Both people who care for animals and those who have embarked on a vegetarian lifestyle are prone to criticism for projecting human feelings onto animals that cannot experience them in the same way as we do. These criticisms, while they may be partly true (after all, as bipedal and massively social primates we experience reality in very particular ways), do not cease to sin from the very ones they criticise: affirming universal truths based on faith.

The truth is that none of us can get into the head of another living being, much less if that living being is seven branches away from our position on the evolutionary tree. The love between species is a phenomenon that is difficult to study, especially when the behavior that would be expected from an animal emotionally involved with a human is very similar to the behavior that would also be expected from a living being that has learned to manipulate its caretaker to obtain better treatment.

However, science provides us with tools to know indirectly the cognitive and emotional phenomena that occur in other organisms. There is one study, in particular, that gives reason for optimism to all those people who believe that love between species exists.

To speak of love between species is to speak of reductionism

How can love be studied scientifically ? To do so, there is no choice but to resort to a reasonable dose of reductionism. The sensations and moods of non-human animals are so different from our own that, in order to study them, we must focus on the essential aspects that make them similar to us. In this case, to pull reductionism means to focus on a concrete and objective aspect associated to the moods linked to love or affection both in our species and in many others. Normally, this is done through research focused on the study of hormonal flows.

Love between species is such a broad concept that it needs to be reduced to very concrete operational terms if we are to investigate it. At this point, the measurement of oxytocin levels is especially important.

The dog-human bond of affection

Oxytocin is a hormone associated with the creation of bonding relationships of trust and maternal behaviour. It is present in a wide variety of living beings, and therefore oxytocin levels are an appropriate indicator to quantitatively estimate the moods we relate to love.

With an analysis based on the levels of this substance, it is possible to know indirectly what the animals are experiencing when interacting with their human carers, and vice versa, thanks to the use of the same meter for both species.

Based on this premise, a team of Japanese researchers set out to study the emotional states that are triggered in the organism of domestic dogs when they interact with their carers. To do this, they allowed the dogs and humans to interact with each other in pairs and then took urine samples from both the dogs and their playmates.

The results published in the journal Science , while still based on the measurement of a chemical, tell us about animals that create powerful emotional bonds with Homo sapiens. When dogs look humans in the eye, both species begin to generate more oxytocin. This fact is easier to explain from the “love between species” hypothesis than from that of animals taking advantage of their masters, since the experiment does not include any material reward for dogs.

Puppies and emotional loops

Oxytocin, like all hormones, generates loop dynamics , since it is both a method of sending instructions from the brain and a substance that informs the brain about what is happening in the body. In the case of dogs and their masters looking into each other’s eyes , researchers have also documented the existence of a loop: the fact that the animal pair is looking at each other longer (caused by higher than normal levels of oxytocin) causes the latter to generate more oxytocin, which in turn means a tendency to look at each other longer, etc.

The existence of this hormonal loop, typical of the complex relationships established between humans, is not so well documented in the relationships between our species and others, among other things because there are few animals whose habits make easy the peaceful and sustained interaction with organisms with which they share little evolutionarily. However, this research provides support for the idea that the process of hormonal feedback can be found far beyond our own evolutionary family.

A special case

Of course, while what is documented in the paper of these researchers may be interpreted as an example of love between species (or affective states associated with love), that does not mean that all species couples are equally likely to be emotionally involved in the same way. In the end, dogs are a special case because they have learned to c live very well with the sapiens . As in almost all subjects, science advances at an ant-like pace and few results can be generalized to a large number of cases.

This research also supports the idea that the evolutionary path of domestic dogs may have prepared them particularly well for understanding us. The scientists repeated the experiment by replacing the dogs with wolves and, by studying the behaviour and hormone levels of these carnivores, they found that they neither held up as long looking into the eyes of the carers, nor did their oxytocin levels increase in a way that was comparable to their domestic relatives.

It should be noted that the dog and the wolf are part of the same species, so the difference between them could be due to a process of recent adaptation that was carried out on the dogs and not on their wild siblings. The dogs could have developed a special interest in the human face and certain baskets, but the wolves would not have had that need. Or perhaps, who knows, the key to these different results is that humans do not look at some dogs the same as others.