Sentience and Animal Welfare

Donald M Broom

• Publisher: CAB International
• Year: 2014
• Print ISBN: 9781780644042
• eBook ISBN: 9781789244519
• Topic: Medicine
• Subtopic: Veterinary Medicine

Sentience – the ability to feel, perceive and experience – is central to the animal welfare debate as it raises the question of whether animals experience suffering in life and death. This book explores and answers these questions in an objective way, based on the latest research and empirical evidence. Beginning with an introduction to sentience, the book investigates why we are so interested in sentience, when, as a species, humans became sentient and how it has changed over time. The book defines aspects of sentience such as consciousness, memory and emotions, and discusses brain complexity in detail. Looking at sentience from a developmental perspective, it analyses when in an individual's growth sentience can be said to appear and uses evidence from a range of studies investigating embryos, foetuses and young animals to form an enlightening overview of the subject. With a full chapter covering ethical decisions such as animal protection and experimentation, this book is not only an invaluable resource for researchers and students of animal welfare and biology, but also an engaging and informative read for veterinarians and the general public.

1 The Qualities That Make Up Sentience

1.1 Why Are We Interested in Sentience?

1.2 How Do People View Species Perceived to be Like Us or Unlike Us?

1.3 The Concept of Sentience

1.4 Definitions and Descriptions of Components of Sentience

1.1 Why Are We Interested in Sentience?

People have always wondered what is the essential quality that makes us human. We differ from inanimate objects in that we are alive: breathing by using oxygen and producing carbon dioxide; metabolizing using a variety of enzyme systems; repairing the body; sometimes growing and reproducing. The basic aspects of these capabilities we share with other animals and plants. However, people have always sought a means of differentiating ourselves from other organisms. The plants, at least most of them, have the great advantage of being able to produce energy from sunlight using chlorophyll, so we share an inadequacy with other animals. Most people do not appreciate that we are inadequate in comparison with plants and assume that animals are superior. Starting from this premise, our major perceived rivalry is with other animal species. We share a wide range of capabilities with vertebrate and invertebrate animals, such as digesting, locomotion, sensory functioning and brain control of a variety of processes. Some of the details of these abilities have been known to people for a million years or more. As explained in later chapters, observations of behaviour indicate that, while we have knowledge of the functioning of other animals, many other animals also appreciate that individuals of their own and other species need air, food and other resources.

In order to promote the idea that people are special in some way, efforts have been made to describe unique qualities. It was difficult to do this because of our great similarity to other species. Hence somewhat nebulous concepts of the essence of humanity were devised. In human societies, a soul or a psyche or a spirit is attributed to people, or at least to some people. It is often emphasized that humans have ‘free will’ and it is assumed that other animals do not, or at least have much less of it. The view is based on prejudice, as it is obvious from observations of behaviour that most animals are far from being automata with no control of their lives. While soul, psyche, spirit and free will are qualities of individuals, they might also be shared to some degree with others, or linked to a concept of God. When Descartes wrote about individuals having a social spirit he was making a biological and a religious statement. This idea is discussed further in Chapter 2 and has been developed, by the author and others, in books about the biological basis for morality and religion (Ridley, 1996; de Waal, 1996; Broom, 2003).

The soul, psyche or spirit of a person has many components that are also thought of as components of sentience. Although the idea of sentience is more recent, it fulfils some of the same functions as the older ideas, especially when used to refer to humans rather than non-humans. When Descartes referred to the spirit, which he and others have sometimes called soul or mind, he considered it to be separate from the body (see for example Rowlands, 2012, 2013). While the spirit implied connection to others, the soul or mind was the individual part of the spirit. What is the mind? Biologists would now say that behaviour, and some of the physiological functioning of the body, is controlled by the brain. An individual’s perception, cognition, awareness and feelings occur in the brain of that individual and are the consequence of, or cause of, the functioning of sensory mechanisms, muscular responses, glandular responses and other bodily changes. The organs of the body – for example the heart – will influence brain function, but thoughts and feelings are in the brain and not in the heart or any other part of the body. With this role of the brain established, it is not useful for the concept of mind to be considered separately from the brain (Broom, 2003), except perhaps where it means the same as soul, or a component of spirit, and refers to links among individuals.

