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Can you outthink your own brain?
8 classic cognitive bias traps. Even experts fall for half of them. See where your reasoning slips.
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A bat and a ball cost $1.10 total. The bat costs $1.00 more than the ball. How much does the ball cost?
Answer: 5 cents. The trap (System 1 says 10¢): if ball = $0.10, bat = $1.10, total = $1.20 — wrong. Algebra: ball = x, bat = x + 1.00, total = 2x + 1.00 = 1.10, x = 0.05. Ball costs 5¢, bat costs $1.05.
Linda is 31, single, outspoken, a former philosophy major active in social-justice causes. Which is more likely?
Answer: Linda is a bank teller (always — adding details can only narrow the probability). The "conjunction fallacy" — Kahneman & Tversky's famous Linda problem. The set of bank tellers is always larger than the set of feminist bank tellers, so option A must be at least as likely. Most people get this wrong.
Estimating without thinking too hard: how many African countries are in the UN? You happen to see the number "10" first. Likely effect:
Answer: Your estimate will be biased lower than reality. Anchoring: even a clearly unrelated number drags estimates toward it. The actual answer is 54 — but people anchored at 10 typically guess much lower than those anchored at 65.
Most people overestimate the risk of dying from a shark attack and underestimate the risk of dying from a falling vending machine. Why?
Answer: Availability heuristic — vivid examples dominate memory. Availability bias: easily recalled events feel more probable. Shark attacks make news; vending-machine deaths do not — yet the latter kills more Americans per year.
You've spent $50 on movie tickets, $100 on dinner, then realise you're tired and the movie has bad reviews. Rational choice:
Answer: Skip it — the $150 is gone either way; choose the better next 2 hours. Sunk-cost fallacy: past spending is gone regardless. The only relevant question is whether the next 2 hours at the cinema beat the next 2 hours at home. The bill is irrelevant to that comparison.