Animal Sentience: The Controversy

Clever Animals

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As will become apparent from the following discussion, the debate over animal sentience has, like a growing number of present-day issues, become rather polarized.

A case in point was the recent Annual Meeting of the Canadian Veterinary Medical Association (CVMA) where a summit was held called "Animal Sentience: What Does It Mean, Why Is It Difficult to Define, and What Effect May It Have on the Veterinary Profession?" Dr. Tim Arthur, the CMVA’s newly elected president, told me this was the first time this topic was discussed at one of their conventions. He directed me to the recently issued CVMA Position Statement on Animal Sentience which states, “Sentience in this document means having the capacity to experience positive and negative feelings such as pleasure, excitement, fear, hunger, pain, and distress ... The CVMA holds that many species of animals are sentient.”

Professor Georgia Mason, in the Department of Integrative Biology, at the University of Guelph was one of the speakers at the conference. I contacted her to seek her views on animal sentience.

She said she fully supported the CMVA’s position paper. In response to my question, she explained the difference between sentience and consciousness by saying that sentience is a type of basic consciousness. “It is the ability to feel or be aware, sometimes described as the ‘what it is like’ aspect of a state. Sentience does not imply self-awareness, theory of mind, or anything else 'higher order' (i.e. complicated/cognitively sophisticated.”

Mason uses sentience to refer to just the sub-type that is most ethically relevant, emotions, an animal's capacity for pain or other forms of conscious affect. Mason has referred to measures such as discriminating between stimuli, displaying Pavlovian conditioning, and even learning simple instrumental responses as “red herrings” that should not be used to infer sentience because they are also present in non-sentient organisms, notably those lacking nervous systems, like plants and protozoa.

In Canada, the Canadian Council for Animal Care, “utilizes affective states as the primary determinant of animal welfare” while internationally, the World Organization for Animal Health says that “an animal experiences good welfare if the animal is … not suffering from unpleasant states such as pain, fear and distress.”

Mason, a passionate animal welfare advocate, agrees. “Pain and suffering is morally relevant. The guiding question should perhaps not be, “Is there evidence that this species is sentient?” But instead: “Are we sure it is not?”

The Cambridge Declaration on Consciousness, signed by a prominent group of scientists, which Mason thinks goes too far, states that “the absence of a neocortex does not appear to preclude an organism from experiencing affective states. Convergent evidence indicates that non-human animals have the neuroanatomical, neurochemical, and neurophysiological substrates of conscious states along with the capacity to exhibit intentional behaviors."

Personally, I agree with this statement. It seems to me that many scientists overvalue the role neurons and the neocortex play in consciousness. Cells, tissues, organs, and animals form various kinds of minds along a continuum from the simplest to the most complex. There is little difference between neurons and other cell types. Synaptic proteins, ion channels, and gap junctions already existed in our unicellular ancestors and were used by electrically active cells to coordinate their actions at the beginning of time. Neurons evolved from these much simpler cell types and some of the brain's speed-optimized functions emerged around the time of bacterial biofilms. Neurons are specialized cells like red blood cells or liver cells. But there is nothing magic about neurons.

I thought that perhaps Professor Nicolas Rouleau might provide a different perspective on the topic of animal sentience. So, on a sunny day in July, I drove to Wilfrid Laurier University to meet with Nic, as he likes to be called. Sitting in his fifth-floor office in the Department of Health Sciences I asked him to comment on Mason and Lavery’s paper on animal sentience. “The authors” he remarked, “remove supposed ‘red herring’ measures of sentience precisely because they are present in a group of organisms that they've a priori determined are non-sentient. Theirs is a circular argument which is not based on evidence but simply a prejudice, namely the lack of a nervous system.

Nic is a neuroscientist who contends that all attributions of cognition (i.e., mental actions), including sentience, are always inferred based on embodied behaviours, including verbal self-report in humans. He says, “If felt states in humans and other animals are always inferred, why is the same leap from observable behaviour to inferred sentience not afforded to other organisms, including plants?”

I want to know how he differentiates between simple reflexes and conscious behaviour. “Behaviours are fundamentally cognitive,” he says, “because they are goal-directed, anticipatory, flexible, and adaptive. These qualities are unlike simple reflexes, which are comparatively rigid, typically inborn, and do not require any accompanying mental action.”

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I wonder, does a being require a neural substrate to be sentient? “Not at all. A function is said to be substrate-independent when it can be achieved without the contingency of a particular material or physical medium. Computation, for example, can be implemented in many ways by machines and living organisms alike. It is quite possible that felt states can be achieved in multiple ways and by many different biological substrates.”

After a most stimulating morning, Nic took me on a tour of his lab where he introduced me to his wife, Nirosha Murugan, who is also a professor at WLU. These two young scientists are doing incredible research on cancer and embodied and bioengineered tissues to model neural diseases. I would not be surprised if they receive the Nobel eventually.

Nic did post-grad work at Tufts University in Boston. One of his mentors was Michael Levin, Distinguished Professor of Biology and Director of the Allen Discovery Center. Levin conducts research at the intersection of developmental biology, computer science, and behavioral science. In my opinion, he is one of the most brilliant scientists alive today. A few years ago, at the end of a long conversation with him, I asked what being human means to him. His answer still rings in my ears: “Being human is to have moral concern and compassion for every being.”