Dictionary definitions of sentient refer to: (i) feeling or being capable of feeling; or (ii) being able to exercise the senses and respond to sensory stimuli (Merriam Webster, 2005; Concise Oxford English Dictionary, 2011). Most early usage of the term sentience (see Section 1.3) implied that the individual has the level of awareness and associated brain function that makes it possible to have positive and negative feelings. DeGrazia (1996) refers to a sentient being as one that is capable of having feelings. He develops this idea, quoting Sapontzis (1987) who argues that there is no point in an individual having the capacity for feeling unless they can recognize, desire and pursue pleasure and avoid pain. DeGrazia also considers that sentience does not ‘make sense’ without conation, that is, having a drive to perform acts, with or without knowledge of the origin of that drive; and conation does not ‘make sense’ without sentience. Kirkwood (2006) also considers that sentience is the capacity to feel something. Webster (2010) does not define sentience but he says that ‘a sentient animal has feelings that matter’. He explains what matters to animals in terms of strength of preference studies.

When the words sentient, aware, conscious, emotion and feeling are used, they are often used together. Efforts to define or explain one of these terms often involve the use of the others. This is because it is difficult to find other descriptive, definitive words. For example Le Doux (1995), writing about emotion, says ‘a subjective emotional experience, like the feeling of being afraid, results when we become consciously aware of an emotion system of the brain like the defense system’. As in most of the writing about these subjects, his focus is on humans. It is assumed that the reader will understand what is meant when ‘subjective’ is used, will appreciate what a feeling is and will recall being consciously aware and afraid. When other people are discussed, our empathy for them and some observations that we can make lead us to believe that their brain processes are very similar to ours. If another animal species is considered, we have some empathy, but may have doubts about it. Also, we may have a more limited set of observations of the behaviour of that species, and may have been told either that animals of that kind have very different brain structure, or that they are very similar to us. Hence we may or may not conclude that processes like those of humans occur in the brain of such an animal. The prejudices of those in the academic community may well be the reason why many scientists are not willing to say that non-human animals can be conscious, aware or have feelings.

A major change in attitudes to the idea of awareness and feelings in non-human animals has occurred as studies of behaviour have become more detailed. In addition, brain mechanisms have been studied using new methods such as brain recording and scanning: electroencephalography (EEG), positron-emission tomography (PET-scanning), magneto-encephalography (MEG) and frequency-modulated magnetic resonance imaging (fMRI). For some methods now, and for other methods during most of the time since their development, these scanning procedures required that the individual be immobile inside or attached to laboratory apparatus. This precluded their use for freely moving animals and was too frightening to the animals to allow useful studies. Only largely automatic mechanisms could be investigated. This situation is just starting to change as new methods are developed.

One anomaly in the writings of biological scientists (pointed out by Rollin, 1989) has been that while many were unwilling to attribute feelings such as pain and anxiety to any species other than man, laboratory animals have been used for many years as models for humans in work on pain and anxiety. Most scientists would say that a substantial part of the mechanisms involved in pain and anxiety exist in mice and other laboratory species, but that there is some key difference in higher processing. However, this key difference is assumed not to invalidate the application of the laboratory results to humans.

It is assumed that people are sentient, but when did humans or their fore-bears become sentient? The idea that some races of people alive now differ significantly from others in their level of brain function is now known to be incorrect. Also, there is no evidence for differences between races in sensory abilities and feelings, for example capacity to feel pain. The range of human ability within each race is much greater than the range across races. Similarly, the idea that early humans were primitive in every way and very different from modern humans is not supported by written or archaeological evidence. Bronze Age people in Eastern Britain 4000 years ago (e.g. Flag Fen near Peterborough) were living in complex communities, using boats and trading goods with people on the other side of the English Channel. Paintings by people who lived a million years ago indicate sophisticated social living and a good understanding of the environment. Sentience would seem to have existed in people throughout the ages. The question of when sentience arises during development, and when it is lost due to pathology, injury or senility is considered in Chapter 9.

