What’s Going on?
Browsing in the library is a dangerous pastime. I exercise this foolish endeavour in the Dickson Public Library in Canberra. Like many ‘professional’ browsers, I have my favourite places. There’s a wall section where some books are left on display to tempt you. Some in this small selection are for normal loans, while others can be borrowed for one week only. However, that’s for beginners. Past those temptations, I go over to the stacks, where there’s short display sections with books that are being recommended. After glancing at those and checking for anything new by my favourite writers, I browse the shelves. In Fiction I look for books by an individual author, and then decide if I’ve found a writer to sample. Non-fiction is harder. So many categories, it can feel overwhelming. I’ve learnt to make a note of the Dewey number for books I’ve read and enjoyed, and then see what else has been shelved in and around that section. I think that’s how I discovered Ed Yong’s book An Immense World, which explores the complex and diverse sensory world of animals. As the book’s subtitle explains, it is a study of How Animal Senses Reveal The Hidden Realms Around Us.
Two examples in the book are moderately well known. In fact, Yong explains that back in the 1880s, John Lubbock, who was something of a polymath, decided to use a prism to shine light broken up into the colours of the rainbow on to some ants. Why he decided to do that, I have no idea, but I have to assume it was a typical example of the ‘gentleman doing science’ world that existed back then. Anyway the ants scurried away from the light, but this included exiting a region just beyond the rainbow’s violet end, which looked dark to Lubbock. This was a region of ultraviolet (or UV) light, largely invisible to us, but must have been “apparent to the ants as a distinct and separate colour (of which we can form no idea)”, Lubbock presciently wrote. He added, “It would appear that the colours of objects and the general aspect of nature must present to them a very different appearance from what it does to us.”
Yong writes that back then many scientists believed that animals were either colourblind or saw the same spectrum that we do. Lubbock’s experiment seemed to suggest ants were exceptional, but today we now know they aren’t. Half a century later, researchers had found that bees and minnows could see ultraviolet, too, although they assumed this was a rare ability. By the 1980s, researchers had shown that many birds, reptiles, fish, and insects have UV-sensitive photoreceptors, but not mammals. Then in 1991, yet further research showed that mice, rats, and gerbils have cones in their eyes that were ‘tuned’ to UV, so small mammals could have UV vision, too. There was more! In the 2010s, researchers found that reindeer, dogs, cats, pigs, cows, ferrets, and many other mammals can detect UV. They probably see UV as a deep shade of blue rather than as a separate colour, but they can sense it, nonetheless. Incidentally, there’s evidence that so can some humans.
Perhaps you aren’t surprised to read this. Nor will you be surprised to read about echolocation by bats. This was realised some 80 years ago, when scientists discovered bats were emitting high pitch calls, and were using the echoes that bounced back off the objects around them to navigate and hunt in total darkness. Bats ‘see’ with their ears. I had always assumed that this was an ability unique to bats. However, Yong’s book reveals that once the bat’s ability had been identified, so examples of echolocation in other creatures were identified. Dolphins and toothed whales can do it, some other animals, some bird varieties, several small mammals too, and, surprise, a small number of ‘special’ humans as well.
Ed Yong’s point is that the existence of examples like UV vision and echolocation makes clear how human-centric we are in our thinking. As Yong comments: “Things like ‘bird’s-eye view’, I suppose. A bird doesn’t see like we do. We just think of it as being from really, really high up. You’re right, but if a human actually tried to take a real bird’s-eye view, many weird things would happen. We would have close to wrap-around vision. Just watch a duck in a pond, like a simple duck that no one even thinks about. That duck can probably see the entirety of the sky without having to move its head, which seems incredible to me. They can also see a whole range of colours that we can’t perceive. So, yeah, even when we use language like ‘a bird’s-eye view’ to talk about perspective taken by other species, we radically underestimate the differences.”
Of course, a phrase like ‘a bird’s eye view’ implies we observe as a bird does. The only problem is that we can’t! That was brought home to me when I first read Thomas Nagel’s wonderful article on What It’s Like To Be a Bat. When I first read that title, I thought this should be interesting. Little did I know. This was a deeply analytical piece, powerful and, for me, convincing – even if there are some who disagree with elements of Nagel’s argument.
