Bias↕ | Category↕ | Discovered By↕ | Real-World Example↕ | Why It Happens↕ |
|---|---|---|---|---|
Confirmation Bias | Belief | Peter Wason (1960) | Only reading news that agrees with your politics | Brain seeks info that confirms existing beliefs — disconfirming info feels threatening |
Dunning-Kruger Effect | Self-assessment | Dunning & Kruger (1999) | Beginner programmer thinks they're an expert after one tutorial | Low skill prevents recognizing low skill — you don't know what you don't know |
Anchoring Bias | Decision-making | Tversky & Kahneman (1974) | 'Was $500, now $199!' makes $199 feel like a steal | First number you see becomes the reference point — even if it's arbitrary |
Availability Heuristic | Risk Assessment | Tversky & Kahneman (1973) | Fear of shark attacks after watching Jaws (actual risk: 1 in 3.7 million) | Easily recalled events seem more likely — vivid memories distort probability estimates |
Survivorship Bias | Selection | Abraham Wald (1943) | 'Drop out of college like Bill Gates!' ignoring millions who dropped out and failed | We only see the winners — the failures are invisible so we draw wrong conclusions |
Halo Effect | Social | Edward Thorndike (1920) | Attractive people perceived as smarter and more trustworthy | One positive trait bleeds into overall perception — appearance biases everything |
Loss Aversion | Decision-making | Kahneman & Tversky (1979) | Losing $100 hurts ~2x more than gaining $100 feels good | Evolution favored those who avoided losses over those who sought equal gains |
Hindsight Bias | Memory | Baruch Fischhoff (1975) | 'I knew Bitcoin would crash' (said after the crash, not before) | After learning an outcome, brain rewrites memory to think it was obvious all along |
Spotlight Effect | Social | Thomas Gilovich (2000) | Thinking everyone noticed your stained shirt (they didn't) | You're the center of YOUR world but barely a pixel in everyone else's |
IKEA Effect | Value | Norton, Mochon, Ariely (2012) | Overvaluing furniture you assembled yourself vs. identical pre-built furniture | Labor leads to love — effort invested inflates perceived value |
Status Quo Bias | Decision-making | Samuelson & Zeckhauser (1988) | Keeping the same phone plan for years despite better options existing | Change feels risky, doing nothing feels safe — even when doing nothing IS the risk |
Bandwagon Effect | Social | — | Buying something because it has 10,000 5-star reviews | Social proof feels like evidence — if everyone's doing it, it must be right (it might not be) |
Peak-End Rule | Memory | Kahneman (1993) | A vacation remembered by its best moment and the last day, not the average | Brain doesn't average experiences — it snapshots the peak and the ending |
Fundamental Attribution Error | Social | Lee Ross (1977) | 'He cut me off — what a jerk!' vs. 'I cut him off — I was in a rush' | We explain others' behavior by character but our own by circumstances |
Negativity Bias | Emotion | Rozin & Royzman (2001) | One bad review stings more than 50 good ones | Evolution: missing a threat kills you, missing a reward just costs an opportunity |
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