language

How are languages and genes related to each other? Anthropology is an interdiscipinary subject, and this is probably the topic that pushes that envelope the furthest, in terms of calling on the expertise of many different disciplines in the humanities and sciences.

As an organizing principle, many workers have begun with the hypothesis that languages and genes each form genealogical relationships among populations, and that the coevolution of languages and populations should make these genealogies resemble each other. In other words, French, Spanish, Portuguese and Italian all descend from Latin, and the present-day populations of France, Spain, Portugal, and Italy all descend from the population of the Roman Empire. Hence, the relations of the languages and the relations of the populations are parallel to each other.

This general idea is older than Darwin’s Origin of Species, but Darwin’s words on the subject have been quoted more often than anyone else’s:

Like many of Darwin’s words, however, these are generally pulled from the surrounding context without further discussion. The sentence actually serves as an example in Darwin’s defense of the phylogenetic tree as a description of relationships. In the previous paragraph, he points out that the similarities among different species cannot be made to fit any simple series. Instead, a hierarchical, genealogical arrangement can account for many of their similarities and differences. And after this sentence, he describes differences in rate of language change as an analogy for the evolution of organisms:

Thus, Darwin’s discussion—in which language relationships are an example—raises two separate issues: (1) Whether similarities are described by seriation or hierarchy, and (2) Whether differences arise at a constant or changing rate. His readers would have been aware of historical linguistics, including the observation that no ”Great Chain” of languages could be constructed out of grammatical and phonological changes that are manifestly hierarchical. Likewise, they would be familiar with two ancient languages that had manifested long-term stasis in a small community of speakers.

These points discussed by Darwin remain active elements of debate about the relationships of recent human languages and genes:

• How much of linguistic diversity is attributable to the genealogical relations among languages, and how much derives from horizontal modes of transmission, such as the borrowing of words and syntactic patterns?
• How often do populations undergo language shifts?
• How much of human genetic variation is attributable to ancient population divergences, and how much to recent gene flow?
• Are genes today the same as those present in ancient populations, or have they been replaced by selection or other demographic processes?

Each point considers a way that the genealogy of languages may come to differ from genetic relationships of populations. Within a single generation, there is a very high concordance between language and genes: People inherit their genes from their parents, and they tend to learn the same language as their parents. But only a slight mismatch in each generation may, over the course of many generations, add up to a huge difference in the histories of the two systems. And if those differences are biased in some direction, instead of random noise, then they may not only obscure the real history; they may strongly point to a false one.

To return to our example: French, Spanish, Portuguese, and Italian are not the only major Romance languages: there is also Romanian, for example. Romanians are genetically most similar to their neighbors in southeastern Europe, such as Serbs and Greeks—neither Romance speakers. In this case, population movements after the Roman period, such as the migrations of Slavic peoples, transformed the languages spoken in the Balkans without fundamentally altering the genetic similarities. And the persistence of Greek reminds us that the vast expansion of the Roman empire could not supplant some linguistic communities, and did not itself erase some earlier genetic patterns.

So should we expect the ”perfect pedigree” of human populations to resemble the genealogy of languages? It would help if there were factors that tended to reinforce such similarities instead of destroying them. We have to go beyond the simple statistical comparison of language and gene trees, which over enough time really shouldn’t resemble each other very much—at least, if the deviations in their evolutionary patterns are just noise. Instead, we have to consider how demography shapes genetic and linguistic transfer.

References

That's the question posed by Ronald Butters in a recent book review, discussed by Geoffrey Pullum at Language Log. The book is Language in the USA, edited by Edward Finegan and John Rickford. I don't get Language, but Pullum pulls this quote from Butters:

What they do not really explain is why [language extinction] is necessarily anything other than a rather good thing. Shouldn't we WANT to 'integrate' -- read 'absorb' -- these worthy people into mainstream economic and cultural life? Isn't it just inevitable? Isn't that why I am a member of the educated middle class and not mucking around without indoor plumbing in some Swedish monolingual farm community like my mother's grandparents? Yamamoto and Zepeda's answer (177), to someone who believes in the prevalent American linguistic ideologies, seems both effetely romantic and hideously self-serving: (a) 'When we lose a language, it means a "tremendous loss to the cultural richness and distinctness of the native communities" (Goddard 1996:3)'; and (b) 'the loss of linguistic diversity is a loss to scholarship and science'. Most of the students and other naifs who may be forced to read this book come from families who wear nice clothes and live in nice houses with numerous electronic appliances and good foreign cars in the driveway; most of the rest come from families who are struggling to find the means to live that way. Should people really be forced (or even encouraged) to 'preserve' languages if to do so might stand in their way of achieving middle-class comforts -- even if they get some vague additional promise of 'cultural richness' -- simply because linguists want to be able to study the living languages?

