What is Confirmation bias?
Tasdiqlash moyilligi
In short
Seeing only information that supports your view and ignoring evidence against it. In trading: missing the warning signs because "the stock will go up anyway".
Confirmation bias is the tendency to look for and value information that supports your view while ignoring or downplaying evidence against it. It's a natural feature of human thinking, but in trading it gets expensive.
How it shows up in trading
- After buying a stock, reading only posts and news from its fans.
- Seeing only bullish signals on the chart and dismissing warnings — a broken trendline, fading volume — as "noise".
- Interpreting a bad earnings report as "the market didn't get it".
- Removing the stop because "this stock will go up anyway".
Why it's dangerous
The market doesn't know your opinion and won't adapt to it. A trader who ignores contrary evidence realises things have changed last — with a big loss. It works together with loss aversion and the sunk cost fallacy to make losses bigger.
What helps
- Before entering, write down an invalidation condition: "if price closes below $X, my idea is wrong".
- Deliberately look for the strongest arguments on the other side: "why could this stock fall?"
- Record the reason for each entry in your trading journal and compare it with the outcome.
Example
A trader bought 100 shares of an illustrative stock at $120. No invalidation was written down before entry.
Over the following weeks the company cut its guidance, price fell below the 50-day moving average, and volume rose on down days. The trader read only forum posts saying "it will go up in the long run anyway".
- Exiting at $110: loss of 100 × $10 = $1,000.
- Holding to $95: loss of 100 × $25 = $2,500.
Had "a daily close below $110 cancels the idea" been written before entry, the decision would have rested on a rule rather than on feelings. See how much of a gain is needed to recover from a decline in the drawdown calculator.
Mistakes and tips
For every trade, write down in advance the exact price or condition that proves the idea wrong.
After opening a position, read less bullish content about it and more opposing analysis.
Before deciding, ask yourself: "If I didn't own this stock, would I buy it right now?"
Frequently asked questions
- How does confirmation bias hurt traders?
- The trader misses warning signs and exits losing positions too late, so small losses turn into big ones.
- How can you protect yourself from confirmation bias?
- Writing an invalidation condition before entry, deliberately reading opposing views and reviewing decisions in a journal all help.
Learn it in the Academy
This term is covered with hands-on examples and a quiz in these lessons of the interactive course.
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