I was well into my thirties before I figured out that most people did not see a color associated with every letter and number, did not see shapes associated with sounds, and didn't view a year as a big hamster wheel with a rung for every day. Before you counsel me to take my meds, there's more to say about this phenomenon, known as "synethesia." As with left handers, you might think we synesthetes are a little mixed up, but we are in fine company! There is a long list of famous synesthetes, from Richard Feynman to Wassily Kandinsky.
The graphic I included above is something I did years ago to try to approximate the colors letters have for me. Oddly enough, most synesthetes tend to see "S" as yellow, "Z" as black and "A" as red, and so do I. So, now you know what color Zsa-Zsa's name is! Or should be, anyhow.
Synesthesia is a fairly common neurological phenomenon that suggests a little more about how the brain works, and a lot more about the overlap between art and science.
"Twenty years ago, synesthesia—the automatic joining of two or more senses—was regarded by scientists (if at all) as a rare curiosity. [Now] it may well be the basis for human imagination and metaphor." —Neurologist and writer Oliver Sacks
Synesthesia in the public eye
Some synesthetes know from very young that they have some unusual sense associations. My own suspicions about perceiving things differently began around age 30, when I asked my husband what colors went with certain letters, because I was sure that his colors would be different from mine. "What are you talking about?" came his answer. I suspected that he was either very unimaginative, or disliked being grilled by the wife. Comparing notes with others of my family and friends produced the same results, along with some searching, pitying looks.
I first heard of the term synesthesia back in the 1990s, on a radio program the origin of which I've long since forgotten. I recollect that it mainly dealt with "Sound-Color" synesthesia, and of the sort that is "projected" into space like an hallucination, rather than as something seen in the mind's eye. Since I had also always associated sounds with shapes since before I could read, and saw music flowing by my inner eye like a scintillating braid, I thought I might have synesthesia, and I set about researching it, beginning with the fairly young World Wide Web.
You know those dorks who honk and wave at you on the highway because you're driving the same model car? On-line synesthetes are like that, endlessly willing to wave "Hi" and compare notes in their various bulletin boards (see Further Reading, below). Is the letter T silver or teal? So and so knows when the roast is done because it smells woolly rather than smooth. It was in those sorts of forums where I learned that there were a bunch of people out there who would not shoot the pitying looks, were glad to find each other, and that a lot of them, just as I did, saw letters and numbers in colors, number sequences as forms, music as colors or shapes, and so forth.
Meanwhile, synesthesia enjoyed a rather gee-whiz renaissance in the media in the past decade or two. Mostly in connection with great composers, artists, or Rainman-type savants. Study of it had bloomed in the 19th century, but faded out with the rise of behavioralism, which tends to discount anything not observable or objective. But as behaviorism's star set, new researchers such as Richard Cytowic (above) and David Eagleman began to look at synesthesia with a gimlet eye and a brain-based approach.
Descriptive criteria
Synesthesia is not in any manual of disorders, since it normally doesn't interfere with a person's functioning in daily life. It's just a trait, a variation of normal, rather like being a taster or non-taster of PTC, or being left-handed.
And while there are seemingly endless variations on the triggers and the perceptions, there are some commonalities across large groups. For instance, in people for whom sounds evoke colors, higher sounds tend to evoke lighter colors and lower sounds darker colors. Then there is the tendency for certain letters to produce the same colors that I mentioned in the introduction. And although people can have more than one form of synesthesia, few people have more than two senses involved at a time. In trying to find common criteria, Cytowic whittled synesthesia down to these basic qualities:
- Synesthesia is involuntary and automatic.
- Synesthetic perceptions are spatially extended, meaning they often have a sense of "location." For example, synesthetes speak of "looking at" or "going to" a particular place to attend to the experience.
- Synesthetic percepts are consistent and generic (i.e., simple rather than pictorial).
- Synesthesia is highly memorable.
- Synesthesia is laden with affect.
#1 is fairly clear. With respect to #2, Cytowic later discovered that the majority of his subjects experienced these perceptions in the mind's eye, and not as a kind of sensory overlay on the external world. As for #3, the perceptions are never great elaborations, just simple sensations. In #4, memorable means that the perceptions are often more memorable than the triggering sensations. For instance, I might remember not that a person's name was "Rod," but that it was bluish-black. Finally, in #5, laden with affect means that vivid emotions might attach to some of these perceptions.
