Can humans ever understand how animals think?

[Eva Libre]

The eye of a hippopotamus seen at Bioparque Wakata in Jaime Duque park, near Bogota, Colombia Photograph: Raúl Arboleda/AFP/Getty Images

A flood of new research is overturning old assumptions about what animal minds are and aren’t capable of – and changing how we think about our own species

by Adam Kirsch

Giraffes will eat courgettes if they have to, but they really prefer carrots. A team of researchers from Spain and Germany recently took advantage of this preference to investigate whether the animals are capable of statistical reasoning. In the experiment, a giraffe was shown two transparent containers holding a mixture of carrot and courgette slices. One container held mostly carrots, the other mostly courgettes. A researcher then took one slice from each container and offered them to the giraffe with closed hands, so it couldn’t see which vegetable had been selected.

In repeated trials, the four test giraffes reliably chose the hand that had reached into the container with more carrots, showing they understood that the more carrots were in the container, the more likely it was that a carrot had been picked. Monkeys have passed similar tests, and human babies can do it at 12 months old. But giraffes’ brains are much smaller than primates’ relative to body size, so it was notable to see how well they grasped the concept.

Such discoveries are becoming less surprising every year, however, as a flood of new research overturns longstanding assumptions about what animal minds are and aren’t capable of. A recent wave of popular books on animal cognition argue that skills long assumed to be humanity’s prerogative, from planning for the future to a sense of fairness, actually exist throughout the animal kingdom – and not just in primates or other mammals, but in birds, octopuses and beyond. In 2018, for instance, a team at the University of Buenos Aires found evidence that zebra finches, whose brains weigh half a gram, have dreams. Monitors attached to the birds’ throats found that when they were asleep, their muscles sometimes moved in exactly the same pattern as when they were singing out loud; in other words, they seemed to be dreaming about singing.

In the 21st century, findings such as these are helping to drive a major shift in the way human beings think about animals – and about ourselves. Humanity has traditionally justified its supremacy over all other animals – the fact that we breed them and keep them in cages, rather than vice versa – by our intellectual superiority. According to Aristotle, humans are distinguished from other living things because only we possess a rational soul. We know our species as Homo sapiens, “wise man”.

Yet at a time when humanity’s self-image is largely shaped by fears of environmental devastation and nuclear war, combined with memories of historical atrocity, it is no longer so easy to say, with Hamlet, that man is “the paragon of animals” – the ideal that other creatures would imitate, if only they could. Nature may be “red in tooth and claw”, but creatures whose weapons are teeth and claws can only kill each other one at a time. Only humans commit atrocities such as war, genocide and slavery – and what allows us to conceive and carry out such crimes is the very power of reason that we boast about.

In his 2022 book If Nietzsche Were a Narwhal, Justin Gregg, a specialist in dolphin communication, takes this mistrust of human reason to an extreme. The book’s title encapsulates Gregg’s argument: if Friedrich Nietzsche had been born a narwhal instead of a German philosopher, he would have been much better off, and given his intellectual influence on fascism, so would the world. By extension, the same is true of our whole species. “The planet does not love us as much as we love our intellect,” Gregg writes. “We have generated more death and destruction for life on this planet than any other animal, past and present. Our many intellectual accomplishments are currently on track to produce our own extinction.”

If human minds are incapable of solving the problems they create, then perhaps our salvation lies in encountering very different types of minds. The global popularity of the documentary My Octopus Teacher, released by Netflix in 2020, is just one example of the growing hunger for such encounters. In the film, the South African diver Craig Foster spends months filming a female octopus in an underwater kelp forest, observing most of her lifecycle. Foster presents himself as the anti-Jacques Cousteau; he doesn’t go underwater to study the non-human, but to learn from it.

Humility is a traditional religious discipline, and there is a spiritual dimension to Foster’s quest and to the film’s success. On YouTube, where the trailer has been viewed 3.7m times, thousands of people testify that My Octopus Teacher made them weep, changed their understanding of the world and made them resolve to lead better lives. It’s clear that, for modern people who seldom encounter animals except for pet cats and dogs, entering into a close relationship with a non-human mind can be a sacred experience.

The idea of the octopus as the nonhuman mind par excellence was popularised by the 2016 bestseller Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness, by Peter Godfrey-Smith. A philosopher rather than a marine biologist, Godfrey-Smith got an opportunity to see the creatures in action at a site off eastern Australia known to researchers as Octopolis. There he discovered that octopuses are “smart in the sense of being curious and flexible; they are adventurous, opportunistic”, prone to making off with items such as tape measures and measuring stakes.

