Exploring the limits to our understanding of whether fish feel pain

Abstract

In the United Kingdom, the Animals (Scientific Procedures) Act 1986 (HMSO, 1986) regulates experimental work on vertebrate animals. The European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes (Council of Europe, 1986) covers the same ground. Both the British law and the EU Convention use a closely similar set of criteria to judge the status of a scientific procedure. The British law states that “a regulated procedure on a protected animal under the 1986 Act is one that may have the effect of causing that animal pain, suffering, distress or lasting harm.” The same words are used in the EU Convention to define a procedure as being regulated. Recently in the UK the Animal Welfare (Sentience) Act 2022 (HMSO, 2022) takes the topic even further in that it is “an Act to make provision for an Animal Sentience Committee with functions relating to the effect of government policy on the welfare of animals as sentient beings.” It goes on to say that “in this Act ‘animal’” means (a) any vertebrate other than Homo sapiens, (b) any cephalopod mollusc and (c) any decapod crustacean. For scientists working with fish the existence of these acts means that there is a need to understand whether fish can or cannot suffer from pain. To get to a point of sufficient understanding we need to ask whether fish are conscious, can feel pain and can suffer. At present we do not have certain knowledge about how fish experience the world. More broadly it is probably safe to claim that we do not know how all but a handful of non-human animals experience the world (Birch et al., 2020). In the current debate about pain and suffering in fish, the evaluation of evidence is biased by philosophical confusions and the prejudices of the protagonists. In many papers dealing with phenomena which are not directly observable in non-humans, such as consciousness, pain or fear, authors use terms derived from human usage and assume that these terms can be applied to non-humans with the same meaning. Consequently it is essential to cut back the undergrowth of philosophical opaqueness and to identify the assumptions made so that the important features of the debate are left clear and distinct for further analysis and discussion. The starting point for this article is the hypothesis that without some form of self-aware consciousness, there is no possibility of experiencing pain as we humans know it. Pain in humans is a subjective mental phenomenon that a robot responding to external stimuli would be unlikely to experience. The first task is to establish the justification for proposing this hypothesis. Before going further it is important to deal with three factors that can get in the way of rational discussions of whether or not fish experience pain (see also Hart, 2016): (a) humans work on the assumption that consciousness is more influential than it really is in deciding how we behave; (b) complex behaviour must imply consciousness and (c) language used by humans to describe and discuss their consciousness can be used in the same way for non-humans. Each will be discussed in turn. A little introspection shows that much of our behaviour is accomplished with little or no participation of conscious processes (Gray, 2004). You may tell yourself repeatedly that it is time to get out of bed at 06.00 hours in the morning, but is the final decision that propels you from your warm bed a conscious one? Recent evidence would suggest not (Custers & Aarts, 2010). For many motor tasks, such as returning a tennis ball, the conscious experience of the event lags behind the action by about one fifth of a second (Gray, 2004). Consciousness reviews rather than directs. Evolution has favoured the myth of a conscious self by which our lives are directed. Humphrey (2006, 2007, 2022) argues that through this myth we create a sense of self to which events can happen, which further gives us the ability to create goals and give life meaning. For most humans, the myth of conscious control of their lives is so powerful and persuasive that action without it, even in non-humans, seems impossible. If, instead, one takes the view that many of the complex behaviours that we employ are monitored and informed by consciousness but are not directed by it, then we are freer to assess non-human behaviour for what it is. If humans can drive a car, walk, give birth to a baby, play the violin, produce sentences in speech, all without the aid of conscious direction then surely non-human animals can also do complex things without conscious direction. The most startling illustration of the relationship between consciousness, awareness and complex behaviour is what has been called blindsight (Humphrey, 2022; Humphrey & Weiskrantz, 1967; Isa & Yoshida, 2021). First discovered in rhesus macaque monkeys (Macaca mulatta), but subsequently also found in humans with damage to the visual cortex, adolescent monkeys that had had their visual cortex removed were discovered to be able to avoid or pick up objects as if they could see them. Humans with damage to the visual cortex report that they cannot see, yet behave in a way that shows that they can. Both in monkeys and humans, the subjects are at first hesitant about employing this skill of which they are not consciously aware. It is a widespread tendency to assume that because an animal shows complex behaviour, it must be conscious, because if you believe that consciousness is of over-riding importance to complex human behaviour then this must be true of non-human animals too. Otherwise one has to acknowledge that unconscious processes can direct complex