Innate trigger mechanism

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Innate triggering mechanism (AAM; at times also: innate triggering scheme ) is a technical term of the instinct theory of classical comparative behavioral research (ethology) developed primarily by Konrad Lorenz and Nikolaas Tinbergen . It enables an animal “to 'innate recognition' of a biologically relevant environmental situation”. An AAM is therefore a “stimulus filter device” that responds to a specific key stimulus ; In addition, it also ensures the “coupling of the 'recognized' stimulus to a certain behavior ( motor coordination).” This means that the AAM also causes a certain “ phylogenetically programmed, hereditary-coordinated movement” ( instinctive movement ) to be set in motion whose help the environmental situation determined by the key stimulus is mastered with “innate ability”.

The term innate trigger mechanism and the physiological properties ascribed to it were "born" "in night-long discussions" by Nikolaas Tinbergen and Konrad Lorenz during a symposium on instincts that the Dutch zoologist Cornelis Jakob van der Klaauw had convened at the University of Leiden in 1936 . Later, the construct of the innate release mechanism - initiated primarily by a publication by the Austrian zoologist Otto Storch (head of the Zoological Institute in Graz) in 1949 - was supplemented by an AAM (EAAM) modified through experience. In 1962, Wolfgang Schleidt also introduced the acquired release mechanisms (EAM), "in which the originally existing framework of the AAM is no longer detectable, or which came about without the involvement of an AAM".

AAM and key stimulus

Behavioral observers have always noticed that many newborn animals are immediately able to take in the food that is beneficial for them: be it chicks that seem to know what food is and how to peck food immediately after hatching; be it mammals that immediately push to the mother's teats without any help. Evidence of an innate behavior can most easily be carried out in test animals raised without experience; For example, birds newly hatched from the egg had no opportunities for visual perception before they hatched. This is one of the reasons that almost all early ethologists were involved in ornithology .

Similar to Pavlov's connection of conditioned stimulus and conditioned reflex , Konrad Lorenz first presented the concept of the interaction of key stimulus and AAM in his early work The Kumpan in der Vogel Umwelt des Vogel in 1935 ; However, at that time Lorenz used for this - postulated as a subsystem of the central nervous system - 'switching point', which allows the specific 'input' to be followed by a specific 'output', instead of AAM still the designation triggering scheme . “The instinctual innate triggering schemes play a special role in birds . If the triggering scheme of a reaction is instinctually innate, it always corresponds to a relatively simple combination of individual stimuli, which in their totality represent the key to a particular instinctual reaction. The innate triggering scheme of an instinctive act picks out a small selection from the abundance of stimuli, to which it responds selectively and thus sets the action in motion. "

It is the AAM that prevents the "action-specific excitement" continuously generated according to instinct theory for certain instinctive movements from being released in unsuitable situations and, conversely, ensures that it is only released in the appropriate situations by the individual in a certain, inherited manner becomes. According to Lorenz, these “key combinations ” selected by the AAM as if by a filter must have “a minimum level of general improbability”, that is, they must be largely forgery-proof and, at best, may very rarely erroneously initiate an instinctual movement, “for the same reasons which are given a generally improbable shape to the beard of a key. ”In a certain sense, the AAM fills the black box so called by classical behaviorists and can be characterized by three properties:

  1. the recognition of a key stimulus and the behavior that follows it is innate and species-specific;
  2. without AAM there can be no adequate response to a key stimulus;
  3. the response following a key stimulus is stereotypical, since each key stimulus is assigned its own AAM and a specific response.

