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The World of Visual Illusions by Sarcone and WaeberThe World of Visual Illusions: Optical Tricks That Defy Belief!, Gianni A. Sarcone and Marie-Jo Waeber (Arcturus 2012)

A bigger, better and brain-bendy-er version of Eye Bogglers by the same authors, The World of Visual Illusions has nine chapters of old and new illusions. The illusions aren’t just entertaining: they raise some very profound philosophical and scientific questions and teach you some important lessons. For example, on page 97 there’s a simple arrangement of multi-coloured blocks and thick black lines. But Sarcone and Waeber ask this: “Do you perceive bright ‘ghost’ blobs or smudges at the intersection of the lines?”

I do and so will almost everyone else. But when I look directly at a blob or smudge, it disappears. Why? What’s going on? No-one knows for sure: “there are many explanations and counter-explanations regarding this illusion, which is related to the Hermann grid illusion.” So this illusion is multum in parvo: much in little. It’s very simple, but it baffles modern science. And, like many other illusions here, it teaches you that your senses aren’t reliable. They can be subverted and you aren’t in control of what your eyes tell you. Even when you know that the lines on page 109 are “perfectly straight and parallel”, it’s impossible to see them like that because of the background they’re set against.

That kind of trickery can also be applied to words and ideas, and although Sarcone and Waeber don’t talk about advertising or politics, the implications are obvious. Appearances can be deceptive and simple things may have hidden depths. So may complicated things: Holbein’s The Ambassadors (1533) would be a rich and detailed painting even without the anamorphic skull that hovers between the feet of its two subjects. Sarcone and Waeber give the painting a page and a handful of words, but there’s enough there for a long book (John Carroll analyses the painting in a chapter of The Wreck of Western Culture).

There’s enough in the other illusions here for a library, but you don’t have to puzzle over how they work if you don’t want to. We aren’t all equal in intellect or education, but vision is much more egalitarian and this book will entertain all ages and all levels of intelligence. What you experience in an instant can take decades or even centuries for scientists to understand:

It looks like this cat has green eyes. Actually, only one eye is green – the other one is shown in black and white but seems tinted because of the purple context. Thanks to a mechanism of colour adaptation, the brain desensitizes itself to the purple veil which covers the right side of the cat’s face and by doing that it subtracts a bit of purple from the gray eye, which then become yellowish-green. (pg. 120)

I’d like to see Sarcone and Waeber look at other senses. Sight is the most important and powerful sense for human beings, but the ears, nose, mouth and skin can also be illuded. And what about the role of illusions in biological competition and evolution? It’s a big field, often fun, always fascinating.

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Life: Extraordinary Animals, Extreme Behaviour, Martha Holmes and Michael Gunton (BBC Books 2009)

Probably the best BBC book I’ve seen: the beautiful photographs and the enlightening text complement each other perfectly. It’s not advanced biology, with equations and game theory, and it doesn’t give scientific names. But it does include some recent discoveries, like the rehabilitation of the Komodo dragon. If that’s the word:

The tissue damage from the bite is not enough to kill. Until recently, it was thought that bacteria in the dragon’s saliva poisoned its prey. But it has been shown now that the dragon, like some snakes, has venom, making it the world’s largest venomous animal. (ch. 5, “Frogs, Serpents and Dragons”, pg. 134)

The Komodo dragon has become more frightening. And also more interesting. But the book isn’t only about big and frightening: it’s also about strange and beautiful, like:

A tall Gersemia soft coral bending over to sweep tiny animals from the sediment. It does this when there isn’t enough food in the water for its polyps to trap. Once it has consumed everyting in a circle around itself, it will detach from whatever it is holding onto and crawl to a new spot. (ch. 1, “Extraordinary Sea Creatures”, pg. 39)

Germesia soft coral
That’s in very cold water under “the ice in McMurdo Sound, in Antarctica’s Ross Sea”, as part of an “ancient, isolated and utterly unique community” of marine life: there are also sponges, starfish, proboscis worms and sea-urchins. The Gersemia looks both beautiful and graceful, bowing to the sediment like a jewelled and mobile tree, but those are human terms for an organism that probably isn’t even conscious. And all of those organisms that are conscious, like the mammals in the final three chapters, aren’t aware of how they look to us. Natural beauty – and its absence – aren’t designed for us, but the aesthetics of animals is an interesting topic.

Television wants powerful images and this book reproduces them from the series, like the “lioness charging across a river in the Okavango” on page 228. But I think the static image must be more powerful than the mobile one: the photograph freezes the chaos of splashing water and the pale gold perfection of the lioness herself. She wears a look of immense concentration and purpose and I’ve rarely seen a better example of the power and beauty of the big cats. On page 219, there’s an image of one of the big cats’ greatest enemies. It’s also powerful, but in a different way: “a yawning spotted hyena revealing a perfect set of teeth, specialized for cutting, tearing and grinding.” Hyenas are interesting but not attractive. Big cats are both, from the charging lioness to the cheetahs on pages 231-5 and the alert lynx on page 237.

So why is the cat-family, big and small, generally much more attractive than the dog-family? And why are bats often so grotesque? The bulldog bat sweeping up a fish on pages 242-3 has a flat snarling face, ginger fur, taut, veined wings, hook-like hind claws and what looks like a small dangling penis. Birds are often very attractive. Why not bats? Their hairiness and leathery wings are part of it, as are their faces, which are adapted for sonar and eating, not for appealing to human beings.

And then we come to the primates in the final chapter. Now we’re getting closer to home. The faces of each species has a distinct effect on humans, from the endearing spectral tarsier to the choleric red uakari and the melancholy macaque. And chimpanzees look more intelligent than gorillas. Their faces haven’t evolved for our eyes, but they trigger mechanisms in our minds all the same.

So do the insects, birds and fish earlier in the book. And the plants in the single chapter devoted to them, like the bamboo and the dragon’s-blood tree. Colour and line: beautiful and ugly, attractive and repulsive. But all of this bio-aesthetics is interesting and all of it’s governed by natural and sexual selection. And behind it all is Mathematica Magistra Mundi, Mathematics Mistress of the World, from the circle swept by a soft coral on the floor of an icy ocean to the pattern of veins in a bat’s wing and the stripes in a tiger’s pelt.

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