fact that the number area of the brain which represents visual numbers as shown by brain imaging studies, that number area is right next to it, almost touching the colour area of the brain so we said this can't be a coincidence, how come the most common type of synesthesia is number/colour and the number area and colour area are almost touching each other right next to each other in the same part of the brain? Maybe what's going on is these people have some accidental cross-talk, or cross-wiring, just as in my experiments on phantom limbs in my London lecture I showed that the face area becomes cross-wired with the hand area in the cortex, except in this case it happens not because of amputation but because of some genetic change in the brain. And now we've done imaging experiments on people with synesthesia and showed that if you show just black and white numbers, they get activation in the colour area.
Now the next question is why does this cross-wiring or cross-activation occur? Well remember I said it runs in families. Well this suggests there's a gene or set of genes involved. What might this gene be doing, this bad gene? Well one possibility is we are all born with excess connections in the brain. In the foetus there are many more redundant connections than you need and then you prune away the excess connections to produce the modular architecture characteristic of the adult brain, like Michelangelo chipped away everything that doesn't look like David to produce David. That's how you generate a brain. So I think what's happened in these people is that gene is defective and therefore there's defective pruing so there's cross-activation between adjacent areas of the brain - or there could be some kind of chemical imbalance that produced cross-activation between adjacent parts of the brain that are normally only loosely connected and this produces a hyperconnectivity between these parts of the brain.
Now what we found next was even more amazing. Take the same two synesthetes. Instead of showing them Arabic numbers- actually I should call them Indian numbers but it doesn't matter - Indian/Arabic numbers, you show them Roman numbers, Roman V which looks like a V or a 6. Guess what happens? They say oh I know it's a five but it doesn't look coloured, it's black and white so Roman numbers don't give colours. Now what does that prove? It's very important because it shows it's not the numerical concept that drives the colour but the visual appearance of the Indian/Arabic number and it fits with what I'm saying because the fusiform gyrus represents the visual appearance of numbers and letters and things like that, not the abstract concept of sequence or ordinality.
Where does that occur, the abstract idea of number? We don't know but a good guess is angular gyrus in the left hemisphere. We know that because when that's damaged in patients they can no longer - they're fluent in conversation, they are intelligent and all of that but they can't do even simple arithmetic. You say what's seventeen minus three, he'll say oh is it nine? Gets it completely wrong. So we think that abstract number concepts are represented in the angular gyrus and remember this chap's cross-wiring, is in the fusiform gyrus but in the visual appearance of a number and the colour.
Now, however, we then found this is not true of all synesthetes. All synesthetes are not made equal. We then ran into other synesthetes where it's not merely a number that evokes colour but even days of the week evoke colours. Monday is red, Tuesday is indigo, Wednesday is blue, months of the year evoke colour, December is yellow, January is red, February is indigo. No wonder people thought they were crazy! But remember, if you're a clinician you know when somebody sounds crazy it usually means you're not smart enough to figure it out. He isn't crazy. What do calendars, what do days of the week, months of the year and numbers have in common? What they all have in common is the abstract idea of sequence or ordinality. So what I am claiming is that's represented in the angular gyrus, higher up in the TPO junction, temporal parietal occipital junction in the vicinity of the angular gyrus, and guess what? The next colour area in the sequence is higher up in the general vicinity of the TPO junction, not far from the angular gyrus so what I'm arguing is - in these people the cross-wiring is higher up in the angular gyrus. Then you get a higher synesthete, so if the faulty gene is selectively expressed in the fusiform gyrus, lower at an earlier stage in processing, you get a lower synesthete driven by the visual appearance. If it's expressed selectively higher up in the vicinity of the angular gyrus, you get a higher synesthete driven by the numerical concept rather than by the visual appearance.
OK next question - why did this gene survive?
