Thinking about how they think

Why​ should we try to understand the lives of animals? The English moral philosopher Mary Midgley’s Beast and Man (1978) ended with a succinct answer: humankind ‘can neither be understood nor saved alone’. No philosophy can hope to understand ‘human nature’, Midgley argued, without acknowledging our integration into incomparably larger and older natural systems. Unfortunately, the philosophy and science of animal behaviour, as she found it, was not up to the task: it generally set out to prove the scientists’ preconceptions instead of basing its conclusions on close observation. Midgley called for a new approach that built on the work of Konrad Lorenz and Niko Tinbergen, the mid-20th-century pioneers of animal ethology – the study of animal behaviour as it occurs under natural conditions, or at least under experimental conditions that approximate natural ones. In their view, animal behaviour was determined by real motives and complex drives, not merely mechanical causes and imperatives. Midgley believed this approach could be helpful in rethinking the relationship between human and non-human because it placed all behaviour on the same continuum, rather than treating animals as wholly different phenomena.

Frans de Waal, who has been widely celebrated as an original and iconoclastic primatologist since his ground-breaking Chimpanzee Politics (1982), follows the grand tradition of animal ethology, having studied under Gerard Baerends, Tinbergen’s first student. Like his predecessors, his approach has been holistic and empathetic, as well as rigorously scientific: he treats animals as sentient agents who act with intelligence, emotion and character. This view has often been dismissed as imprecise and anthropomorphic by both hard-headed behaviourists, who hold that animal minds are unknowable and therefore irrelevant to the study of behaviour, and the type of ‘selfish gene’ determinists who hold that animal behaviour can be reduced to gene-automated profit-maximising protocols – ‘biological Thatcherism’, in Midgley’s memorable phrase.

Drawing on his experiences with primates, especially chimpanzees, de Waal suggests that anthropomorphic language, although it can at first seem sentimental, may turn out to be a more accurate, even more scientific, way of describing animal behaviour. ‘Anthropomorphism is problematic only when the human-animal comparison is a stretch,’ he writes, ‘such as with regards to species distant from us.’ Apes often greet each other ‘by placing their lips gently on each other’s mouth or shoulder and hence kiss in a way and under circumstances that greatly resembles human kissing’. Similarly, it may be that the hoarse breathing that young chimps produce when they’re tickled is best described as laughing. Even the way they behave towards the person doing the tickling seems familiar, first pushing the tickler’s hand away then coming back ‘begging for more, holding their breath while awaiting the next poke in their belly’. Some argue that calling the apes’ behaviours ‘kissing’ and ‘laughing’ introduces unwarranted associations with specifically human behaviour and therefore misinterprets what’s happening. But to de Waal, this position is both silly and unscientific:

Dubbing an ape’s kiss ‘mouth to mouth contact’ so as to avoid anthropomorphism deliberately obfuscates the meaning of the behaviour. It would be like assigning Earth’s gravity a different name from the moon’s, just because we think Earth is special. Unjustified linguistic barriers fragment the unity with which nature presents us. Apes and humans did not have enough time to independently evolve strikingly similar behaviour, such as lip contact in greeting or noisy breathing in response to tickling. Our terminology should honour the obvious evolutionary connections.

This isn’t just an argument about language: it’s about recognising genuine biological similarities between human and non-human behaviour. De Waal, like Midgley and Lorenz, has always been interested in the cognitive and behavioural continuities between humans and other creatures rather than the differences. ‘We’re not comparing two separate categories of intelligence,’ he writes, ‘but rather considering variation within a single one. I look at human cognition as a variety of animal cognition.’ Examining those connections without obscuring them with ‘anthropodenial’ – ‘the a priori rejection of humanlike traits in other animals or animal-like traits in us’ – is essential if we are to shed the anthropocentric attitudes that distort the study of animal intelligence.

This change in approach has consequences when it comes to devising new experimental techniques. It’s no use treating the intelligence of a rat or a parrot as though they were lower rungs on a ladder that has the human mind at its top. Empathy in mammals has always been one of de Waal’s preoccupations, and he suggests a dose of empathetic imagination is needed. The early 20th-century German biologist Jakob von Uexküll came up with the term Umwelt to describe species-specific experience and de Waal thinks we need to use our imaginations to get inside the Umwelten of other animals, in order to think seriously about how they think. As students of animal cognition, ‘we are trying to get under the skin of other species, trying to understand them on their terms.’ How do other creatures experience their worlds? How can we begin to understand animal intelligence if we don’t examine the aptitudes that have developed in response to those worlds?

