The Use of Analogous Reasoning for Assessing Discomfort in Laboratory Animals
Geplaatst door
T. Rivas
When assessing discomfort in animals analogous reasoning is often used.This practical rule of thumb can be based on an 'analogy-postulate'. We think that there are sound reasons for accepting this analogy-postulate.

This article was published in Animal Welfare 1992, 1: 77-84 (Universities Federation for Animal Welfare).

F. R. Stafleu (1,3) , E. Rivas (2), T. Rivas(2), J. Vorstenbosch (3), F. R. Heeger (3), and A. C. Beynen (1)

Institutes in 1992
(1) Department of Laboratory Animal Science, State University of Utrecht, P O Box 80.166, 3508 TD Utrecht, The Netherlands.
(2) Faculty of Social Sciences, Institute of Theoretical Psychology, State University of Utrecht.
(3) Centre for Bio-ethics and Health Law, State University of Utrecht.

When assessing discomfort in animals analogous reasoning is aften used, namely, that the causes or symptoms of discomfort in people will also apply to animals. This practical rule of thumb can be based on an 'analogy-postulate'. This postulate takes into account the anatomical and physiological similarities of vertebrate nervous systems and the comparability and homology in the behavioural and physiological responses to discomfort of humans and other vertebrates in similar situations. There are theoretical and practical problems with this analogous reasoning. Theoretical objections include claims that feelings do not exist, are irrelevant or that scientific knowledge is not necessary to recognize feelings. Practical problems will occur when assessing the discomfort of animals without proper knowledge of the relevant species-specific information. Nevertheless, we think that there are two equivalent sound reasons for accepting the analogy-postulate. First, there is more evidence in favour of acceptance of the postulate than of its rejection. Secondly, the negative moral consequences of erroneously rejecting the postulate are far greater than those of mistakenly accepting it.

Keywords: analogy, animal welfare, assessment, discomfort, postulate

Animal welfare implications
There are theoretical and practical arguments against the use of analogous reasorung in assessing discomfort of laboratory animals. However, these are outweighed by arguments in f avour of analogous reasoning and by the negative moral consequences of incorrectly assuming that animals cannot suffer from discomfort.

When people attempt to assess the degree of discomfort (1) in laboratory animals (2), they often resort to reasoning based on the analogy between humans and animals. In an experiment Stafleu et al (1989) asked people to read a hypothetical protocol of an animal experiment and to assess the anticipated discomfort in the animals. They were also asked to defend their assessments; frequently the respondents used the argument that what causes discomfort in humans will have a similar effect on animals. Unfamiliarity with clinical and pathological changes to be expected in the animals under study, resulted in more frequent use of this type of analogous reasoning. Where respondents did have information about the clinical and pathological changes, they referred directly to them. However, this also is a form of analogous reasoning. When using clinical and pathological signs as indicators for animal discomfort, one makes the assumption that the sensations of people and animals are analogous when showing similar symptoms. Thus, there are two forms of analogous reasoning. The first one supposes analogy of discomfort in animals and humans as induced by comparable stimuli. The second one focuses on analogy of discomfort in animals and humans associated with comparable behaviour.
Both forms of analogous reasoning can be criticized. In the first part of the paper we attempt to clarify the basis of this criticism. In the discussion we will state our position with respect to this criticism and add a moral argument to justify the use of analogous reasoning when assessing feelings of discomfort in laboratory animals.

The analogy-postulate (3)
The question which has to be posed is whether the analogy between humans and animals with regard to similar stimuli can be justified and whether it is defensible to use the analogy to interpret clinical changes in terms of animal discomfort. There are many differences between humans and animals, so that symptoms such as sitting hunched up do not necessarily point to discomfort.
In the literature (Flecknell 1984, Morton & Griffiths 1985, Singer 1975, Wemelsfelder & Verhoog 1988) justification for the two types of analogous reasoning has been postulated. To ‘postulate’ is defined here as formulating a statement based on practical or systematic arguments.

