The gambler's fallacy
Atlas of Cognitive Biases #1 · Randomness and probability. The market doesn't owe you a bounce
What it looks like in trading
- “Five red candles in a row, it has to bounce now.”
- increasing risk after a losing streak because “it has to work now”
- believing a decline is “certain” after a few up days
An example from a session
Five 1-minute down candles in a row on MYM. The trader sees “oversold” and waits for a bounce as if it were certain. In our data, after 1–4 candles in one direction, the next one went the same way 50–52% of the time: practically a coin toss (Biases by the numbers #1).
What the research says
The most famous example is the Monte Carlo casino in 1913: black came up 26 times in a row, and gamblers lost fortunes betting on red. Amos Tversky and Daniel Kahneman (1971) described the source of the error: we expect even short sequences to look “representative”, i.e. like the whole.
The shield: how to defend yourself
- write down the base rate: how often does the market actually reverse after such a streak?
- judge the situation by its context (level, day type), not by the length of the streak
- a losing streak is a signal to take a break and review, not to win it back
Exercise
For a week, tag every situation in your journal where you notice this bias in yourself with #1, even when it didn't affect your decision. After the week, count them and write down the conditions in which it appeared most often.
Educational content, not psychological advice or an investment recommendation. You make every decision yourself, in line with your own plan.
Related biases
- The hot hand fallacy (#2)
- The law of small numbers (#3)
- The clustering illusion (#4)
Frequently asked questions
What is the gambler's fallacy?
The belief that after a series of identical outcomes the opposite outcome is “due” – as if chance had a memory and cared about evening the score.
How does the gambler's fallacy show up in trading?
Typical signs: “Five red candles in a row, it has to bounce now.”; increasing risk after a losing streak because “it has to work now”; believing a decline is “certain” after a few up days.
How do I defend myself against this bias?
Write down the base rate: how often does the market actually reverse after such a streak?; judge the situation by its context, not by the length of the streak; a losing streak is a signal to take a break and review, not to win it back.
Educational content, not psychological advice or an investment recommendation.