Prospect theory: how loss aversion affects trading behaviour
Prospect theory is a behavioural economics model that explains how people make decisions when outcomes are uncertain. In simple terms, it shows that people often react differently to gains and losses, even when the amounts are the same. Developed by psychologists Daniel Kahneman and Amos Tversky and published in 1979, the theory challenged the idea that people always make fully rational decisions under risk. It has since become one of the most important ideas in behavioural finance and trading psychology.
Takeaways
- Prospect theory explains that people judge outcomes against a reference point, not in absolute terms.
- Loss aversion means losses can feel more intense than equivalent gains.
- The theory helps explain why traders may sell winning positions too early and hold losing ones too long.
- In leveraged CFD trading, these effects may feel stronger because price moves can have a larger impact on position value.
- Knowing about prospect theory does not remove its influence. Awareness is a useful first step, but structure matters too.
- Stop-losses, written plans and pre-defined risk parameters may help traders make more consistent decisions.
What is prospect theory?
Prospect theory describes how people make decisions when there is risk or uncertainty. Rather than asking how a perfectly rational person should behave, it looks at how people tend to behave in real situations. The key idea is that people do not judge outcomes only by the final amount of money gained or lost. They judge them against a reference point. In trading, that reference point might be the price where a position was opened, the account balance at the start of the day, or a recent high.
For example, a $500 gain may feel very different depending on the starting point. If a trader was previously down $1,000, the move may feel like partial recovery. Conversely, if they were already in profit, the same $500 gain may feel like further progress. The financial amount is the same, but the psychological experience is different.
Prospect theory uses a value function to describe this effect. The term may sound technical, but the basic idea is simple: gains and losses do not feel equal. As gains increase, each extra gain tends to feel less satisfying than the one before it. As losses increase, each extra loss may feel painful, but the response can also become less sensitive at larger amounts.
Most importantly, losses tend to feel stronger than gains of the same size. This is known as loss aversion. For traders, this can affect how they respond to open positions, especially when a trade moves against them.
Origins and development of prospect theory
Prospect theory grew out of research into how people make choices under risk. Before Kahneman and Tversky developed the theory, economists often used models based on the idea of the rational decision-maker.
Expected utility theory – the rational baseline
Before prospect theory, the main model was expected utility theory, developed by John von Neumann and Oskar Morgenstern in 1944. It assumes that people weigh up possible outcomes, consider their probabilities, and choose the option that gives them the best expected result. In this model, people are generally risk-averse. That means they often prefer a certain outcome to a risky one with the same expected value. But real choices do not always follow that pattern. In 1953, the Allais Paradox showed that people often prefer certainty in ways expected utility theory cannot easily explain. This did not replace the older model, but it showed that a more realistic description of decision-making was needed (Britannica, accessed 12 June 2026).
Kahneman and Tversky’s research programme
During the late 1960s and 1970s, Daniel Kahneman and Amos Tversky ran experiments in which people chose between different risky outcomes. Their work showed clear and repeated patterns. People reacted more strongly to losses than gains. They relied heavily on reference points. They also treated probabilities unevenly, often giving too much weight to small chances and too little weight to higher probabilities. Their 1979 paper, ‘Prospect Theory: An Analysis of Decision under Risk’, brought these findings together into one model. It remains a major reference point in behavioural economics and finance (ScienceDirect, accessed 12 June 2026).
Cumulative prospect theory
In 1992, Tversky and Kahneman developed the theory further with cumulative prospect theory, making the model more flexible and better suited to situations with more than two possible outcomes. Daniel Kahneman received the Nobel Prize in Economic Sciences in 2002 for work linked to decision-making under uncertainty. Amos Tversky died in 1996, and Nobel prizes are not awarded posthumously (UBS, accessed 12 June 2026).
Key principles of prospect theory
Prospect theory has several core ideas. Together, they help explain why traders may behave differently when they are in profit compared with when they are in loss.
Reference point dependence
People judge outcomes against a reference point. In trading, this often means the entry price of a position. A trader who bought an asset at $100 may see $95 as a loss. Another trader who bought the same asset at $90 may see $95 as a gain. Both are looking at the same price, but their experience is different because their reference points are different. This matters because trading decisions are not made in isolation. They are often shaped by where the trader started, what they expected, and whether they feel ahead or behind.
The value function – why gains and losses feel different
The value function describes how people experience gains and losses. For gains, the effect of each extra gain tends to shrink. The first $100 of profit may feel more significant than the move from $1,000 to $1,100. A similar pattern can happen with losses. The difference between losing $100 and $200 may feel larger than the difference between losing $1,000 and $1,100. This does not mean larger losses do not matter. They do. But it helps explain why traders may sometimes become less responsive as losses build, especially if they are focused on getting back to their original reference point.