The reasoning behind this ‘analogy-postulate’ is as follows:

1. The nervous systems of vertebrates are anatomically and physiologically comparable and also homologous (4) .
2. The behaviour of animals in situations in which humans would feel discomfort shows similarities to that of the humans in similar situations. The combination of these two facts makes the following postulates plausible:
a. Animals can have feelings of discomfort comparable to those in humans.
b. Similar feelings of discomfort in humans and animals are elicited by comparable stimuli.
c. Behaviour in animals which resembles that in humans is indicative of similar feelings.
Thus there are two arguments that form the basis of the analogy-postulate. One uses evolutionary theory and focuses on anatomical and physiological similarities. The other uses similarities in behaviour. Below we discuss the theoretical problems of the postulate, followed by the practical ones.

Theoretical problems with the analogy-postulate
As we are dealing with a postulate, it must be plausible on the basis of practical and/or theoretical arguments. A postulate is not a scientific theory which can be proven true or false. Instead. it is a reasoning process which should persuade people to use it as a basis for their actions; its plausibility depends on the arguments (5). The validity of these arguments is determined by premises. Often these premises are implicit and thus may cause confusion.
A pivotal premise is that we need an analogy-postulate because the translation of scientific (in the sense of measurable, i.e. controllable and objective) knowledge into feelings of other beings cannot be substantiated scientifically. This is because feelings cannot be measured and thus can only be perceived subjectively. So, for example, scientific knowledge of behaviour cannot be directly translated into information about feelings of discomfort. However, we need this information to guide our actions with respect to animals.

This premise can be criticized in three ways:
1. By stating thatfeelings can be directly measured
The mechanistic view is that feelings are purely physiological phenomena. Because such phenomena can be scientifically monitored, there is no need for a higher postulate. At the very least, there is not yet sufficient scientific knowledge to make an objective statement.
2. By stating that feelings are irrelevant.
From a behaviouristic point of view, feelings are irrelevant because they cannot be adequately described. Whatever happens ‘inside’ a human or animal is not of interest. One cannot adequately describe feelings because they cannot be scientifically monitored. Feelings may exist, but make no scientific sense. Thus there is no need to relate scientific facts to feelings, because the latter are meaningless in science.
2. By stating that scientific knowledge is unnecessary to recognize feelings.
From a phenomenological standpoint, it is not necessary to translate scientific knowledge into feelings. By observing an animal, we can directly assess its feelings.
Many people who work and live with animals claim that they know when animals suffer or enjoy themselves. These people consider the analogy-postulate as academie and not relevant to everyday life. If one accepts that feelings can be ascribed to animals and that these feelings cannot be reduced to physiological phenomena alone, then it becomes relevant to scrutinize the premises underlying the arguments used in the analogy-postulate itself.
An important premise is that evolutionary theory is true and relevant. Without this theory the biological term homologous has no basis and the evolutionary relationship between man and animals will then have no meaning. Without evolutionary theory, the analogy-postulate must be founded upon totally different grounds from those which are currently accepted.
Evolutionary theory may also be regarded as irrelevant, as is the case when it is stated ihat the power to use language (in the human sense) is an essential criterion for the existence of any form of consciousness. It is then argued that it is not possible to have feelings without some form of consciousness. According to this view, language is indispensable as a means of formulating and communicating feelings. The inability to formulate feelings therefore sheds doubt on whether they exist and, as a consequence of taking the view that there is no distinction between the language of feelings and the feelings themselves, proponents of this view conclude that animals cannot be accredited with feelings.

