While heuristics often enable quick and reasonably accurate judgments, they also produce systematic errors. The availability heuristic leads people to estimate the probability of an event by how easily examples come to mind, which causes dramatic or recent events — plane crashes, shark attacks, terrorist attacks — to be overestimated. The representativeness heuristic pushes people to judge probabilities by how closely something resembles a prototype, often ignoring base rates and producing conjunction fallacies, such as overestimating the probability that a quiet, book-loving person is a librarian rather than a farmer.
The anchoring effect is one of the most robust biases in the behavioral literature. People rely too heavily on the first piece of information — the anchor — when making subsequent judgments, and even arbitrary starting points can significantly influence final estimates. This happens because System 1 automatically generates an initial estimate based on the anchor, and System 2 insufficiently adjusts from it, leaving the final judgment biased. In price negotiations, the initial asking price pulls settled prices toward itself; in financial markets, investors anchor on metrics such as 52-week highs, IPO prices, or round numbers, distorting valuation judgments. In the classic wheel-of-fortune experiment, Kahneman and Tversky showed that participants who spun a rigged wheel produced estimates of African UN membership that were strongly influenced by the random number the wheel landed on. Financial analysts exhibit similar anchoring, often adjusting insufficiently from prior price targets or consensus estimates even when fundamentals change dramatically.
Many other biases compound the effects of heuristics. Confirmation bias leads people to seek out and remember information that confirms pre-existing beliefs while ignoring contradictory evidence, creating echo chambers that prevent recognition of when to exit a losing trade. Hindsight bias makes events seem predictable after the fact, distorting memory and lessons drawn from past decisions. The affect heuristic drives judgments based on current emotions rather than objective analysis, as when investors avoid industries they associate with negative feelings. The Dunning-Kruger effect shows that people with low competence tend to overestimate their abilities, leading novice investors to take on excessive risk. The gambler's fallacy — the mistaken belief that past random events alter future probabilities — and its mirror image, the hot-hand fallacy — believing past success predicts future success in independent events — both misinterpret statistical independence. Closely related is regret aversion, where people avoid actions that might trigger the anticipated emotional pain of a wrong decision, often producing overly conservative choices or conformity to the herd. Loss aversion, by contrast, concerns the pain of actual losses already incurred, while regret aversion centers on the emotional anticipation of having chosen poorly.