1.2 How Do People View Species Perceived to be Like Us or Unlike Us?

When people have the concept that they have a soul, or have sentience, there will be discussion about whether or not other groups of people, or other kinds of animals, have that quality. There is a widespread tendency to identify more with some species than with others because of their obvious, human-like characteristics. If the body form and behaviour of an animal are similar to those of humans, that animal is more likely to be respected and more likely to be judged to have a soul or to be sentient. Qualities often perceived to indicate that the animal species deserves respect include possession of a relatively flat face, hands, a distinct head, vocalizations ranging in pitch, fur or hair, body length of 1–2 m, warm blood, red blood, lack of body armour and relative uniformity of tooth size. These judgements are related to biological qualities of the animal species but do not always take account of biology in the way that a scientist would evaluate it. It is obvious that similarity to human form and function is an important aspect of this judgement. However, similarity to animals used by man as companions is another aspect. Being a species regarded as dangerous to man or being thought of as a pest make an animal less likely to be respected.

The more different from humans an animal appears to be, the less likely it is to be evaluated as sentient. This is one reason why fish, reptiles such as snakes, insects, spiders and molluscs tend to receive little human respect. However, another category of animals that are respected less than might be expected from their anatomy and behaviour, are those that people keep so they can eat them. In order to be able to eat animals, many people feel that they must denigrate and devalue them by saying that they are stupid or are in some way less similar to humans than they really are. Farm animals have long been misrepresented in this way in human writing and media.

These attitudes to animals are translated into law and codes of practice so animals perceived to be human-like are protected more than those that are not (see Chapter 10). However, there has been a change in laws in recent years, because biological information is becoming more important in decisions about laws and unscientific prejudice is becoming less important. The European Union (EU) Treaty of Lisbon (European Union, 2007) says in the course of a statement about animal protection and welfare (Article 6b), ‘since animals are sentient beings… ’. This wording had the intention to protect the animals commonly used by man, for example on farms, in the laboratory, or as companions, but actually refers to all animals. The term animal refers to flatworms, flies and snails as much as it refers to parrots, dogs and chimpanzees. A question that is raised (Kirkwood, 2006) is whether or not we should give equal protection to a dog and to the fleas on a dog. Part of the aim of this book is to explain the evidence about the components of sentience in a wide range of animals and in humans, ranging from a fertilized egg to a functioning adult, or to a scarcely functioning brain-damaged adult.

1.3 The Concept of Sentience

Animals vary in the extent to which they are aware of themselves (DeGrazia, 1996) and of their interactions with their environment, including their ability to experience pleasurable states such as happiness and aversive states such as pain, fear and grief. This capacity may be referred to as their degree of sentience. As explained above, the term ‘sentience’ has generally been used to mean that the individual has the capacity to have feelings: that is, sentience means having the awareness and cognitive ability necessary to have feelings. This raises the question of what abilities are needed in order to have this capacity. Sentience implies a range of abilities, not just having feelings. A definition, slightly modified from Broom (2006c), is: a sentient being is one that has some ability: (i) to evaluate the actions of others in relation to itself and third parties; (ii) to remember some of its own actions and their consequences; (iii) to assess risks and benefits; (iv) to have some feelings; and (v) to have some degree of awareness. The various aspects of this definition will be explained in this chapter and addressed in the remainder of this book.

The definition of sentient being stated above enlarges on the short definition of sentience as ‘having the capacity to feel’ by Kirkwood (2006). However, Kirkwood also says ‘to be sentient is to have a feeling of something’. I do not agree that an individual is only sentient when having a feeling, and also think that to be sentient is more than just having feelings. Neither do I find it helpful to say, as Kirkwood does, that sentience is something that we experience; or, as in some definitions, to include having simple perceptions as an alternative meaning of sentience.

Human opinion as to which individuals of our own and other species are sentient has generally changed over time in well-educated societies to encompass first all humans, instead of just a subset of humans, and then certain mammals that were kept as companions; animals which seemed most similar to humans such as monkeys; the larger mammals; all mammals; all warm-blooded animals; then all vertebrates; and now some invertebrates.

