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Fixed Action Pattern: Definition & Examples

By Charlotte Nickerson, published March 16 2022


  • A Fixed Action Pattern, often abbreviated as FAP and known alternatively as Instinctive Movement or Instinct Bewegung, is a predictable series and stereotypical sequences of complex actions triggered by a cue.
  • Konrad Lorenz and Tinbergen first brought the idea of the Fixed Action Pattern to light in the late 1930s. The researchers considered Fixed Action Patterns to be fundamental units of behavior that help organisms to navigate the environment, detect necessary resources, avoid danger, and interact with others.
  • Fixed Action Patterns share a number of defining traits, such as their innateness, rigidity, inheritability, invariability, and complexity.
  • Fixed Action Patterns are useful to both psychologists and biologists in determining the extent to which organisms are related as well as analyzing the evolutionary origins of behavior.

Fixed Action Patterns are sequences of innate behavior that are often performed in a seemingly fixed and stereotypical manner of all members of a species. They are triggered by a cue in the environment.

Scientists sometimes call this cue a key stimulus or sign stimulus. Although Fixed Action Patterns are more complex than reflexes, they are still automatic and involuntary. Once triggered, Fixed Action Patterns will go on to completion, even when the key stimulus is removed. 

The first people to propose the idea of a Fixed Action Pattern were Konrad Lorenz (1981) and Tinbergen. Lorenz considered behavior to be composed of basic units such as classical reflexes and Fixed Action Patterns specific to species.

In later years, Lorenz would focus on specific circuits that control reflexes and Fixed Action Patterns on the environmental level such as “Innate Releasing Mechanisms'' (often abbreviated as IRM), “appetites and aversions,” and so forth.

Each of these units provided organisms with basic behavioral skills that helped them navigate their environment, detect necessary resources, avoid danger, and interact with their fellow organisms. Learning can play a role in each of these units. 

Lorenz’s concept of the Fixed Action Pattern and Innate Releasing Mechanisms was inspired by the classical concept of stimulus and response.

According to the classical model of stimulus and response, stimuli become paired with responses in a participant’s mind. For example, Pavlov’s classical conditioning experiment involving dogs showed that, when trained to associate the ring of a bell with eating meat, simply ringing a bell triggered a salivation response, regardless of whether or not meat was subsequently given to the dogs.

The idea of the Fixed Action Pattern elaborated upon this concept by accounting for the spontaneity of behavior in many Fixed Action Patterns, such as locomotion, courtship behavior, and certain types of bird song.

Lorenz’s “psychohydraulic” model applied this reasoning in explaining the control of aggression in animals and humans (2021; Schleidt, 1974).

The concept of the Fixed Action Pattern has played an important role in the history of ethology, which is the study of human behavior and social organization from a biological perspective.

Historically, scientists have defined a Fixed Action Pattern in reference to the absence of external stimuli in controlling the form of the moment (Hinde, 1970).

This literature defined Fixed Action Patterns as belonging to a distinct class of response events. 


According to Barlow (1977), Fixed Action Patterns have 11 major characteristics:

  1. Fixed Action Patterns are triggered, and not controlled by external stimuli: although Fixed Action Patterns can involve a relatively complex pattern of muscle contractions, the Fixed Action Pattern cannot be fractioned into a series of responses to different external stimuli responsible for their evocation.

    Every component of a Fixed Action Pattern must be elicited by the same stimulus or group of stimuli that elicited the entire Fixed Action Pattern.

  2. Fixed Action Patterns are composed of a rigid sequence of component acts, and their order is invariant: Fixed Action Patterns must involve a temporal sequence of acts, such as muscular contractions, that are independent of afferent regulation, or regulation resulting from the body’s reactions to external stimuli (Moltz, 1965).

    This distinguished Fixed Action Patterns from so-called “taxes,” where a movement that is elicited by one stimulus continues to be directed by events external to the animal and cease to occur when the external stimulus is removed.  

  3. The Fixed Action Pattern is not learned by an individual organism: Fixed Action Patterns exclude the possibility that a movement or movement pattern has been specifically learned prior to its first occurrence.

    According to Lorenz and Timbergen (1938), even wide fluctuations in environmental conditions will not alter the Fixed Action Pattern when the health of an organism is not impaired (Moltz, 1965).

    This has been shown in studies where scientists have removed animals at the time of birth or hatching from other members of the species and determined whether a given response will be performed in a way identical to that of animals reared with other members of the species (Eibl-Eibesfeldt, 1961).

