overconfidence and confirmation bias

Ask a roomful of drivers whether they are above-average. Far more than half raise their hands — which is mathematically impossible. We tend to think we are better, smarter, luckier, and more right than the evidence warrants. And once we hold a belief, we go looking for facts that flatter it and quietly skip the ones that don't. These two linked habits — overconfidence and confirmation bias — are among the most expensive mistakes the human mind makes.

Overconfidence is the tendency to overestimate our own knowledge, abilities, and the accuracy of our predictions: people who say they are '90 percent sure' are right far less than 90 percent of the time. Confirmation bias is the close partner: once we have a view, we seek, notice, and remember evidence that confirms it while discounting evidence against it. Together they form a trap — overconfidence makes us sure, and confirmation bias feeds us only the data that keeps us sure, so we rarely get the correction that would humble us.

In economics and finance the cost is enormous. Overconfident investors trade too much (and earn less), entrepreneurs overestimate their odds, managers overpay in acquisitions, and forecasters miss crises while feeling certain. Confirmation bias hardens bubbles, deepens political polarization, and lets people ignore warning signs. The defenses are real but partial: actively seek disconfirming evidence, ask 'what would prove me wrong,' invite dissent, and keep a track record to check your past confidence against outcomes. The caveat is that some confidence is useful — it helps us act and lead — so the goal is calibration, matching how sure you feel to how sure you should be.