Sentience

Sentience is the ability to feel, perceive and experience subjectively. Subjective experiences are often referred to as 'qualia'.

Sentience allows for the awareness of one's own surroundings (consciousness) and the subjective interpretation of such, although not all sentient beings are conscious at all times (unconsciousness).

What is sentience?

For a better understanding of what sentience is and what it implies, an understanding of where it originates and what process is required for its formation is necessary.

To see how sentience works, the formation of a subjective experience can be explained by showing the four steps required in the nervous system for it to exist:

• 1 - The somatosensory system - which is responsible for being able to perceive things (perception of sight, noise, touch, taste, smell, pressure, pain, temperature, position, movement, vibration).

• 2 - The thalamus - which is responsible for 'gathering' the sensory signals given by the somatosensory system.

• 3 - The thalamocortical radiations - which are fibers between the thalamus and the cortex, and are the carriers of information between the thalamus (gatherer) and the cortex (interpreter), relaying the information from the former to the latter and allowing them to communicate, to be able to have the data interpreted subjectively.

• 4 - The cortex, which is responsible for awareness and subjective interpretation of the information given. The mid-brain (the more primitive part) is also sufficient enough to allow for basic capacities for subjective experiences. [1]

To understand this more clearly, a comparison can be made with delivering a letter, where the letter is an information that can be interpreted subjectively:

1- Without the somatosensory system, there is no letter. The delivery person (thalamus) carries nothing, and the receiver (your awareness) receives nothing.

2- Without the thalamus, there is no delivery person. The letter is there, and you're ready to receive it, but nothing happens.

3- Without the thalamocortical radiations, you can't grab the letter from the delivery person and open it, nor can you and the delivery person see each-other. The letter exists, and it's ready to be delivered, but it's not able to be grabbed and opened.

4- Without the cortex, you don't know how to read the letter. The letter exists, it's delivered, and it's opened, but it's unreadable.

In all the cases, you won't know what the letter has to say (can't be aware/sentient).

Noting all these parts, it becomes apparent that sentience requires complexity and size.

That's why with microorganisms, for example, it's safe to assume they aren't sentient, simply because the small size doesn't allow for a complex enough neural network for the microorganisms to have sentience - they don't have the structure for it (being able to do movements and reacting to stimuli isn't sentience without all the other components). That's why certain insects like termites are in a grey area - they are probably a good example of what is at the edge of sentience vs non-sentience.

Sentience is also often confused with sapience. The two are completely different things, with the former meaning the ability to be aware, to have wants and to subjectively experience, and the latter meaning 'having wisdom and discernment' (which is correlated with the degree of sentience, and depends from sentience but not vice-versa).

Where is sentience found?

The more complex and 'evolved' these parts are, the higher degrees of sentience are there.

After understanding what sentience is and how it comes in place, it's very clear that sentience, and the ability to subjectively experience, is not exclusive to humans.

In fact, the Cambridge Declaration on Conciousness, which is an assessment of the concious state in non-human animals done by an international group of cognitive neuroscientists, neuropharmacologists, neurophysiologists, neuroanatomists and computational neuroscientists gathered at The University of Cambridge in 2012, states as follows:

"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. Consequently, the weight of evidence indicates that humans are not unique in possessing the neurological substrates that generate consciousness. Nonhuman animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates." [2]

There's a direct correlation between volume/complexity of the nervous system and brain, and higher degrees of sentience.

The complexity and magnitude of the central nervous system (brain) and of the cognitive capabilities to process subjectively and interpret the information through the thalamocortical complex (which is the collective set of the thalamus, the thalamocortical radiations, and the cortex) are directly correlated with higher intelligence and more complex ability to experience subjectively in species.

This would make sense because of two things:

• A more complex nervous system and brain leads to more complex, and therefore more subjective and unique, experiences
• A higher amount of nerve endings and neurons leads to more intense feelings, perceived at a higher magnitude

Because a bigger structure for higher complexity is necessary, the bigger the brain, and the higher the cognitive capabilities, the bigger the animal usually is. As you can see in the image on the right, there's a correlation between animal size and amount of brain mass.

Considering how sentience has different levels of complexity, as there are beings of lower/higher levels of sentience, it'd be correct to see sentience as a spectrum, with fleas, bedbugs, termites and other very small insects on the lowest end, and elephants, whales, chimpanzees and humans on the highest end.

A good way to understand what sentience as a spectrum of different degrees means, is by looking at the Dennett's creatures model.