  4. The apparatus for an organism performing a Fixed Action Pattern is inherited: Instinct theorists believe that organisms inherit Fixed Action Patterns in the same way that they inherit physical features (Eibl-Eibesfeltdt and Kramer, 1958).

    From the beginning of the history of Fixed Action Patterns, theorists have believed that Fixed Action Patterns are genetically encoded in the organization of neural centers that control and coordinate the sequence of muscle actions involved in performing the patterns (Moltz, 1965). 

  5. The Fixed Action Pattern is characteristic of all appropriate members of a species

  6. The Fixed Action Patterns behaviors have little variability between members of the same species: Fixed Action Patterns are stereotypical.

    Historically, ethologists and instinct theorists have made a distinction between appetitive behavior and consummatory acts (Moltz, 1965), using the term appetitive behavior to refer to the initial components of a behavior sequence, and consummatory acts to describe the rigid and terminal actions in sequences (Thorpe, 1954; Moltz, 1965).

    Usually, the movements that scientists have described as Fixed Action Periods are consummatory acts, as they usually comprise the terminal aspects of a response sequence and because they are stereotypical and constant in form among members of the same taxa (Lorenz, 1956). 

  7. Fixed Action Patterns are more complex than reflexes.

  8. Fixed Action Patterns can be triggered in inappropriate situations.

  9. Fixed Action Patterns lack conscious purpose and thus may contain imperfections.

  10. The threshold for eliciting a Fixed Action Period may not depend on external conditions: Fixed Action Patterns are spontaneous, meaning that they have thresholds for being triggered that are independent of changes in external conditions.

    In general, this means that an organism’s readiness to perform a particular Fixed Action Pattern and the intensity with which the performance occurs depends on the time elapsed since the movement was last evoked.

    Perhaps the most dramatic evidence for the non-role of external stimuli in mediating Fixed Actions Patterns are the tendency for Fixed Action Patterns to happen when an organism is completely withdrawn from the external stimulus that supposedly triggers them, such as in Van Iersal’s (1953) fish fanning studies (Moltz, 1965).

    In a similar fashion, Lorenz has called attention to how the weaver bird sometimes performs its complex nest weaving behavior in the absence of the plant fibers that would normally serve to create a nest (Lorenz, 1956).

    Scientists have used this characteristic to distinguish Fixed Action Patterns from reflexes (Eibl-Eisbesfeld and Kramer, 1958; Lorenz and Tinbergen, 1938; Moltz, 1965). 

  11. The acts comprising a Fixed Action Pattern have common causal factors that differ from the factors that cause other Fixed Action Patterns.


Male Three-Spined Stickleback Fish

Tinbergen (1959) studied what has become a classic example of a key stimulus and Fixed Action Pattern in the male three-spined stickleback fish.

The male stickleback must aerate their nests in order to maintain the oxygen concentration of the surrounding water at a level appropriate for egg development.

Male sticklebacks do this through a movement called fanning, where the fish use their fins and tails to exert backwards and forwards pressures on the water.

The sequence of movements performed by these bodily structures are the same regardless of when the fanning has been exhibited (Baerends, 1957). Indeed, even in circumstances where the fish must adopt an unusual position, the fish nonetheless patterns and coordinates its movements in the same way. 

Van Iersal (1953) later demonstrated the role of spontaneity in the fanning of male stickleback fish. When male stickleback fish are prevented from fanning for several minutes, a significant increase in the intensity of fanning will occur after the fish is allowed to fan again.

This was not due to extrinsic conditions such as the accumulation of carbon dioxide and other gases released by the eggs, as evidenced by the researchers obtaining the same result when they repeated the same experiment with the nest completely covered (van Iersel, 1953; Moltz, 1965).

In yet another experiment, van Iersel (1953) reported that stickle-backs who have no nest occasionally show fanning behavior.

Additionally, there are yet more reports of sickle-backs who have been reared in isolation performing a typical zigzag courting dance before they had ever seen another male stickleback.

Indeed, that male sticklebacks performed this dance the first time that they saw a cardboard model of a female stickleback (Tinbergen, 1942; Cullen, 1960; Moltz, 1965).

The Egg-Retrieving Greylag Goose

Lorenz and Tinbergen (1938), in their differentiation between so-called taxis and the Fixed Action Pattern, describe the egg-retrieval patterns of the greylag goose. 

While brooding, a greylag goose who has witnessed an egg rolling out of its nest reacts characteristically. The goose slowly rises from the nest and approaches the displaced egg.

When it reaches the egg, it extends its neck downward and forward so that the undersurface of the bill rests against the far side of the egg.

