fixed-action pattern

Meaning: A fixed-action pattern (FAP) is an innate, stereotyped sequence of behaviors triggered by a specific environmental cue called a sign stimulus (or releaser). It is typical of a species, needs no learning, and once triggered usually runs to completion even if the stimulus disappears. Ethologists such as Tinbergen and Lorenz studied it as an example of instinct.

On the MCAT: A passage describes an animal giving the same rigid response to a simple cue: a male stickleback attacking anything with a red underside, a greylag goose rolling a displaced egg back to the nest, or a gull chick pecking a red spot on a parent's beak. Questions ask you to classify the behavior as innate rather than learned, identify the sign stimulus, or predict that a crude model with the key feature still triggers it. A goose that keeps rolling after the egg is removed is the classic sign.

Common confusion: Students confuse an FAP with a reflex or a conditioned response. A reflex is a rapid, simple response to a stimulus, while an FAP is a longer, coordinated sequence. A conditioned response depends on a learned association, whereas an FAP appears without prior experience of the cue.