One in two hundred people have this peculiarity of seeing coloured numbers and it's completely useless so why hasn't it vanished from the population and I'm going to suggest it's a bit like sickle cell anaemia - there's a hidden agenda. These genes are doing something else important. What? Well one of the odd facts about synesthesia which been known for a long time and again been ignored, is the fact that synesthesia is much more common among artists, poets, novelists, you know flaky types! So now why is it much more common? Well one view is that - in fact according to one study it's seven times more common among artists poets and novelists and the reason is what do artists, poets and novelists all have in common? Just think about it. What they all have in common is they're very good at metaphor, namely linking seemingly unrelated concepts in their brain, such as if you say 'out out brief candle', so it's life, why do you call it a candle? Is it because life is like a long white thing? Obviously not. You don't take the metaphor literally, although schizophrenics do and we won't go into that. So why do you that? Well it's brief like a candle, it can be snuffed out like a candle, it illumines like a candle very briefly. Your brain makes all the right links and Shakespeare of course was a master of doing this. Now imagine one further assumption - if this gene is expressed more diffusely instead of being just expressed in the fusiform or in the angular, if it's expressed in the fusiform you get a lower synesthete, in the angular gyrus TPO junction you get a higher synesthete. If it's expressed everywhere you get greater hyperconnectivity throughout the brain making you more prone to metaphor, links seemingly unrelated things because after all concepts are also represented in brain maps. This may be seem counter-intuitive but after all a number, there's nothing more abstract than a number. You can have five pigs, five donkeys, five chairs - it's fiveness - and that's represented in a fairly small region namely the angular gyrus so it's possible that concepts are also represented in brain maps and these people have excess connections so they can make these associations much more fluidly and effortlessly than all of us less-gifted people.
Now, remember I said the third thing you have to do in science is show that this is not just some quirk. It has vast implications. Well what implications does synesthesia have? I'm going to show all of you that synesthesia is not just a quirk in some people's brain. All of you here are synesthetes, and I'm going to do an experiment. I want all of you to imagine in front of you, to visualise in front of you a bulbous amoeboid shape which looks a bit, has lots of curves on it, undulating curves. And right next to it imagine a jagged, like a piece of shattered glass with jagged shapes. And just for fun, I'm going to tell you this is Martian alphabet. Just as in English alphabet, A is a, B is b, you've got each shape with the particular sound, this is Martian alphabet and one of these shapes is kiki and the other is booba, and I want you to tell me which is which. How many of you think the bulbous shape is the kiki, raise your hands? Well there's one mutation there. In fact what you find is if you do this experiment, 98% of people say the jagged shape, the shattered glass is kiki, and the bulbous amoeboid shape is a booba. Now why is that? You never learnt Martian and nobody here is a Martian. The answer is you're all synesthetes but you're in denial about it. And I'll explain. Look at the kiki and look at the sound kiki. They both share one property, the kiki visual shape has a sharp inflexion and the sound kiki represented in your auditory cortex, in the hearing centres in the brain also has a sharp sudden inflexion of the sound and the brain performs a cross-modal synesthetic abstraction saying the only thing they have in common is the property of jaggedness. Let me extract that property, that's why they're both kiki. So what? Well I'll explain.
We have taken the same patterns I have just told you about, the booba/kiki, and shown them to patients who have damage, very small lesion in the angular gyrus of the left hemisphere and guess what? If you show them these two shapes and ask them to associate kiki with the two shapes, kiki and booba, they're random and by the way we don't use just these two shapes. We have a whole set of them and they cannot do this cross-modal associations even though they're fluent in conversation, they're intelligent, they seem normal in other respects. This makes perfect sense because the angular gyrus is strategically located at the crossroads between the parietal lobe (concerned with touch and propriaception) the temporal lobe (concerned with hearing), occipital lobe> (concerned with vision) so it is strategically placed to allow a convergence of different sense modalities to create abstract modality-free representations of things around you. Now think of what this involves. Think of the jagged shape and the sound, kiki. They have nothing in common. One is photons hitting the retina in parallel, and the other is a sharp sound hitting the hair cells sequentially but the brain abstracts the common denominator saying - but jaggedness is common, or the property of undulation is common, so what you're seeing here in the angular gyrus is the beginnings of a property that we call abstraction that us human beings excel in. And another point I'd like to make is why did this ability evolve in humans in the first place, cross-modal abstraction? Well it turns out if you look at lower mammals, compare them with monkeys, then compare them with the great apes and then with humans, there's a progressive enlargement of the TPO junction and angular gyrus, almost an explosive development and it's especially large in us humans. Why? Well I think this ability evolved because imagine your ancestors scurrying up on the treetops trying to grab branches, jumping from branch to branch, they've got a visual horizontal branch and then they have to adjust the angle of the arm and the fingers so that the proprioceptive map has to match the horizontality of the visual appearance and that's why the angular gyrus became larger and larger. But once you develop this ability to engage in cross-modal abstraction, that structure in turn became an exaptation for other types of abstraction that us humans excel in, be it metaphor or any other type of abstraction, so that's the claim being made here.
