Confirmation Bias

The Story

James is convinced that Tesla is the future. He reads articles about electric vehicle adoption, follows Elon Musk's posts, and watches YouTube videos about why Tesla will dominate. When he sees negative news — production delays, competition catching up, overvaluation warnings — he dismisses it. "Haters," he thinks.

James doesn't realise it, but he hasn't made an informed decision. He's made a decision and then found information to support it.

What Is Confirmation Bias?

Confirmation bias is the tendency to search for, interpret, and remember information that confirms your existing beliefs, while ignoring or downplaying information that contradicts them.

It's one of the most pervasive cognitive biases, affecting everything from politics to personal relationships to investment decisions.

Confirmation Bias in Finance

This bias is particularly dangerous with money:

• Stock picking: Researching only the bull case for a stock you've already bought
• Property: Focusing on reasons why property prices will keep rising while ignoring risks
• Fund selection: Choosing funds that confirm your market view
• Economic views: "The market will crash" — then only reading bearish news
• Crypto: Following only true believers in a specific coin or token

The problem isn't having a view. It's the asymmetric treatment of evidence. Information that supports your position gets accepted easily; information that challenges it gets scrutinised, questioned, or ignored.

Why It's So Dangerous

In investing, confirmation bias can:

• Keep you in a losing position long after the evidence says sell
• Make you over-concentrate in one asset or sector
• Prevent you from diversifying
• Create an echo chamber of like-minded investors who reinforce each other's views

Research finding: Barber and Odean (2001) found that individual investors who trade more frequently (often driven by overconfidence reinforced by confirmation bias) underperform by approximately 6.5% annually compared to simple buy-and-hold strategies.

How to Fight It

1. Actively seek the opposing view — if you're bullish on something, deliberately read the bear case
2. Create a "pre-mortem" — before investing, write down three reasons why this investment could fail
3. Diversify by default — index funds force you to own everything, not just what you believe in
4. Keep an investment journal — write down why you're buying at the time you buy. Review later to see if your reasoning was sound or biased
5. Follow people you disagree with — intellectually honest investors engage with opposing views

Reflection Questions

1. Think of a financial belief you hold strongly. When was the last time you genuinely engaged with evidence against it?
2. Have you ever held onto an investment despite mounting negative evidence? What kept you holding?
3. Where do you get your financial information? Is it diverse, or does it tend to confirm what you already think?

Research Note

Confirmation bias is extensively documented in Peter Wason's original selection task experiments (1960) and has been applied to financial markets by multiple researchers. Rabin and Schrag ("First Impressions Matter", Quarterly Journal of Economics, 1999) show that even rational agents who process information with a slight confirmatory bias can converge on the wrong belief with high confidence.