🧠Cognitive Biases in Investing

Humans evolved to survive in the savannah, not to manage portfolios. Our brains use mental shortcuts (heuristics) that worked great for avoiding lions but are terrible for investing. These shortcuts create predictable, repeatable mistakes called cognitive biases.

The good news: once you know what they are, you can build defenses against them. The bad news: knowing about them doesn't make you immune. Even professional fund managers fall for them regularly.

Real disaster: In 2021, retail investors poured savings into meme stocks (GME, AMC) driven by social media euphoria. Many bought at peaks of $300+ and rode them down to $20. The biases at play: herding, FOMO, overconfidence, and anchoring to unrealistic price targets. Billions in savings evaporated.

Losing €100 feels about twice as painful as gaining €100 feels good. This is loss aversion, and it causes two dangerous behaviors:

Selling winners too early: You lock in profits quickly because you're afraid they'll disappear.

Holding losers too long: You refuse to sell at a loss because realizing the loss makes it "real." Meanwhile, the stock keeps falling.

The fix: set clear rules BEFORE buying. Decide your sell criteria (fundamental deterioration, not price movement) and write them down. A falling price alone is not a reason to sell — and a rising price alone is not a reason to sell either.

Your brain "anchors" to the first number it sees. If you bought a stock at €50, you keep measuring everything against €50 — even if the company's fundamentals have completely changed.

Example: You bought Intel at €60. It drops to €25. You hold because "it was worth €60 before." But was it really? Maybe €60 was the overvalued price and €25 is fair.

The fix: regularly ask yourself "If I didn't own this stock, would I buy it TODAY at this price?" Your cost basis is irrelevant to the stock's future prospects.

After buying a stock, you unconsciously seek out positive news and ignore negative signals. You read bullish articles and skip bearish ones. You dismiss bad earnings as "one-time events."

This is confirmation bias, and it's extremely dangerous because it prevents you from updating your thesis when the facts change.

The fix: actively seek out the bear case for every stock you own. Read the most pessimistic analyst report. If you can't find strong arguments against your position, you probably haven't looked hard enough.

FOMO (Fear Of Missing Out) makes you buy stocks after they've already run up 50% because "everyone else is making money." This is how people buy at market tops.

Herding is the tendency to follow what everyone else is doing. If all your friends are buying crypto/meme stocks/AI plays, you feel pressure to join. But by the time something is popular, the easy money has already been made.

The fix: remember that the best investments are usually boring. Buffett's biggest winners were GEICO, See's Candies, and Dairy Queen — not exciting, not trendy, just great businesses bought at fair prices.

1. Investment journal: Write down WHY you buy and WHAT would make you sell. Review monthly.

2. Cooling-off period: Wait 48 hours after wanting to make a trade. If it still makes sense after sleeping on it twice, proceed.

3. Pre-mortem analysis: Before buying, imagine the stock drops 40%. What could have caused it? If you can't identify risks, you don't understand the investment.

4. Devil's advocate: For every bull thesis, write the bear thesis. If the bear case is stronger, pass.

5. Checklists: Use a standardized checklist for every purchase (fundamentals, valuation, risk, position size). This forces rational analysis over emotional decision-making.