomes as gains and losses from a reference point. Both are alternatives to expected utility theory, and they replace different parts of it.
Does prospect theory assume people maximize?
Prospect theory keeps maximization and changes the objective. A chooser is still assumed to compare options and take the highest ranked one, but the ranking uses a value function over gains and losses from a reference point, with losses weighted more heavily, plus weights that overstate small probabilities. Bounded rationality is the model that genuinely drops maximization, replacing it with a stopping rule that accepts the first option clearing an aspiration level.
Which idea explains turning down a bet with a positive expected value?
Prospect theory explains that refusal through loss aversion. Take a fair coin flip that pays 60 dollars on heads and costs 50 dollars on tails, an expected value of 5 dollars. Give losses an illustrative weight of twice the weight on gains and the felt value becomes half of 60 minus half of 100, which is a negative 20. Bounded rationality would explain a refusal differently, as a rule of thumb adopted because the odds were not worth computing.
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