One of the cornerstone ideas of the animal rights movement is that there are no fundamental differences between humans and animals: humans are just animals, only more intelligent (Ryder, 1991). Therefore, some argue, since having a larger brain is just another quirk, like having larger tusks, animals should have many of the same rights as humans. In particular, they should have a right to life, a right to freedom and a right not be used by humans. Moreover, the well-being of humans should not be put above the well-being of animals (Singer, 1991), so that doing research on animals cannot be justified by improvements in human health, as scientists claim (Ringach, 2011; Bennett and Ringach, 2016). Of course, all of this flies in the face of the values of all human societies from prehistory to date, which have used animals for food, clothing, work and entertainment. No matter, says the animal right activist, that is unethical and has to stop (Reagan, 1985).

In the past, justification for human primacy over animals came from religions that stated that humans are superior to animals because they have an immortal soul, and that God commanded humans to rule over animals. However, the Theory of Evolution and modern physiology have pushed back against those beliefs, showing that there is an evolutionary continuum between animals and humans and that there are no fundamental differences between the physiology of the humans and other mammals (Rachels, 1990) . If the only difference between humans and animals is that of a higher intelligence, does that justify that we treat ourselves better than the animals? Or is this just self-interested behavior, “speciesism”, as the animal rights proponent Richard Ryder has called it (Ryder, 1991)? To strengthen their case, animal right proponents invoke the “marginal case”: these include infants and those with significant mental impairment who, lacking superior intelligence, then should presumably be treated the same way as animals (Reagan, 1985; Singer, 1991). Otherwise, they argue, we should be prepared to give animals the same rights that we readily give these marginal case humans.

However, modern neuroscience has in fact uncovered many differences between humans and the rest of the animals that makes us unique. These differences are not limited to a quantitative difference in intelligence but extend to many other mental and behavioral abilities that make us completely unique (Penn et al., 2008), a qualitatively different type of being. Below I provide a list of the most important of those abilities.

Theory of Mind is the ability to understand what other people are feeling and thinking [pp. 172-178 in (Blackmore, 2004); pp. 48-54 in (Gazzaniga, 2008)]. We do that by running inside our heads a model of what is happening in other person’s mind. Of course, the model is not always right, but nevertheless it is extremely valuable because it lets us predict the behavior of people around us. Theory of mind seems to require the right anterior insula, a part of the brain cortex that evolved very rapidly in apes. The function of the right anterior insula is to create hypothetical models of the internal state of our body in different circumstances (Craig, 2010, 2011). For example, when we imagine what it would feel like to stab our toe, is the right anterior insula doing that. Likewise, the right anterior insula can make a model of the internal state of the body of another person. Of course, theory of mind is much more than that and involves the cognitive abilities of many other parts of the brain. Research on theory of mind has revealed it to be uniquely human (Penn and Povinelli, 2007), although some studies claims to have found it in rudimentary form in chimpanzees (Call and Tomasello, 2008; Yamamoto et al., 2013). One negative aspect of theory of mind is that it often creates the delusion of attributing human consciousness to inanimate objects or animals. The same way we project our thoughts and feelings to a person that we see behaving in a way similar to us, we project human thoughts and feelings to an animal or an object we see doing something that resembles human behavior. This delusional form of theory of mind is responsible for the anthropomorphizing of animals that is so common in modern culture.

Episodic memory . There are two basic forms of memory: procedural and declarative [pp. 303-306 in (Gazzaniga, 2008)]. Procedural memory is present in both humans and animals and consists in the retention of perceptual, motor and cognitive skills that are then expressed non-consciously. For example, when we walk, swim, ski, listen to music, type on a keyboard or process the visual information we get from a television screen, we use procedural memory. Declarative memory stores information about facts and beliefs about the world, and can be further divided into semantic and episodic memory. Semantic memory is about facts in the world that stand by themselves, independently of our self, whereas episodic memory is remembering things that happened to us. That is, episodic memory retains events as they were experienced by ourselves in a particular place and time. Episodic memory appears to be uniquely human, because it involves subjective experiences, a concept of self and subjective time. This is important because it allows us to travel mentally in time through subjective experiences, while animals are locked in the present of their current motivational state.