Gibbons, for instance, were long considered to be less intelligent than chimpanzees and other monkeys because they performed poorly in the tool-using tests other primates passed easily. Even picking up a stick from the ground and using it to move a banana so that they could reach it seemed beyond them. Researchers couldn’t understand why they had such difficulty, despite their obvious similarities to chimpanzees and humans, until they realised that the problem was with the test, not the gibbons. Unlike other primates, gibbons are brachiators: they swing and hang in trees, rarely descending to ground level. Their hands are evolved for this life, and they can’t pick up objects from the ground very well because they lack a fully opposable thumb. When the experiments were redesigned with gibbon-friendly props the gibbons performed as well as chimpanzees. The researchers hadn’t taken account of the gibbons’ specific lives, bodies and environment before designing their experiments: no wonder they failed.

De Waal talks the reader through a series of problems that have arisen in the study of animal intelligence, illustrating each one with copious examples. In every case he attends to a phenomenon conventionally thought to be unique to humans – the perception of time, natural language, politically complex social skills – and shows that close observation and suitably sympathetic tests, on all manner of species, have at the very least seriously complicated assumptions of human uniqueness, where they haven’t demolished them. Take the capacity to ascribe mental states to others, which has long been considered beyond the reach even of apes. De Waal prefers to call it ‘perspective taking’ and extends it to include not only what someone else might think or know, but also what they might need or want. Empathetic perspective taking is, he argues, ‘a biological imperative’: ‘knowing what others want or need, or how best to please or assist them, is likely to be the original perspective taking, the kind from which all others stem,’ given that it must inform how mammals care for their young – they have to be able to tell when their offspring are ‘cold, hungry, or in danger’.

De Waal presents numerous suggestive cases of perspective taking in animals. In an experiment at Kyoto University, two chimps were separated by a windowed partition. One was provided with a range of tools, the other with some out-of-reach food. The first chimp managed to look through the window and pass her partner the most useful tool, enabling the second chimp to get at the food. De Waal concludes that the chimps thereby demonstrated ‘a capacity to grasp the specific needs of others’. In another example, capuchin monkeys were presented with an opportunity to share food through a window. Food sharing is normal behaviour among primates, but spontaneous food sharing through a partition is different, because in that situation – without their relatives or more dominant monkeys around them – it’s possible for the monkeys to avoid sharing altogether. As it turned out, the capuchins preferred to share, except when they had seen the other monkeys already eating, at which point they became stingy. ‘The monkeys,’ de Waal writes, ‘judged the need, or lack thereof, of their companions based on what they had seen them eat.’

The idea that perspective taking is an ability of the human mind alone is now, as de Waal puts it, ‘in the trash bin’. Homo sapiens is still a very special animal – ‘in some ways we evidently are,’ he writes, and leaves it at that – but it has become much less clear what mental functions that specialness derives from. Concrete claims for the source of human uniqueness have a ‘miserable track record’, and it’s only getting worse.

In keeping with his expertise, de Waal concentrates on chimpanzees and other primates. But he also presents an array of disorientating cases from other regions of the animal kingdom: octopuses easily open bottles and jars, seemingly play with toys, and can differentiate between different human keepers; magpies demonstrate self-awareness when presented with a mirror (a long-established test for the woolly quality known as ‘consciousness’), while ravens make political alliances among themselves; wasps and sheep are both adept at recognising individual faces among members of their species; wild African elephants respond to human languages differently depending on which groups of humans have historically hunted them, and also seem able to tell the gender of the speaker; individual dolphins have ‘signature whistles’ that are used, to all intents and purposes, as personal names. In every region he examines, the evidence for widespread, highly complex cognitive abilities in animals has stacked up incontrovertibly.

De Waal reminds us that it took a long time to get to this point, that it is only in the last twenty years that his position has become broadly accepted. He says he has lost count of the times he has been called ‘naive, romantic, soft, unscientific, anthropomorphic, anecdotal or just a sloppy thinker for proposing that primates follow political strategies, reconcile after fights, empathise with others, or understand the social world around them.’ Much of the resistance had to do with the language de Waal was using, and his refusal to peddle scientistic obscurities when everyday language was perfectly adequate. Peter Wohlleben’s The Hidden Life of Trees takes a similar line when it comes to describing the behaviour of trees, but unlike de Waal Wohlleben is not a professional scientist. He is a forester who has worked with scientists, and it is his decades-long experience of living and working in the forest that informs his thought-provoking account of the lives of trees.

Wohlleben​ started out as a Forestry Commission logger in the Eifel region of western Germany, evaluating trees in terms of the profit they would bring as lumber. By his own admission he knew no more about the trees themselves than ‘a butcher knows about the emotional life of animals’. This began to change when he started guiding tourists around the forest he managed; their interest in the gnarled old trees he habitually overlooked helped him rediscover his childhood curiosity in the natural world. At around the same time, a contingent of scientists interested in forest ecosystems arrived from Aachen University. Their work caught Wohlleben’s imagination. He began practising forestry with the systemic health of the forest in mind and switched to an ecologically holistic method of managing the area under his stewardship, reducing interference in the natural processes of growth, banning heavy machinery and using only horses when heavy work was necessary.