As you might have guessed (or know if you have read the paper), Nagel’s analysis was focussed on consciousness. Central to this perspective is the view that consciousness is and can only ever be a subjective experience. Only you can ‘know’ consciousness. You can describe what you know, of course. You can describe what you see in your visual field. You can explain what words mean to you. You can set out the steps you have used in reasoning. However, all that ‘objective’ description doesn’t take away from the fact that only you can know what it means to be you. Our subjective experience cannot be explained in material terms. It is how we experience from our individual point of view.
To make his argument clear, Nagel focussed on the bat. Why bats? Well, they are mammals, and it seems likely they have conscious experiences (today, many writers argue consciousness is a property shared by most living things, but that wasn’t the case back in the 1970s). More to the point, they have that very sophisticated echolocation sensory system, which allows them to fly, at night, and yet identify objects in their flight path. You could say they navigate and see using a system something like a sophisticated form of sonar. That analogy is useful, because we can’t observe the sound waves and their reflection as an ‘aural’ picture: we have to translate it into a visual form, using a sonar image created through a transducer (converting sound waves into visual equivalents). However, Nagel points out the limits of that analogy: bats use echolocation by “detecting reflections, for the objects within range, of their own rapid, subtly modulated, high frequency shrieks”. Their brains “correlate the outgoing impulses with the subsequent echoes, and the information thus acquired enable bats to make precise discriminations of distance, size, shape, motion and texture”, all inflight and at a high speed (from page 170 of Nagel’s 1979 essay, ‘Mortal Questions’).
Since its publication, there’ve been many critiques of Nagel’s essay, but Yong argues his conclusion is hard to challenge:
“we won’t know, because it is fundamentally impossible to really understand the subjective experience of another creature, which is why, firstly, you always need to make an imaginative leap. You always need this little speck of faith, this little willingness to be creative to get to that destination, and you need a bit of humility and understanding, like, ‘I actually won’t ever quite get there but it’s the journey that matters. It’s the effort that matters.’ And so, for me writing this book, like I know I don’t have all the answers, but I can give you everything we know, and I can give you informed speculations about what the animal might be going through. And that’s what I tried to do. I tried to take us to like the very edge of that chasm between our subjective experience and other animals. Like let us peer over the edge, maybe do that thing where I’m like, woah, and then pull you back. And it’s not easy. One thing that made it a little easier was just asking people who work in these fields and who think about these creatures, and to ask them how they think about the creatures that they study. Because all of this I’ve just talked about, like these imaginative leaps, they tend to not be in papers, right? They’re a little antithetical to what we shove into the scientific literature. But I guarantee you that everyone who really works in this field, every sensory biologist, has thought long and hard about what the creatures they study might experience. And if you ask them, you just get some really cool stuff.” (Yong writing in Nature, 1 July 2022)
Each chapter of Yong’s book is concerned with a different form of sensory input. The more we travel into the unfamiliar, the harder it becomes to imagine what it might be like to have access to a rather different form of experience. One example that brought this home to me was the ability to ‘feel’ electricity. I had read about electric eels. These dubious creatures kill their prey using electric shocks, with zaps up to 860 volts. Naturally enough, reading about them made me slightly nervous until I discovered they were only to be found in the northeast part of South America – in Guiana, norther Brazil and the lower reaches of the Amazon. Also, and again contrary to my somewhat worried imagination, they are fish eaters, and don’t wander the rivers waiting for an unwary human to shock into oblivion.
However, electric eels are not quite as interesting as electric fish, fish with a relatively weak electric field that they use to sense their environment. They do this by creating this electric field around their bodies, and the field get ‘distorted’ by the objects around them, both items that can conduct electricity, like much vegetable matter, or non-conductive material like rocks and riverbanks. Amazingly, these fish can not only sense the distortions, but appear to use it to ‘map’ the environment around them.
Actually, that’s old news. Apparently, scientists have been studying electric fish for a long time, and there is good understanding about both how the electric field is generated and how it is ‘sensed’. However, Ed Yong asked a really great question of one of the neuroscientists working in the area: what do the distortions in the electric field feel like to the fish? His reply? “[He] imagined that if the fish is swimming past, like a rock, for example, you might imagine like a cool sensation moving down its flank that would indicate an insulating object is in the environment. So, he imagined it as something akin to touch, but operating in a distance several inches away from the fish’s body. And that gives me a little portal to what it might be like for the fish. Is that exactly what it’s like? Absolutely no idea”.
