Читать книгу Animal Welfare - John Webster - Страница 14

This exploration of the minds of sentient animals draws heavily on scientific studies of animal psychology and behaviour. The scientific investigation of animal behaviour is concentrated on two main themes. The first is the study of how animals behave in their natural habitat. This can establish their behavioural needs and the actions they perform to meet these needs. From this, we can build up a reasonably comprehensive picture of the resources (e.g. diet, physical and social environment) they require to achieve a sense of physical and mental wellbeing. With this information to hand, we can devise management policies that seek to address these needs whenever we modify their natural habitat to suit our own needs for food, companionship, sport, safety or scientific endeavour.

The second approach is to present animals with a set of questions relating to their perceived needs and measure their responses. This is the science of motivation analysis (16). The simplest version of this approach is the Preference Test. In a typical experiment, the animal is given a choice, e.g. between two foods or two environments and invited to demonstrate a preference. The choice may be between options that we guess might create more or less satisfaction (e.g. two types of bedding material for pigs), or between options that may be more or less aversive (e.g. barren vs. enriched cages for hens). One classic approach is to place the animal in a T maze that allows it to choose between the two options of taking the path to the right or the left. This can tell us quite a lot. Pet food manufacturers may discover flavours preferred by cats (although cats are fickle creatures). Designers of enriched environments for intensively reared pigs or chickens can get some idea of the fixtures and fittings that these animals appear to favour or avoid. However, preference tests can sometimes reveal evidence to indicate that the scientist and the experimental animals are not thinking the same way. In one such experiment, mice were asked to choose between two environments deemed by the scientist to be more or less enriched by traversing a narrow tunnel between the two. Most mice chose to spend the majority of time in the tunnel. For them, this was better than either of the choices on offer (66). The scientists had assumed the mice would choose on the basis of comfort, whereas, in their minds, we must assume that the primary need was for a sense of security. The scientists posed a specific question to these mice and got an unexpected answer. It was the wrong question, but they had a better understanding of mice as a result.

The main limitation of the preference test is that it makes no distinction between choices that are trivial and those that really matter. A more advanced approach to motivation analysis is to measure the strength of motivation by how hard an animal is prepared to work to get a reward in the form of a pleasant experience such as food, or relief from an unpleasant experience such as cold, pain, isolation, or a barren environment (16,45). Examples of the currency used to measure cost include the number of times the animal has to press a lever, or the amount of pressure it has to exert on a gate to obtain the reward. Specific rewards are ranked as more or less price elastic or price inelastic. Most animals, unless satiated, will continue to work for a food reward as the price is increased, which makes it price inelastic. The marginal reward of a different lying surface, e.g. straw vs. wood shavings may be price elastic: i.e. not worth too much effort. While the preference test can do no more than establish behavioural priorities, motivation analysis can determine how much these things matter.

The aim of motivation analysis is to devise tests that enable an animal (e.g. a rat or chicken) to demonstrate, by way of its actions, how it feels about the challenge with which it is faced, positive, negative, or indifferent. Having demonstrated that the test animal is motivated to act to receive a specific reward such as food or avoid a potentially unpleasant experience such as isolation or confinement, the scientist then measures the price the animal is prepared to pay to improve its welfare. They observe this behaviour, review the results in the light of current understanding as already described in the scientific ‘literature’ and form conclusions based on evidence as to the preferences and strength of motivation of the animal. This will be set out for publication in words, tables and diagrams. The scientist has used the medium of language to describe conclusions and decisions that arose first in the mind of the rat or chicken in order that other humans might better understand how it feels to be that chicken. This is reverse anthropomorphism, pure and simple.

There is another profound conclusion to be drawn from studies such as these; one that is key to our understanding of the minds of our fellow mortals. Presented with a specific question, which can be quite complex, the rat or chicken has analysed the problem, worked out a satisfactory response and memorised the actions necessary to achieve that response without recourse to the uniquely human medium of the spoken and written language. Moreover, as we shall see later, the ability to solve simple problems set by scientists in the laboratory can be a very limited measure of an animal’s mental capacity. It pales into insignificance when set, for example, alongside the detailed large‐scale maps that a pigeon needs to carry in its head if it is to navigate its way home. Animals with sentient minds have the ability to acquire and retain a great deal of knowledge and understanding without the need for language as we understand it nor reference to external banks of information stored in libraries and/or Google. What is more, these animals may be able to convey this understanding to their offspring, i.e. to engage in the process of education. We are only just beginning to understand the capacity of non‐human animals to develop thought without language and convey these thoughts to others, but it is an ability worthy of the greatest respect.