Heuristics
Heuristics are mental shortcuts that allow quick judgements, often well but sometimes with predictable errors.
The mind cannot weigh everything, so it takes shortcuts. Heuristics are those shortcuts, and they are mostly a feature, not a bug.
Heuristics are mental shortcuts, simple rules of thumb, that let people make judgements and decisions quickly without exhaustive analysis. They trade some accuracy for speed and effort, and most of the time the trade is worth it.
Why shortcuts are necessary
A mind that deliberated fully over every choice would be paralysed. The world presents far more information and options than anyone can process, so people rely on heuristics to cope: judging probability by how easily examples come to mind, estimating from a starting anchor, going with what is familiar. These shortcuts are fast, frugal, and usually good enough, which is why they evolved and why they persist.
When they misfire
The same shortcuts that usually serve well produce systematic errors in particular situations. The availability heuristic makes vivid, recent events seem more likely than they are; anchoring lets an arbitrary number distort an estimate; representativeness leads people to ignore base rates. These are not failures of intelligence but predictable side effects of useful rules applied where they do not fit. Studying when heuristics misfire is much of what behavioural economics does.
Not simply flaws
There is a debate about how to regard heuristics. One view, associated with the study of biases, stresses the errors they cause. Another, associated with the idea of ecological rationality, stresses that simple heuristics often outperform complex analysis in the uncertain, data-poor conditions of real life, where elaborate models overfit. Both are right in their domains: heuristics are neither merely flawed nor always wise, but tools whose value depends on the match between the rule and the environment.
Heuristics are how human judgement actually works most of the time, and understanding them is more useful than lamenting that people are not calculators. The practical art is knowing which situations a given shortcut handles well and which ones quietly turn it into a trap.