Pullum reflects on this point, paraphrasing it and calling for tolerance of this view:

In short, widespread faith in the ideal of linguistic and cultural assimilation should -- especially in a democracy -- be treated with respect and considered thoughtfully, not snapped at as if it were ignorant bigotry.

Which makes me sort of wonder just how sore this point is among linguists. The rest of Pullum's post emphasizes the diversity of attitudes attributed to linguists on this issue. He points out instances where linguists are painted as the "bad guys" because they have claimed that language extinction cannot possibly be stopped:

An odd coincidence is that in the week that this issue of Language reached me, the obituary of the week in The Economist (February 9th) was about Marie Smith, the last speaker of the now extinct language Eyak. But far from echoing anything like the tough-minded what-economic-benefit thinking that Butters alludes to, the Economist obituarist's discussion of the Eyak language, though well-written and interesting, is entirely devoted to sentimental musing about its many words for trees and roots and spruce needles and resin and abalone and nets and mixing bowls, and the way the word for "leaf" was the same as the word for "feather", as if that were the crucial thing we needed linguistic diversity for. It even adds, apropos of Marie Smith's dream of a future revival of the Eyak language: "impossible, scoffed the experts: in an age where perhaps half the planet's languages will disappear over the next century, killed by urban migration or the internet or the triumphal march of English, Eyak has no chance."

This post got picked up by Megan McArdle, guest-blogging at Instapundit, who added her own reflection:

LIKE MOST IRISH-AMERICANS, I have a sort of vague sentimental notion that the conversion of Ireland to an English-speaking nation is a linguistic and cultural tragedy. Like most Irish-Americans, I also would not want to actually live in a non-English-speaking nation. What I really want is to have learned Irish from my Grandmother, and be able to impress friends by ordering drinks in my ancestral tongue while on holiday. This is the sort of thing that makes my Irish friends complain--justly--that Irish-Americans would really like to see the whole country preserved as a sort of Colonial Williamsburg with shamrocks and twee wool caps.

Why is it that writing about linguistics brings out the witty language use? I guess I'm an exception, in not being especially inspired to write wittily about language. In fact, I have nothing original to say on this subject at all, but I think it's fascinating to read other peoples' takes on it.

McArdle's post got picked up by Confessions of a Language Addict:

Ironically, the French people whose culture is slowly destroying Breton culture are largely other people whose regional cultures were destroyed by the Paris-dominated version of French culture. If you root for the Bretons to make a comeback, do you also root for the Provençaux, the Alsatians, etc.? If you do, soon there's no such thing as French culture, and that prestigious world language you spent so much time learning is just the regional dialect of the middle of what Caesar called Gaul. That's no good!

It is true -- today's languages are inevitably the result of past language extinctions. Somehow people have an easier time imagining the complexity of the situation when they consider relict European languages -- but the issues are similar everywhere: power and economic participation favor strongly the adoption of already-common languages; tradition and community oppose the loss of distinctive dialects and languages. These forces interact in complicated ways: In some professions, a down-home southern accent may be a necessity; in others it's charming; in still others it's a career-killer.

We may say, "Sure, but the Normans, Bretons, and Burgundians got something much more for giving up their dialects than today's indigenous peoples are getting -- and those dialects and languages ultimately weren't nearly so distinctive as many native languages being lost today." But that's only obvious in hindsight, and is a highly selective view of history in any event. Did the Irish gain when Gaelic was suppressed? Sure, their descendants gained some things, but lost others -- including a degree of cultural isolation. More important, the things gained by the descendants were hardly the priorities of the ancestors.

