What is Confirmation Bias?
Confirmation bias is the tendency to favor information that supports your existing beliefs and to dismiss or underweight information that contradicts them. In investing, this manifests as seeking out bullish analysis for stocks you own while ignoring warning signs, or reading only news sources that align with your market outlook. This bias is deeply ingrained in human cognition and affects even experienced investors.
Impact on Investment Decisions
An investor who believes a particular stock will rise may focus on positive earnings reports and analyst upgrades while dismissing declining market share or increasing debt. This selective attention can lead to holding losing positions too long or concentrating too heavily in a single investment. Research shows that investors who actively seek disconfirming evidence make significantly better decisions over time.
Key Considerations
To combat confirmation bias, deliberately seek out opposing viewpoints before making investment decisions. Create a written investment thesis with specific conditions that would invalidate it. Regularly review your portfolio with fresh eyes, asking whether you would buy each position today at its current price. Diversification itself is a structural defense against confirmation bias in any single investment.