Definition
A fixed-action pattern is a complex, stereotyped sequence of behavior that runs in nearly identical form every time it is triggered. The concept comes from classical ethology (Tinbergen, Lorenz) and describes innate behavior programs in animals: courtship displays, mothering rituals, territorial defense. The key feature is that the sequence is launched by a single trigger feature in the environment, not by an analytic appraisal of the whole situation.
Cialdini imports the concept into social psychology to describe human compliance. The "cheep-cheep" sound that triggers a mother turkey to brood anything making it — even a stuffed polecat — is analogous to the "because" word that triggers humans to grant a small favor (Langer et al., 1978).
Why it matters
How it works
In animals, the pattern is wired by genes plus species-typical experience. In humans, the equivalent shortcuts are mostly learned — cultural rules of thumb like "expensive equals good," "uniformed person is in charge," "free gift creates an obligation." These shortcuts function like fixed-action patterns even though their content is acquired. They run fast, they consume little attention, and they are launched by a single feature of the situation.
The "click, run" phrasing Cialdini uses captures the two-step structure: click (trigger detected), run (program executes). The window for intervention is between click and run — which is small, but trainable. Most of Influence is about how to widen that window in specific contexts.