But that's why our ancestors don't get to make our choices for us.

This week's Science has an interesting paper by Quentin Atkinson and colleagues, titled "Languages evolve in punctuational bursts." It's a brief communication, so there's no abstract, but here's the conclusion:

Our results, representing thousands of years of language evolution, identify a general tendency for newly formed sister languages to diverge in their fundamental vocabulary initially at a rapid pace, followed by longer periods of slower and gradual divergence. Punctuational bursts in phonology, morphology, and syntax, or at later times of language contact, may also occur. Linguistic founder effects could cause these rapid changes if newly formed languages emerge in small groups, such as in Austronesian. Alternatively, as the example of American English illustrates, speakers often use language not just as a means of communication but as a tool with social functions, including promoting cohesion and group identity (6, 7). Punctuational language change may thus reflect a human capacity to rapidly adjust languages at critical times of cultural evolution, such as during the emergence of new and rival groups.

They studied Bantu, Indo-European, Austronesian, and Polynesian language families, which leads to a possible criticism: each of these families is associated with one or more large-scale geographic dispersals, so how do we assess whether sheer distance is the cause of rapid changes instead of splitting by itself? I expect that they would respond that their method doesn't really test the difference between these scenarios (both being potentially "punctuational"), and therefore the details must be resolved by examining more language families.

Anyway, I think the most likely hypothesis for why languages might change quickly at or around their origin is that these times are the most likely to involve relatively small communities of speakers. In this case, different language families might share the feature that most changes occur near the time of language splitting, even though the families have different overall rates of change. That appears to be what the data show. Additionally, the effect of splitting might be less for groups that maintain smaller population sizes in between language splits. If this were true of the Austronesian language family, the data also would be consistent with this prediction.

Still, I wouldn't like to be in the position of trying to quantify language differences in all the categories this paper includes. It's a straightforward statistical analysis once you have the data, but these are hard data to acquire systematically in a comparable way.

References:

Atkinson QD, Meade A, Venditti C, Greenhill SJ, Pagel M. 2008. Languages evolve in punctuational bursts. Science 319:588. doi:10.1126/science.1149683

A short paper in this week's Nature finds that neurons in the human auditory cortex have an unusual capacity for perceiving small frequency differences:

Just-noticeable differences of physical parameters are often limited by the resolution of the peripheral sensory apparatus. Thus, two-point discrimination in vision is limited by the size of individual photoreceptors. Frequency selectivity is a basic property of neurons in the mammalian auditory pathway. However, just-noticeable differences of frequency are substantially smaller than the bandwidth of the peripheral sensors. Here we report that frequency tuning in single neurons recorded from human auditory cortex in response to random-chord stimuli is far narrower than that typically described in any other mammalian species (besides bats), and substantially exceeds that attributed to the human auditory periphery. Interestingly, simple spectral filter models failed to predict the neuronal responses to natural stimuli, including speech and music. Thus, natural sounds engage additional processing mechanisms beyond the exquisite frequency tuning probed by the random-chord stimuli.

The similarity with bats reminds me of a number of papers about FoxP2 -- although this is a totally different pathway. Is it about language?

This paper is totally full of jargon and extraordinarily difficult to read (and frequent readers know I wouldn't say that lightly!).

The main features are:

1. this is about the sensitivities of neurons in the auditory cortex of the brain, not anything about the ears or auditory nerves;

2. their mammalian comparisons include macaques but not apes, so it is not evident that this relates to recent human evolution (although it may);

3. the neuron responses seem to explain actual sensory acuity in humans:

These results are relevant to the apparent paradox of frequency hyperacuity demonstrated repeatedly in human psychoacoustics. Subjects with normal hearing, even untrained, successfully detect spectral differences substantially narrower than the presumed bandwidth of single auditory nerve fibres. Our results demonstrate that frequency differences smaller than 3% could be reliably detected from single-trial responses of single units in human auditory cortex. This value is comparable to the minimum detection threshold reported in untrained subjects. Thus, the responses of one of these cortical neurons could, in principle, underlie behavioural performance on a single-trial basis. Tramo et al. reported that bilateral lesions of human auditory cortex cause significant elevations in frequency discrimination thresholds, suggesting a functional role for the electrophysiological findings reported here.

