Confirmation Bias
Confirmation bias is the tendency to search for, interpret, and remember information in a way that confirms your pre-existing beliefs. It's arguably the most pervasive and damaging of all Cognitive Biases.
Why It Matters
- Investment decisions: Once you've decided a company is great, you'll unconsciously filter news to support that view. Charlie Munger warns that this bias has destroyed more investment theses than bad math ever has.
- Science: Researchers may unconsciously design experiments or interpret data in ways that support their hypothesis. The replication crisis is partly a story about confirmation bias at scale.
- Everyday reasoning: People choose news sources that align with their existing views, creating echo chambers that reinforce rather than challenge beliefs.
Defenses
Inversion is one of the best defenses: actively asking "What would prove me wrong?" forces you to seek disconfirming evidence. Probabilistic Thinking helps by requiring you to assign actual numbers to your confidence, making it harder to hide behind vague certainty.