Key idea: System 1 shortcuts make thinking efficient but produce predictable biases.
Thinking and its errors
System 1 (fast)
Automatic, effortless, intuitive — handles most decisions quickly using shortcuts (heuristics).
System 2 (slow)
Deliberate, effortful reasoning — can check and override System 1, but tires easily and is often not engaged.
Predictable biases
Shortcuts cause errors like anchoring (over-weighting the first number) and confirmation bias (favouring what fits our beliefs).
Fast · Slow · Biased
Take buying a phone. System 1 anchors on the first 'was £900' price, so £600 feels cheap; confirmation bias makes you notice only reviews that praise it. Only System 2, if engaged, checks the actual value. Decision-making is often not fully rational — a clear case of bias.
Go further — higher-level insight: Bias is efficiency backfiring, not stupidity. System 1's shortcuts are usually adaptive and fast; they only mislead in situations designed to trip them up. Framing bias this way — as the cost of an efficient system — is a high-level evaluative point.
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Key idea: The same choice described as a gain or as a loss leads to different decisions: the framing effect.
Tversky and Kahneman (1981) described a disease expected to kill 600 people. When programmes were described in terms of lives saved, most chose the sure option; when the same outcomes were described in terms of deaths, most chose the risky one.
Why the frame matters
Gains
When outcomes are framed as gains, people prefer a sure thing.
Losses
When framed as losses, people gamble to avoid them.
System 1
The words trigger a fast emotional reaction before any calculation.
Gain · Loss · Risk
What HL adds: The technology extension: apps and websites frame choices deliberately, such as defaults and 'only 2 left', so the same biases can be used to steer users.