Definition
Judgmental heuristics are mental shortcuts that allow people to make rapid decisions by relying on a single feature or rule of thumb instead of analyzing all available information. Examples include expensive = good (price as a quality proxy), more popular = better (social proof), and expert says so = true (authority deference). The term comes from Tversky and Kahneman's foundational work in the 1970s; Cialdini uses it explicitly in Topic 1 of Influence to explain why the seven weapons work.
Heuristics are not bugs. They are necessary compression for a finite mind facing a complex world. The cost — occasional errors when the heuristic fires in the wrong context — is usually outweighed by the benefit of fast, low-cost decisions across millions of routine choices.
Why it matters
How it works
A heuristic is a rule of the form if feature F is present, then judgment J. It runs fast because it consults only one feature; it runs reliably because the feature has historically correlated with the judgment.
When the environment changes — when an operator can engineer the feature without the underlying judgment being warranted — the heuristic produces a systematic error. Cialdini's compliance professional learns the trigger features and stages them, knowing the heuristic will fire.
The two main families of heuristic in Influence are representativeness (similarity to a known case → confidence in the judgment) and availability (ease of recall → estimate of frequency or importance). Both are exploitable; both are also indispensable.