I’m back from the Beyond Belief II conference at the Salk Institute in La Jolla, which packed an extraordinary amount of intellectual stimulation into a few short days. Any conference where you wander into the opening reception, get drawn into a conversation about reductionism and meaning with Stuart Kauffman, Rebecca Goldstein, and Sir Harold Kroto, and end up closing down the bar, is bound to be a good one, and this did not disappoint. (The title notwithstanding, much of the conference had little to do with atheism or religion — the subtitle “Enlightenment 2.0” gave a better flavor.) The talks provided fodder for at least ten to twenty blog posts, of which I’ll probably get around to writing one or two.
One of the talks was by local neuroscientist V.S. Ramachandran, or “Rama” to his friends. (Like any good neuro person, his web page includes a fun collection of optical illusions.) He talked about his experiments with synesthesia, the phenomenon in which people see graphemes (e.g. numbers or letters) as associated with colors. I do that a little bit — five is certainly yellow, seven is red, and eight is blue — but it’s closer to a vague association than a vivid experience. Some people report very strong synesthetic reactions, and for a long time researchers have wondered whether the experience was mostly metaphorical or something stronger.
To test synesthesia, Rama and collaborators designed an experiment where they could measure the vividness of the colors associated with the numbers 2 and 5. They chose those because you can make them look almost identical, although reversed, by choosing a boxy font. Then they made up a picture (on left) of mostly fives, with a few twos scattered within there. Then they asked people to pick out the twos. Most ordinary folks could do it within about twenty seconds or so.
But true synesthetes could do it immediately. That’s because to them, the twos popped out as a brightly colored triangle (right). This established beyond much doubt that synesthesia was “real,” and more particularly that was a measurable phenomenon with real consequences.
This, in turn, strengthened the hypothesis that the origin of synesthesia was to be found in the structure of the brain. Indeed, it turns out that the region of the brain responsible for processing graphemes lies adjacent to the region responsible for processing colors.
It’s fairly easy to imagine that small alterations in “normal” brain wiring — strengthening some pathways, inhibiting others — could be responsible for synesthesia. To test this idea further, Rama had synesthetes look at alternative representations of the numbers — using Roman numerals, for example — and found that the colors did not appear. That’s perfectly consistent, as the relevant bits of brain are responsible for processing the graphical representation of the number 5, not the abstract mathematical concept of “five.” Further studies using functional magnetic resonance imaging have found that the brains of synesthetes and non-synesthetes really do light up in different ways when they look at numbers. (There are other ways to be synesthetic — associating colors with sounds or smells, for example — which may also be traced to connections between different parts of the brain.)
But then here’s my favorite part. They found a synesthete who was color blind. That may seem strange, but what it really means is that the subject had problems with his retina that left him able to distinguish only an extremely narrow range of wavelengths when looking at most images in the world — his brain was fine, but his eyes weren’t quite up to the job. But when he saw certain numbers, he experienced colors that he otherwise never saw. Here is Ramachandran in Scientific American:
We also observed one case in which we believe cross activation enables a colorblind synesthete to see numbers tinged with hues he otherwise cannot perceive; charmingly, he refers to these as “Martian colors.” Although his retinal color receptors cannot process certain wavelengths, we suggest that his brain color area is working just fine and being cross-activated when he sees numbers…
The effect is most obvious and pronounced in the colorblind synesthetes, but occurs in “regular” synesthetes as well. The colors evoked by cross activation in the fusiform gyrus “bypass” earlier stages of color processing in the brain, which may confer an unusual tint to the colors evoked. This is important for understanding the phenomenon of synesthesia, because it suggests that the qualia label–that is, the subjective experience of the color sensation–depends not merely on the final stages of processing but on the total pattern of neural activity, including earlier stages.
Martian colors! How awesome is that?
If there are difficulties with these test, why not do more sophisticated tests like PET scans where you can really see if the people really see colored letters instead of black and white letters?
That it happens in the brain ;).
Essentially, imaging studies have shown that the color-processing areas of the higher-visual cortex (specifically, v4, and more specifically, v4/v8) are active when you present graphemes that are associated with a color experience.
Yes, but can they see the color Octarine?
Scott Atran’s talk came in two parts — the first part, where he was continuing some sort of debate from Sam Harris from last year, was kind of meandering. The second part, where he discussed his research into the origins of terrorism, was amazing, probably the best talk of the conference. If I can find some good sources about what he was talking about I’ll try to blog about it.
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and
are both very good, useful questions.
The two hybrid experiments that I know of, the so-called ambiguous grapheme experiments (Dixon et al., 2006; Myles et al., 2003) say that context largely dictates the color of the ambiguous grapheme. So if you stick a hybrid between a letter and a number in a list of letters, it’ll be parsed as a letter and come out as that letter’s color. Ditto for numbers. Of course, we have a small n in both cases, but given how preferential words are for our brains, it’s not terribly surprising.