4. the paper mentions that auditory fine-tuning may be related to language ability. In a press release, one of the authors suggested that the fine-tuning may be at too fine a level to be useful for language:

"This is remarkable selectivity," said Fried, who is also the co-director of UCLA's Seizure Disorder Center. "It is indeed a mystery why such resolution in humans came to be. Why did we develop this? Such selectivity is not needed for speech comprehension, but it may have a role in musical skill. The three percent frequency differences that can be detected by single neurons may explain the fact that even musically untrained people can detect such frequency differences."

I wouldn't be so quick with this interpretation. People may comprehend language despite many hearing challenges, but that doesn't mean there was no selection on hearing in association with language. Besides, speech includes a wide array of auditory information beyond words. The tonal qualities of a person's voice enable individual recognition. The fine tonal differences in a single person's speech indicate qualities such as emotional state. Plus, there are tonal languages, which may also advantage the perception of small pitch differences.

5. The last paragraph of the paper puts the auditory cortex into the context of other brain regions which have been found to have highly sensitive coding of responses in single neurons:

Previous studies in alert human subjects have shown very selective responses in single neurons from other brain areas. Notably, Quiroga et al. reported highly specific responses to individual people or landmarks from a subset of medial temporal lobe neurons, suggesting an invariant, sparse code. The high selectivity reported here may be a counterpart of the same phenomenon, resulting in a sparse coding of frequency in auditory cortex. We can only speculate why a low-level cue such as frequency is represented so explicitly and predominantly in single neurons of human auditory cortex but not in the auditory cortex of other terrestrial mammalian species.

This seems like a very interesting trend in brain research. New equipment and instrumentation allows researchers to register the outputs of single neurons, which explains why these kinds of results keep coming up recently.

If various kinds of brain processing are really organized into so-called "sparse arrays," we may need to re-evaluate the importance of gross anatomical features like brain size or the relative sizes of different brain areas. Very tiny levels of organization within brain regions may explain much of human brain evolution, with overall size -- or even the size of local regions -- being secondary.

This study also reminds us that selection on a complex structure like the brain may be accomplished along many different dimensions. Here, we see a change in the function of individual neurons, possibly enabled by local organization that functionally differentiates different neurons from each other. This is irrespective of larger structural changes to the auditory cortex, the size of the auditory cortex relative to other brain regions, the extent of lateralization of processing, or the size of the brain overall. It is also irrespective of the auditory nerve, the cochlear cells that receive sound, and the rest of the structures that influence acoustic properties of sound. Yet, every single one of those other pathways might also be targets of selection related to auditory processing; some stronger, and some weaker.

So it should be no wonder that it is hard for geneticists and neuroscientists to work these things out!

References:

Bitterman Y, Mukamel R, Malach R, Fried I, Nelken I. 2008. Ultra-fine frequency tuning revealed in single neurons of human auditory cortex. Nature 451:197-201. doi:10.1038/nature06476

HOMER: But I'm just one man. What can I do?

LISA: You can destroy that evil plant!

HOMER: But what can I do as an individual?

Last week, I wrote a bit about research into the affect of "gossip" in decision-making. By putting people in a situation where they played an economic game with a series of different opponents, the research found that people sometimes behaved as if short pieces of "gossip" about other players determined their decision-making much more than information about those players' past game play. In other words, a short opinion about another player from a third party was more influential than a long list of the other player's actual game history.

I wrote that it was likely a matter of priming:

The relevant point here is that the positive and negative "gossip" terms carry vastly less information than the statistics. And that's what makes them valuable. The choice before a given player is binary -- should you give your partner 1.25 or not? This choice is made vastly easier by the supply of a single bit of information -- is he a jerk, or not? You may be able to derive this information from the statistics, and if you trust someone else, you may make the wrong decision. But it's not hard to see that this experimental setup primes the players to seek a binary information source, the cost of a "wrong" judgment is pretty low, and there is no benefit in giving "wrong" advice.