Practical problems with the analogy-postulate
Practical problems are raised by the question as to whether the two basic arguments of the postulate (comparability between humans and animals as to physiological symptoms and behaviour) are valid in a given situation.
Most people assume that there is a high degree of comparability and homology between the nervous systems of vertebrate animals and humans. Iggo (1985) however, points to the fact that the frontal lobes of animals are much smaller than those of humans. When the frontal lobes have been damaged, patients report feeling pain without suffering from it. So the capacity to suffer from pain is situated in the frontal lobes. Are the relatively smaller frontal lobes of animals connected with a decreased capacity to suffer?
Problems also arise about the comparability of behaviour and how it should be interpreted; also which particular actions are indicative of comfort or discomfort. When interpreting animal behaviour, one has to take into account species-specific characterislics. Otherwise, conclusions will be based on a direct translation of observed behaviour into human concepts, which is anthropomorphic reasoning. The analogy-postulate may then be considered appropriate without taking into account species-specific aspects of behaviour. This may lead to false negative or false positive conclusions. This can be illustrated by the following examples.
A false positive conclusion can be based on the screaming of piglets. Even the slightest touch makes a piglet scream. Hearing the intensive screaming of a piglet being picked up, the anthropomorphic conclusion might be that the animal suffers considerable pain. However, the species-specific context that applies, in this situation, is that piglets run a great risk of being crushed to death by their mother in the nest. Thus pigs have evolved a low threshold for screaming to alarm the mother. This is not necessarily accompanied by a low threshold for pain, A knowledge of the particular species indicates that it is plausible that the ‘heartbreaking’ screaming of piglets is not necessarily indicative of pain. (However, it might suggest a low threshold for anxiety). Screaming by piglets may indicate pain when they are being castrated without anaesthesia; however, the sound frequency in this situation differs from that emitted when piglets are only being picked up (Wemelsfelder & Van Putten 1985). The fact that ‘piglets always scream’ should not be used to justify the belief that they are never in pain when doing so.
A false negative conclusion may be arrived at when animals show no altered behaviour in situations where people would do. This usually does not concern acute pain, for most animals will react by avoiding the damaging stimulus. In cases of more chronic pain, like post-operative pain or that associated with disease, there are often fewer behavioural signs than might be expected. Anthropomorphic reasoning might conclude that these animals are not in pain. However, species-specific information would indicate that it is not advantageous for the particular animal to show pain. This is often the case in species where assistance between group members has not evolved as part of the social repertoire. In some species it can even be counter-productive to show pain. A sign of weakness may provoke an attack from predators or subordinate members of the group (Van Hooff 1988). In these circumstance it may even be more important for the animal in pain to act naturally.
So when using the analogy-postulate in practice, one should use critically species-specific knowledge to avoid false negative or false positive conclusions.

Now we have clarified the problems associated with the analogy-postulate we shall justify its acceptance and use. First we shall put forward theoretical arguments and secondly practical ones and will conclude with a moral argument.
We accept the view of behaviourists that feelings cannot be known scientifically (in the sense of being measurable etc). However, we disagree with their opinion that this makes it scientifically irrelevant to talk about feelings. We believe that science can provide adequate circumstantial evidence for making assumptions about feelings in other beings. The fact that we cannot scientifically prove something does not make it worthless. We are dealing with a practical problem and, if someone wishes to ignore all the circumstantial evidence and take the view that we cannot be absolutely sure and therefore must remain agnostic, this is of little practical help. Russell (1976, Ch. 8) points out that, in theory, we cannot even be certain about the quality of the feelings of our fellow human beings: ‘We are not content to think that we know only the space-time structure of our friends’ minds, or their capacity for initiating causal chains that end in sensations of our own. A philosopher might pretend to think that he knew only this, but let him get cross with his wife and you will see that he does not regard her as a mere spatio-temporal edifice of which he knows the logical properties but not a glimmer of the intrinsic character. We are therefore justified in inferring that his scepticism is professional rather than sincere.’
Also the mechanistic view is of no practical help. Even if it were correct to assume that everything can be measured, at present, we do not even have sufficient knowledge to measure feelings and so must seek other methods.
The phenomenological point of view has the advantage of fitting nicely into the intuitions which many people have about animals. But intuition, without a theoretical background is a doubtful justification for action. We believe that the analogy-postulate provides a good theoretical background, for intuition.
It is impossible to know scientifically the mental state of other beings so that if someone argues that the differences between humans and animals are such that the former can suffer and the latter not, it cannot be proven wrong. But is such a view really plausible? We cannot see that the ability to express feeling in language is more than a technical difference. Why should words communicate more reliably than behaviour? They might seem to be clearer to us, but there remain considerable problems of interpretation. Language does not provide direct access to other peoples’ minds. We will always have to make the assumption that speech really relates to someone else’s subjective mind and is not the direct result of a machine generating words in the manner of a speaking computer.
Visual comparability should not be overemphasized. The crucial point is whether behaviour can be explained as an adaptive response to discomfort. If, in a given case, after careful scrutiny of physiological and clinical signs, behaviour cannot be considered as an adaptation to discomfort, then the postulate should be considered irrelevant in that particular case. So far we are not aware of such a case.
Although we feel that the analogy-postulate is plausible, as stated, there will always be people who disagree. Still, even those people who fail to see the strength of the analogy argument, will have to consider the moral outcomes of the different theoretical positions one can adopt. The practical consequences of wrongly believing that animals can suffer from pain will be that we shall make needless work for ourselves, such as the administration of analgesics, or the imposition of other refinements in animal care. These consequences have predominantly an economic rather than a moral value. But the results of treating animals as insentient beings, whereas in reality they are sentient, may have the effect of inflicting pain or discomfort on the animal and therefore have a negative moral value. We would be inflicting discomfort without good reasons, which is immoral.
Furthermore, we would be causing discomfort that could have been prevented. To decide whether or not to accept the analogy-postulate, the strength of arguments not only play a role, but also the consequences of acceptance versus rejection. People who denounce the analogy-postulate and assume that animals cannot suffer, should weigh the consequences of their point of view. Unjustly treating animals as insentient has a far more negative impact than unjustly treating them as sentient. Thus, they should give the animals the moral benefit of their scientific doubt

