Pro Investor Academy
LESSON 8.4
6 min learning time

Loss Aversion

Losses tend to feel roughly twice as painful as equivalent gains feel pleasant, and that asymmetry shapes bad decisions.

The short answer

Well-documented behavioural research suggests losses feel roughly twice as heavy as an equivalent gain feels good. That asymmetry pushes investors to hold losing positions too long hoping to avoid realising a loss, and to sell winning positions too early to lock in a gain — often the opposite of a sound long-term posture.

Learning objectives

  • Describe loss aversion and its rough emotional asymmetry between losses and gains
  • Explain the connection between loss aversion and holding losers or selling winners too early
  • Describe two opposite checking habits — anxious over-monitoring and avoidance after losses — and a planned review process
  • Explain how a written policy and position sizing reduce the pressure loss aversion creates

The asymmetry

Behavioural research associated with Kahneman and Tversky suggests that, for many people, a loss feels roughly twice as painful as an equivalent gain feels rewarding.

That imbalance is not a character flaw. It appears to be a common feature of how people process gains and losses generally, not only in investing.

Two common results

Holding a losing position far longer than the evidence supports, to avoid the discomfort of turning a paper loss into a realised one.

Selling a winning position quickly, to lock in a gain before it can turn into a loss — sometimes cutting off a position that still had a sound long-term case.

Checking too often — or not at all

People do not all react to losses the same way. Some check anxiously and often, and each look at a painful number adds pressure to act. Others do the opposite: research on real retirement-account logins (Sicherman, Loewenstein, Seppi and Utkus, 2016) found many investors logged in less after market declines — an "ostrich effect" also described by Karlsson, Loewenstein and Seppi (2009). Both habits can hurt: over-monitoring invites reactive trades; avoidance can mean missing a real problem, a needed rebalance or a changed goal.

Limits: these studies describe average patterns in specific U.S. samples and periods; they do not predict what any one person will do.

  • Pick a review date in advance (for example, quarterly or yearly) and keep it in rising and falling markets
  • Use a short checklist: allocation versus target, cash needs, any thesis broken, any change in your life
  • Decide in writing what would make you act before looking at the balance
  • Between reviews, only act on the triggers written in your policy

What reduces the pressure

A written policy, decided in advance and while calm, describes what would justify selling — separate from price movement alone.

Sizing positions so that no single holding can produce an unbearable loss also reduces the emotional intensity of any one decline, which makes it easier to stick to the plan.

Loss aversion's two common mistakes
Losing positionHeld too long

To avoid realising the loss

Winning positionSold too early

To lock in the gain before it disappears

The same underlying bias tends to distort decisions in opposite directions.

Key concepts

Select a term to read its definition.

  • Loss aversion

    The tendency for losses to feel more painful than equivalent gains feel good.

    View in the glossary
  • Realised loss

    A loss locked in by selling below your cost basis. A decline you have not sold is an unrealised loss.

    View in the glossary
  • Position sizing

    Deciding how much to hold in one investment. It limits how much a mistake can cost; it does not make the choice unimportant.

    View in the glossary
See the full glossary

Why this matters

An asymmetry this common and well-documented is worth planning around in advance, rather than discovering it in the middle of a decline.

Common mistakes

  • Holding a position well past the point the original evidence supported, purely to avoid realising a loss
  • Selling a sound long-term holding shortly after a modest gain, out of fear of losing that gain

Check your understanding

No score is recorded. This is only here to test whether the lesson landed.

1. What does loss aversion describe?
2. True or false: loss aversion can cause investors to hold losing positions too long and sell winning positions too early.
3. An investor checks their account daily during a market decline and feels growing pressure to sell. What does this lesson suggest as a more durable approach?

0 of 3 answered. Answer every question to see the answers.

Key takeaways

  • Losses tend to feel roughly twice as heavy as equivalent gains, for most people
  • This asymmetry can cause losers to be held too long and winners to be sold too early
  • Some investors over-monitor during declines and others avoid looking; a scheduled review avoids both
  • A written policy and sensible position sizing both reduce the pressure loss aversion creates
Written by
Pro Investor Academy Research Team
Content type
Educational article
Published
2026-09-13
Last reviewed
2026-09-13

Sources

FOMO and HypeConfirmation Bias and Overconfidence

Educational content only. This lesson is not investment, tax or legal advice and does not recommend buying or selling any specific investment. All investing involves the risk of loss.