A horse, pictured competing in the World Equestrian Games in France. Photograph: Régis Duvignau/Reuters

The fascination of the octopus is that while its behaviour seems recognisable in human terms as mischief or curiosity, its neural architecture is immensely different from ours. Since Darwin, humans have grown used to recognising ourselves in our fellow primates, whose brains and body plans are similar to our own. After all, humans and chimpanzees share a common ape ancestor that lived in Africa as recently as 6m years ago. Our most recent common ancestor with the octopus, by contrast, is a worm-like creature thought to have lived 500-600m years ago.

Because the mind of the octopus evolved in a completely different fashion from ours, it makes sense of the world in ways we can barely imagine. An octopus has 500m neurons, about as many as a dog, but most of these neurons are located not in the brain but in its eight arms, each of which can move, smell and perhaps even remember on its own. In Godfrey-Smith’s words, an octopus is “probably the closest we will come to meeting an intelligent alien”. When such a being encounters a human at the bottom of the ocean, what could it possibly make of us?

For most of the 20th century, animal researchers wouldn’t even have asked such a question, much less attempted to answer it. Under the influence of the American psychologist BF Skinner, scientific orthodoxy held that it was neither legitimate nor necessary to talk about what was going on in an animal’s mind. Science, he argued, only deals with things that can be observed and measured, and we can’t directly observe mental faculties even in ourselves, much less in animals. What we can observe is action and behaviour, and Skinner was able to modify the behaviour of rats using positive reinforcement, such as rewards of food, and negative reinforcement, such as electric shocks.

When Jane Goodall first went to study chimpanzees in Tanzania in the 1960s, the very notion of animal subjectivity was taboo. Her practice of giving names to the individual chimps she observed – such as David Greybeard, who her studies made famous – was frowned on as unscientific, since it suggested that they might be humanlike in other ways. The standard practice was to number them. “You cannot share your life with a dog or a cat,” Goodall later observed, “and not know perfectly well that animals have personalities and minds and feelings. You know it and I think every single one of those scientists knew it, too, but because they couldn’t prove it, they didn’t talk about it.”

Today, the pendulum has swung in the other direction. Scientists speak without embarrassment about animal minds and consciousness. In popular writing on the subject, Skinner appears only as a villain. In his 2016 book Are We Smart Enough to Know How Smart Animals Are?, primatologist Frans de Waal discusses a mid-20th-century experiment in which researchers at a primate centre in Florida, educated in Skinner’s methods, tried to train chimps the way he had trained rats, by withholding food. “Expressing no interest in cognition – the existence of which they didn’t even acknowledge,” De Waal writes, the researchers “investigated reinforcement schedules and the punitive effect of time-outs.” The staff of the primate centre rebelled and started feeding the chimps in secret, causing Skinner to lament that “tender-hearted colleagues frustrated efforts to reduce chimpanzees to a satisfactory state of deprivation”. You could hardly ask for a better example of how the arrogance of reason leads to cruelty.

Meanwhile, animals without “rational souls” are capable of demonstrating admirable qualities such as patience and self-restraint. Among humans, the ability to sacrifice immediate pleasure for future gain is called resisting temptation, and is taken as a sign of maturity. But De Waal shows that even birds are capable of it. In one experiment, an African grey parrot named Griffin was taught that if he resisted the urge to eat a serving of cereal, he would be rewarded after an unpredictable interval with food he liked better, such as cashew nuts. The bird was able to hold out 90% of the time, devising ways to distract himself by talking, preening his feathers, or simply throwing the cup of cereal across the room. Such behaviours, De Waal notes, are quite similar to what human children do in the face of temptation.

More intriguing than the convergences between human and animal behaviour, however, are the profound differences in the way we perceive and experience the world. The reason why an encounter with an octopus can be awe-inspiring is that two species endowed with different senses and brains inhabit the same planet but very different realities.

Closeup of African elephant. Photograph: Gaertner/Alamy

Take the sense of smell. As humans, we learn about our surroundings primarily by seeing and hearing, while our ability to detect odours is fairly undeveloped. For many animals, the reverse is true. In his 2022 book An Immense World, the science journalist Ed Yong writes about an experiment by researcher Lucy Bates involving African elephants. Bates found that if she took urine from an elephant in the rear of a herd and spread it on the ground in front of the herd, the elephants reacted with bewilderment and curiosity, knowing that the individual’s distinctive odour was coming from the wrong place. For them, a smell out of place was as fundamental a violation of reality as a ghostly apparition would be for us.