Loss aversion
Loss aversion is one of the best-known parts of prospect theory. It means losses usually feel more intense than gains of the same size. Experimental estimates often suggest that losses may feel roughly two to 2.5 times as strong as equivalent gains, though this varies by person and situation. For a trader, this means a $500 loss may feel more powerful than the satisfaction of a $500 gain. That emotional imbalance can affect decisions, especially when a trader is deciding whether to close, hold, or adjust a position.
Probability weighting
People do not always treat probabilities in a straight line. They may give too much weight to small chances and too little weight to more likely outcomes. This can affect trading in different ways. A trader may focus heavily on a small chance of a large gain. Another may focus heavily on a small chance of a sharp loss. In both cases, the decision may be influenced by how the probability feels, not just by what the numbers suggest.
The four-fold pattern of risk attitudes
When reference points, loss aversion and probability weighting combine, they can create a common pattern:
- People may take profits early when gains feel likely.
- People may hold losing positions when they hope the market will recover.
- People may be drawn to low-probability, high-reward outcomes.
- People may over-protect against rare but severe losses.
This pattern helps explain why the same trader can be cautious in one situation and risk-seeking in another. The difference often depends on whether they feel they are in the gain or loss zone.
Prospect theory in financial markets
Prospect theory has been used to explain several behaviours seen in financial markets. It does not explain every market move, but it offers a useful way to understand how human behaviour can shape trading decisions.
The disposition effect
The disposition effect is the tendency to sell winning positions too early and hold losing positions too long. It was identified by Hersh Shefrin and Meir Statman in 1985. Prospect theory helps explain why this can happen. When a position is in profit, closing it creates a certain gain. That can feel satisfying, even if the original trading plan suggested holding for longer. When a position is in loss, closing it makes the loss real. A trader may hold on because there is still a chance the position could recover. This can lead to greater risk, especially if the loss continues to grow.
The equity premium puzzle
The equity premium puzzle asks why stocks have historically produced returns above risk-free rates by more than traditional models might predict. Loss aversion offers one possible explanation. If investors feel losses more strongly than gains, they may require a higher potential return to accept the ups and downs of equity markets. In this view, the emotional cost of losses makes risky assets feel more difficult to hold.
Momentum and underreaction
Loss aversion may also contribute to slower market reactions. If investors are reluctant to sell losing positions, they may delay responding to negative news. Where many market participants behave this way, prices may adjust gradually rather than immediately. This can contribute to momentum, where assets that have been moving in one direction continue in that direction for a time.
Prospect theory and trader behaviour
For individual traders, prospect theory can show up in everyday decisions: when to close a trade, when to hold, when to adjust a stop, and when to add to a position.
- Widening stop-losses: a trader may move a stop-loss further away as the market approaches it, often to avoid closing at a loss. If this wasn’t part of the original plan, it may increase risk.
- Cutting winning trades too early: when a trade is in profit, the gain can feel valuable and fragile. A trader may close early to lock it in, even if the original plan allowed for a larger move.
- Averaging down on losing positions: adding to a losing position can reduce the average entry price, but it also increases exposure. In CFD trading, leverage can magnify losses and create margin pressure.
- Taking more risk to avoid losses: once a position is losing, a trader may become more willing to take extra risk to avoid making the loss real.
- Mental accounting: a trader may treat positions separately, such as focusing on smaller winners while ignoring one larger loss. This can make the account feel more manageable than it is.
- Looking at total exposure: a more structured approach considers the full picture: open positions, total exposure, margin use and the potential impact of further price moves.
Applying prospect theory to CFD trading
CFD trading has features that can make prospect theory especially relevant. These include leverage, short selling, fast price moves and frequent decisions about stop-losses and take-profits.
Leverage can make emotions stronger
Leverage magnifies both gains and losses. With a 10:1 leveraged position, a 1% price move produces a 10% change in position value. This can make the emotional impact of gains and losses stronger. A loss on a leveraged position may feel more intense than an equivalent gain feels positive, even if the financial amount is the same. This does not mean leverage is always unsuitable. It means traders need to understand how it changes both financial exposure and emotional pressure.
Pre-setting stops can add structure
One way to reduce in-the-moment decision-making is to set stop-loss levels before opening a trade. This matters because decisions can feel different once a trade is live. Before entry, the trader can assess risk more calmly. Once the position is open and moving against them, loss aversion may influence the decision. A pre-set stop-loss does not remove risk, and not all stop-losses are guaranteed. But it can help turn a difficult real-time decision into a rule decided in advance.