Well, there's another context in which this kind of priming is important -- and it shows the same story from the opposite side. Razib points me to a paper about priming and charity-giving. In the paper, the authors -- Deborah Small and colleagues -- discover that donors respond poorly to statistical information. The abstract sums it up:

When donating to charitable causes, people do not value lives consistently. Money is often concentrated on a single victim even though more people would be helped, if resources were dispersed or spent protecting future victims. We examine the impact of deliberating about donation decisions on generosity. In a series of field experiments, we show that teaching or priming people to recognize the discrepancy in giving toward identifiable and statistical victims has perverse effects: individuals give less to identifiable victims but do not increase giving to statistical victims, resulting in an overall reduction in caring and giving. Thus, it appears that, when thinking deliberatively, people discount sympathy towards identifiable victims but fail to generate sympathy toward statistical victims.

In this experiment, the potential "donor" was either told a "Save the Children"-type story about a hungry child in Malawi, or she was told a set of statistics about the health toll of food shortages across Africa. The experimenters were interested in the extent to which personifying a crisis increased giving (the "poster child effect").

But what they discovered was surprising -- personifying a problem may increase giving, but giving statistical information depresses charitable giving, even when the problem is personified by a story about a victim:

Apparently, statistical information dampens the inclination to give to an identifiable victim. This result is consistent with the tendency to give less to an identifiable victim after learning about the discrepancy in giving. When jointly evaluating statistics and an individual victim, the cause evidently becomes less compelling. This could occur in part because statistics diminish the reliance on one’s affective reaction to the identifiable victim when making a decision (Small et al. 2007:149).

Of course, this observation is problematic if the proximate goal of charitable giving is to increase social welfare. However, if people give to make themselves feel better, then you would probably expect statistical information to reduce giving -- the main effect of statistical information being to show how small one person's contribution is compared to the size of the problem. In that vein, we should only expect huge donors like the Bill and Melinda Gates Foundation to respond positively to statistics. And indeed, Bill Gates makes malaria statistics a major focus of his public talks -- he has been swayed! For individual donors, you should expect person-to-person kinds of donation to be more effective: they match the individual effect to the same size of problem.

The commonality between this situation and the "gossip" situation is obvious: people use the available information to make decisions. When the amount of information approaches binary (hungry child bad, food good), the decision is more readily made. Introduce complicating factors, and the decision is much more complicated. Notice how those commercials never show the childrens' parents? Introducing that complicating factor provides information that would suppress giving.

In terms of charity, statistical information tends to integrate the problem more fully within a potential donor's worldview, and that's bad for giving. A dollar a day won't solve the hunger problem in Africa, but it will supply you with coffee. At least, non-Starbucks coffee. Those giant problems are the government's problem, anyway.

Stories about poster children are, naturally, propagandistic -- they provide a selected "frame" on the problem, excluding information likely to detract from giving. "Gossip" is often (but not always) propaganda on a personal level. The effect of both is to reduce information, not increase it.

I don't like the way that Small and colleagues frame their paper, by promoting charitable giving as "good" and a reduction in giving as "callousness." Failing to give charitably in response to statistical information is quite rational: people have their own problems, and when you bring their attention to the fact that their money will make a very small difference, it should be no surprise that they may prefer to keep their money! Perhaps charitable giving increases "social welfare," as the study assumes. But that assumes that the frequent resort to propaganda has no social costs.

References:

Small DA, Loewenstein G, Slovic P. 2007. Sympathy and callousness: the impact of deliberative thought on donations to identifiable and statistical victims. Organizational Behavior and Human Decision Processes 102:143-153. doi:10.1016/j.obhdp.2006.01.005

John Tierney describes some research into the effects of "gossip." In the experiments, subjects repeatedly played a simple money donation game with a series of different people. Well, I'll let Tierney describe:

On each turn, the players would be paired off, and one of them was offered a chance to give 1.25 Euros to the other. If he agreed, the researchers added a bonus of .75 Euro so that the recipient ended up gaining 2 Euros.

So far, so good. If you give 1.25 to the other player, you lose 1.25. If everybody is altruistic, then everyone comes out ahead. But in a single contest, a cheater always wins.

The trick with repeated contests is reputation: cheaters get a bad reputation, and so people stop giving them money. In this research, the experimenters provided two different kinds of information to the players: potential donors could see the record of the other player's previous games, and they could hear a comment from one of that player's previous partners -- something like "nice guy," or "jerk."

