Tinbergen's four questions
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Tinbergen's four questions, named after Nikolaas Tinbergen, are complementary categories of explanations for behavior. It suggests that an integrative understanding of behavior must include both a proximate and ultimate (functional) analysis of behavior, as well as an understanding of both phylogenetic/developmental history and the operation of current mechanisms. 
Four categories of questions and explanations 
When asked about the purpose of sight in humans and animals, even elementary school children can answer that animals have vision to help them find food and avoid danger (adaptation). Biologists have three additional explanations: sight is caused by a particular series of evolutionary steps (phylogeny), the mechanics of the eye (causation), and even the process of an individual’s development (ontogeny). Although these answers may be very different, they are consistent with each other. This idea was hashed out in the 1960s when Tinbergen delineated the four questions based on Aristotle's Four Causes. This schema constitutes a basic framework of the overlapping behavioral fields of ethology & anthropology, behavioral ecology, sociobiology & evolutionary psychology, and comparative psychology.
Table of categories 
|Diachronic vs. Synchronic Perspective|
Explanation of current form in terms of a historical sequence
Explanation of the current form of species
|How vs. Why Questions||Proximate View
How an individual organism's structures function
Developmental explanations for changes in individuals, from DNA to their current form
Mechanistic explanations for how an organism's structures work
|Evolutionary (Ultimate) View
Why a species evolved the structures (adaptations) it has
The history of the evolution of sequential changes in a species over many generations
A species trait that evolved to solve a reproductive or survival problem in the ancestral environment
Evolutionary (ultimate) explanations 
1 Function (adaptation) 
Darwin’s theory of evolution by natural selection is the only scientific explanation for why an animal’s behavior is usually well adapted for survival and reproduction in its environment. The literature conceptualizes the relationship between function and evolution in two ways. On the one hand, function and evolution are often presented as separate and distinct explanations of behavior.  On the other hand, the definition of adaptation, a central concept in evolution, is a trait that is functional to the reproductive success of the organism and that is the result of natural selection; that is, function and evolution are inseparable. Given this, it is best to conceptualize function as an evolutionary explanation. The term “function” is preferable to “adaptation”, because it is understandable to students prior to an explanation of evolution. Many examples are well-known. For instance, in the winter birds fly south where there's food and warmth, and mammalian mothers nurture their young, thereby having more surviving offspring.
2 Phylogeny (evolution) 
Phylogeny captures all evolutionary explanations other than function/adaptation. There are several reasons why natural selection may fail to achieve optimal design (Mayr 2001:140–143; Buss et al. 1998). One entails random processes such as mutation and environmental events acting on small populations. Another entails the constraints resulting from early evolutionary development. Each organism harbors traits, both anatomical and behavioral, of previous phylogenetic stages, since many traits are retained as species evolve. Reconstructing the phylogeny of a species often makes it possible to understand the "uniqueness" of recent characteristics: Earlier phylogenetic stages and (pre-) conditions which persist often also determine the form of more modern characteristics. For instance, the vertebrate eye (including the human eye) has a blind spot, whereas octopus eyes do not. In those two lineages, the eye was originally constructed one way or the other. Once the vertebrate eye was constructed, there were no intermediate forms that were both adaptive and would have enabled it to evolve without a blind spot.
Proximate explanations 
3 Causation (mechanism) 
- Brain: For example, Broca’s area, a small section of the human brain, has a critical role in linguistic capability.
- Hormones are chemicals used to communicate among cells of an individual organism. Testosterone, for instance, stimulates aggressive behavior in a number of species.
- Pheromones are chemicals used to communicate among members of the same species. Some species (e.g., dogs and some moths) use pheromones to attract mates.