Inevitably, investigations into various animal senses can lead to speculation about human ‘extrasensory perception’ or ESP. This area received a boost back in the 1930s, when a psychologist, J B Rhine, with his wife, Louisa E Rhine, started research ESP, using the so-called Zener cards, each with one of five symbols (circle, square, wavy lines, cross, and star) on the face. A typical pack (an ESP pack) has five of each type of card in a pack of 25.
The cards were used in three forms of experiment’. To test for ‘telepathy’, the ‘sender’ looks at a series of cards while the ‘receiver’ guesses the symbols. In a more complex test, for clairvoyance, the pack of cards is hidden from everyone while the receiver guesses. Finally, to test for precognition, the order of the cards is determined after the guesses have been made. Rhine’s results were exciting, but, sadly, staff in psychology departments have attempted and failed to repeat them. At Princeton University W. S. Cox tried, with 132 subjects over no less than 25,064 trials in 1936. He concluded “There is no evidence of extrasensory perception either in the ‘average man’ or of the group investigated or in any particular individual of that group. The discrepancy between these results and those obtained by Rhine is due either to uncontrollable factors in experimental procedure or to the difference in the subjects.” Despite many claims since, there has been no reliable evidence for ESP.
Most apparent findings turn out to be flawed as a result of methodological problems. First many ESP studies confront what is known as the ‘stacking effect’. Studies using a “closed” ESP target sequence (as is the case with Zener cards) violates the condition of independence used for most standard statistical tests. Multiple responses for a single target cannot be evaluated using statistical tests that assume independence of responses. Such an approach increases the likelihood of card counting and, in turn, increases the chances for the subject to guess correctly . Another common flaw involves cues through sensory leakage, as when the subject receives a visual cue. This could be the reflection of a Zener card in the holder’s glasses, with the result the subject in the study can ‘guess’ the card correctly because they can see it! On top of all that, poor shuffling can make the order of the cards easier to predict.
All over? Probably, but I do admire Ed Yong. As he explains that while much of what he writes has been researched and proven, “I think if you didn’t do any of the imaginative stuff, the book would just be joyless. Whereas if you just went on like flights of fancy all the time, it would feel like almost like a work of science fiction. This is very much a non-fiction book. And I’m trying to show both what we know but also the limits of that knowledge”.
In an interview with Benjamin Thompson he gives one more example, based on research on the larger whales. Apparently, they make ‘very deep infrasonic calls’, at a level well below what humans hear. These can travel long distances, even from one end of an ocean to the other. How has this been discovered? Well, scientists near Europe using hydrophones picked up the sound of a blue whale ‘singing’, the sounds coming from a whale swimming off the coast of America! However, he suggests the real question is not whether whales can hear each other across an ocean. Rather, what can they communicate through sounds across thousands of kilometres? Harder to imagine, but not impossible. So, do whales talk when right next to each other, in visual proximity? Can they be separated by miles, even tens or hundreds of miles? We don’t know. But Ed Yong likes to stretch our minds. As he points out, the sound travels, whales are intelligent, they’re social animals, and … and who knows. It’s a ‘flight of fancy’, but it’s an example to make us think. Our sensory abilities are limited to the point we may not know what’s going on with whales, or many other creatures.
Yong finishes his speculations with a few thoughts about magnetoreception – the ability to sense the Earth’s magnetic fields – an ability that songbirds, turtles and probably a lot of other animals have too. He suggests magnetoreception remains one of the biggest mysteries in sensory biology. “It is the only sense where we don’t actually know what the sense organ is or what the receptor is – the cell that actually detects magnetic fields. We know that for everything else, right? So, vision, very obviously, is a thing that eyes do. I know exactly which cells inside my retina are responsible for detecting light. I can trace all the pathways from those cells to my brain. But with magnetoreception, we don’t have any of that. We don’t know what the receptor is. We don’t know how they could work.” Yong wouldn’t say it, but in suggesting that this is the ‘last great unknown sense’, I can’t help wondering if it really is the last sense to be found. I agree ESP is nonsense, but the ability to communicate with others using a sense we don’t yet understand or even recognise, that’s certainly possible. My sense is that this is an area with which it’s worth keeping in touch!