People have long appreciated the sentience of various domestic and other well-known animals and have often thought of their dog or horse as an example to follow or a friend who would help, rather than just as a resource object. However, a rabbit is viewed differently according to whether it is a family pet, a laboratory animal, an animal kept for meat production, or a wild animal that eats your crops. This is not scientifically sound. A rabbit is a rabbit and each one feels pain or has cognitive function (Broom, 2007a).

1.4 Definitions and Descriptions of Components of Sentience

Key issues in any discussion of the sentience of all animals, including fish and invertebrates, are: (i) whether they are aware of what is happening around them; (ii) whether they are capable of cognitive processing; and (iii) whether they can have feelings such as pain. The meaning of awareness is discussed in Chapter 6. A definition by Broom (1998) is modified here: awareness is a state during which concepts of environment, of self, and of self in relation to environment result from complex brain analysis of sensory stimuli or constructs based on memory. Its existence can be deduced using careful observation, generally in controlled, experimentally contrived situations. The information obtained can help us to understand which of the several levels of awareness is indicated (Sommerville and Broom, 1998). A conscious individual is one that has the capability to perceive and respond to sensory stimuli. This is essentially the definition of Blood and Studdert (1988): ‘capable of responding to sensory stimuli; awake; aware’.

As explained further in Chapter 9, animals are more likely to be considered sentient if they can learn much, learn fast and make few errors once they have learned. These abilities are the basis of evaluating the actions of other individuals and remembering actions and their consequences. For any individual, assessing risk and benefit is also an important part of appreciating its environment in a way that allows some control of interactions with it. Learning is a change in the brain, which results in behaviour being modified for longer than a few seconds, as a consequence of information from outside the brain (Broom and Johnson, 1993). These topics are discussed in detail in Chapters 4, 5 and 6. As discussed further in Chapter 4, cognition is having a representation in the brain of an object, event or process in relation to others, where the representation can exist whether or not the object, event or process is directly detectable or actually occurring at the time.

The ability to feel pain and some forms of pleasure are generally included among the capabilities of sentient animals. A feeling is a brain construct, involving at least perceptual awareness, which is associated with a life-regulating system, is recognizable by the individual when it recurs and may change behaviour or act as a reinforcer in learning (Broom, 1998). The concept of ‘emotion’ overlaps with that of ‘feeling’. As discussed at length in Chapter 5, emotion is describable using physiological measures.

As explained by Broom (2003), the reluctance of scientists to attribute complex abilities and feelings to non-humans has slowed the development of our knowledge of sophisticated brain function in non-humans. Researchers have been unwilling to carry out studies in the area because, if they used words such as awareness, feeling, emotion and mood, they risked the scorn of other scientists and having difficulties in future in obtaining research funding and getting papers published.

2 Ethics, Morality and Attitudes

2.1 Ethics

2.2 Morality, Selfishness and Altruism

2.3 Obligations

2.4 Rights

2.5 Freedom

2.6 Brief History of Attitudes to Animals

2.1 Ethics

Something is moral if it pertains to right rather than to wrong. The question of what is right, or good, or beneficial is discussed further by Broom (2003). However, as Midgley (1994) has emphasized, morality should not be thought of as a topic that is obscure and difficult to comprehend. We each have many clear ideas about actions that are good or not good. Most people would agree that behaving morally involves judging right and wrong and behaving accordingly (Planalp, 1999). Hence decisions about moral issues are taken many times during every day. People ‘behave morally’ most of the time and often discuss questions of what is right or wrong. In doing this they express an interest in ethics which is the study of moral issues. Determining what is moral is sometimes very obvious but, at other times, involves considerable thought. While several capabilities have arisen during evolution that promote moral behaviour, the idea that ethics can be entirely based on ‘uneducated gut feelings’ is not supported by ...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Glossary
• 1 The Qualities That Make Up Sentience
• 2 Ethics, Morality and Attitudes
• 3 Animal Welfare Science: History and Concepts
• 4 Brain Complexity and Cognitive Ability
• 5 Feelings and Emotions
• 6 Awareness and Consciousness
• 7 Motivation and Needs
• 8 Welfare Assessment
• 9 Sentience During Development, Brain Damage and Old Age
• 10 Ethical Decisions About Humans and Non-humans
• 11 Sustainability, Welfare Attitudes and Education
• References
• Author Index
• Subject index