Konrad Lorenz and Nikolaus Tinbergen chose the term innate triggering scheme in 1936 because the organism “does not respond to a designed overall picture of the adequate environmental situation, but to a sum of very specific, sketchy, 'schematic' stimulus combinations that characterize this situation. The term innate schema has been abandoned because it still suggests the idea of ​​a picture, albeit a simplified one, of the overall situation or the object of behavior. We now speak of the innate trigger mechanism (AAM) [...], and it is clear from the start that different living beings and at different levels of integration of their cognitive performance and behavior make very different demands on the selectivity of their response to stimuli and that there are very different physiological demands Are mechanisms that meet these requirements. "

Regarding the AAM, which has been changed by experience - the EAAM - Lorenz noted in 1978: “One of the most widespread learning processes and possibly the most primitive of them is that an AAM is made more selective by learning additional features that characterize the triggering stimulus configuration. Of course, this means an adaptive modification of the behavior. "

The neurobiological basis of the AAM

The “innate triggering scheme”, later renamed “innate triggering mechanism”, was postulated in 1936 as a purely conceptual construct , i.e. without an experimental basis. It was initially based only on the observation that animals evidently react to certain environmental stimuli in a certain, predictable way even without prior learning, that is, that they have specific innate environmental knowledge and a specific innate behavioral repertoire. Such a rigid coupling of external “key stimulus ” and instinctive movement requires a neurophysiological filter and activation system: In this respect, the AAM was a mandatory link between stimulus and reaction. However, this raises methodological problems: key stimuli and AAM cannot be experimentally investigated separately from one another, because a key stimulus is defined precisely by the fact that it triggers a certain instinctive movement thanks to an AAM, and conversely, an AAM is defined by the fact that it has a certain key stimulus assigned. The postulated construct of the AAM can thus be viewed more as an epistemological , natural-philosophical construct and less as a scientific one. It therefore hardly plays a role in current scientific research.

Nevertheless, the “innate recognition” of a biologically relevant environmental situation has been described many times by behavioral researchers and neurophysiologists and is considered to be certain. However, it is still less well established how exactly a certain AAM must be designed so that the associated “key stimulus” can be answered in a situation-appropriate manner. Konrad Lorenz himself had admitted in 1978: “Today we know very little about the physiological functions that carry out the AAM's selective stimulus filtering.” And in 1994, the neurophysiologist Jörg-Peter Ewert wrote : “Based on our current knowledge, there is no generally valid neural assignment Centers as locations of trigger mechanisms possible ”. The exact determination of neural ensembles, which represent a neurophysiological equivalent to the AAM, was only possible for individual special cases in the decades thereafter.

Lorenz also referred to such a special case in 1978 as evidence for his hypotheses: Jerome Lettvin , Humberto Maturana , Warren McCulloch and Walter Pitts first detected receptive fields in the leopard frog ( Rana pipiens ) in 1959 and shortly afterwards reported that certain neuronal interconnections in the retina were involved contribute to the fact that a frog “recognizes” a small insect flying past as prey , whereas a larger flying object as an enemy : “Groups of visual elements are each connected to a ganglion cell, some of them respond to light or dark, others to this specific stimuli, such as a light-dark border with a convex dark edge that runs in a certain direction across the visual elements of the group. A visual element can be a member of a whole series of groups, ie it can be connected to different ganglion cells. One is downright tempted to postulate a next higher integrating entity towards the center of these groups, which integrates a message such as 'fly passing from right to left' from the information of such subsystems. "

Based on such neuroethological research, Jörg-Peter Ewert recommended in 1994 a 'rescue' of the term trigger mechanism independent of the historical instinct theory and under cybernetic and system-theoretical aspects: "Today we should understand trigger mechanisms as trigger systems in which feature filters, location, motivation and Interlocking learning systems. With the inclusion of such a differentiation, the term trigger mechanism retains its fertility - especially for neuroethological research. "