Animals that perceive the world through scent, such as dogs, even have a different sense of time. We often talk about the importance of “living in the moment”, but in fact we have no other choice; since visual information reaches us at the speed of light, what we see around us are things as they existed an infinitesimal fraction of a second ago. When a dog smells, however, “he is not merely assessing the present but also reading the past and divining the future”, Yong writes. Odour molecules from a person or another dog can linger in a room long after the source is gone, or waft ahead before it appears. When a dog perks up long before its owner walks through the front door, smell can seem like a psychic power.

If giraffes can do statistical reasoning and parrots understand the concept of the future, then where does the distinctiveness of the human mind really lie? One favourite candidate is what psychologists call “theory of mind” – the ability to infer that each person is their own “I”, with independent experiences and private mental states. In The Book of Minds, the science writer Philip Ball describes the classic experiment that tests the development of this ability in children. A child and an adult watch as an object is hidden under one of three cups. Then the adult leaves the room and the child sees a second adult come in and move the object so it’s under a different cup.

When the first adult returns, where does the child expect she will look for the object? Very young children assume that she will know its new location, just as they do. Starting around age four, however, children start to understand that the adult only knows what she has seen herself, so they expect her to look under the original, now empty cup. “Indeed,” Ball writes, “they will often delight in the deception: in their knowing what others don’t.”

Developing a theory of mind is necessary because we can never know what is going on inside other people in the same immediate way we know ourselves. Sane adults take for granted that other people have the same kind of inner life they do, but this remains a kind of assumption. René Descartes was one of the first philosophers to wrestle with this problem, in the 17th century. “What do I see from the window but hats and coats which may cover automatic machines?” he asked. “Yet I judge these to be men.” But Descartes didn’t extend the same benefit of the doubt to animals. Even more than Skinner, he saw them as automata without any inner experience, “bêtes-machines”. Ball notes that Descartes dissected live animals to study the circulation of the blood, “and dismissed any cries of pain that procedure elicited as a mere mechanical response, not unlike the screech of a poorly oiled axle”.

A common octopus. Photograph: Reinhard Dirscherl/Getty Images

Four centuries later, De Waal complains that science still hasn’t overcome the tendency to draw a dividing line between the inner lives of humans and those of other creatures. The reason that scientists have focused on theory of mind, De Waal believes, is because no animal has been shown to possess it. Such “interspecific bragging contests”, he writes, are designed to flatter our sense of superiority. In fact, it seems that even here we’re not clear winners. According to Ball, recent attempts to replicate the theory-of-mind experiment with chimps and bonobos suggest that the majority of them pass the test, though the evidence is ambiguous: since the subjects can’t talk, researchers gauge their expectations by tracking their eye movements.

Even if other species were conclusively found to possess a theory of mind, of course, it would not challenge our monopoly on the kind of “rational soul” that produced the pyramids and monotheism, the theory of evolution and the intercontinental ballistic missile. As long as these quintessentially human accomplishments remain our standard for intellectual capacity, our place at the top of the mental ladder is assured.

But are we right to think of intelligence as a ladder in the first place? Maybe we should think, instead, in terms of what Ball calls “the space of possible minds” – the countless potential ways of understanding the world, some of which we may not even be able to imagine. In mapping this space, which could theoretically include computer and extraterrestrial minds as well as animal ones, “we are currently no better placed than the pre-Copernican astronomers who installed the Earth at the centre of the cosmos and arranged everything else in relation to it”, Ball observes. Until we know more about what kinds of minds are possible, it is sheer hubris to set up our own as the standard of excellence.

Xenophanes, a pre-Socratic philosopher, observed that if horses and oxen could draw pictures, they would make the gods look like horses and oxen. Similarly, if non-human beings could devise a test of intelligence, they might rank species according to, say, their ability to find their way home from a distance unaided. Bees do this by detecting magnetic fields, and dogs by following odours, while most modern humans would be helpless without a map or a GPS. “Earth is bursting with animal species that have hit on solutions for how to live a good life in ways that put the human species to shame,” Gregg says.

But if human and animal minds are so essentially different that we can never truly understand one another, then a troubling thought arises: we would be less like neighbours than inmates who occupy separate cells in the same prison. The kind of understanding Foster achieved with his octopus, or Goodall with her chimpanzees, would have to be written off as an anthropomorphising illusion, just as Skinner warned.

The possibility of true interspecies understanding is the subject of Thomas Nagel’s landmark 1974 essay What Is It Like to Be a Bat?, to which every writer on animal cognition pays their respects, sometimes wearily. Nagel, an American philosopher, concluded that humans can never really understand a bat’s inner experience. Even if I try to picture what it’s like to fly on webbed wings and spend most of my time hanging upside down, all I can imagine is what it would be like for me to be a bat, not what it’s like for a bat to be a bat.