Dennett's creatures are divided into 5 subcategories:

• 1 - Darwinian creatures are non-sentient (out of the sentience spectrum). They have pre-designed and fixed competences, and are created by random mutations. Their design and structure doesn't allow for sentience - which makes sense evolutionarily speaking, since their only goal is to reproduce, and improvement happens globally via selection, instead of individual learning. (i.e. bacteria, viruses)

• 2 - Skinnerian creatures are the primitive example of sentience, and can change their behavior by learning through reinforcements. In a trial and error fashion, actions with a favorable result are reinforced and want to be repeated, while actions with an unfavorable result are disliked and want to be avoided. Unlike with Darwinian creatures, the single individual learns and improves throughout its lifetime - hence why sentience makes sense from an evolutionary perspective, to allow the Skinnerian creature to be able to be aware of their surroundings and to experience subjectively, to then be able to improve individually from their experiences (i.e. early human and other mammal babies, most insects). To simplify, Skinnerian creatures ask themselves "what do I do next?".

• 3 - Popperian creatures are higher on the sentience scale than Skinnerian creatures. The difference from Skinnerian creatures is that Popperian creatures tend to evaluate from a different number of options which one is the better one before they take an action. They can evaluate the possible future outcomes of those actions, and then choose the less 'stupid' ones. To be able to do this, they can gather a subjective understanding of their environment, and internally simulate the possible outcomes of a certain action before committing to it (i.e. mammals, birds, reptiles, fish). To simplify, Popperian creatures ask themselves "what do I think about next?".

• 4 - Gregorian creatures use mind-tools (language) to create an inner environment/frame of work that better (in a more complex/more defined way) represents the outer world. This allows the Gregorian creatures to have a good understanding of something with the knowledge passed on by others' experiences/communicated by others (i.e. primates). To simplify, Gregorian creatures ask themselves "how can I learn to think better about what to think about next?".

• 5 - Scientific creatures, similarly to Gregorian creatures, create a better understanding of the world with language and other tools, but do so also in an organized process of making and learning from mistakes in public, and of getting others to assist in the recognition and correction of their own mistakes. Testing is done socially and feedback is taken into consideration - a process which reduces the chance for error (i.e. humans - albeit not all).

Why does sentience matter?

Once an understanding of what sentience is and of how it works is there, it's self-intuitive why sentience would matter morally.

The term morality is commonly used as the framework used to determine whether something is right or wrong, and the distinction between right and wrong.

To understand why sentience is at the core of morality, one must ask what morality would be without sentience. To determine what's right or wrong, consequences of actions have to be looked at, and the impact that they have - and to understand if something is right or wrong, the amount of suffering caused/going against someone's interests (something a sentient being would want to avoid) vs the amount of happiness/satisfaction brought (something a sentient being would want to pursue) has to be looked at.

Sentience is the line to determine whether something is aware and perceives, and has desires and wants, and sentience is the quality without which something can't be aware of anything, nor experience subjectively.

Therefore, without sentience, the consequences of your actions would have no impact whatsoever, as they couldn't be perceived and felt. Without sentience, there are no wants your actions could go against, nor beings that could feel pain as a result of your actions.

It then becomes clear that to have something that would matter morally (i.e. wants, feelings, subjective perception), sentience is an absolute requirement, and that morality wouldn't matter and wouldn't have meaning without sentience.

For example, in a universe without any sentient beings, there would be no need to care for anything. No amount of destruction, or even complete annihilation, could inflict any amount of suffering - as there are no sentient forms that can experience suffering.

Once sentience is brought to the equation, morality has meaning. To determine the right or wrong thing, one must take into consideration the potential suffering caused, and therefore the sentient beings involved - as they are the ones and the only ones that would experience.

For the formal explanation:

P1. Moral evaluation requires consideration of preferences about the state of the universe.
P2. Consideration of preferences about the state of the universe requires the existence (at some point in time) of preferences about the state of the universe.
C1. Moral evaluation requires the existence (at some point in time) of preferences about the state of the universe.

P1. If preferences about the state of the universe are not innate then the existence (at some point in time) of preferences about the state of the universe requires developing preferences about the state of the universe prior to their [the preferences] existence.
P2. Preferences about the state of the universe are not innate.
C2. The existence (at some point in time) of preferences about the state of the universe requires developing preferences about the state of the universe prior to their [the preferences] existence.

P1 (from C1). Moral evaluation requires the existence (at some point in time) of preferences about the state of the universe.
P2 (from C2). The existence of preferences about the state of the universe requires developing preferences about the state of the universe prior to their [the preferences] existence.
C3. Moral evaluation requires developing preferences about the state of the universe prior to their [the preferences] existence.

P1. Developing preferences about the state of the universe prior to their [the preferences] existence requires developing a concept of the universe prior to that development.
P2. Developing a concept of the universe prior to that development requires prior sense experience of the universe (sentience).
C4. Developing preferences about the state of the universe prior to their [the preferences] existence requires prior sense experience of the universe (sentience).