behaviour. It is increasingly the case that scientists studying animal behaviour are adopting language that assumes that the animals have conscious feelings and emotions because they show complex behaviour. For example, Verheijen and Flight (1997) conclude unequivocally that fish have subjective experiences and can suffer, yet they present no convincing evidence for this sweeping conclusion. Yue et al. (2004) report a study in which they investigated the response of a rainbow trout (Oncorhynchus mykiss) to a simulated predator, and argue that the fish feels fear as a result of the experience. Like pain, fear is a human experience where the agent needs to be self-aware to suffer from it, so making the claim that fish are experiencing fear is demanding a high level of behaviour. In a similar vein, Bateson and Matheson (2007) and Bateson et al. (2011) attribute feelings of pessimism to starlings (Sturnus vulgaris) and honeybees (Apis melifera) and, more generally, Wiepkema and Koolhaas (1992) consider that all vertebrates employ emotions to deal with their environment. Baars (2005) and Edelman et al. (2005) also discuss this approach. Because of the human meanings that they carry, the use of the language of feelings and emotions by these authors is dangerous, and we need to adopt a more cautious terminology. The modern resurgence of research that considers mental states as legitimate targets of investigation is a reverse of the practice of early ethologists. For example, Tinbergen (1951, p. 4) wrote that “… to ascribe a causal function to something that is not objectively observable (e.g., consciousness or feelings) often leads to false conclusions.” Although there are ways for exploring the mental states of non-humans, as demonstrated by Cheney and Seyfarth (1990, 2007), many present-day researchers are abandoning the evidence-based to understand animal and making use the words and in about other humans because we have to believe that our mental experiences even have processes that the of so us a what they are (e.g., & also know that humans have and behaviours that are closely similar to our so we feel in that and feel as we p. has mental states to complex as a human is by the way of understanding words such as and are words we use to describe and our and mental it to non-humans, and this is true of fish, we cannot use the words or in the same as we have no whether a fish or any other non-human can and if it can what it is is the most important point of this a clear view of how a can be used and what we to we employ it we cannot make sense of the world. The way is to be has been discussed by many in a but influential that language used to create a of with a between words and objects and with the of the world. that words we use to discuss of the have no and as a result the with we cannot about we must in as we do not know the of the applied to a fish we cannot about pain in In that the of words is by their use in a called a the of which we in early In how a to use the to the it experiences it has has and and then to and and, the In this view of the of words we can on how to use a if we a view of the world (see we do not a view of the world with a fish, can we then use words from human experience to describe the experiences of a In the on animal welfare scientists consciousness, pain and suffering in non-humans use these as if they were have to in the human the use of these words is but have that we are not in the same words about non-humans. is a case for a much more to how such as and are used to non-humans. these in we need to be much more about what consciousness is. The is in some of the animal welfare that consciousness is of as by all as is a or a and has (e.g., et al., It is that we are clear on what consciousness is and what in then can we to what it means to say that a non-human animal is p. a of and takes on the of consciousness are the features of consciousness that any to that the way is to features of and of animal consciousness The human has a awareness of being a is to all of us and is as a being from the (see Humphrey (2006, 2007, 2022) an hypothesis as to how a sense of self has and how important this sense is to a A sense of self is essential for our with other and with the world It is also essential to make us experience suffering a is to an experience for a with no in The of up and to of the First the mental of not what had to their or would make a claim for as the most important attribute of consciousness in humans and the consciousness in the first being in a we can see how we are in to and be of the of our (2004) of consciousness is not and other more have been such as that by et al. and et al. are also or For considers that there are to human consciousness, and considers that the is to be found in humans and a of non-humans, the is to be found in a of animals. that be the for non-humans experiencing pain but that some of the criteria that we humans use to identify feelings in our humans are unlikely to be in the same way in non-humans. Cheney and Seyfarth p. consider that consciousness is “… the ability to about at some of our knowledge and and know what we is to The essential to be is that consciousness is a complex and phenomenon which is to define for humans and even to in non-humans. such as some and to have a of and it is that as by is to be more in animals than is The with it a of often by the in which it is and it is clear that use the it is not the case that they will all be it with the same see also of on how we to use a Pain has been as a of which are the subjective experiences that the can You see you on but you do not know how it feels to You cannot see or