Given this information, people didn't make their decisions based only on the records: they rewarded players who had good "buzz."

The donor was told that the source of the gossip didn't have any extra information beyond what the donor could already see for himself. Yet the gossip, whether positive or negative, still had a big influence on the donors' decisions, and it didn't even matter if the source of the gossip had a good reputation himself. On average, cooperation increased by about 20 percent if the gossip was good, and fell by 20 percent if the gossip was negative.

Now, you might think the gossip mattered just in borderline cases -- when the partner had a mixed record of generosity, and the donor welcomed outside guidance in making a tough decision. But the gossip had an impact in other situations, too. Even when a player saw that his partner had a record of consistent meanness, he could be swayed by positive gossip to reward the partner anyway. Or withhold help from a perfectly nice partner just on the basis of malicious buzz.

But wait a minute. I didn't describe the "gossip" in quite the same way that Tierney did -- the German-speaking experiment used different words than "jerk" or "nice guy." And yet, what words in this situation are not going to elicit the same response -- a disproportionate response compared to the numerical record of the games?

The relevant point here is that the positive and negative "gossip" terms carry vastly less information than the statistics. And that's what makes them valuable. The choice before a given player is binary -- should you give your partner 1.25 or not? This choice is made vastly easier by the supply of a single bit of information -- is he a jerk, or not? You may be able to derive this information from the statistics, and if you trust someone else, you may make the wrong decision. But it's not hard to see that this experimental setup primes the players to seek a binary information source, the cost of a "wrong" judgment is pretty low, and there is no benefit in giving "wrong" advice.

To me, this has nothing to do with gossip and the evolution of language. You don't need language to convey binary information about somebody. Particularly in a primate group, where nobody is anonymous.

And if you don't need language, you certainly don't need math. Where in the world did anybody get the idea that people would be innately good at judging the statistical results of repeated trials of a game?

Seed is running a little article on the evolution of language, by lingust Juan Uriagereka:

A quasi-paradox has persisted within the field of linguistics, because the sudden emergence of such a complex, limitless system in a single species is hard to rationalize in terms of standard evolution. Its rapid spread makes language seem more like a viral epidemic that swept through the human population rather than a trait inherited through the typical dynamics of evolution.

Luckily, two recent advances have made it possible to rigorously address the problem of language's evolution for the first time. Molecular biology (including the publication of the human genome) and the so-called evo-devo paradigm now permit us to establish new and often quite unexpected connections among very different species. In addition, linguists' understanding of syntax -- how words are strung together into grammatical sentences—has developed to the point where language can be broken down into its basic procedural components. These components can now be seen to resemble traits observed in other species -- with functions that appear to be completely unrelated to familiar thought processes. Language may indeed be unique to humans, but the processes that underlie it are not.

It hits on many of the big topics, including the comparative biology of communication in finches, the regulatory role of FoxP2 in birdsong, and the brain processes underlying syntax.

I will differ from Uriagereka on this point:

The publication of the Neanderthal genome should tell us just how different their FoxP2 gene really is from our own.

Human FoxP2 differs from chimpanzees by two derived amino acid substitutions. If Neandertals were different from us (which seems likely, given the recent evidence of selection on the gene), then they would have had only one of these substitutions. It's an answer we don't actually need the Neandertal genome for. Now, if only we could start thinking about some other language-related genes.

It's the wonder gene that makes the mute birds sing, the mute mice squeak and the mute Neandertals talk. And now, we find out that it fights mosquitoes, too. Echolocation has selected for a variety of FoxP2 mutations in different lineages of bats, according to this PLoS ONE study by Gang Li and colleagues:

FoxP2 is a transcription factor implicated in the development and neural control of orofacial coordination, particularly with respect to vocalisation. Observations that orthologues show almost no variation across vertebrates yet differ by two amino acids between humans and chimpanzees have led to speculation that recent evolutionary changes might relate to the emergence of language. Echolocating bats face especially challenging sensorimotor demands, using vocal signals for orientation and often for prey capture. To determine whether mutations in the FoxP2 gene could be associated with echolocation, we sequenced FoxP2 from echolocating and non-echolocating bats as well as a range of other mammal species. We found that contrary to previous reports, FoxP2 is not highly conserved across all nonhuman mammals but is extremely diverse in echolocating bats. We detected divergent selection (a change in selective pressure) at FoxP2 between bats with contrasting sonar systems, suggesting the intriguing possibility of a role for FoxP2 in the evolution and development of echolocation. We speculate that observed accelerated evolution of FoxP2 in bats supports a previously proposed function in sensorimotor coordination.

