Touching with sound: a scientific illustration of bats by Ernst Haeckel. Image: Florilegius / Alamy Stock Photo

The way animals think

Other animals understand the world in wondrous and alien ways that we are only just starting to understand
September 8, 2022
An Immense World: How Animal Senses Reveal the Hidden Realms Around Us
Ed Yong
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An Englishman, an elephant and a bat walk into a bar. This is not the set up to a joke, but a thought experiment of the kind that you might encounter in Ed Yong’s jaw-dropping new study of animal perception.

To the Englishman, the bar is cosy and inviting: the wood-panelled room, the warm light, the low wooden beams and the generous selection of single malts. The elephant is aware of, but less impressed by, the interior decor. She is more interested in the mysterious, low-frequency rumbling of trains as they pass beneath the building; to her, they seem like blares of white noise. Who could relax somewhere like this? The bat, now airborne, emits thousands of clicks and squeals as it circumnavigates the room. From the pattern of returning sound, it recognises the hardness and irregularity of the flagstone floors, the smooth surface of the windows and an insect’s unmistakeable flutter from the corner.

Yong’s compendium of the strange and surreal shows that our world is experienced very differently by the various species who move through it. What might it be to live as a scallop, wearing 200 eyes arrayed around the rim of your shell, offering sight in all directions but no cohesive visual “scene”? Or a beaked whale who, through the medium of sound, might admire the ornate design of its fellow whales’ skulls? There are, notes Yong, “animals with eyes on their genitals, ears on their knees, noses on their limbs and tongues all over their skin.”

In 1909, the German biologist Jakob von Uexküll outlined the concept of the umwelt. An umwelt is the sensory bubble within which we all live, the cave wall on which shadows dance. My own umwelt and yours will likely be similar, given our close relation and matching physiology, although we can never be entirely sure of what another person of our own species might perceive. What we can be sure of is that our interpretation of the world is almost wholly incompatible with that of an octopus, say, whose eight arms are run semi-independently by their own mini-brains. Or a mantis shrimp, which has more than a dozen types of colour receptor (compare our own paltry three) but, rather than visualising a hyper-Technicolor dream world, uses them merely to scan the environment for colour combinations found in foodstuffs and rivals, like a barcode reader.

Any attempt of ours to comprehend their inner experience is possibly doomed. In a famous 1974 paper, the philosopher Thomas Nagel argued that we could never really know what it was like to be a bat—the structure of our minds simply won’t allow us to. Riddled with baffling and mind-boggling case studies of animal behaviour, Yong’s book does little to undermine Nagel’s point. But what Yong does make clear is that the attempt to understand is still important: the study of the sensory experience of animals has brought us insight into the world around us, technological breakthroughs and a better understanding of how to be good citizens of our shared planet.

In making this attempt, imagination and analogy are our best assets. Though we might not be able to experience, say, a robin’s instinctive knowledge of the Earth’s magnetic fields, we might be able to visualise a “bright spot in the direction of north” or “a gradient of shade painted over the landscape.” In one memorable example, an electric fish researcher attempts to conjure us inside the mind of his subjects; swimming past a piece of metal, he tells Yong, might be akin to “a small cool sensation like a piece of ice rolling down one side of my body.”

Elsewhere, technology allows the imperceptible to be transcribed into a mode that we can appreciate. The leaf vibrations caused by treehoppers, tiny sap-drinking insects, are readily converted into audio (“a purr, but a startlingly deep one, more lion than house cat”), while the infrasonic rumblings of elephants—normally silent to the human researchers, although occasionally experienced as a “deep shuddering sensation” in their bodies—can be speeded up to reveal what sounds like “cows mooing.”

Yong tells the stories of these researchers, dramatising their eureka moments and epiphanies so that we too might share in their moments of revelation. One description of the discovery of whale song—recorded inadvertently by naval surveillance analysts during the Cold War—made my hair stand up. Imagine dipping a hydrophone into seawater for the first time and hearing a “deluge of oceanic noises” never before broadcast to human ears. Slip on a pair of headphones and enter an alien landscape: the white noise of boat engines, the ping of sonar, and then these eerie alien wails, moans and rumbles.

One “especially enigmatic” sound—a monotonous hum around an octave lower than the lowest key on a piano—was so loud and steady that it was assumed to be manmade. But when the researchers followed the sound to its source, a fin whale was almost invariably at the other end. The biologist Roger Payne calculated that these calls might travel for 13,000 miles. He was laughed out of town, but we now suspect that whales remain in constant contact, even while separated by a literal ocean. To understand how a whale’s brain operates, as one researcher tells Yong, “you have to stretch your thinking to completely different levels of dimension.”