The goose then uses two distinct movement to roll the displaced egg in the direction of the nest - a sagittal movement, or a movement along the plant that intersects the front side of its body symmetrically, that keeps the egg rolling forward toward the nest, and a side-to-side movement that keeps it from deviating too far to the right or left (Lorenz and Tinbergen, 1938; Moltz, 1965). 

Scientists have described the goose's sagittal movement as a Fixed Action Period because the form of the movement remains constant despite the irregularities of the terrain that the goose must roll the egg over and differences in the shapes of the objects that researchers have substituted experimentally for the egg.

In addition, in cases where the egg rolls completely away from the bill, the goose will often continue to perform the rolling movement as if the egg were present, indicating that the movement does not continue to be controlled by an extrinsic stimulus (Moltz, 1965). 

Meanwhile, scientists have classified the lateral movement of the egg-retrieving greylag goose as a taxi because it is both evoked and continuously directed by the contact of the egg with the undersurface of the bill.

This means that, if the egg deviates from the middle plane of the bird, the goose compensates by flexing its muscles to the right or left to restore the egg to its path.

In cases where researchers have substituted unlikely to deviate objects for eggs, such as cylinders or wooden cubes, the goose perform few or no lateral movements; and if the egg rolls completely away from the bill, the lateral movement, unlike the sagittal movement, ceases (Lorenz and Tinbergen, 1938; Moltz, 1965). 

Significance of Fixed Action Patterns

Fixed Action Patterns are important for a variety of reasons. Three ways that Moltz (1965) considers Fixed Action Patterns to be important involve taxonomy, evolution, and genetics.

Moltz considers Fixed Action Patterns to be taxonomically important in that behavior patterns that appear to be belonging to a Fixed Action Pattern can be used to classify how organisms are related, particularly because Fixed Action Patterns are stereotypical across species (Moltz, 1965).

In taxonomy, structural and behavioral data may lead to conflicting classifications of organisms, and taxonomists have traditionally relied on behavior to classify species that are nearly impossible to tell apart physically.

For example, Crane (1966) used certain display movements to classify species of fiddler crabs that are extremely similar anatomically (Moltz, 1965).

In a similar sense, Hinde (1955), Lorenz (1981), and Tinbergen (1959) all used motor patterns involved in aggression and courtship to elucidate the relationships between closely related birds (Moltz, 1965).

Fixed Action Patterns can also be used as a means for studying how behavior has evolved over time in organisms.

For example, Hinde and Tinbergen (1958), and Tinbergen (1959) have used Fixed Action Patterns to analyze the evolution of display movements in birds, and Baerends and Baerends-van Roon (1950) have done a similar study on cichlid fish.

Fixed Action Patterns are well-suited for evolutionary analysis because they are easily discriminated from other behaviors in a specie’s repertoire, resist changes that happen as an organism develops, and tend to be distributed among related taxa in a way that is neither too conservative nor too divergent (Moltz, 1965). 

Thirdly, Fixed Action Patterns allow scientists to study gene-behavior relationships. Fixed Action Patterns are independent of the environment, are stereotypical, and have a fixed and quantifiable sequence of behaviors. This makes them well-suited for research by psychogeneticists (Moltz, 1965). 

Fixed Action Patterns are also significant for helping psychologists understand behavior on a theoretical level. Historically, psychologists have thought of Fixed Action Patterns as a fundamental unit of animal responses encoded in the genome that subsequently interlocks with all acquired elements of behavior (Moltz, 1965). 

One implication of this theoretical perspective is that, in its early history, researchers tended to investigate Fixed Action Period through first distinguishing the Fixed Action Patterns that a species exhibits, analyze their properties, and investigate their influence on all other components of behavior (Moltz, 1965).

Theorists believed that because these behaviors were genetically encoded, their organization would not be influenced by experiential events. 

Lastly, and most psychologically, theorists have historically treated Fixed Action Patterns as temporally integrated. This means that Fixed Action Patterns Have a unique organization and characteristic properties that make it useful in searching for the “innately determined preceptory mechanisms” that, upon beings activated by specific environmental stimuli, function to release the Fixed Action Pattern (Lorenz, 1981; Tinbergen and Perdeck, 1951; Moltz, 1965).

About the Author

Charlotte Nickerson is a member of the Class of 2024 at Harvard University. Coming from a research background in biology and archeology, Charlotte currently studies how digital and physical space shapes human beliefs, norms, and behaviors and how this can be used to create businesses with greater social impact.

How to reference this article:

Nickerson, C. (2022, March 15). Fixed Action Pattern: Definition & Examples. Simply Psychology.


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