This gene is a great example of the way that comparative and experimental genetics contribute to our understanding of genetic networks. FoxP2 was recognized as important to human language performance from traditional pedigree studies.

Then, comparative genetics showed that humans differ from chimpanzees at two amino acid sites, despite the fact that the sequence is strongly conserved in most vertebrates. That suggested positive selection on the gene sometime during human evolution.

Additionally, the distribution of variation around the gene in humans suggested that an adaptive variant swept to fixation sometime during the last 200,000 years. That is the only element of the story so far that has involved the genetics of populations, as opposed to phylogenetic comparisons.

These findings prompted experimental genetic work. FoxP2 knockout mice were created, and these mice vocalize less, in particular as juveniles.

Studies of the expression of FoxP2 during brain development show that, along with the similar FoxP1, it regulates the expression of other genes in ways that may regulate the integration between sensory information and movement. Humans share these expression patterns with songbirds (Teramitsu et al. 2004), and song-learning birds like zebra finches appear to have different patterns of FoxP2 expression from non-learning birds (Haesler 2004). Dolphins and whales also share amino acid substitutions relative to non-cetaceans, flanking one of the functional changes in the human sequence (Webb and Zhang 2005).

Still, we don't know exactly what the gene does, or why it is so conserved in non-vocal-learning species of vertebrates. It appears to interact with FoxP1 during cortical development, possibly guiding neuron migration. But as yet it is unclear what genes it may regulate, or what gives rise to its expression pattern. More experimental analysis of the knockouts may help unravel these problems, or statistical analysis of expression. Since it has changed recently in human evolution, we can expect that some of the genes in its interaction network probably changed as well.

References:

Enard W, Przeworski M, Fisher SE, Lai CS, Wiebe V, Kitano T, Monasco AP, Pääbo S. 2002. Molecular evolution of FOXP2, a gene involved in speech and language. Nature 418:869-872.

Haesler S, Wada K, Nshdejan A, Morrisey EE, Lints T, Jarvis ED, Scharff C. 2004. FoxP2 expression in avian vocal learners and non-learners. J Neurosci 24:3164-3175. doi:10.1523/JNEUROSCI.4369-03.2004

Li G, Wang J, Rossiter SJ, Jones G, Zhang S. 2007. Accelerated FoxP2 Evolution in Echolocating Bats. PLoS ONE 2(9): e900. doi:10.1371/journal.pone.0000900

Teramitsu I, Kudo LC, London SE, Geschwind DH, White SA. 2004. Parallel FoxP1 and FoxP2 expression in songbird and human brain predicts functional interaction. J Neurosci 24:3152-3163. doi:10.1523/JNEUROSCI.5589-03.2004

Webb DM, Zhang J. 2005. FoxP2 in song-learning birds and vocal-learning mammals. J Hered 96:212-216. doi:10.1093/jhered/esi025

The PNAS early edition is like a one-stop shop today. Here's a paper where the authors set up an experimental model for language origins:

The emergence of simple languages in an experimental coordination game

Reinhard Selten and Massimo Warglien

We investigate in a series of laboratory experiments how costs and benefits of linguistic communication affect the emergence of simple languages in a coordination task when no common language is available in the beginning. The experiment involved pairwise computerized communication between 152 subjects involved in at least 60 rounds. The subjects had to develop a common code referring to items in varying lists of geometrical figures distinguished by up to three features. A code had to be made of a limited repertoire of letters. Using letters had a cost. We are interested in the question of whether a common code is developed, and what enhances its emergence. Furthermore, we explore the emergence of compositional, protogrammatical structure in such codes. We compare environments that differ in terms of available linguistic resources (number of letters available) and in terms of stability of the task environment (variability in the set of figures). Our experiments show that a too small repertoire of letters causes coordination failures. Cost efficiency and role asymmetry are important factors enhancing communicative success. In stable environments, grammars do not seem to matter much, and instead efficient arbitrary codes often do better. However, in an environment with novelty, compositional grammars offer considerable coordination advantages and therefore are more likely to arise.

