Understand how your mind deceives you.

A cognitive bias is a systematic error in thinking that affects how we process information, make decisions, and judge situations. Rather than evaluating each situation neutrally, the brain takes mental shortcuts — called heuristics — that often work well, but sometimes lead us astray. Confirmation bias, anchoring bias, and availability heuristic are among the most well-known examples.

Cognitive biases are the systematic patterns of deviation from rational judgment that the human mind produces. They affect everything from what we remember to what we believe to how we evaluate risk. They are not a sign of low intelligence — they appear in experts and novices alike — but understanding them helps us recognize when our intuition is leading us in the wrong direction.

Cognitive biases exist because the brain evolved to make fast decisions under uncertainty with limited energy. Most of the time, mental shortcuts are efficient and good enough. The trade-off is that the same shortcuts misfire in modern contexts — statistics, complex markets, social media — that did not exist when these mechanisms developed. Daniel Kahneman called this the difference between fast, intuitive System 1 and slow, deliberate System 2.

Researchers have catalogued over 200 distinct cognitive biases in psychology and behavioral economics literature. Wikipedia's Cognitive Bias Codex lists roughly 180, organized into four broad categories. This site covers 105 of the most well-established and practically relevant biases, each with definitions, real examples, and concrete advice for recognizing and counteracting them.

First, build awareness: simply knowing a bias by name makes you more likely to spot it in your own thinking. Second, slow down on important decisions — engage System 2 by writing the choice out, listing alternatives, and considering disconfirming evidence. Third, seek outside perspectives: ask someone who disagrees, use structured checklists, or apply pre-mortems where you imagine the decision has already failed and ask why.