Beyond the Cerebral Cortex and Into the “Grey Areas” of Sentience


Most animal ethicists maintain that if a being is sentient, then it has moral status, i.e., it is owed direct moral consideration (see Francione, Steiner, Warren, DeGrazia, Rollin, Palmer, and just about every other animal ethicist with the exception of Regan). To say that a being has moral status or considerability is to say that we “may not treat it [sic] just in any way we see please; we are morally obliged to give weight in our deliberations to its needs, interests, or well-being” (Warren 1997, 3). So, if sentience is that keystone feature (or one of the keystone features) that bestows moral considerability upon a being, we must afford special consideration to the following questions: What is sentience? How do we know if a being is sentient? Which beings are sentient?

What is sentience?

A sentient being is often defined in one of the following ways: a being with the capacity to suffer; a being who is subjectively aware and has phenomenal experiences; a being who prefers, desires, or wants and can furthermore experience or feel frustration or satisfaction of its interests; a being that perceives pain; a being that consciously experiences the negative affective component of pain.

Note that there is more to being sentient than just “having pains” (a being can “have pains,” i.e., an aversive sensory experience from a noxious stimuli, without having an accompanying negative attitudinal state of “hurting”); a sentient being furthermore experiences those pains in the sense that there is a negative affective component that accompanies the pain. To experience the negative affective component of pain, one must be conscious of that pain. In a nutshell, a sentient being is a being who is conscious; a sentient being has conscious experiences of pains, pleasures, and so forth.

*For the purpose of this discussion, we will assume that the term sentience and consciousness are synonymous.

How do we know if a being is sentient?

Typically, there are three common methods employed in order to “determine” whether or not a being is sentient: (1) by evaluating a being’s neurological wiring and physiological properties (including brain anatomy and nociceptive system), (2) by evaluating a being’s behavior (such as “pain guarding behavior,” withdrawal from or aversive reaction to noxious stimuli), and (3) by evaluating a being’s physiological reactions (such as cardiovascular changes like increased heartbeat, increased pulse, or sweating).

human pain

Perhaps the most common way to determine whether a particular being is sentient is to focus on “brain evidence.” In recent year, significant pressure has been put on neuroscientists to discover the “neural correlates of consciousness.” Through EEG and fMRI scans, it is assumed that neuroscientists are able to pinpoint the activity in a particular part of the brain, or a particular pattern of global brain activity, which gives rise to consciousness. Through their research, neuroscientists have informed us that the presence of a thalamocortical complex (the thalamus and cerebral cortex), is the strongest, and perhaps the only reliable, evidence that a being is conscious.This is because, in humans, the cerebral cortex is said to give rise to the experience of pain as unpleasant, unbearable, and so forth.

fish pain

While most animals have a significant amount of neurological hardware that is necessary for “having pains” (but not necessarily sufficient for being sentient), such as nociceptors, prostaglandins, and neuronal opioid receptors, a number of nonhuman animals do not have a cerebral cortex (or they have a very small, primitive cortex). Thus a being who has nociceptors, but not a cerebral cortex, might be said to “have pains” in the form of a purely neurological or neurochemical event, but they might not actually experience the unpleasant aspect of that pain; that is, they might not actually suffer. Fish, for example, have nociceptors, but they have a very small cortex. Thus, neuroscientists frequently assume that, since fish lack the relevant brain areas to process pain and/or nociceptive events, they cannot be said to be sentient. While it is granted that fish can undergo a process referred to as nociception (the neural processes of encoding and processing noxious stimuli), with the aid of nociceptors (also called pain receptors), neuroscientists often deny that fish can consciously experience the negative affective component of pain. Nociception, then, can trigger automatic responses/reflexes which makes certain animals, like fish, behave as though they are in pain even though they are not actually in a negative attitudinal state of “hurting.”

Through neuroscience, scientists hope to draw a sharp line between beings who are sentient and beings who are not sentient: if a being has a sufficiently developed cerebral cortex, then it can be said to be conscious. If it does not have a human-like cortex, then it is not conscious. Sounds easy enough, right?

