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.