Cognitive Biases

Your brain is not a truth-finding machine. It’s a survival machine.

Evolution optimized for quick decisions, not accurate ones. The result: systematic errors in thinking that were useful on the savanna but misleading in modern life.

These errors are called cognitive biases. Everyone has them. They operate automatically. And they distort your perception, memory, and judgment without you realizing it.

You can’t eliminate them. But you can learn to notice them.

Why this matters

Biases affect everything:

What you remember (and what you forget)
How you evaluate information
What decisions you make
How you predict the future
How you interpret the past
Who you trust
What you believe

Most bad decisions involve cognitive biases somewhere. Understanding them helps you catch errors before they cost you.

The major biases

There are dozens of documented biases. Here are the ones most likely to mess with your life:

Confirmation bias

You seek and interpret information in ways that confirm existing beliefs.

Found an article supporting your view? Compelling evidence! Found one challenging it? Flawed methodology!

This creates filter bubbles. You end up more and more convinced of things that may not be true, because you only encounter “evidence” that supports them.

Counter: Actively seek disconfirming evidence. Ask “what would prove me wrong?” Steel-man opposing views before dismissing them.

Availability heuristic

You judge probability by how easily examples come to mind.

Plane crashes are memorable, so people overestimate flying danger. Heart disease is boring, so people underestimate it (even though it kills far more).

Media amplifies this. Vivid, scary, unusual events get coverage. Common, important, mundane events don’t.

Counter: Check actual data before trusting your intuition about frequency. Ask “is this easy to remember because it’s common, or because it’s vivid?”

Anchoring

The first number you hear influences your judgment, even if it’s irrelevant.

If I ask “Was Gandhi older or younger than 140 when he died?” and then “How old was he?” - you’ll guess higher than if I’d said 20.

Salespeople know this. The initial price (even if absurd) anchors negotiation.

Counter: Generate your own anchor before hearing others. Ask “what would I estimate without any anchor?”

Sunk cost fallacy

You continue investing in something because of past investment, not future value.

You keep reading a bad book because you’re halfway through. You stay in a bad relationship because you’ve invested years. You keep working on a failing project because you’ve spent so much already.

Past costs are gone. They can’t be recovered. Only future costs and benefits matter for decisions.

Counter: Ask “if I were starting fresh today, would I choose this?” Ignore what you’ve invested. Focus on what you’ll gain or lose going forward.

See also: Sunk Cost

Hindsight bias

After something happens, you think you “knew it all along.”

You didn’t. You’re rewriting history to create a narrative where the outcome was obvious. This makes you overconfident in your ability to predict the future.

Counter: Record predictions before outcomes. You’ll be humbled by how often you were wrong about “obvious” things.

Fundamental attribution error

You attribute others’ behavior to their character, but your own behavior to circumstances.

They’re late because they’re irresponsible. You’re late because traffic was bad.

This creates unnecessary conflict and misunderstanding.

Counter: Ask “what circumstances might explain this behavior?” Give others the same benefit of the doubt you give yourself.

Dunning-Kruger effect

The less you know, the more confident you are. Beginners overestimate their competence. Experts underestimate it.

This is because competence helps you see what you’re missing. Incompetence blinds you to gaps.

Counter: Assume you know less than you think, especially in new domains. Calibrate confidence by getting feedback.

Loss aversion

Losses hurt more than equivalent gains feel good. Losing $100 feels worse than finding $100 feels good.

This makes people irrationally risk-averse in some situations and irrationally risk-seeking in others (to avoid realizing losses).

Counter: Reframe decisions in terms of final outcomes, not gains/losses from current state. Ask “what would I choose if starting from scratch?”

Present bias

You overweight immediate rewards relative to future rewards.

This is why you scroll instead of sleep, eat junk instead of healthy food, skip the gym, procrastinate.

Future you is a stranger. Present you has all the power.

Counter: Make good future choices the default. Remove friction from good behaviors, add friction to bad ones. Pre-commit to things.

Optimism bias

You think bad things are less likely to happen to you than to others.

“Other people get divorced. Our marriage is different.” “Other smokers get cancer. I’ll be fine.”

This isn’t hope - it’s distorted probability estimation.

Counter: Check base rates. Ask “what happens to most people in this situation?” Assume you’re not special.

Working with biases

You can’t eliminate biases through willpower. They’re baked into brain architecture. But you can:

1. Know they exist. Just knowing about biases makes you more likely to notice them. This list is a starting point.

2. Slow down important decisions. Biases operate most strongly when thinking fast. For important decisions, deliberately slow down and check for bias.

3. Seek outside perspectives. Your biases are invisible to you but visible to others. Trusted advisors can catch what you miss.

4. Use checklists. For recurring decisions, create checklists that force you to consider alternatives, check assumptions, and look for bias.

5. Track your predictions. Keep a record of what you predicted and what happened. Review it. Calibrate your confidence.

6. Create systems. Don’t rely on resisting bias in the moment. Design environments and habits that work around your biases.

The deeper lesson

Biases are humbling. Your brain - the thing you use to think - is systematically unreliable in predictable ways.

This doesn’t mean you can’t trust your judgment at all. It means you should hold your judgments lightly, check them against reality, and assume you might be wrong.

Intellectual humility isn’t weakness. It’s calibration.

Related: Uncertainty (why certainty is often false), First Principles (checking assumptions), Decisions (making better choices)