Prospect Theory: Loss Aversion & Framing

What is prospect theory (loss aversion and framing)?

Prospect theory, developed by Daniel Kahneman and Amos Tversky, describes how people actually decide under risk — which often differs from the "expected value" a calculator would pick. Two ideas do most of the work. First, we judge outcomes as gains and losses relative to a reference point (usually where we are now), not as final wealth. Second, losses loom larger than equal gains: losing $100 hurts more than winning $100 pleases, roughly twice as much. This loss aversion makes us cautious when we are ahead and protecting a gain, yet willing to take risks to avoid a sure loss. Because the reference point is chosen, the same choice can be described — "framed" — as a gain or a loss, and the framing alone can flip the decision: a policy that "saves 200 of 600 people" feels better than one where "400 of 600 die", though the numbers are identical. Prospect theory also says we overweight small probabilities and underweight large ones, which is why the same person buys both lottery tickets and insurance. It doesn't claim people are foolish — it maps the predictable shape of real choices, which is what makes those choices easier to anticipate.

How the simulation shows it

You face the same bet described two ways — once as a gain, once as an equivalent loss — and watch your own preference switch, even though the odds and payoffs never change. Feeling the switch is the fastest way to see that framing and a reference point, not just the math, drive risky choices.

Common misconceptions

• Loss aversion isn't the same as risk aversion. People often become risk-seeking to avoid a certain loss — gambling to get back to even — which pure risk aversion can't explain.
• It doesn't say people ignore probabilities; it says we distort them. Tiny chances feel bigger than they are and near-certainties feel smaller, which is why lotteries and insurance appeal to the same person.
• Framing effects aren't a sign of stupidity. Very capable people flip their choice when a problem is reworded, because the reference point does real work in how an outcome feels.

Frequently asked questions

What is prospect theory in simple terms?

It describes how people really choose under risk: we judge outcomes as gains or losses from a reference point, feel losses more strongly than equal gains, and distort small and large probabilities.

What is loss aversion?

Loss aversion is the tendency for a loss to hurt more than an equal gain feels good — roughly twice as much — which makes us protective when ahead and risk-seeking to avoid a sure loss.

What is a framing effect?

It is when the same choice, described as a gain or as a loss, leads to different decisions. Because the reference point is chosen, wording alone can flip a preference even when the underlying numbers are identical.

Why does the same person buy lottery tickets and insurance?

Prospect theory says we overweight small probabilities, so a tiny chance of a huge win (a lottery) and a tiny chance of a huge loss (needing insurance) both feel larger than they are.

Does prospect theory say people are irrational?

No. It maps the predictable shape of real decisions — reference points, loss aversion, and probability weighting — which makes those decisions easier to anticipate, not foolish.