In ethology, a fixed action pattern (FAP) is an instinctive behavioral sequence that is indivisible and runs to completion. Fixed action patterns are invariant and are produced by the innate releasing mechanism that responds to an external sensory stimulus known as a sign stimulus or releaser (a signal from one individual to another).
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.
Another example of a FAP is the red-bellied stickleback (fish). The male turns a bright red/blue colour during the breeding season. This colour change is the fixed action pattern in response to an increasing day length which is the sign stimulus. During this time they are also naturally aggressive towards other red-bellied sticklebacks, another FAP. However anything that is red will bring about this FAP. The proximate response to this is that due to the stimuli, a nerve sends a signal to attack that red item. The ultimate cause of this behavior stems from the fact that the stickleback needs the area in which it is living for either habitat, food, mating with other sticklebacks, or other purposes. This interaction was studied by Niko Tinbergen.
Yet another ecological example is where a water fowls, such as a goose, will move an egg near its nest back into its nest if when it has rolled away somehow. The sight of the displaced egg triggers a this mechanism. However, it will also attempt to move other egg shaped objects, such as a golf ball, door knob, or even a volleyball back to the nest.
Although fixed action patterns are most common in animals with simpler cognitive capabilities, humans also demonstrate fixed action patterns. For example, infants grasp strongly with their hands as a response to tactile stimulus. This is thought to be a vestigial mechanism where when threatened by a predator a young primate would grab on to a parent's fur so the parent could climb to safety without having to hold its child[citation needed] (see also reflex action). Another FAP shared by some animals, including humans, is yawning, which often triggers yawning in other individuals. Yawns last around 6 seconds and are difficult to stop once initiated. Yawning, whether seen, heard or both, then serves as a releaser in nearby animals.<ref>Provine, R. R. (1986) Yawning as a stereo-typed action pattern and releasing stimulus. Ethology 72:109-122.
See also
References
- Campbell, N. A. (1996) Biology (4th edition), Chapter 50. Benjamin Cummings, New York ISBN 0-8053-1957-3
- Alcock, J. (1998) Animal Behavior: An Evolutionary Approach (6th edition), Chapter 5. Sinauer Associates, Inc. Sunderland, Massachusetts.
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