Drawing the Boundaries of Animal Sentience

Why we cannot find a clear line marking which animals are conscious.

Posted Jul 08, 2020

In a recent article published in Animal Sentience (the flagship journal for animal consciousness) by Bryce Huebner and myself, we argue that recent research on animal consciousness suffers from a line-drawing paradigm that seeks to draw a line in the sand of which animals are sentient and those that aren't and can thus not be part of our moral community. The article is titled "Drawing the boundaries of animal sentience," (hence the title of this post), and tries to replace this paradigm:

Photo by Lisa Fotios from Pexels
Are bees conscious?
Source: Photo by Lisa Fotios from Pexels

Here we draw on a letter sent by Rene Descartes to William Cavendish in 1646, (1991, 173-175) in which he considers three possibilities regarding the distribution of sentience:

(i) no nonhuman animals are sentient, because the only plausible evidence of sentience is the use of a language to reveal an awareness of what things mean

(ii) some nonhuman animals are sentient, because they engage in nonlinguistic behaviors so flexible that they are not fully explicable in mechanistic terms

(iii) all nonhuman animals are sentient, because the cross-species continuity of biological mechanisms reveals that differences in sentience are a function of biological complexity.

Like most philosophers and scientists, Descartes rejects (iii), arguing that it would require incorrect attributions of minimal sentience to simple organisms like oysters and sponges. He also rejects (ii) because it would require arbitrarily stipulating what degree of complexity is sufficient to yield sentience and could include forms of behavior that could be performed insentiently. Descartes therefore proposes accepting that only humans are sentient. (Veit & Huebner 2020, p. 1)

While the Cartesian view of animals as mere machines was once popular, it is now generally taken to be ludicrous. Few, if any, scientists or philosophers nowadays accept Descartes' assertion that only humans can feel — that is, have sentience (which is a less ambiguous term than consciousness).

But although Descartes’s a priori approach to animal sentience has few contemporary adherents, his concern to address the problem of determining the boundaries of sentience persists among animal sentience researchers today, with an enhanced focus on the kinds of states that would place an animal within the bounds of our moral community. Birch (2020), for example, contends that there is a dividing line in nature “between the entities that have no experiences of any kind, and those entities that do,” although he notes that “[f]inding that line, and understanding how it was crossed, is a challenge for evolutionary biology (p. 288). (Veit & Huebner 2020, p. 2)

We argue that the situation is "similar in the case of attempts to draw a clear line marking when a developing fetus becomes sentient. Here too, there are numerous policy-making decisions that must be made about how to balance the relevant risks, with the risk-balancing decisions typically influenced by cognitive and affective biases (see Lyerly et al. 2007 and Lyerly et al. 2009)."

For policy purposes, it seems that we need a line determining at which point abortion is permissible and when it isn't. If there is a point at which a fetus has no feelings, it seems less problematic to terminate it — and so for animals that lack feelings. But is it really so easy to draw a line? We think the debate rests on a mistaken assumption:

Disputes about where this line should be drawn have recently unfolded around the ability of fishes to feel pain. Consider Key’s (2016) target article against fish sentience, which rests on the claim that fishes lack the neocortical structures responsible for human experiences of pain. As Michel (2019) notes, many of the commentaries attack this way of drawing a line, insisting on the possibility that pain could be realized in multiple ways (Braithwaite & Droege 2016; Manzotti 2016; Seth 2016; Ng 2016; Elwood 2016; Godfrey-Smith 2016; and Segner 2016; Merker 2016a,b,c, commented three times on the boundary problem). Michel concludes that we could never empirically settle the question of whether nonhuman animals such as fishes can feel pain. This reasoning, however, rests on the false premise that unless we can provide a boundary line between sentience and insentience, there is nothing to say about animal sentience. (Veit & Huebner 2020, p. 2)

This is a mistake. Consciousness comes in degrees and we may thus be forced to revise our simple dualistic picture regarding the ethical treatment of animals.

Click here for part 2 on how to treat animals and investigate their degrees of consciousness once the line-drawing paradigm is abandoned.