One day, while walking in the forest, Wohlleben’s attention was drawn to what he had always thought was a group of moss-covered rocks. On closer inspection they turned out to be remnants of the ancient stump of a huge beech, felled centuries ago; but why had they not rotted away completely? Wohlleben scratched at the bark with his knife. Under the bark, the wood was still green: the stump was alive. How was this possible, he wondered, with no leaves for photosynthesis, and so no way of producing energy. He didn’t want to disturb the stump so didn’t dig down to investigate, but, working from scientific papers on similar phenomena, he inferred that ‘the surrounding beeches were pumping sugar to the stump to keep it alive.’ It was being cared for by its neighbours. This realisation led Wohlleben towards a thorough reassessment of the ways trees behave and interact with each other. He presents them not as a mute collection of organisms lacking any sort of guiding consciousness but as a networked, intentionally collaborative and talkative community. Trees are unambiguously self-aware agents: they ‘experience pain and have memories … tree parents live together with their children.’ They make decisions, they have personalities and they can behave well or badly – a ‘well-behaved’ tree in a healthy forest has a ‘ram-rod straight trunk with a regular, orderly arrangement of fibres’. Some trees are bullies; others are greedy, or spendthrift with energy, or recklessly impatient to grow. They are aware of falling temperatures in the autumn and, because they have memories, they can ‘compare day lengths… and count warm days’ in the spring. If a neighbouring tree falls down, trees nearby suffer ‘the temptation to do something stupid’ by growing a new branch into the newly clear space. Only a few trees give in to this desire; it’s ‘an individual choice and, therefore, a question of character’.

This is a long way away from the conventional view of plant life, and from de Waal’s phylogenetically argued case that a chimp’s kiss is best called a kiss – a suggestion that seems almost cautious next to Wohlleben’s claim that trees ‘pass their knowledge on to the next generation’ through teaching and learning, or that they make actual decisions about how and when to grow. Unless it’s an accidental consequence of the translation, he certainly seems to mean a large amount of this literally: the language of agency, intention and mind used throughout the book strongly implies that Wohlleben believes trees, and maybe even forests as a whole, to be in some sense conscious and aware social agents with a high degree of control over how their own bodies grow and function.

Certainly, the kind of consciousness Wohlleben proposes is so different from ours as to be utterly alien: it is a diffuse, blind intelligence located in the sensitive, questing filaments of thousands of root-tips, or a networked language of chemical messages, fanning out through the forest floor via a ‘wood wide web’ of symbiotic fungal mycelium. It is a sensory alertness present in every leaf. Wohlleben gives the example of a tree attacked by caterpillars: as the larvae bite into a leaf, the tree can ‘taste’ the species of pest that has attacked it. The ‘leaf tissue sends out electrical signals, just as human tissue does when it is hurt’, and these signals prompt the release of ‘defensive compounds’ which spoil the leaves (oak trees, for instance, release tannins). Trees also warn their neighbours of attack, broadcasting chemical and electrical ‘news bulletins’ to other trees, which then pre-empt a similar attack, again by releasing chemical compounds. When umbrella thorn acacias are nibbled by giraffes they release ethylene, which deters them; but the chemical also drifts to nearby acacias, and ‘all the forewarned trees also [pump] toxins into their leaves to prepare themselves.’

This portrait of the forest as a networked system of constant intercommunication is not unlike that of the American poet Gary Snyder in his ecological essay ‘The Practice of the Wild’:

The world is watching: one cannot walk through a meadow or forest without a ripple of report spreading out from one’s passage. The thrush darts back, the jay squalls, a beetle scuttles under the grasses, and the signal is passed along. Every creature knows when a hawk is cruising or a human strolling. The information passed through the system is intelligence.

Wohlleben, like Snyder, is trying to bring about a revolution in our perception of plants and ecosystems. ‘Even though every schoolchild knows trees are living beings,’ he writes, ‘they also know they are categorised as objects.’ It is this disavowal of the status of plants as fully living beings that he wants to challenge. In this he is close to de Waal in spirit, though unlike the meticulous primatologist he can be cavalier with his sources and imprecise with language. We would do well to keep in mind de Waal’s cautionary observation that the animal keepers in research facilities often hold the intelligence of their charges in much higher regard than the scientists. This is certainly true of Wohlleben in his forest. But de Waal went through a long struggle to get animal cognition recognised in the first place and his book is a carefully weighted, confident dispatch from the ramparts of what is becoming a dominant discourse. Wohlleben is a visionary; it remains to be seen whether he’ll be vindicated.