Occasionally, human outliers can offer special insight. Daniel Kish, for example, is a blind man who uses echolocation to navigate the world. It came to him naturally; for hundreds of years, blind people have been recorded walking unassisted through crowded streets or avoiding obstacles via some mysterious “obstacle sense” they have often been unable to explain. Some merely listen, sensing distant obstacles from the general soundscape. Others snap their fingers. Kish clicks his tongue—which he has done since he was a toddler. To Kish, echolocation feels like “touching with sound”: to him, a tree reveals itself as a “solid vertical post that is topped by a larger, softer blob”—a description that may, or then again may not, give us some better answer to Nagel’s question of what it’s like to be a bat.

Often sensory signals we don’t perceive are characterised in the literature as “secret” or “hidden,” but they are all happening in plain sight. We just don’t have the ability to see them. We only “tap into a small fraction of reality’s fullness,” writes Yong, and what we don’t sense we tend to dismiss as insignificant.

To some extent, it is insignificant, at least to humans. Every species’ umwelt has developed in concert with their specific evolutionary pressures. Perceiving the world requires energy, so we tune in only to the channels that are most pressingly relevant. This leaves many species, including our own, with strange blind spots. We can’t see the ultraviolet messaging daubed across the environment for the benefit of pollinating insects; nor can we sense the signature electrical signals emitted by all living things. Bees perceive both. Most insects, on the other hand, are entirely deaf. Sound might be ubiquitous but it is not sufficiently useful for those species to bother decoding.

That’s not to say we can’t have an impact on what we can’t perceive. The blue-throated hummingbird sings ultrasonic songs that it can’t itself hear—perhaps to flush out insects that can. Like hunters blowing bird-call whistles, they likely have no concept of what they are saying; they merely know it works.

Yong is a science writer for the Atlantic who last year won a Pulitzer Prize for his coverage of the Covid-19 pandemic. Those skills are on full display here, as he clearly and succinctly sketches out complex scientific and philosophical ideas in terms that are understandable for the lay reader. (For example, he likens convergent evolution to different organisms “showing up at life’s party in the same outfits.”)

He is funny and sharp, sprinkling his weightier arguments on the nature of being with amusing asides from the frontlines of cognitive ethology. We meet an English pointer called Sir Satan who has greatly illuminated our understanding of his fellow dogs’ breathing patterns; an octopus bored with opening jars; a dolphin who will readily don “eye cups” in exchange for fish but refuses to wear a “sound-blocking mask.” Working with mantis shrimps, notes Yong after a visit to one demoralised researcher, “borders on masochism,” thanks to their extreme violence and recalcitrance. Hunter flies are delightful—these miniature, winged predators launch from a fingertip, then return with newly captured prey “like a (very tiny) falcon to its falconer.”

Often the experiments verge on the absurd. There are manatees in blindfolds; electric eels experiencing virtual reality; otters sorting cards. At other times they have been unarguably cruel. Creatures of all stripes have been zapped with electricity, injected with acid and sliced with scalpels in the name of scientific progress. Historically, researchers did so secure in the belief that their charges could not experience emotions we might recognise. Over time, however, that misplaced confidence has drained away as researchers observe evidence of pain responses in everything from mice to goldfish to squid. A hermit crab given an electric shock will jump from its shell, groom the affected part of its body, and later appear reluctant to return to that same shell. This kind of work is “morally challenging,” Yong admits, but has important implications for living in tune with our environment.

As well as inflicting pain, we have the capacity to cause a great deal of irritation and disturbance to other species via indirect means, often without our realising. In a chilling final chapter, Yong rails against sensory pollution. Our fondness for artificial light means that a quarter of the Earth’s surface now lies smothered in “a luminous fog”—throwing bird migration out of whack, sending sea turtle hatchlings crawling in the wrong direction and making “prisons” for moths out of well-lit roads.

The ambient noise created by towns, roads, mines and oil extraction “can act as an invisible bulldozer” pushing animals from their home ranges. In the sea, busy shipping channels and the scraping of trawling and dredging cause a similar issue. “As ships pass in the night, humpback whales stop singing, orcas stop foraging, and right whales become stressed. Crabs stop feeding, cuttlefish change colours, damselfish are more easily caught.” We are noisy neighbours who have been playing loud music and flashing disco lights all night every night for decades.

All of this we are only just coming to understand, and there is still much to learn. We may never know for sure what it’s like to be a bat, but our cackhanded attempts to understand these creatures might at least mean we can learn to leave them in peace.