experience of how a would to that this have have been is as not the to about the of pain in how to use the to report on some scientists are about how non-humans to they use the to describe the response of an animal to an and do not assume that the animal also has a subjective of pain. use the to the subjective feelings that humans have experiencing an or et al., discussed this has little from the evidence and is of where we use our to animal behaviour (see the with the and how we use it in to non-humans is that our are by the to which we the in with our other humans have many with it is a hypothesis that if shows behaviour that we with the feelings of pain, then they must also be pain. are up a by view of what as we use the is a the which of Although we are not in the true sense of the in this the way we use words such as is by the way in which we use words in our A to understanding pain in a more way is to et al., “… that we have a that to out which events in the world are as we have that use to the and of things in our or that use to the of an et al. p. the have to be consciously by the human agent for the of this to be If this is the then can we use the to describe the of events in all argue that we as pain as we know it is a subjective experience and we do not know whether other animals experience the is by the way we to a (Gray, p. our but and then we to experience pain. of the from the it that in with the of pain may not be and it will not be essential for the of the from the It be that the use of the for non-humans is not the use of the or because pain has may be but the existence of not that the animal is or is pain. of the made by et al. is that we are to that and will in the at of (e.g., for see but it to pain, we it as a with one et al., is that the many all of of all the not tell us which to which is no that of the pain are also found in have that have been to stimuli et al., and they have a with a have also that of human with pain have in the fish (see et al., p. between of tell us little about the that in animals are on a of which and from the (Gray, 2004). time have been to the it to increasingly from the & because fish have of the that humans it not that they in the same For fish do not have a as by humans, and as p. “… research show that conscious experience of pain is with not in the but in the more If this out to be true then if fish are to experience pain they will have to be able to the conscious experience by means of a Although this is not the of the which on what is it that fish have not the to be and is discussed more in the For fish, we would need to be able to how many of (2004) features are a of their conscious experience. we could et set of can really do this we understand how consciousness is in then will we know the will know which are of the how they are and how the functions to human consciousness is we can to for a in the of other A to this is found in the of from a of The from the are as an of p. and the is then The the the more complex is the which the of the the then the time at which a in the is on the hypothesis that consciousness is an of a complex The is we are not the to understanding how human consciousness is (2004) this a of it time we understand more about how consciousness is in humans but we have to that it may be that we will be able to understand how experiences are and how they our behaviour. has been by argues that as by for a we cannot that our will be able to understand about the world. considers that consciousness, will and are all of human experience that we will be able to understand because of our time and further research will whether or not is but then a if we human consciousness, would we fish to all by If to what would we these to be of are so that it would not be for a fish to show one but not For example, in a sense of self is essential if the is to see as an which has on other The sense of self is so to many of our other conscious experiences as that it would be to experience without it. is probably true of pain in in that without a sense of self as an to would we attribute a of the in understanding consciousness in humans, most scientists cannot for a understanding whether fish have the same have been by at fish (a) for that are with in the human that are to be or are to be in the of of consciousness and (b) studying and of fish and then whether consciousness for a can be about The first is on the hypothesis that consciousness is a of and that if they in a then the will experience consciousness (see the of et al., are with this hypothesis. The first is that we do not know with that the of certain of means that consciousness can be The second is that we would have to have a way of consciousness in a non-human we could with the means that we are back with the of how to whether a non-human is conscious or The second is on the hypothesis that complex and the animal to be conscious for to has been where that the we have as humans in the of conscious processes us that complex behaviour cannot without Cheney and Seyfarth (2007) evidence from shows that they have a knowledge of the of the in which they It is to conclude that this is evidence for the animals some of of and of what other are must be is that all the behaviours by Cheney and Seyfarth (2007) can also be by that the animals are at the of behaviour. For example, a in a certain must give rather than is from an animal that is to in the and get the Cheney and Seyfarth (2007) how important it is to the evidence for a hypothesis. It is that the dealing with the possibility of consciousness in fish and other non-humans, there are many the of evidence evaluation and a (see also et al., The on consciousness in fish and other non-humans can be to three (a) The judge that fish are not up to conscious experience. 