Confirmation Bias
Definition
Confirmation bias is the tendency to seek out, notice, and remember information that supports a trade idea you've already formed — while subconsciously filtering out evidence that contradicts it.
Example
“I was so convinced the stock was going higher that I ignored the fact that relative volume was half of what I'd want to see and the broader market was breaking down. Every bullish sign felt meaningful; every warning felt like noise.”
Detailed Explanation
Confirmation bias is particularly dangerous in trading because markets give you plenty of signals on both sides at any given time. If you've decided a stock is bullish, you can always find reasons to agree with yourself: the pattern looks right, there's support nearby, the sector is strong. The process of actively looking for contradictory evidence is what separates disciplined analysis from rationalization. The question isn't "why should I take this trade?" but "what would need to be true for this trade to fail — and is that happening?"
Social media and trading chatrooms amplify confirmation bias dramatically. When you're in a stock and see a hundred other traders posting about how great the setup looks, it feels like validation. But they were probably drawn to the same stock for the same reasons, which means you're all sharing the same blind spots. Popular opinion in trading communities is often a contrarian indicator — when everyone agrees, the setup is usually already crowded and late.
One practical way to fight confirmation bias is to write down your invalidation criteria before you enter a trade. "This trade fails if X happens." Then during the trade, you're not asking whether the trade still looks good — you're asking whether the specific condition that would prove you wrong has occurred. This reframes your analysis from seeking comfort to seeking truth, which is a much more useful mindset.