P1 (from C3). Moral evaluation requires developing preferences about the state of the universe prior to their [the preferences] existence.
P2 (from C4). Developing preferences about the state of the universe prior to their [the preferences] existence requires prior sense experience of the universe (sentience).
C5. Moral evaluation requires prior sense experience of the universe (sentience).

Misconceptions about sentience

What degrees of sentience mean

As explained above (Dennett's creatures), different degrees of sentience mean different moral value. It's therefore important to not assign a higher/lower degree of sentience where it's not due.
One example where this can happen, is by solely relying on the being's sensitivity of senses (more complex/developed sematosensory system) to judge the level of sentience, where a higher moral value is assigned to the being with the better senses (i.e. X person with better sight having a higher moral value than Y person that is myopic, or a cockroach with incredible sense of smell having a higher moral value than a mammal with average senses).

It's important to remember that, while for sentience to take place to begin with a somatosensory system is needed, the level of sentience is based on cognition and the ability to subjectively interpret things and have wants. A somatosensory system is needed to gather information about the universe to be able to interpret things subjectively, but it's not actively required to have sentience (i.e. if a person loses their sight or is born blind, they can still gather information about the universe through their other sensory experiences and develop preferences, or use the information they gathered before going blind).

The lack of certain senses doesn't mean lower levels of sentience, and it is correct to focus on the being's cognition instead. X being may have extraordinary senses, but not have enough cognitive capabilities to interpret such information subjectively and make something out of it as much as Y being, which may have impaired senses but cognitive capabilities that allow for more complex interpretations and understanding - and, therefore, wants and interests of a higher magnitude.

Sentient or non-sentient?

Not all animals are sentient, as explained above. Below are some examples of animals that aren't sentient, and some examples of animals commonly thought to be non-sentient that actually are.

Are sponges sentient?

Sponges are certainly non-sentient.

They have 0 neurons and no nervous system. They cannot feel or perceive, nor can they posses any thoughts or experience. While biologically animals, they are effectively equivalent to a plant or a rock in terms of sentience.

However, moral consideration when dealing with sponges must be had in that they filter water, making them beneficial for others that are sentient.

Are bivalves sentient?

Bivalves are most likely non-sentient.

While they do have a nervous system, they lack a central nervous system (brain) to process information.

They do react to stimuli, but, as made present before, a reaction to stimuli does not mean sentience, the same way a computer responding to a command or a sunflower following the sun is not equivalent to sentience.

Just like with sponges, bivalves filter and clean water, making them useful for sentient beings.

Another consideration to make is the risks that eating bivalves carry, considering that environmental contaminants and heavy metals are accumulated in their tissues because of the filtering they do.

Bivalves have been a strong controversy in the vegan community, with a side arguing for their chance to be sentient as a reason not to eat them, and the other side arguing for their impossibility of sentience as a reason not to exclude them. That said, rather than focusing on their questionable sentience--safe to assume to be non-existent--, bivalves are preferably avoided as a food regardless, because of the risks associated with eating meat and because of the contaminants they contain.

Are shrimp sentient?

Shrimp are sentient (on the low end of the spectrum).

Shrimp have simple brains, but are motile and respond to negative stimuli by swimming or running from a threat, and that takes some measure of intelligence (compared to just closing when touched, which can be done by reflex). They possess some level of sentience.

The fact that they have a central nervous system (brain) and complex somatosensory functions indicating sentience (like sight and olfact) means that their level of sentience is more than just negligible. Considering that they're sentient, even if on the low end of the spectrum, and that plants are certainly not, there's no reason to go out of our way to eat shrimp rather than plants.

Another consideration to be made is that, while shrimps may be on the low end of the sentience spectrum, a large quantity of shrimp is required for a food portion, meaning that multiple shrimp will have to die for a single meal--this would effectively multiply the magnitude of the consideration that has to be made for their moral worth when it comes to food.

Shrimp farming is also not environmentally friendly, being responsible for problems such as wetland destruction for the construction of shrimp farms, water usage, and the impact due to shrimp farms' toxic chemicals (organosphates, malachite green, methylene blue, potassium permanganate, sodium bisulfite, formalin, and more). [3] The amount of toxicity in farmed shrimp is significant, and some of the chemicals are carcinogenic.

Because of the toxic chemicals used in shrimp farms, the cheaper the shrimp are, the more likely it comes from farms, the more likely it carries toxic substances, the more unhealthy it is to eat--and this is not taking into consideration the risks that eating meat carries regardless of toxic chemicals.

While with shrimp that are wild-caught, an even greater deal of environmental destruction and suffering (because of bycatch [4]) is caused by deep-sea trawling, which has devastating impacts [5][6] and has been banned in many places.