Tinbergen: The Four Questions & Super Stimulus

Nikolaas (Niko) Tinbergen (1907 – 1988) was a Dutch-born Ethologist and Zoologist who moved to England shortly after World War II and went on to teach many bright young sparks – Richard Dawkins included – at Oxford University. Together with the Austrians Konrad Lorenz (1903 – 1989) and Karl von Frisch (1886 – 1982), Niko won the Nobel Prize in Physiology or Medicine in 1973, helping to establish a new science – Ethology: “the comparative study of behaviour”. He pioneered the use of simple, but ingenious field experiments, many of which are still part of biology curriculums around the globe.

In 1963 Niko wrote “On aims and methods of Ethology” with the objective of defining the field of Ethology and it was in this paper that he first introduced the concept of the four questions. He argued that in order to fully understand a behaviour, four questions had to be put forward and answered:

  1. Causation – What are the stimuli that produce the response?
  2. Survival Value – How does the behaviour contribute to the animal’s survival and reproductive success?
  3. Ontogeny – How does the behaviour develop during the animal’s lifetime?
  4. Evolution – How did the behaviour arise in the species?

Causation and Ontogeny are said to be proximate mechanisms, in other words what the behaviour is composed of, whilst Survival Value and Evolution are ultimate mechanisms; a behaviour should have a purpose. Tinbergen was a firm believer (as am I) in using this methodology for humans as well as for the rest of the animal kingdom, so let’s us now use the four questions to dissect a familiar human behaviour: A baby’s cry.

  1. Causation – Pain, discomfort, hunger or separation.
  2. Survival Value – Signal that elicits caregiving (holding or food), conveys information.
  3. Ontogeny – Develops via cognitive maturation, environmental factors and responses from caregivers, even in adult-hood crying conveys a strong message, but becomes relatively rare.
  4. Evolution – A supplemental means of enforcing the mother-infant relationship where visual and/or olfactory signals are insufficient, crying episodes differ amongst cultures: in modern westernised populations babies tend to cry more.

Another of Niko’s explored concepts was that of “super normal stimuli”, defined as an exaggerated version of a stimulus which already produces a response, or any stimulus that elicits a response more strongly that the stimulus for which it evolved. A prime example would be a moth flying into a flame, ultimately to its death.

One of his classic studies on super stimuli was the begging behaviour of herring gull (Larus Argentatus) nestlings. Within an hour of hatching the chicks begin to peck at their mother’s beak – seemingly at the red spot – stimulating her to regurgitate food. The chick does not look for its mother, it merely responds to certain types of visual stimulation or as Niko termed them “signal stimuli”. The response is a hard-wired fixed action pattern (FAP) and essential to the chick’s fitness and survival; if the chick cannot consistently feed it will die. He examined which features of a mother’s beak induced chicks to peck by using various models of herring gull heads in different shapes and colours. His findings are illustrated here:

Contrast: Chicks tended to peck more aggressively at those models with a higher level of contrast between the spot and the rest of the beak. Colour made little difference, except for red (slight increase) which revealed that the signal stimulus was contrast, not colour.

Shape: When the beak was elongated the chicks pecked more aggressively and when the beak was thinned the chicks exhibited even more of a response, in fact nearly twice as much pecking as for a normal beak.

After discovering this, Niko attempted to design the perfect beak. He painted a long stick red and added three white lines. The chicks loved it. Even though the model looked nothing like their mothers’ beaks, it presented three important stimuli – redness, contrast and elongation.

 

Fixed action patterns are essential, but unfortunately predictable, which can lead to exploitation. Other animals encounter supernormal stimuli mainly by way of man-made experimentation, but humans design and create their own for each other. Is this leading us down a path of self-destruction?  The world is a very different place compared to when modern humans first walked the savannahs of Africa. Technologically advanced and densely populated cities overlook vast suburban communities and agricultural land. Temptations lie in every direction – Junk food, video games, cosmetics, pornography and weapons are all examples of super normal stimuli that appeal to our basic human urges. There is something for everybody.  The key is self-control which is easier said than done, I know.

 

Further Reading:

On aims and methods of Ethology – Nikolaas Tinbergen, 1963

http://www.thoughtfill.com/docs/aimsmethods.pdf

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Author: OakBlood

Light aircraft pilot - godless heathen - strident feminist. Likes nature, reading the news and glitter. Dislikes americanisms (i.e. spelling) and bad manners.

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