Alternatively spelled synaesthesia in the U.K.*, synesthesia has Greek roots meaning together and sensation; emotional or sensory input through one channel (sound, smell, touch, sight, or taste) triggers automatic and involuntary input through a separate pathway. (Robot-speak provided by Wikipedia.)
Shruti Ravindran, in her fascinating article "A Circus of the Senses" posted in the online journal Aeon today, describes it thusly:
"Synaesthetes see letters and numbers wreathed in fixed, seemingly idiosyncratic colours. Grapheme-colour synaesthesia, the term for this variety, is the most common sub-type of synaesthesia, occurring among four people in 100. It’s also the most widely studied. Other common varieties are chromaesthesia, in which tones or notes set off flashes of colour and a symphonic wall of sound can summon a three-dimensional landscape, and spatial-sequence synaesthesia, in which seconds, weekdays, months or years encircle those who experience it, like planetary rings. Some have lexical-gustatory synaesthesia, which lends every word or name a strong, specific taste, making some delicious, and others too bitter to utter. Still other synaesthetes report ordinal-linguistic personification, in which they ascribe distinct genders, colours or personality types to letters and numbers: ‘4’ might be an ill-tempered, ungenerous man, constantly heckling his wife, while ‘6’ turns out to be a dignified, genteel woman with exquisite manners."
ANYhoo... My interest in synesthesia spiked when Roman letterboarded the following question to Soma a couple of weeks ago: "why feelings are so cloudy when sad?" Soma said that many of the autistic children she works with have synesthesia, and that for Roman, sadness might actually look or feel like clouds.
A 2013 study of synesthesia found that is to occur three times as much in people with autism.** Coincidence? It's all in the wiring.
Apparently, we humans come pre-loaded with synesthesia- babies experience the world as a sort of seamlessly vivid sensory wonderland. Most typical brains undergo a neural pruning process by the age of 9 though, giving our nervous systems a break and allowing us to develop the ability to separate different inputs into discrete sensations. We outgrow it to varying degrees, and all of us could be plotted on another matrix - the synesthesia spectrum.
On the contrary, FMRI brain scans of certain autists show strengthened neural connectivity between separate sensory centers. So for chromasthesia, the visual center might simultaneously recruit the auditory center to play a B Flat to the color indigo. Or grapheme-color synesthetes might experience the letter A as red. It's currently estimated that about 18% of autists maintain this melded sensorium; this dense neural underbrush is at play behind the intense world theory of autism, and suggests why a disproportionate percentage of people with autism also have epilepsy.***
Ravindran quotes neuroscientist Edward Hubbard as saying that "speech perception is actually this multisensory phenomenon, where we bring together inputs from various senses." Perhaps this is also a clue as to why language development is often delayed in so many of our spectrum kiddos- the words and numbers triggering a cyclone of colors, soundscapes, tactile sensations and tastes that whisk them away to faraway cloudlands. (All I'm saying is that I wouldn't come back for math class...)
The synesthethia annals are lousy with artists and inventors, including musicians Itzak Perlman and Duke Ellington, painters Wassily Kandinsky and David Hockney, writers Valdimir Nabokov and Joanne Harris (of Chocolat fame), inventor Nikola Tesla, and autist-savant Daniel Tammet, whose book Born on a Blue Day chronicles his experiences with color-graphemic synesthesia. (<- He is able to recite over 22,000 numbers comprising Pi. He is extremely mathletic.)
Besides suiting up for a brain scan, the most reliable way to diagnose synesthesia is via a test-retest scenario. Subjects are given a list of a hundred or so words - generally including all the letters of the alphabet, days of the week (Monday is definitely brown.), numbers 1-10, proper names, feelings, and random words - then asked to describe each in detail. Three hours later, a random sampling of 10 words from the list is retested. Then 10 weeks later, the entire list. Synesthetes usually score in the 90% accuracy range. (Yes, this means that I'm out, as I can't remember ANYthing for 10 weeks.) However, I am plotting a homemade test of Roman's associations with a selection of colored crayons and the letterboard stencil. *tents fingers*
PS Perhaps ordinal-linguistic synesthesia is behind the confounding French gender system, where the same bicycle can be either feminine or masculine depending on the word choice (un vélo, or une bicyclette)? Conspiracy theories aside, this could be the work of Medieval French synesthetes!
PSS The image is of Romi and Lu at LACMA in August of 2009 - they are in front of Choi Jeong-Hwa’s site-specific installation entitled HappyHappy.
* Because the Brits encourage the A and the E to share a special hug. Ask your parents, kids.
** "Is Synaesthesia More Common in Autism?" in the journal Molecular Autism. <- Not currently on my night table.
*** Knocking on wood over here.