2007), et al. and Humphrey argue for this approach. (b) The that the evidence is not to whether fish are or are not conscious but to assume for the of that they this are by et al. et al., and et al. et al. and (c) The the evidence and adopt the that as yet the out on animal of this work on fish, are Cheney and Seyfarth (1990, 2007), and et al. argues that fish do not have the that are in conscious experience in humans and cannot have Humphrey an hypothesis as to how consciousness is and argues that it is unlikely that cannot the high of the a result the view that and are for non-human In et al. argue that consciousness can be by in so fish have also much time to between human and fish et al. have demonstrated the existence of in rainbow trout do not show that fish are able to feel pain. The to fish and may be in the from but then are to these conscious states et al., do not yet know whether fish have the to It is by some that because a fish no to a this means that the fish pain the of the It is that the the response to the so that the not with consciousness is for this to The of consciousness in fish argue that complex behaviour is a of complex mental processes and that consciousness cannot be how this assumption can be behaviour is being and between of one at a The to the that the fish could other and could between and The assumption that this because have and the to fish from a human where is the it is to assume that a that has must use for all their important work by et al. that could tell the between fish from the same or but were to The also that this with a in the by and we the and made assumptions about the and of the suggest that the from a of the which us to assume that the fish used the same as humans and that they had mental than they in shows that it is to to or assumptions about what animals can If one assumes that fish have complex mental then there is a the for to experimental to need to know much more about the of the fish we can conclude that a certain of behaviour complex mental gives one of the of the way in which we about animal consciousness and how animal of is that we do not need to know whether non-humans are conscious to to have made clear we need to of what we by more a behaviour than we have evidence for and by the of In other words we first for the also of the study by Cheney and Seyfarth The analysis in this article shows that studying consciousness in non-humans it is to know what an animal is experiencing in a subjective argues that if one that all the important of animals have through an then consciousness must have a Humphrey (2006, 2007, 2022) and the same approach. If animals have consciousness, then it must make a to their and that gives for the existence of consciousness in non-humans is that in all of a in one so we and early of the ability to in other also the point that of consciousness produce a which can be used to create as to what the animal be experiencing (see also et al., 2020). has been in by Cheney and Seyfarth (1990, seems rational and to show how one could that consciousness for The is one cannot do the cannot of a with and without consciousness and how consciousness a to their is a further with this and that is one would need to know that of a were conscious one could do the A way the of other animals is through their of has been by Cheney and Seyfarth (1990, and Seyfarth and Cheney their of monkeys and they have a understanding of how these animals their world. us a about their mental Seyfarth and Cheney in about the between and in a say that a in their analysis is “… the that and and that a between animal and human then on to say that because most animals with the of cannot attribute mental states to from they not to that are of the cannot be as that the monkeys are conscious, but it show that their mental world is more than Each lives in mental world with no that have the same experiences as It also that monkeys are not in the way we cannot see as see (see also & If such to humans have a mental world which is so from our is it that fish are conscious, the of their at present we really do not know whether fish are or are not conscious and we cannot say that they do or do not experience pain and suffer from it. at the of this how in the law relating to animal welfare by the UK a understanding of how non-humans experience the world. the for the discussed it will be a time it can be with any of whether or not fish and other non-humans are or are not conscious, but at this point do not that the of consciousness is to the debate about fish conscious humans, can the and of we feel to all life where we can. on a in the is a which be one has for the Animals are and we do all in our to that they lives from be on the of a analysis where we up the to the non-human world the to humans from the (see also & discussed by et al. and the assumption that fish are conscious to policy for animal welfare will have for many human such as for and (see and out by et al. it is essential to the of scientific to the on and as have to make clear in there are many are to the task of to the evidence and not to Humans cannot in the world without with and it. need to make that the we make are are no more than and are on the A is that the evidence has to be and it is to employ and to to non-human animals for which there is no a of about pain and consciousness in fish, to and about the and to as in this a of to the for the and from Humphrey is for to the and are for their which have the

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