Humans emotions . Mammals, birds and some other animals have a set of six basic emotions listed by Ekman: anger, fear, disgust, joy, sadness and surprise. However, we humans are able to feel many other emotions that regulate our social behavior and the way we view the world: guilt, shame, pride, honor, awe, interest, envy, nostalgia, hope, despair, contempt and many others. While emotions like love and loyalty may be present in mammals that live in hierarchical societies, emotions like guilt, shame and their counterparts pride and honor seem to be uniquely human. There is much controversy these days on whether dogs feel guilt and shame, there is evidence that they do not, but they may also have acquired this emotion as a way to interact with humans. What is clear is that many of the emotions that we value as human are not present in animals.

Empathy and compassion . Empathy is defined as the capacity to feel what another person is feeling from their own frame of reference. It is a well-established fact that many animals react to distress by other animals by showing signs of distress themselves. However, this does not seem to represent true empathy as defined above, but a genetically encoded stress response in anticipation of harm. Since empathy requires feeling what the other person is feeling from their own frame of reference, it seems to require theory of mind. Only if we stripe the requirement of adopting the other’s frame of reference we can say that animals have empathy. Empathy involves the newly evolved anterior insula in humans (Preis et al., 2013), bonobos and chimpanzees (Rilling et al., 2012). Compassion is currently thought to be different from empathy because it involves many other parts of the brain. It seems to be associated with complex cultural and cognitive elements. Therefore, it seems safe to assume that animals are not able to feel compassion.

Language and culture . Although animals do communicate with each other using sounds, signs and body language, human language is a qualitative leap from any form of animal communication in its unique ability to convey factual information and not just emotional states. In that, human language is linked to our ability to store huge amounts of semantic and episodic memory, as defined above. The human brain has a unique capacity to quickly learn spoken languages during a portal that closes around 5-6 years of age. Attempts to teach sign languages to apes has produced only limited success and can be attributed to a humanization of the brain of those animals, raised inside human culture. The effectiveness of spoken and written language to store information across many generations gave raise to human cultures. The working of the human brain cannot be understood without taking culture into account. Culture completely shapes the way we think, feel, perceive and behave. Although there are documented cases of transmission of learned information across generations in animals, producing what we could call an animal culture, no animal is as shaped by culture as we are.

Esthetic sense or the appreciation of beauty also seems to be uniquely human. Of course, animals can produce great beauty in the form of colorful bodies, songs and artful behavior. What seems to be lacking is their ability to appreciate and value that beauty beyond stereotypical mating and territorial behaviors. Even attempts to teach chimps to produce art by drawing have largely failed.

Ethics is the ability to appreciate fairness, justice and rights. It is at the very core of our ability to form stable societies and to cooperate to achieve common goals. It depends on theory of mind (which allows us to “put ourselves in somebody else’s shoes”); on social emotions like guilt, shame, pride and contempt; on empathy and compassion, and on cultural heritage. Lacking all those mental abilities, animals have no sense of ethics. Even though some studies have shown that monkeys have a primitive sense of fairness (particularly when it applies to their own interest), it is but a pale anticipation of our sense of justice. It simply goes to show how that ethics is rooted in our evolutionary history. The fact that animals cannot even remotely comprehend the concept of rights is a strong argument for why they should not have rights. What sense does it make to give animals something that they do not know that they lack?

Extended consciousness . They question of what is consciousness has been called by scientists and philosophers “the hard problem” due to the difficulty of answering it (Blackmore, 2004). Therefore, the related question of whether animals have consciousness, or what animals have it, remains similarly unanswered in the strict sense. However, based on their behavior, we commonly assume that animals like cats, dogs and horses are conscious and able to make some autonomous decisions. On the other hand, unless we invoke some mystical definition of consciousness, it is safe to assume that animals with small nervous systems, like jellyfish, worms, starfish, snails and clams have no consciousness whatsoever. They are like plants: living beings able to react to the environment as automatons. That leaves a lot of animals for which it is hard to guess whether they are conscious or not: insects, fish, octopi, lizards and small mammals like mice and rats. What has been becoming clear is that we humans possess a kind of consciousness that no other animal has: the ability to see ourselves as selves extending from the pass to the future [pp. 309-321 (Gazzaniga, 2008)]. This special kind of consciousness has been called by neuroscientist Antonio Damasio “extended consciousness” [Chapter 7 in (Damasio, 1999)] and allow us a sort of “mental time travel” to relive events in the past and predict what may happen to us in the future (Suddendorf and Corballis, 2007). Extended consciousness is based on our ability to have episodic memory and theory of mind. Episodic memory configures remembered events around the image of the self, whereas theory of mind allows us to create a model of our own mind as it was during a past event or to hypothesize how it would be in a future event. I should also point out that a few animals (apes, dolphins and elephants) may turn out to have episodic memory, theory of mind and hence extended consciousness. However, this is still very much in doubt.