Maybe not.

Quite to the contrary, studies concerning convergent evolution inform us that different species can develop the same function through anatomical structures that may be quite different from human anatomical structures. This is because the neuroanatomy of some animals is very different from that of humans. Thus we might want to pause to consider whether there might be “species-specific” indicators of pain, i.e., whether different anatomical structures, other than a cortex, might give rise to consciousness in other animals.

In acknowledging that the “human criteria of consciousness” is not necessarily the “criteria of consciousness” for ALL species, we can better explain why certain animals who lack a cortex (or have a very small cortex), still exhibit pain behavior which provides us with convincing evidence that they are in fact sentient. Such animals include fish, octopuses, lobsters, and so forth which are sometimes referred to as the “grey cases.” Take octopuses for example: they have sophisticated nervous systems, they withdraw from noxious stimuli, they can learn from electric shock and remember pain, they have outstanding learning abilities and so forth. But, they don’t have a cortex, and little is known about whether they have nociceptors, endogenous opiates, and whether they respond to analgesics in a way that indicates they can experience pain in the way that “humans do.” (Also note that there is convincing evidence that hydranencephalic human children, children who lack a cerebral cortex, are conscious in a robust sense.)

An octopus is opening a bottle of soda

Despite the fact that research regarding convergent evolution has informed us time after time that there might be a “species specific” criteria of consciousness, we insist on comparing the physiology, brain anatomy, and behavioral responses of animals to humans in an attempt to make conclusions about consciousness. We insist on holding humans up on a pedestal, demanding that we demonstrate that the physiological and neurological processes of other animals are “similar enough” to that of humans if we are to include them in the “sentient club.”

The million dollar question: which beings are sentient?

In order to answer this question, we need to first give up the dogmatic view that humans set the one and only standard for consciousness. We need to stop running to science to confirm what we already know but are ashamed to admit because it would call our every day actions, choices, and habits into question. Octopuses, fish, lobster, and other beings who obviously demonstrate pain behavior are sentient and, if we are honest with ourselves, we will find that we have always intuitively known this.

Marc Bekoff often writes that science is continually trying to catch up with what so much of us already understand. His point is that we don’t need to consult our science textbook to learn about nociception and its possible relation to sentience in order to come to an informed opinion as to whether a lobster who clings to the sides of a container when she is immersed into boiling water suffers from excruciating pain. We do not need scientists to explain the basic concepts of physiology and neuroscience in order to draw a conclusion about what it means when we hear the rattling and clanking in the kitchen as a lobster, who is slowly boiled alive, tries to push off the cover of the pot she is trapped in.

Cartoon of two lobsters about to toss a baby into a pot of water on the stove. One says, "I hate the way they scream when you boil them!" The other says, "It's not screaming, it's just the air escaping!"

Let’s start using common sense, along with a little empathy, compassion, and kindness, when drawing conclusions about the mental lives of other animals. And let’s stop using science to justify our selfish, gluttonous, and unreflective actions that so often cause an incredible amount of pain and suffering to beings like fish and lobster who we readily consume after we’ve convinced ourselves that they are too unlike us to have any moral siginificance.

The moral of the story:

Individuals in positions of power have the bad habit of assuming that only beings “like them” count. In this case, the claim is that only beings with brain structures, physiology, and behaviors “like humans” make it into the moral community. But this sort of arrogance is not limited to the human-animal relationship: this sense of self-importance presents itself, to some degree, in the relationship between men and women, citizens and foreigners, combatants and prisoners of war, and so forth. When “strange” or “different” beings do not live up to the “standard” of the privileged, the privileged too often assume that they have a license to mistreat, exploit, and oppress these beings who are “too different to matter.”

Moral progress demands that we accept the basic moral teaching we often heard as children: a being can have value or worth even when it is different from us. Let us, once again, embrace our childlike morality and give due consideration to the octopus, lobster, fish, and every other creature who we intuitively know is conscious. And if we happen to show compassion to a being who we mistakenly take to be conscious, just remember: it does not hurt to be too kind.