Confirmation Bias Explained
What is it?
Confirmation bias is the tendency to seek out, notice, and remember information that supports a belief you already hold, while ignoring or dismissing information that contradicts it. In investing, this means once you've decided a fund or sector is good, you tend to only notice the positive news about it and overlook warning signs.
Why should you care?
Confirmation bias prevents investors from objectively reassessing their holdings. If you bought a fund because a friend recommended it, you may unconsciously filter out later evidence it's underperforming, holding on far longer than the evidence would justify — turning a manageable mistake into a large one.
Real-life example
An investor who buys into a sector fund based on a bullish news article may, from that point on, only read articles that reinforce the bullish thesis, while skipping or discounting articles raising concerns about the sector's valuations. When the sector eventually corrects, the investor is caught off guard — not because the warning signs weren't available, but because confirmation bias filtered them out of view long before the correction happened.
Common mistakes
- Only reading news and opinions that agree with a fund choice you've already made, rather than actively seeking out counter-arguments.
- Interpreting a fund's temporary bad performance as "noise" while treating any good performance as proof you were right, an inconsistent double standard.
- Asking for opinions only from people likely to agree with you, rather than seeking a genuinely independent view.
Confirmation bias vs. objective review when evaluating a fund you already own
| Confirmation bias | Objective review | |
|---|---|---|
| Good news about the fund | Noted as validation | Checked for substance |
| Bad news about the fund | Dismissed or ignored | Investigated seriously |
| Underperformance | Explained away as "temporary" | Compared against category and benchmark data |
FAQ
How is confirmation bias different from recency bias?
Recency bias overweights recent events regardless of prior belief; confirmation bias overweights information that agrees with a belief you already hold, regardless of when it occurred. They often act together — for example, recent good news about a fund you like gets doubly overweighted.
How can I check my own portfolio without confirmation bias?
Use objective, standardised data — like FundSageAI's fund comparison and benchmark analysis tools — rather than relying only on your own memory of news you've read, which is naturally filtered by what you already believe.
Is it bad to feel confident about an investment decision?
Confidence isn't the problem — the problem is confidence that isn't periodically tested against new, possibly contradictory, evidence. A periodic, scheduled portfolio review is a good structural defence against this bias.
Does confirmation bias affect fund managers too?
Yes, professional investors are subject to the same cognitive bias — it's one reason disciplined, rules-based investment processes and periodic independent reviews are considered good practice even for professionals.
See this concept applied to your own portfolio
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