Suffering and happiness . It is a common mistake to confuse suffering with pain and happiness with joy. Pain is the representation of a bodily state and the emotion associated with it (Craig, 2003). Likewise, joy is an emotion associated with an excited but pleasant body state in an agreeable environment. Suffering and happiness are much deeper than that, and refer to the totality of a mental state, encompassing cognition, emotion and state of consciousness. Although suffering and happiness are normally associated with certain emotions, there is not always a correspondence with them. For example, one can be happy while feeling scared or sad, or suffer even in the presence of a passing joy. The error of philosophers like Peter Singer (Singer, 1991) and Tom Reagan (Reagan, 1985) is that they consider suffering as something that occurs independently of cognition and other mental abilities, when it does not. Arguably, happiness and suffering require some continuity in time, which would seem to require extended consciousness. Furthermore, conceptions of happiness extending to antiquity refer to lifelong attitudes like hedonism (the quest for personal pleasure) and eudemonia (working to acquire virtue or to achieve goals that transcend oneself), pointing to the fact that human happiness depends on cultural values. In view of all this, we need to wonder whether happiness and suffering can exist in beings that have no episodic memory, no extended consciousness, no sense of self, and no culture. Can happiness and suffering really be attributed to animals lacking these mental abilities? Or is this an illusion, an anthropomorphizing caused by the overreaching of our theory of mind? Without going to that extreme, it is quite clear that we humans have a capacity to be happy and to suffer that goes far beyond what animals can experience. So human suffering counts more than any suffering than an animal could have.

There are many more differences between human and animals. However, the ones that I have listed here are important because they give us our special feeling of humaneness. All of them are based on scientific facts about the human mind that are slowly being unraveled by neuroscience, not on religious beliefs or on ideology. However, what cannot be based on science is the value we attribute to those differences. Ultimately, this is a decision based on our ethical intuition. Still, for most people what determines how much consideration we should give to a being is its ability to be conscious; to feel empathy; to feel guilt and pride and shame and all other human emotions; to be happy as we are happy and to suffer like we suffer.

An important corollary of the ideas proposed here is to utterly refute the “marginal case” argument. Thus, even when a human brain is damaged by disease, accident or old age, most of the properties that I have listed here remain because they are deeply engrained in the way the human brain works. Theory of mind and extended consciousness appear early in human life and are the last things to go in a deteriorating brain. It takes coma to deprive us of them. A person may have a reduced intelligence or other cognitive disabilities, but s/he still has theory of mind, empathy, compassion, extended consciousness and all those human emotions. That is why when we encounter those people we recognize them as humans and we know we should treat them as humans. They are not animals and should never be treated as such. Intelligence is just a tiny part of what it means to be human.

Another important idea is that there are vast differences in the mental abilities of animals and, therefore, in the way they should be treated. Many animals, like jellyfish, worms and clams, do not have any mental capabilities at all, do not feel pain, and can be treated the same as plants. In the other side of the mental spectrum, it is possible that we will find that the great apes, dolphins and elephants have some form of theory of mind and extended consciousness, and therefore deserve a special treatment compared to other animals. Dog and cats have evolved special ways to communicate with humans that make them special in our eyes. So, when it comes to ethical consideration, animals should not be put in a general category, but each species should be assigned its own value. Otherwise, we may find ourselves in the quandary of not being able to rid our dog of fleas because these insects have the same “rights” as the dog. This is, in fact, what we have been doing all along: to establish a hierarchy of animals that deserve more or less consideration based on their mental abilities, putting humans at the top. Speciesism is unavoidable because we cannot treat different species of animals the same way.

Let me finish by saying that this is not an argument to treat animals cruelly or poorly. It is only an argument to treat humans better than animals and to keep using animals for our benefit. We should care about the welfare of animals, even as we try to understand how similar and how different they are from ourselves. What moves us to treat animals well is our empathy, our compassion, our sense of fairness and our cultural values. Things that animals do not have. Ultimately, we must treat animals right not because of what they are, but because of who we are.

by Juan Carlos Marvizon, Ph.D.

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