(1) We use the expression discomfort in a broad sense: any unpleasant experience like pain, nausea, boredom etc. is included in it.
(2) The Dutch law on animal experimentation refers to vertebrate animals only. In this paper we mean vertebrate animals when speaking of laboratory animals.
(3) In the Netherlands the term analogy-postulate has been used in this context. In the Anglosaxon literature, this term has not become popular but the justificacion for analogous reasoning is stated in the form of a postulate.
(4) We use the term homologous in the biological sense as ‘similarity in structure and development of organs because of common anceslry and similar genetic basis’ (Hickman et al 1978).
(5) These arguments may consist of scientific theories or scientific facts. These can be proved or falsified. However the translation of objective knowledge into an assessment of feelings can only be considered more or less plausible. Therefore, the assessment of discomfort can only be based on a postulate.


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- Hickman, C.P., Hickman C.P.(jr), Hickman F M 1978 Biology of Animals. C V Mosby Company: Saint Louis.
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- Russell, B. 1976 Human Knowledge, lts Scope and Limits. Allen and Unwin: London.
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- Stafleu, F.R., Heeger, F.R., Beynen, A.C. 1989 A case study on the impact of clinically observed abnormalities in mice with gallstones on the ethical admissibility of a projected experiment with gallstone-bearing mice. Alternatives to Laboratory Animals 17: 101-108.
- Van Hooff, J.A.R.A.M. 1988 On the ethology of pain, its experience and expression. In: Beynen A C, Solleveld H A (eds) New Developments in Biosciences: Their Implications for Laboratory Animal Science, pp 41-46. Martinus Nijhoff: Dordrecht.
- Wemelsfelder, F., Van Putten, G. 1985 Behaviour as a Possible Indicator for Pain in Piglets. Report B-26. Research Institute for Animal Production ‘Schoonoord’: Zeist.
- Wemelsfelder, F., Verhoog, H. 1988 Het bewuste dier. In Visser, M.B.H., Grommers F.J. (eds) Dier of Ding. Pudoc: Wageningen.

Contact: titusrivas@hotmail.com

Dit artikel werd in 1992 gepubliceerd in Animal Welfare 1: 77-84

Gebruikte steekwoorden
other minds, sentience, animal ethics, assessment, analogy postulate, discomfort, animal, animal welfare
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