literature

Individual evidence

  1. ↑ a b c Konrad Lorenz : Comparative behavior research. Basics of ethology. Springer, Vienna and New York 1978, p. 122, ISBN 978-3-7091-3098-8 .
  2. ^ Uwe Jürgens and Detlev Ploog : From ethology to psychology. Kindler Verlag, Munich 1974, p. 9, ISBN 3-463-18124-X .
  3. ↑ Konrad Lorenz: Comparative behavior research. Basics of Ethology, p. 6.
  4. ^ Klaus Taschwer and Benedikt Föger : Konrad Lorenz. Biography. Zsolnay, Vienna 2003, p. 72, ISBN 3-552-05282-8 .
  5. ↑ Ute Felbor: Racial Biology and Hereditary Science in the Medical Faculty of the University of Würzburg 1937–1945. Königshausen & Neumann, Würzburg 1995 (= Würzburg medical historical research. Supplement 3; also dissertation Würzburg 1995), ISBN 3-88479-932-0 , p. 96.
  6. ↑ Otto Storch : Hereditary motor skills and acquisition motor skills. In: Academic indicator of the medical and natural science class of the Austrian Academy of Sciences. Issue 1, Vienna 1949.
  7. ↑ Wolfgang M. Schleidt : The historical development of the terms "innate triggering scheme" and "innate triggering mechanism" in ethology . In: Zeitschrift für Tierpsychologie. Volume 19, No. 6, 1962, pp. 697-722, doi: 10.1111 / j.1439-0310.1962.tb00800.x .
  8. ↑ Konrad Lorenz: The friend in the environment of the bird. In: Journal of Ornithology. Volume 83, No. 2-3, 1935, pp. 137-215 and pp. 289-413, doi: 10.1007 / BF01905355 .
  9. ↑ Konrad Lorenz: The friend in the environment of the bird. Reprinted in: The Same: About Animal and Human Behavior. From the development of the theory of behavior. Collected papers, Volume 1, p. 268, Piper, Munich 1965, ISBN 3-492-01385-6 , full text (PDF) .
  10. ↑ Konrad Lorenz: The friend in the environment of the bird. Reprint, p. 117.
  11. ↑ Konrad Lorenz: Comparative behavior research. Foundations of Ethology, p. 137.
  12. ↑ Hanna-Maria Zippelius : The measured theory. A critical examination of the instinct theory of Konrad Lorenz and behavioral research practice. Vieweg, Braunschweig 1992, p. 13, ISBN 3-528-06458-7 .
  13. ↑ a b Konrad Lorenz: Comparative behavior research. Basics of Ethology, p. 125.
  14. ↑ a b Jörg-Peter Ewert : Is the concept of the release mechanism still up to date? In: Gerd-Heinrich Neumann and Karl-Heinz Scharf (eds.): Behavioral biology in research and teaching. Ethology - Sociobiology - Behavioral Ecology. Aulis Verlag Deubner, Cologne 1994, p. 223, ISBN 3-7614-1676-8 .
  15. ↑ Jerome Lettvin , Humberto Maturana , Warren McCulloch and Walter Pitts : What the Frog's Eye Tells the Frog's Brain. In: Proceedings of the Institute of Radio Engineers. Volume 47, No. 11, 1959, pp. 1940–1951, full text (PDF) .
  16. ^ Humberto R. Maturana, Jerome Y. Lettvin, Warren S. McCulloch and Walter H. Pitts: Anatomy and Physiology of Vision in the Frog (Rana pipiens). In: Journal of General Physiology. Volume 43, No. 6, 1960, 129–175, doi: 10.1085 / jgp.43.6.129 , PMC 2195076 (free full text)
  17. ↑ Jörg-Peter Ewert: Neurobiological Basis for the Recognition and Localization of Environmental Signals: How Does a Toad Brain Recognize Prey and Enemy? In: Same: Neuroethology. An Introduction to the Neurophysiological Fundamentals of Behavior. Springer, Berlin and Heidelberg 1980, pp. 69-128, ISBN 978-3-642-67502-7 .
    Jörg-Peter Ewert: The Neural Basis of Visually Guided Behavior. In: Scientific American. No. 3, 1974, pp. 34-42, full text (PDF) .

Remarks

  1. ↑ "Selective stimulus filtering" = selective stimulus filtering