Investment Psychology Dictionary: Loss Aversion Bias—How 'Not Wanting to Lose' Distorts Profit-Taking and Stop-Losses

Key Points

Loss Aversion Bias = A psychological tendency to feel the impact of a loss more intensely than a gain of the same amount.
As a result, there is a tendency to lean toward 'taking profits quickly' and 'avoiding the realization of losses.'

When to use:

Pause the moment you feel, 'I don't want to reduce this profit' or 'I don't want to admit this loss.'
For that position, check if you can write down the following in three lines:
1. How much upside you are expecting (numerical value)
2. What facts would trigger an exit (conditions)
3. How long you will monitor the situation (time limit)
If you cannot write these down, consider the position a candidate for reduction or exit.

1. Definition

Loss Aversion Bias is the tendency to feel the pain of a loss more strongly than the pleasure of an equivalent gain when comparing the two.
In the market, this manifests as 'wanting to lock in even small profits' and 'wanting to postpone realizing losses,' which disrupts the balance between profit-taking and stop-losses.

2. Common Situations

・You quickly take a 10% unrealized profit, but continue to hold a 10% unrealized loss while saying, 'I'll wait until it recovers.'

・As the price approaches a pre-determined stop-loss line, you lower the line.

・You cannot get a single loss out of your head, and because you feel, 'I don't want to lose that much again,' you become unable to enter the next opportunity.

3. How it distorts investment

・Imbalance in Risk-Reward
You tend to take small profits quickly and hold onto large losses for a long time.
This easily creates a structure where assets do not grow despite a decent win rate.

・Hollowing out of stop-loss rules
You stop following pre-determined exit criteria for reasons like, 'This stock is special,' or 'It should bounce back from here.'

・Expansion of opportunity cost
The feeling of 'I don't want to lose any more' becomes so strong that you avoid risks you should actually be taking. This erodes long-term expected value.

4. Self-Check (3 Questions)

Check how many of the following questions apply to you.
If any apply, there is a high possibility that loss aversion bias is interfering with your decision-making process.

1.Do you quickly lock in unrealized profits while holding onto unrealized losses for a long time under the pretext of 'waiting to see'?

2.When thinking about reasons for taking profits or cutting losses, do thoughts like 'I don't want to reduce this profit' or 'I don't want to realize this loss' come to mind first?

3.Do you get discouraged by a single loss right in front of you and forget the perspective of 'whether this approach will be profitable in total if I continue it'?

5. How to maintain distance

・Decide the risk-reward ratio in advance
Before entering a trade, determine the ratio of 'acceptable loss' to 'target profit' (e.g., at least 2 units of profit for every 1 unit of loss), and do not enter trades that do not meet this condition.

・Determine stop-losses based on conditions, not monetary amounts
Instead of deciding based on 'how much money is lost,' write down fact-based exit conditions in a single line, such as 'if the closing price falls below X' or 'if a certain indicator deteriorates.'

・View losses as a 'percentage'
Think of losses not in terms of 'X amount of yen,' but as a 'percentage of your assets.' This makes it harder to be swayed by the weight of the monetary amount and allows you to pre-determine the acceptable range of fluctuation.

・View trades as a 'series' rather than individual events
Judge trades not by individual wins or losses, but by whether the 'expected value is positive when this rule is followed over the long term.' This perspective helps prevent overreacting to the pain of a single loss.

6. Neru's Pocket Memo

I believe that fearing loss is not a sign of weakness as an investor, but a natural human reaction.

The problem is whether that fear takes control of the steering wheel of your judgment, rather than the fear itself.

It is actually easier on the mind to admit from the start that 'losses are painful.'
With that in mind, 'I am willing to pay this much pain for the sake of the future'—draw your own line.

Loss aversion bias might be something you have to live with by acknowledging, 'I know you're there,' while keeping a little distance, rather than trying to eliminate it entirely.

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■ Related (for further reading)
・Inability to cut losses is not weakness—'Expectations,' the sunk cost effect, and the psychology of investing [Investment x Psychology]
　── A practical look at situations where the pain of cutting losses intersects with 'expectations' and the feeling of 'what a waste.'

・Dictionary of Investment Psychology: Sunk Cost Effect
　── A memo on the mechanism by which 'I've endured this much' delays decision-making, and how to shift your focus back to the future.

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