Now, some people say that concept is not enough. So seeing an intersection of three branches might not trigger “three” without a visual representation of the number three. That’s where you start running into the questions about whether synesthesia is top-down or bottom-up. Bottom-up means that synesthesia is a response to the physical shape of the stimulus. So someone who saw “V” the roman numeral would parse it the same as “V” the letter. Top-down means that the context and meaning are important, so “V” the roman numeral would be parsed as the number 5, while “V” the letter would be a letter.
Problem is that half the synesthete I’ve chatted with say the first and half say the second. The best we can say at this point is that context is important and is useful, but it may not be sufficient.
(And they can only see octarine after 4-5 years at Unseen.)
One of the most remarkable syneasthetes is Daniel Tammet:
http://en.wikipedia.org/wiki/Daniel_Tammet
It’s thought that his savant abilities are facilitated by the associations synaesthesia provides. When I first heard about Tammet, I immediately thought of the Feynman quote in #8, and wondered if he also benefitted from this quirk of neurology.
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Sean, I’ll put my vote in for a post on Scott Atran’s talk. His recent work on terrorism seems really important and interesting. He had a long Nature or Science article about it not long ago (a couple of months?), too.
Here’s the Science article:
http://www.sitemaker.umich.edu/satran/files/atran_et_al_science_mag_240807.pdf
More relevant, perhaps, is the PNAS article:
http://www.sitemaker.umich.edu/satran/files/pnas_sacred_bounds.pdf
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People never believe me when I tell them numbers and letters have colours. I was excited to test how strong my connection is, but I glanced at the colourised version of the graphic before the black and white one, which spoiled the test. I often remember things like phone numbers, exam grades, and website addresses are based on their colours.
Oh, but what happens if 2 and 5 are the same colour? For me they’re quite close—orange and red respectively. The test would still work, but with false negatives.
I laid out my colours a few months ago:
http://www.booberfish.com/blog/2007/01/everything-has-a-colour/
I’m both a synaesthete and an astrophysicist.
Likewise, in the past I was always accused of lying when I said my 3’s were red. I didn’t know that others didn’t see the world this way, or that there was a name for the “condition,” until about November of 1999 when Discover Magazine published a popular article on the subject.
I’ve heard that synaesthesia is not all that uncommon, but I’ve never met another synaesthete to my knowledge. Admittedly it’s not something that comes up in conversation due to the oddity and the potential embarrassment factor.
I can address a few points from my point of view:
1. Yes, I see mathematical expositions in a flurry of colors.
2. For color-grapheme associations, context does matter, to a certain extent. For example, the color of a character will change depending on whether I think it’s a number 5 or a letter S. I can force a character to “change” colors.
2a. For some reason this doesn’t apply to Roman numerals, which for me always retain the colors associated with their “alphabetness.”
3. Despite point 2, I have noticed that I can sometimes read highway signs from a distance based on the colors I see even if the characters are a bit too blurry for me to consciously make them out. But perception of perception is fuzzy — my brain must be recognizing the graphemes somehow even if I don’t.
4. I occasionally read things written in non-Roman alphabets. The colors of the characters in these non-Roman alphabets are frequently colored by their corresponding sound, and thus letter, in the Roman alphabet. Amusingly, these non-Roman characters may appear “two-toned” if they carry one sound/color in the corresponding Roman character but also physically resemble another of the non-Roman characters that carries a different sound/color.
5. The triangle of 2’s doesn’t pop out immediately for me, although certainly more quickly than the 20-second average alleged for the non-synaesthetes. I have to recognize the 2’s first.
I would like to know whether color-grapheme synaesthesia in particular is more common among people who learned to read comparatively early. (This would probably have to be disentangled somehow from the tendency of people with higher-than-average IQs to learn to read early; I recall hearing that higher-than-average IQ is associated with synaesthesia, as is autism.) My understanding is that infants don’t prune away these neurological cross-modal associations until age 2 or 3.
P.S. Greg, your colors are wrong. 😉
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Interesting! Last september I wrote about my experience with synesthesia:
http://michaelgr.com/2007/09/14/my-experience-with-synesthesia/
I even used pictures of the Rama test.
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If you think you might be a synesthete, you can check the possibility by doing a computerized battery of tests at this website:
http://synesthete.org/
Personally, I would recommend synesthetes to contact synesthesia research centers at near universities. There are many forms of synesthesia out there (combinations of color, emotions, sequences, spatial locations, graphemes, sensations, sounds, etc.), and usually the researchers need new participants for their experiments. It can be an interesting experience and you’ll be contributing to science.
🙂
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Hey synesthetes! I just found great online synesthesia survey – you can vote what color is letter ‘A’ and each letter or number in your mind and see what color many other people voted for! Really interesting: http://www.tukan.extra.hu