In examining living organisms, biologists are confronted with diverse levels of complexity (e.g. chemical, physiological, psychological, social). They therefore investigate causal and functional relations within and between these levels. A biochemist SCIENCE might examine, e.g., the influence of social and ecological conditions on the release of certain neurotransmitters and hormones, and the effects of such releases on behavior. E.g., stress during birth has a tokolytic (contraction-suppressing) effect. However, awareness of neurotransmitters and the structure of neurons is not by itself enough to understand higher levels of neuroanatomic structure or behavior: "The whole is more than the sum of its parts." All levels must be considered as being equally important: cf. transdisciplinarity, Nicolai Hartmann's "Laws about the Levels of Complexity."
In the latter half of the twentieth century, social scientists debated whether human behavior was the product of nature (genes) or nurture (environment in the developmental period, including culture). The consensus among biologists now is that behavior is the product of gene-environment interaction, in which the whole can be more than the sum of the parts, that is, the genetic and environmental components. By way of contrast, tallness may simply be the sum of “tall genes” and an environment rich in food.
An example of interaction (as distinct from the sum of the components) involves familiarity from childhood. In a number of species, individuals prefer to associate with familiar individuals but prefer to mate with unfamiliar ones (Alcock 2001:85–89, Incest taboo, Incest). By inference, genes affecting living together interact with the environment differently from genes affecting mating behavior. A homely example of interaction involves plants: Some plants grow toward the light (phototropism) and some away from gravity (gravitropism). Such species react differently to the same environment because of different genes.
Many forms of developmental learning have a critical period, for instance, for imprinting among geese and language acquisition among humans. In such cases, genes determine the timing of the environmental impact.
A related concept is labeled “biased learning” (Alcock 2001:101–103) and “prepared learning” (Wilson, 1998:86–87). For instance, after eating food that subsequently made them sick, rats are predisposed to associate that food with smell, not sound (Alcock 2001:101–103). Many primate species learn to fear snakes with little experience (Wilson, 1998:86–87).
Causal relationships 
The figure shows the causal relationships among the categories of explanations. The left-hand side represents the evolutionary explanations at the species level; the right-hand side represents the proximate explanations at the individual level. In the middle are those processes’ end products—genes (i.e., genome) and behavior, both of which can be analyzed at both levels.
Evolution, which is determined by both function and phylogeny, results in the genes of a population. The genes of an individual interact with its developmental environment, resulting in mechanisms, such as a nervous system. A mechanism (which is also an end-product in its own right) interacts with the individual’s immediate environment, resulting in its behavior. Here we return to the population level. Over many generations, the success of the species’ behavior in its ancestral environment (or more technically, the environment of evolutionary adaptedness [EEA]) may result in evolution as measured by a change in its genes.
In sum, there are two processes—one at the population level and one at the individual level—which are influenced by environments in three time periods.
BALLS Four ways of explaining visual perception:
- Function: To find food and avoid danger.
- Phylogeny: The vertebrate eye initially developed with a blind spot, but the lack of adaptive intermediate forms prevented the loss of the blind spot.
- Causation: The lens of the eye focuses light on the retina.
- Development: Neurons need the stimulation of light to wire the eye to the brain (Moore, 2001:98–99).
Westermarck effect 
SCIENCE Four ways of explaining the Westermarck effect, the lack of sexual interest in one’s siblings (Wilson, 1998:189–196):
- Function: To discourage inbreeding, which decreases the number of viable offspring.
- Phylogeny: Found in a number of mammalian species, suggesting initial evolution tens of millions of years ago.
- Causation: Little is known about the neuromechanism.
- Development: Results from familiarity with another individual early in life, especially in the first 30 months for humans. The effect is manifested in nonrelatives raised together, for instance, in kibbutzs.
