Regret Aversion: How Fear of Regret Distorts Investment Decisions

Key Takeaways

• Regret aversion means avoiding choices that could produce regret, even when those choices have the highest expected value.
• Kahneman and Tversky's simulation heuristic shows anticipated regret scales with how easily the missed alternative can be mentally pictured.
• The action bias in regret means losses from actions feel worse than equivalent losses from inaction, driving a bias toward holding and freezing.
• Pre-committed sell rules, set before a position becomes profitable, remove the most regret-charged decisions from real-time emotional judgment.

What It Is

Regret aversion was formalised by decision theorists David Bell and, separately, Graham Loomes and Robert Sugden in 1982. Bell's paper "Regret in Decision Making Under Uncertainty" modelled the extra disutility people feel when they compare a chosen outcome to what they would have gotten from a foregone alternative. In the same year, Daniel Kahneman and Amos Tversky published "The Simulation Heuristic," which showed that the intensity of regret scales with how easy it is to mentally picture the alternative.

In an investing context, regret aversion is the preference for choices that minimise the chance of kicking yourself later, rather than choices that maximise expected return adjusted for risk. The two are not the same.

The Intuition

You choose what to buy, when to sell, and whether to rebalance knowing you will grade yourself after the outcome. Humans grade themselves harshly when a nearby counterfactual looks clearly better. Selling a position an hour before it doubles hurts more than selling the same position a month before it doubles, even though the dollar loss is identical, because the first case is easier to imagine having avoided.

That asymmetry leaks into the decision itself. If you anticipate strong regret from a specific outcome, you start shading your choice toward avoiding that outcome, even when the expected value of doing so is negative.

How It Works

Regret aversion works through two channels. Anticipated regret shows up before the decision. You predict how you will feel after each possible outcome and weight those feelings into the choice. Experienced regret shows up after the decision and pushes your next choice away from anything that resembles the one you just regretted.

Kahneman and Tversky's classic illustration uses two investors. Paul held stock A all year and considered switching to B but did not. George held B all year and switched from A. Both end up with the same dollar loss because B underperformed A. People consistently rate George as feeling worse, because his loss came from an action he took rather than an action he declined. This action bias in regret is why inaction often feels safer than equivalent action.

Regret aversion is tightly linked to loss aversion but is not identical. Loss aversion is about the gap between a gain and a loss. Regret aversion is about the gap between your outcome and the outcome you could have had.

Worked Example

Suppose you hold a stock at 100. You are offered a switch into a peer with better fundamentals, but there is a 30 percent chance the original stock rallies 20 percent over the next quarter while the peer rallies only 5.

Expected value favours the switch if you believe the peer's edge on average. A regret-averse investor still refuses. They imagine the specific scenario where they switched out right before the original ripped, then watched former colleagues discuss the 20 percent rally at every dinner for a year. That imagined scene is vivid. It dominates the cooler expected-value math.

The same investor, offered a direct choice between two new positions of equal expected value, will pick whichever one has a smaller worst-case regret rather than the one with a higher mean return. Over many decisions, the drag from this pattern compounds into meaningful underperformance.

Common Mistakes

1. Confusing regret aversion with risk aversion. A rationally risk-averse investor takes less volatility for less expected return. A regret-averse investor may take a worse expected outcome in any risk bucket just to dodge the most easily imagined negative story.

2. Freezing on a winner. Sitting on a concentrated position long after it has become oversized, because you can vividly picture the trim that happens right before the next double. This is regret aversion dressed up as conviction.

3. Delaying a switch. Refusing to sell a losing fund manager because you can picture the month after you leave being their best ever. In practice, the reverse happens about as often, but it is less vivid, so it gets less weight.

4. Using default options as protection. Picking the target-date fund your employer suggests, not because it is the best fit, but because if it underperforms you can point to the default and say you followed guidance. Regret deflection is a real use of defaults and sometimes rational, but worth naming.

5. Asymmetric post-mortems. After a bad sell, you rerun the decision in detail. After a bad hold, you barely review it. The asymmetry trains your next decision to favour holding, regardless of whether holding is correct.

Frequently Asked Questions

What is regret aversion in simple terms? Regret aversion is choosing options that minimise anticipated regret rather than maximising expected return. You avoid an action not because it has negative expected value, but because you can clearly picture a scenario in which you would kick yourself for having taken it, even when the action is objectively the better choice.

How does regret aversion affect investment decisions? It creates a bias toward inaction. Losses from holding feel less personally blameworthy than losses from switching, Kahneman and Tversky's example shows people consistently rate the switcher's loss as more painful than the holder's identical loss. Over time, this asymmetry pushes toward frozen winners, delayed exits, and stale allocations.

What is a real-world example of regret aversion? A concentrated winner has grown to 20 percent of the portfolio. The rational action is to trim and rebalance. Regret aversion keeps it in place because the investor can vividly picture selling right before the next double, a specific, emotionally charged scenario that looms larger than the abstract but real benefit of diversification.

How can investors manage regret aversion? Set trim and exit rules at position entry, before the gain is on paper. Pre-committed rules remove the most regret-charged decisions from real-time emotional judgment. Also run symmetric post-mortems: if you scrutinise bad sells in detail but barely review bad holds, you are training your process to favour holding regardless of whether it is correct.

How is regret aversion different from loss aversion? Loss aversion is the asymmetric pain of a loss versus an equivalent gain. Regret aversion is the pain of comparing your actual outcome to the one you could have had. Your purchase price can trigger both: it creates the reference point for loss aversion and the counterfactual for regret aversion. Both patterns push in the same direction but through different psychological channels.

Sources

1. Kahneman, D. & Tversky, A. (1982). "The Simulation Heuristic." In Judgment Under Uncertainty: Heuristics and Biases. Cambridge University Press. https://apps.dtic.mil/sti/tr/pdf/ADA099504.pdf
2. Bell, D.E. (1982). "Regret in Decision Making Under Uncertainty." Operations Research, 30(5), 961-981. https://pubsonline.informs.org/doi/10.1287/opre.30.5.961
3. CFA Institute. "The Behavioral Biases of Individuals." Refresher Readings. https://www.cfainstitute.org/insights/professional-learning/refresher-readings/2026/the-behavioral-biases-of-individuals
4. Kahneman, D., Knetsch, J.L. & Thaler, R.H. (1991). "Anomalies: The Endowment Effect, Loss Aversion, and Status Quo Bias." Journal of Economic Perspectives, 5(1), 193-206. https://www.aeaweb.org/articles?id=10.1257/jep.5.1.193

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.