Fixed action pattern

In ethology, a fixed action pattern (FAP) is a complex behavioral sequence that is indivisible and runs to completion. FAPs are invariant and are produced by the innate releasing mechanism that responds to a external sensory stimulus (sign stimulus).

Examples
A mating dance may be used as an example. Many species of birds engage in a specific series of elaborate movements, usually by a brightly colored male. How well they perform the "dance" is then used by females of the species to judge their fitness as a potential mate. The key stimulus is typically the presence of the female.

Human infants grasp strongly with their hands as a response to tactile stimulus.

Fixed action pattern is used in biology to classify ethology