Types
There are over 150 types of sense pairings in synesthesia, most quite uncommon, with much left to be defined, because of the varied, personal and ineffable nature of the phenomenon.
Let's start with the most common form of synesthesia.
Number form
Involuntarily and automatically seeing numbers and sequences of numbers arrayed in physical space is common to one in ten people, many of whom are not technically synesthetes. If a person is among one of those ten percent, however, there is a 60% chance that he or she is a true synesthete. In my case, I always see days, weeks, years and number lines arrayed in space before me like squares in a sidewalk or a board game, with some things, such as weekends and special dates, bolder than others. On the number line, zero and decimals stood out.
These special emphases are common to people who see number forms, and underscore the likelihood that we embed the things that we learn young into our schemata. For me, the summer months are very large and luminous relative to the others, most likely because of my associations with long, sunny days during my school years. That has not changed.
Why do non-synesthetes sometimes see number forms? Does it not make sense to see numbers in their relations with each other when doing math? Richard Feynman saw equations as colored components scattered about him, and wondered what it was that his students saw.
The image above is a number form described by a subject of polymath Francis Galton, in 1880.
Grapheme-color
This is the second most common form of synesthesia. One in 90 people have this form, which pairs a color for each letter and number ("grapheme"). The permutations of this are many. Novelist
Vladimir Nabokov wrote of arguing with his synesthete mother over the color of letters. Some people only see consonants as colored, others only vowels. Sometimes, words take on the hue of their first letter or their vowels. Numbers' colors may or may not correspond to those of similar letter shapes, and other writing systems may also be affected.
"Krug mentioned once that the word 'loyalty' phonetically and visually reminded him of a golden fork lying in the sun on a smooth spread of pale yellow silk." —Vladimir Nabokov, Bend Sinister
In my own case, while all the letters have a consistent color, those of vowels are the most vivid, and darken as the vowel sound gets darker. When I picked up Cyrillic, its vowels took on the appropriate color as I learned them. Oddball letters like "я," which looks sort of like an "R" but has "A" as its vowel sound, look like a combination of R and A to me: red-black. Letters that look like one letter but sound like another tend to match the sound for me. This coloring has usually helped me pick up languages quickly and remember things well, but sometimes it turns around and bites me, as when I confuse names that have similar colors, e.g. "Greg" and "Steve."
Sound-color
As described by Richard Cytowic, "sound → color synesthesia is `something like fireworks': voice, music, and assorted environmental sounds such as clattering dishes or dog barks trigger color and simple shapes that arise, move around, and then fade when the sound stimulus ends." Sometimes, people associate colors with certain tones or keys. For a while, there was an attempt to scientifically correlate notes with colors, but no one could come up with a hypothesis that would hold water; perceptions seem to be mostly idiosyncratic.
Ordinal-linguistic personification
Granted, synesthesia
per se is odd, but I find this category to be
really odd, perhaps because giving an ordered sequence of something a personality or gender seems to transcend a
simple sense. It has been documented for a long time, but largely ignored until recently. Apparently, grapheme-color synesthetes tend to exhibit this one, too.
An example, reported by M.W. Cakins, from 1893:
“T’s are generally crabbed, ungenerous creatures. U is a soulless sort of thing. 4 is honest, but… 3 I cannot trust… 9 is dark, a gentleman, tall and graceful, but politic under his suavity”
Because, in testing, these qualities are amazingly consistent over time and automatic, they are consistent with synesthesia, and theorists have turned to neuroanatomy (more below) for an explanation.
Lexical-gustatory
Tasting a word is fairly uncommon among synesthetes. Here is one account, from James Wannerton:
"Whenever I hear, read, or articulate (inner speech) words or word sounds, I experience an immediate and involuntary taste sensation on my tongue. These very specific taste associations never change and have remained the same for as long as I can remember.
Moreover, a food name will trigger its own taste, commonly, as will words containing that same phoneme: "Egg" tastes like egg, and so do "leg" and "keg." Typically, the tastes that are perceived are ones from childhood. So a lexical - gustatory synesthete will taste things like milk, fruit and candy, but probably will never experience tastes acquired when older, such as aqvavit or anchovies.
