What Chocolate Footsteps Reveal About The Brain

Apart from having a fascinating perspective of our everyday experience, people with synesthesia could also teach us about how our senses work in the first place.

AsianScientist (Jan. 25, 2016) – It’s a world where cabinets taste of carrots, footfall tastes of chocolate, and aeroplanes have the texture of cream soda. Where a trip to the opera evokes the flavors of a—somewhat bizarre—full course dinner, and friends, politicians, and countries are judged by how mouth-watering their names are.

This is the world of Mr. James Wannerton, who has lexical-gustatory synesthesia. It’s a rare form of sensory confusion which means he experiences sounds as tastes on the tip of his tongue. From birdsong to rustling wind, Wannerton’s life is a succession of enticing—and not so enticing—flavors.

For Wannerton, all words and ambient sounds have tastes.

“I’ll think ‘oh that’s a cabinet’ and then I’ll taste a cabinet. I don’t get hunger pangs because I’m eating all day long,” he told Asian Scientist Magazine.

Synesthesia through the centuries

Automatic, involuntary and incorporating any two senses, synesthesia has been baffling scientists since it first piqued the interest of Darwin’s cousin, Sir Francis Galton, in the 19th century. Some smell in zigzags and geometric shapes, while others literally see time as though it’s laid out in front of them.

But there’s no getting away from it: the condition sounds made up. In any case, how can you check up on someone else’s world view? For decades cases were put down to fantasy, mental illness or hard drugs. It took a surge of interest in psychology in the ‘80s, the so-called cognitive revolution, to turn things around.

The first hard evidence came from a remarkably simple test. Led by Professor Simon Baron-Cohen from the University of Cambridge in the UK, researchers pitched two volunteers against each other: an artist known as EP, who claimed to see words in color, and a lawyer with an excellent memory. Both were asked to describe the colors evoked by 100 words. The lawyer wasn’t a synesthete, she was told to make it up.

Ten weeks later, EP was asked again without warning. Even in the face of elaborate descriptions—Moscow was darkish grey, with flecks of spinach-green and pale blue, while Daniel was shiny with tones of deep purple, blue and red—her answers were 100 percent consistent. The lawyer, on the other hand, was given warning and tested after two weeks. She scored just 17 percent.

What does the science say?

Synesthesia was beginning to look like the real deal, but skeptics needed further proof. With this in mind, the field turned to the latest medical imaging techniques, functional magnetic resonance imaging and positron emission tomography.

Imaging experiments rest on the idea that different areas of the brain have specialized tasks. Usually, when people are shown words, letters, numbers or Chinese characters—collectively known as graphemes—the region of the brain that processes graphemes lights up.

The brains of synesthetes like EP don’t show the same pattern. Their grapheme centers activate as normal, but their color centers light up at the same time—grapheme-color synesthesia is no memory trick. Nevertheless, many synesthetes report using the colors they experience as an extra memory clue. Author and savant Daniel Tammet used his to recall 22,514 digits of Pi in 2004.

But there’s one mystery even imaging can’t clear up: why does synesthesia happen at all? It’s a problem Professor Vilayanur Ramachandran, who was born in India and works at the University of California, San Diego, has been wrestling with for his entire career.

Back in 2001 he noticed that the brain’s grapheme and color centers just so happen to sit next to each other, and it got him thinking. Could nearby regions sometimes get mixed up?

The ‘cross-wiring’ theory is one of several possibilities currently locked in fierce debate, and it begins in the womb. It suggests that we’re all born as synesthetes, with hyper-connected brains where adjacent regions are linked up.

Though most people gradually ‘prune’ these connections as they age, synesthetes don’t put up the same barriers between the senses. Because synesthesia tends to run in families, the failure to break up the connections is likely to be genetic.

Others think synesthetes may not be so special after all. In fact we’re pairing dissimilar entities all day long, even if we don’t know we’re doing it. Metaphors like ‘sweet music,’ ‘sharp cheese’ and ‘clear logic’ are so common they are embedded in our everyday language. Is this a form of synesthesia?

Everyone’s a little bit synesthetic

In 2001 Ramachandran and his then-colleague Edward Hubbard set out to test the idea. The scientists decided to repeat a study from 1929, in which participants were presented with spiky or curvy line drawings and asked to pick a name for the shape, either ‘takete’ or ‘baluba’.

Previously, word sounds were thought to be arbitrary, chosen entirely independent of their meaning. And yet the public were unequivocal: ‘takete’ plainly referred to the spiky object, while ‘baluba’ was rounded.

Ramachandran and Hubbard altered the names to ‘kiki’ and ‘bouba’ and conducted their study in India. To reduce the risk of pre-existing sound associations swaying the result, both Tamil-speakers and American college students were asked. The result was identical, with 95 percent in agreement on the objects’ rightful names.

This consensus may arise from the rounded way the lips curve as they form the vowels in ‘bouba’. Ramachandran thinks the kiki-bouba effect may represent an evolutionary leap, from seeing the world literally to thinking in metaphors and abstract concepts. Finding links between seemingly unrelated ideas isn’t just synesthetic: it’s innately human. If he’s right, scrambled senses could be making everyone a little bit smarter.

Finally, what does Asian Scientist Magazine taste of?

“I can’t quite place the ‘Asian.’ The biggest one there is ‘Scientist’—it tastes a bit like fried onions. ‘Magazine’ is like some sort of curd,” said Wannerton with a laugh.

This article was first published in the print version of Asian Scientist Magazine, January 2016.

Photo: Marie Buyens/Flickr/CC.

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Zaria Gorvett is a freelance science writer based in the UK. She graduated with a bachelors degree in biological science from the University of Exeter, UK and a masters degree in medical microbiology from the London School of Hygiene and Tropical Medicine, UK.

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