Now finally I would like to turn to language, how did language evolve? This has always been a very controversial topic and the question is look, here we have this amazing ability called language with all the nesting of clauses, this hierarchical structure of language, this recursive embedding of clauses, our enormous lexicon and it's an extraordinarily sophisticated mechanism. How could it possibly have evolved through the blind workings of chance through natural selection? How did we evolve from the grunts and howls and groans of our ape-like ancestors to all the sophistication of a Shakespeare or a George Bush? Now there have been several theories about this. Alfred Russell Wallace said the mechanism is so complicated it couldn't have evolved through natural selection. It was done by god, divine intervention. Maybe he's right but we can't test it so let's throw it away. Next theory was by Chomsky. Chomsky said actually something quite similar although he doesn't use the word god. He said this mechanism is so sophisticated and elaborate it couldn't have emerged through natural selection, through the blind workings of chance but god knows what happens if you pack one hundred billion nerve cells in such a tiny space, you may get new laws of physics emerging. Aha, that's how you explain language so he almost says it's a miracle although he doesn't use the word miracle. Now even if that's true we can't test it so let's throw it away. So then what actually happened? How did language evolve? I suggest the clue, the vital clue comes from the booba/kiki example, from synesthesia and I'd like to replace this idea with what I call the synesthetic boot-strapping theory of language origins, and I'll get to that in a minute.
So the next idea is Pinker's idea and his idea is look there's no big mystery here. You're seeing the final result of evolution, of language but you don't know what the intermediate steps are so it always looks mysterious but of course it evolved through natural selection even though we don't know what the steps were. Now I think he's right but he doesn't go far enough because as a biologist, we want the devils and the details. We want to know what those intermediate steps are, not merely that it could have happened through natural selection. Of course it happened through natural selection. There is nothing else so let's take the lexicon, words. How did we evolve such a wonderful huge repertoire of words, thousands of words? Did our ancestral hominoids sit near the fireplace and say, let's look at that. OK, everybody call it an axe, say everybody axe. Of course not! I mean you do that in kindergarten but that's not what they did. If they didn't do that, what did they do? Well what I'm arguing is that the booba/kiki example provides the clue. It shows there is a pre-existing translation between the visual appearance of the object represented in the fusiform gyrus and the auditory representation in the auditory cortex. In other words there's already a synesthetic cross-modal abstraction going on, a pre-existing translation if you like between the visual appearance and the auditory representation. Now admittedly this is a very small bias, but that's all you need in evolution to get it started and then you can start embellishing it.
But that's only part of the story, part one. Part two, I'm going to argue, there's also a pre-existing built-in cross-activation. Just as there is between visual and auditory, the booba/kiki effect, there's also between visual in the fusiform and the motor brocas area in the front of the brain that controls the sequence of activations of muscles of vocalisation, phonation and articulation - lips, tongue and mouth. How do I know that? Well let's take an example. Let's take the example of something tiny, say teeny weeny, un peu, diminutive - look at what my lips are doing. The amazing thing is they're actually physically mimicking the visual appearance of the object - versus enormous, large. We're actually physically mimicking the visual appearance of the object so what I'm arguing is that also again a pre-existing bias to map certain visual shapes onto certain sounds in the motor maps in the brocas area.
Lastly, the third factor - I think there's also a pre-existing cross-activation between the hand area and the mouth area because they are right next to each other in the Penfield motor map in the brain and let me give you an example, and I got scooped. Charles Darwin first described this. What he showed was when people cut with a pair of scissors you clench and unclench your jaws unconsciously as if to echo or mimic the movements of the fingers. He didn't explain why but I'd like to give it a name. I call it synkinesia - and that's because the hand and mouth areas are right next
