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Ethics of Research involving animals

Study of animals’ choices

4.22 Another useful way of assessing whether or not specific situations are subjectively unpleasant for animals is to measure animals’ choices. An approach initially proposed by Marian Dawkins, tests animals’ preferences between a given set of options and their motivation to gain access to resources (see Box 4.2).18 While the approach clearly does not bring us any further in getting ‘inside the mind’ of the animals in the philosophical sense (paragraphs 4.4 and 4.6), it can be very useful for understanding species-specific needs while avoiding anthropomorphisms (see paragraph 4.3). Testing animals’ choices can allow researchers to select from a range of possible housing conditions those that are preferred by the animals, thus providing them with resources that they value.

Box 4.2: Choice and avoidance tests and economic demand theory
Choice and avoidance tests

Researchers have designed experiments to measure the choices and avoidances of animals in different situations or environments, and when presented with different stimuli. This kind of research is sometimes carried out to increase knowledge about the species-specific basic behavioural dispositions of particular animals in standardised situations. The experiments may also be used to try to assess, for example, the appropriateness of different cage designs, the provision of enrichments, or to measure the effect of a pharmaceutical intervention on the behaviour of animals that are suffering from a given disease.

A choice and avoidance test might be designed to identify which type of bedding a laboratory animal would prefer. Various materials would be provided to see which is chosen by the animals. Alternatively, a cage comprising two parts could be designed, each with different bedding materials. Animals placed in the cage would then be observed as they make their selection. Choice and avoidance tests have also been designed to test whether animals find certain circumstances or procedures painful. For example, rats have been provided with solutions containing either sugar or pain relieving medicines in their normal laboratory state and when experiencing a condition that would be expected to be painful. Experiments show that healthy rats choose to drink the sugar solution whereas rats with inflamed joints prefer to drink the solution containing an analgesic.*

Tests of economic demand theory
Dawkins developed further choice tests by drawing on the idea of inelastic and elastic demands, which are commonly used in economics.† According to this theory, the demand for a reward will be influenced by price. This type of test can be used to assess whether an animal will escape from what may be an adverse experience irrespective of the cost of escaping. For an animal the cost might be discomfort, pain or an inferior choice of food. Conversely, a beneficial situation can become more or less desirable depending on the costs to the animal. For example, during experiments in which researchers administered an injection that caused some discomfort to rats after they ate a particular food, it was found that the rats did not subsequently choose this food item; they learnt not to choose the short-term benefit.‡ In other experiments, rats have shown a preference for a solid floor over a metal grid floor and the strength of that preference has been investigated. Rats were given a choice of sleeping on a grid floor or lifting a weighed door to obtain access to a solid floor with sawdust bedding. Only when the weight increased to near that of the rats’ own bodyweight did the animals stop trying to access the solid floor. Thus it could be concluded that solid floors are highly important to the behavioural needs of rats.∫

* Colpaert FC, De Witte P, Maroli AN et al. (1980) Selfadministration
of the analgesic suprofen in arthritic rats:
evidence of Mycobacterium butyricum-induced arthritis as an experimental model of chronic pain Life Sci 27: 921–8.
† Dawkins MS (1990) From an animal’s point of view: motivation,
fitness and animal welfare Behav Brain Sci 13: 1–61.
‡ See Bateson P (1991) Assessment of pain in animals Anim Behav
42: 827–39.
∫ Manser CE, Elliott HE, Morris TH and Broom DM (1996) The use
of a novel operant test to determine the strength of preference
for flooring in laboratory rats Lab Anim 30: 1–6.

Chapter 4

The capacity of animals to experience pain, distress and suffering Philosophical problems with regard to assessing the welfare of animals The evolutionary continuum Pain, suffering and distress: meaning and function in animals and humans Representations of pain and suffering and their neurological context Subjective and objective elements of assessing welfare: a correlative approach Evaluation of clinical signs Study of animals’ choices Ethological and ecological data Summary of paragraphs 4.3–4.28 Sources of harm for laboratory animals Sources of harm for laboratory animals - continuation I Sources of harm for laboratory animals - continuation II Summary

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