Tasting fractals: true confessions of a synesthete

Matcha green tea caramels: a volcano of taste.

We were at a bar, discussing the latest lab gossip over flutes of winter ale, when Lyndsay suddenly dug through her bag and presented me with a small, square piece of green candy, wrapped in clear cellophane.

'Our postdoc brought me some of these caramels from Japan,' she said. 'This one's green tea. You should try it.' So I did. An interesting and delicious combination of buttery caramel and invigorating matcha green tea flooded my palate.

'It tastes sort of this shape,' I said, miming a mountain with my hands. 'Sort of...volcano-like. It's rounded, but there's a pronounced indentation at the top where the green tea and the butter caramel intersect.' Both Eric and Lyndsay stared at me as if I'd just confessed to setting a toddler on fire.

'So tastes have shapes to you?' Eric asked.

'Well, kind of,' I said. 'They're more like landscapes than free shapes.' I hesitated. 'But we all have that, right? It's not like I have synesthesia or anything like that.'

'No, Leon, no one else has that,' Lyndsay affirmed. 'No one else tastes shapes.' Eric just laughed, shaking his head furiously. As the first snow of winter started sifting down from pink clouds hugging the town, I started to reconcile myself with the fact that I may have synesthesia.

People with synesthesia show increased connectivity and communication between parts of the brain normally devoted to the processing of different sensory stimuli.

Synesthesia is commonly defined as a neurological condition where stimulation of one of the senses elicits involuntary triggering of another sense. People with synesthesia are dubbed synesthetes, and synesthesia can take many different forms. Some people experience vivid colours when hearing specific sounds (C sharp on the piano sounds golden yellow). Others associate personalities with numbers (4 is such a guarded, introspective number). Still others might associate textures with specific smells (sandpaper smells like strawberries). Much research has been conducted on the cause of synesthesia, suggesting enhanced cross-talk between brain areas usually devoted to separate sensory pathways (see here for an extensive reference list, both peer-reviewed and otherwise). For example, when people who experience coloured-hearing synesthesia are stimulated with spoken words while inside an fMRI, the areas of the brain devoted to the processing of colour information light up like they were watching the psychedelic Star Gate sequence from 2001: A Space Odyssey. The brains of control subjects who don't have synesthesia do not light up in this way, even when they were extensively trained to associate words with specific colours. Science is also beginning to make some progress on the genetic basis of some of the more common forms of synesthesia, with evidence from large-scale genome-wide association studies implicating specific regions on several different chromosomes.

Hearing colours can be quite the space odyssey.

But what about me? My apparent synesthesia has not been confirmed by a neurobiologist, and I've had none of my genes sequenced. Synesthetes are more likely to be left-handed. I'm left-handed. About 40% of synesthetes have a close-relative who also has synesthesia. I...well, I don't know. I've never asked them, and perhaps they, like me, haven't thought it anything unusual and therefore never mentioned it. Also, my kind of synesthesia, morphogeusia (from Ancient Greek morphe, 'form' and geusis, 'taste'), seems to be one of the weirder ones. In addition to taste, it also involves my sense of smell to some extent. I once started to describe the scent of a colleague's perfume as 'very tall, sort of skyscraper-shaped, but with a top that resembles a bisected sphere with indentations...' before trailing off when I saw her raised eyebrows.

Ceylon black tea.

Let me explain what is happening to me. Basic tastes and flavours have pretty basic shapes, and these shapes are not so much felt as seen; they're topography, not texture. All fats and oils elicit the same perception of rounded mounds. Butter is distinctly dome-shaped. This partially explains why those buttery green tea caramels tasted volcano-shaped: it's that mountain of buttery goodness! The taste of rooibos is also rounded, but concave in contrast to the convex dome of butter. Rooibos is therefore bowl-shaped to me, and able to contain other flavours (like the bullets of vanilla), whereas the domed heavy cream of a crème brûlée would go over the top of vanilla. Incidentally, real vanilla is fat and short, whereas artificial vanilla is taller and thinner, more like a rifle cartridge. I had a fine cup of black tea the other day that tasted much like a flight of stairs. Sharp, pungent ingredients like raw onions or wasabi tend to taste like valleys or canyons, and the sharper they are, the more sheer those cliff faces become.

Eggs over easy.

Initially, I took that fact that not every taste seemed to have a shape as evidence that I didn't actually have synesthesia after all. Surely everything must elicit a well-defined topography! But then I realized that it's merely harder for me to see the shapes of things such as eggs and french fries; it's not that they lack landscape, it's just that the topography of that landscape is really shallow. French fries are just shallow ripples, whereas an egg forms a shallow depression, like a dried lake bed. Perhaps surprisingly, the extent of a synesthetic shape does not correlate with my enjoyment of a particular foodstuff. I like both eggs and french fries and don't find their taste one-dimensional, regardless of how shallow and dull their synesthetic features are.

Tart cherries, with a lingering oak finish.

While still an undergrad, I was recruited to a university tasting panel by a friend majoring in food science. Soon my palate was required to evaluate all manner of things, from frozen vegetables to chocolate milk. The sensory evaluators commended my vivid gustatory descriptions for new flavours of potato chips they were developing (though I was careful not to describe them as 'salt flats with interspersed pyramids' or anything similar). However, I'm not a supertaster by any means. Neither do I possess a particularly sophisticated palate. All wine resembles a generic jungle canopy to me. It's as difficult for me to tell one pinot noir from another as it is difficult for me to discriminate between a rain forest from Bolivia and one from Ecuador. Highly complex flavors elicit landscapes that are not very memorable and exceedingly difficult to describe, like the faces of strangers you meet in a dream. What synesthetic shapes did that chilli verde from the other night conjure up? I don't recall exactly, but there was some granularity, I'm sure...

So that's my little personal subjective anecdote about maybe perhaps having synesthesia.

'I'm so happy for you,' a lady in a tea shop said to me the other day, when she overheard me discussing my synesthesia with Eric. 'What a wonderful talent.'

'I'm not sure I'd consider it a talent, as such,' I responded. 'It's not even particularly useful. I'd read about Daniel Tammet, who has high-functioning Asperger syndrome and uses the vivid synesthetic landscapes generated by numbers to recite pi to tens of thousands of digits. I don't have that at all. I'd rather be good at math.'

I didn't tell her about lemons and how they taste like fractals, though. But they do that for everyone, right?

Picture credits:
Matcha green tea carmels from Fusion Sweets
MRI scans from Rouw & Scholte (2007) Nature Neuroscience 10:792-797
Star Gate sequence from 2001: A Space Odyssey (1968)
Stone steps from Steve McCullough
Dry lake bed from Reno Tahoe
Jungle canopy from thaths