Use of the four-question schema as "periodic table" 
The four-question schema is used as the central organizing device in some texts but not others. For instance, it is used in one of the most widely used animal behavior texts (Alcock, 2001) but not in one of the most widely used evolutionary psychology texts (Buss, 2004:12). An advantage of the schema is that it highlights gaps in knowledge, analogous to the role played by the periodic table of elements in the early years of chemistry:
The "periodic table of life sciences" becomes clear, when the following levels are graphed against the questions: the bio-molecule, cell, organ, individual and group level (see also Nicolai Hartmann's "Laws about the Levels of Complexity").
|1. Causation||2. Ontogeny||3. Adaptation||4. Phylogeny|
This "bio-psycho-social" table is a framework of reference, which demonstrates the associations between all non-human biological (levels a–f), as well as all anthropological and human sciences (levels a–g).
Especially in anthropological and human sciences it helps to structure interdisciplinary discussions, teaching and research (i.e. "Fundamental Theory of Anthropology":). In the Table the questions and planes in italics are also the subject of the humanities. In this "periodic table of human sciences", all anthropological disciplines (paragraph C in the table of the pdf-file below), their questions (paragraph A: see pdf-file) and results (paragraph B: see pdf-file) can be intertwined and allocated with each other [for examples how these aspects go into those little boxes in the matrix, see e.g. the paragraphs A, B and C in the table "The Four Central Questions ... using Ethology as an Example" (pdf).]. This “bio-psycho-social” orientation framework is the basis for the development of an interdisciplinary consensus: It is the starting point for a systematical order for anthropological and human sciences, and also the basis for a consistent networking and structuring of their results (see also Interdisciplinarity). In terms of epistemology: Since the answers to the reference planes and to all four central questions must fit together without contradictions, misconceptions can thus be revealed by inconsistencies. The periodic table can help in estimating how much interdisciplinarity is implemented in specific scientific approaches.
- Daly, M & Wilson, M. (1983). Sex, evolution, and behavior. Brooks-Cole.
- Nikolaas Tinbergen, ethology, Cartwright 2000:10; Buss 2004:12)
- ”Phylogeny” often emphasizes the evolutionary genealogical relationships among species (Alcock 2001:492; Mayr, 2001:289) as distinct from the categories of explanations. Although the categories are more relevant in a conceptual discussion, the traditional term is retained here.
- ”Biased learning” is not necessarily limited to the developmental period.
- Alcock, John (2001) Animal Behavior: An Evolutionary Approach, Sinauer, 7th edition. ISBN 0-87893-011-6.
- Buss, David M., Martie G. Haselton, Todd K. Shackelford, et al. (1998) “Adaptations, Exaptations, and Spandrels,” American Psychologist, 53:533–548. http://www.sscnet.ucla.edu/comm/haselton/webdocs/spandrels.html
- Buss, David M. (2004) Evolutionary Psychology: The New Science of the Mind, Pearson Education, 2nd edition. ISBN 0-205-37071-3.
- Cartwright, John (2000) Evolution and Human Behavior, MIT Press, ISBN 0-262-53170-4.
- Krebs, J.R., Davies N.B. (1993) An Introduction to Behavioural Ecology, Blackwell Publishing, ISBN 0-632-03546-3.
- Lorenz, Konrad (1937) Biologische Fragestellungen in der Tierpsychologie (I.e. Biological Questions in Animal Psychology). Zeitschrift für Tierpsychologie, 1: 24–32.
- Mayr, Ernst (2001) What Evolution Is, Basic Books. ISBN 0-465-04425-5.
- Gerhard Medicus. "Tinbergen's four questions in behavioural Anthropology" (pdf).
- Moore, David S. (2001) The Dependent Gene: The Fallacy of ‘Nature vs. Nurture’, Henry Holt. ISBN 0-8050-7280-2.
- Pinker, Steven (1994) The Language Instinct: How the Mind Creates Language, Harper Perennial. ISBN 0-06-097651-9.
- Tinbergen, Niko (1963) "On Aims and Methods in Ethology," Zeitschrift für Tierpsychologie, 20: 410–433.
- Wilson, Edward O. (1998) Consilience: The Unity of Knowledge, Vintage Books. ISBN 0-679-76867-X.