Defining risk-reward ratios in advance
Prospect theory suggests traders may take profits too early because a certain gain feels appealing. Defining risk-reward parameters before opening a trade can help create more consistency. For example, a trader might decide only to consider setups where the potential target is at least twice the stop distance. This does not guarantee a positive result, but it can help align the exit decision with the original plan rather than the emotion of the moment.
Using a demo account to spot patterns
A demo account can help traders observe their own behaviour without risking real funds. They can review whether they often widen stop-losses, close winning trades early, or add to losing positions. The aim is not to prove that a trader has 'solved' loss aversion. The aim is to identify patterns. Once a pattern is visible, it becomes easier to build rules around it.
Criticisms and limitations of prospect theory
Prospect theory is useful, but it is not a complete explanation of trading behaviour. It has several limitations.
- The reference point isn’t always clear: traders may focus on different points, such as the entry price, yesterday’s close, the day’s high or a target. This can change as the trade develops.
- People react differently to gains and losses: loss aversion varies. Some traders may feel losses strongly, while others may be less sensitive due to experience, risk appetite or trading style.
- It doesn’t fully explain time horizons: trading often involves time-based decisions, such as closing before the end of the day or holding overnight. Funding costs, market events and strategy can also affect the decision.
- Other behavioural models matter too: prospect theory is only one lens. Regret, habit, overconfidence and fast-versus-slow thinking can also shape trading behaviour.
- Awareness alone isn’t enough: knowing about loss aversion doesn’t remove the feeling of closing a losing trade. Practical tools such as trading plans, stop-losses, position sizing rules and trade reviews can help add structure.*
*Standard stop-losses aren’t guaranteed. Guaranteed stop-loss orders (GSLOs) incur a fee if activated.
Common misconceptions about prospect theory
Prospect theory is sometimes simplified too much when applied to trading. These are some of the most common misunderstandings.
Misconception 1: ‘Loss aversion means avoiding losses at all costs’
Loss aversion does not mean people always avoid losses. It means losses feel stronger than equivalent gains. In fact, prospect theory suggests people may take more risk when they are already facing a loss. A trader may hold a losing position or increase exposure because they want to avoid closing at a loss. That can create more risk, not less.
Misconception 2: ‘It’s just the same as being risk-averse’
Risk aversion means preferring a safer outcome over a riskier one. Prospect theory is more nuanced. A trader may be cautious when in profit but take more risk when in loss. The shift depends on the reference point. This is why the same person can behave differently across different trades.
Misconception 3: ‘Understanding it will fix the problem’
Understanding prospect theory can help traders recognise what is happening, but it does not remove the emotional response. A written plan, clear position sizing, stop-loss rules and regular trade reviews can help reduce the need to make difficult decisions under pressure.
Misconception 4: ‘It only applies to long-term investors’
Prospect theory can apply to long-term investors, short-term traders and day traders.
In fast-moving CFD trading, the effect may be more immediate because traders make frequent decisions and reference points can update quickly. Each open position can create a new gain or loss zone.
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FAQ
What is prospect theory?
Prospect theory explains how people make decisions when outcomes are uncertain. It shows that people often judge gains and losses against a reference point, and that losses usually feel stronger than equivalent gains. Daniel Kahneman and Amos Tversky developed the theory in 1979.
What did Kahneman and Tversky demonstrate with prospect theory?
Kahneman and Tversky showed that people do not always make decisions in the way traditional economic models predict. Their research found that people react strongly to losses, use reference points when judging outcomes, and treat probabilities unevenly. Their 1979 paper turned these findings into a formal model. Daniel Kahneman received the Nobel Prize in Economic Sciences in 2002 for related work.
How does loss aversion affect trading?
Loss aversion can affect trading by making losses feel more intense than gains of the same size. This may lead traders to hold losing positions too long, sell winning positions too early, or move stop-losses to avoid closing at a loss. In leveraged trading, the effect may feel stronger because gains and losses can be magnified.
What is the disposition effect?
The disposition effect is the tendency to sell winning positions and hold losing ones. Prospect theory helps explain this pattern. A trader may close a winning position to secure a gain, while holding a losing position in the hope that it recovers. Shefrin and Statman identified the effect in 1985, and later research has found it across different markets and asset classes.
How does prospect theory differ from expected utility theory?
Expected utility theory assumes people make rational decisions by weighing possible outcomes and probabilities. Prospect theory describes how people often behave in practice. It focuses on gains and losses relative to a reference point, the stronger emotional impact of losses, and the way people can treat probabilities unevenly.
Can understanding prospect theory improve trading outcomes?
Understanding prospect theory may help traders recognise when loss aversion or the disposition effect could be influencing their decisions. However, awareness alone does not remove the risk. Structural tools such as written trading plans, pre-set stop-losses, position sizing rules and trade reviews may help create more consistent decision-making. No approach eliminates the risk of loss in CFD trading.
