availability and representativeness heuristics
/ rep-ri-zen-TAY-tiv-ness /
After seeing news of a shark attack, the beach suddenly feels dangerous — even though you are far likelier to die driving there. And when you meet a quiet man who loves poetry, you may guess he's a librarian rather than a farmer, even though there are vastly more farmers. These two quick mental moves — judging 'how likely' by 'how easily it comes to mind,' and judging 'what category' by 'how well it fits a stereotype' — are the availability and representativeness heuristics.
The availability heuristic estimates how common or probable something is by how easily examples spring to mind. Vivid, recent, emotional, or heavily reported events feel more frequent than they are, so people overestimate dramatic risks (terrorism, plane crashes, lottery wins) and underestimate quiet ones (diabetes, car accidents). The representativeness heuristic judges probability by resemblance to a mental prototype, which leads us to ignore base rates — the underlying frequencies. Told someone is shy and detail-oriented, we call them a librarian, forgetting there are far more salespeople, so even a 'good fit' is usually outnumbered.
Both shortcuts shape real economic behavior: investors chase recently hot stocks (available), lenders stereotype borrowers (representative), and consumers fear improbable dangers while ignoring likely ones. They also feed market bubbles and panics, where recent vivid events dominate judgment. The honest point is the same as for all heuristics: these are usually efficient and often right — easily recalled events frequently are common — but they fail systematically when memory is skewed by drama or when a story 'fits' too neatly. The cure is to ask for the base rate: how often does this actually happen, regardless of how it feels.
After a widely reported plane crash, many travelers switch to driving — which is far more dangerous per mile. The crash is vivid and 'available' in memory, so it feels more probable than the dull, daily risk of the highway, even though the numbers say the opposite.
What's easy to picture feels likely — even when the statistics disagree.
Both heuristics make us ignore base rates — the underlying frequencies. A story can 'fit' a stereotype perfectly yet still be unlikely simply because that category is rare.