Hypotheses for basis, cause
Reading above you can see suggestions as to neuroanatomical causes. The main theory seems to be "
cross-talk," like the faint chatter of others bleeding through on your telephone connection. Indeed, the areas responsible for perceiving graphemes and colors are adjacent to one another near the back of the brain. So too are the areas relating to auditory perception and taste, as well as between areas for ordinal processing and "theory of mind." Theorists suppose that this may be due to a greater interconnectivity among the parts of the brain via neurons that ordinarily get "pruned" in early childhood in the vast majority of humans. Different imaging studies show significant differences in the brains of synesthetes, such a more robust white matter tracts in certain areas of the brain.
Scientists also believe that synesthesia is highly heritable and a dominant trait, although not in the same way that a gene for hemophilia is. There seems to be no X-link, and incomplete penetrance. Richard Cytowic reports that soon synesthesia may be the first cognitive trait to have its gene mapped.
A common extrinsic cause of synesthesia is using a hallucinogen, such as LSD or mescaline.
Associated traits
The data is coming in slowly. Synesthesia is commonly associated with seizure disorders, autistic spectrum disorders, left/right confusion and trouble with arithmetic, but also with elevated memory. The thinking is that the extra evoked senses provide additional "hooks" on which to hang memories. Also tending to be left-handed and rather creative, people with synesthesia are generally pretty normal, neurologically.
As for me, I have trouble with left and right, have an unusual memory, and, when I was a young child, used to have frequent bouts of micropsia, which might hint at past temporal lobe seizures. My father and grandfather both have great memories and both developed temporal lobe epilepsy and complex seizures in their seventies.
Connections with other fields of study
Synesthesia brings new insight into sensory integration; that is, how the brain combines senses, as well as the nature of consciousness itself. Various researchers are looking into its implications.
Which is Bouba and which is Kiki?
That sight and sound might somehow be inherently connected is also interesting to researchers delving into the evolution of language. If even non-synesthetes tie numbers to forms, and if a majority of synesthetes tend to see "A" as red, could it be that certain shapes naturally lend themselves to certain sounds? Ramchandran and Hubbard conducted a fascinating study on the topic, known as the "Bouba/Kiki Effect." They showed the shapes above to a wide variety of people, young and old, across cultures, and asked which shape was called "Bouba" and which was called "Kiki." Over 90% of people agreed on which was which, suggesting that there might be a hardwired basis for sound symbolism.
Connections with creativity
I've already given up examples of Nabokov, Kandinsky, Feynman and other productive, creative people with actual synesthesia. The list of famous people with synesthesia is long, including
Stevie Wonder,
Eddie van Halen, and
Nikolai Rimsky-Korsakov.
Other creative types produce work that suggests synesthesia. John Updike, in Rabbit, Run, describes trumpets building clusters up into the night. Samuel Delaney, in Dhalgren, speaks of a long silver note that bent. Those were just the first two I plucked out of my head that made me wonder. We all can name writers who have ably imported and mingled the senses in their prose. Even Hemingway managed it.
As Oliver Sachs wrote above, synesthesia may well be the foundation for imagination and metaphor. Metaphor, by etymology and definition, carries something else along with it, and imagination is the literal conjuring of images. If we all didn't retain a little of the synesthete in us, how could we call up Elizabeth Taylor's beautiful face at the mention of her name? How could we think of shimmering waters when we heard symphonic strings?
Further reading
Synesthesia, from good old Wikipedia
Richard Cytowic's web site
The Synesthesia Battery. If you have 40 minutes, take the test on David Eagleman's site. Synesthesia is hard to fake.
Have fun! I look forward to your comments. Bet you're out there, synesthetes!
Updated by rhubarb at Thu Mar 24, 2011 at 10:09 AM CDT
Thanks to those Rescue Rangers!
I just touched on the basics of synethesia. There is a lot more out there, with research rolling in all the time. To answer a few questions that popped up in the comments:
1) Colorblind people who have their color sense paired to stimuli can also see "Martian" colors (h/t Edgar Rice Burroughs) that they have never seen in the external world. They may actually be seeing the colors their retinas do not properly pick up.
2) Yes, PET scans have picked up additional activity in synesthete brains during synesthetic experiences, But despite the localized activity, Cytowic says, the experience is disseminated widely in the brain. The interconnectivity of various areas of the brain is far greater than once previously thought.
3) Yes, synesthesia is heritable. Highly so, although it is not expressed in the same way as a rule. The experiences of identical twins are highly idiosyncratic.