For Nagel, this conclusion has implications beyond animal psychology. It proves that mental life can never be reduced to things we can observe from the outside, whether that means the way we behave or the pattern of electrical impulses in our neurons. Subjectivity, what it feels like to exist, is so profoundly different from what we can observe scientifically that the two realms can’t even be described in the same language.

An emu at Taronga zoo, Sydney. Photograph: Jenny Evans/Getty Images

Few people have ever taken the challenge of Nagel’s essay as literally as Charles Foster in his 2016 book Being a Beast. A barrister and academic by profession, Foster set himself the challenge of entering the mental worlds of five animal species by living as much like them as possible. To be a fox, he writes: “I lay in a back yard in Bow, foodless and drinkless, urinating and defecating where I was, waiting for the night and treating as hostile the humans in the row houses all around.” To be a badger, he dug a trench in the side of a hill and lived inside it with his young son Tom, eating earthworms and inhaling dust. “Tom was filling tissues with silica and blood for a week,” Foster notes.

Foster welcomes all this damage and discomfort, but not in the spirit of a scientist doing fieldwork. Rather, he evokes the medieval flagellants who covered their backs with welts to purge themselves of sin. That Foster defines sin as a transgression against nature rather than God doesn’t make the concept any less religious. “Evolutionary biology is a numinous statement of the interconnectedness of things,” he writes, and his preaching translates easily into Christian terms: “Say, with Saint Francis, ‘Hello, Brother Ox,’ and mean it,” he demands.

Foster’s way of seeking communion with the animals may be extreme, at times comically so, but his basic impulse is shared by many of today’s students of animal cognition, and an increasing number of laypeople as well. Encountering an animal mind can perform the same function as a great work of art or a religious experience: it makes the familiar strange, reminding us that reality encompasses far more than we ordinarily think.

The great difference is that while a traditional religious experience can awaken human beings to God, an animal epiphany can awakens us to the fullness of this world. “What she taught me was to feel that you’re part of this place, not a visitor,” Foster says in the closing lines of My Octopus Teacher, and by “this place” he doesn’t just mean a particular kelp forest, but the Earth itself. At first this might sound like an odd realisation: where else would human beings belong if not on our one and only planet?

But in the 21st century, it is clearly becoming harder for us to think of ourselves as genuinely belonging to the Earth. Whether we look back on our long history of driving other species to extinction, or forward to a future in which we extinguish ourselves through climate breakdown, many humans now see humanity as the greatest danger facing the Earth – a cancer that grows without limit, killing its host.

It is no coincidence that, at the same moment, tech visionaries have begun to think about our future in extraterrestrial terms. Earth may be where humanity happened to evolve, they say, but our destiny calls us to other worlds. Elon Musk founded SpaceX in 2002 with the explicit goal of hastening humanity’s colonisation of Mars. Other “transhumanist” thinkers look forward to a fully virtual future, in which our minds leave our bodies behind and achieve immortality in the form of electromagnetic pulses.

These projects sound futuristic, but they are best understood as new expressions of a very old human anxiety. We have always suffered from metaphysical claustrophobia – the sense that a cosmos containing no minds but our own was intolerably narrow. That is why, since prehistoric times, humans have populated Earth with other kinds of intelligences – from gods and angels to fairies, forest-spirits and demons. All premodern cultures took the existence of such non-human minds for granted. In medieval Europe, Christian and Greek philosophical ideas gave rise to the doctrine of the “great chain of being”, which held that the universe is populated by an unbroken series of creatures, all the way from plants at the bottom to God at the apex. Humanity stood in the middle, more intelligent than the animals but less than the angels, who came in many species, with different powers and purviews.

Filling the universe with hypothetical minds, superior to our own in wisdom and goodness, helps relieve our species’ loneliness, giving us beings we could talk to, think about, and strive to emulate. Our need for that kind of company in the universe hasn’t gone away, though today we prefer to fill the region “above” us in the space of possible minds with advanced extraterrestrials and superpowered AIs – beings that are just as hypothetical as seraphim and cherubim, at least so far.

Our rising interest in animal minds can be seen as a way of filling in the regions “below” us as well. If an octopus is like an intelligent alien, as Godfrey-Smith writes, then we don’t need to scan the skies so anxiously for an actual extraterrestrial. Yong quotes Elizabeth Jakob, an American spider expert, to the same effect: “We don’t have to look to aliens from other planets … We have animals that have a completely different interpretation of what the world is right next to us.” Perhaps simply knowing that these other minds exist can help us make peace with the limitations of our own.