The subjects were given a small set of letters to work with, and a relatively large set of graphical symbols (I'll call them icons) to encode with the letters. The icons are illustrated in the paper; they sort of look like Kanzi-like ideograms. The players had to combine letters to attempt to communicate icons as they appeared on a screen, sending the letters across an anonymous channel with another player. Each player's correspondence of icons and letter-combinations amounts to a code. For this system to work as a communication between the two subjects, they had to arrive at some conventions, so that they would share the same code. The form and effectiveness of the conventions is what the researchers were trying to study.

Out of that abstract, this sentence strikes me as interesting: "Our experiments show that a too small repertoire of letters causes coordination failures."

Why should that be? In the experiment, the use of letters carried a cost to the sender -- like sending a telegram, charged by the letter. So short messages carry a higher payoff. But when there are very few letters to choose from, it is impossible to form many unique messages, unless the messages combine a lot of letters. So players supplied with a "small repertoire" of letters should try to economize communications by packing as many different combinations into as few letters as possible. And that leads to confusion, since messages will be minimally redundant and hard to remember. Give them more letters, and they can make many more combinations with shorter message lengths. Problem solved.

This is essentially an information theoretic explanation for why a large phoneme count is advantageous for human language, which the authors point out:

From a logical point of view, two symbols are sufficient for the construction of a code. In principle, communication could be based on a binary code. However, it seems to be the case that the availability of a sufficiently large variety of letters not only makes it easier to achieve communication efficiency but also has a cognitive effect that facilitates linguistic coordination (Selten and Warlien 2007:7363).

That's not a new insight, but it is interesting that, in these experiments, the value of a relatively large letter diversity is derived from the explicit per-letter cost of transmission together with an apparently greater comprehensibility of messages in systems that employed greater letter diversity. Both the learnability and transmission cost factors work in the same direction in the context of this experiment.

One essential ingredient to a successful game was, in a sense, hidden: two players trying to develop a common code could achieve a higher payoff in the long run if they very quickly differentiated their roles into a single "teacher" and a single "learner." In the context of the game, if both players tried to adjust to each others' codes, they would end up changing past each other, and mismatches still persisted. But if one player consistently changed and the other remained constant, every change tended to increase payoff by increasing the consistency between the two players' use of codes.

Last, the icons themselves were chosen by the experimenters to exhibit some similarities in form that might have been exploited by the players in forming their codes. For example, the symbol set included open circles and triangles, circles and triangles with dots in them, circles and triangles with plus signs in them, etc.

Some players ended up forming codes that randomly assigned sequences (generally pairs) of letters to these icons, irrespective of their shape. Every icon gets essentially a random one or two letters.

Some players arrived at codes in which all circles were encoded by a letter combination beginning with, say, "R", and all triangles by a combination beginning with, say, "S". The researchers considered these codes to be "grammatical", because the letter combinations had a clear syntactic structure with one position assigned to indicate the shape of the icon, and later positions other information.

Some players formed codes that were grammatical, assigning a position to the shape of the icon, and also assigned the same letter for any shape having the same inner sign. So every icon containing a plus sign might have a "M" as the second letter, and every one containing a dot might have a "Z" as the second letter. The researchers considered these grammars to be "compositional", because the two positions each encoded separate information, which when brought together communicated combined information in a consistent way across all icons.

In the context of the experiment, using a grammatical form for the code was somewhat costly, since it predicated that a certain number of letters be used for each figure regardless of the actual frequency with which they were presented.

By the most complicated phase of the experiment, which involved thirty-six different icons to encode with 10 letters, almost everybody who came up with a grammatical code also made it compositional. It just seems like if people were going to systematize their code by shape, they did it, well, systematically -- using different letters to encode different kinds of information about the icons independently. Since the players built up to this phase of the experiment with simpler systems of icons, the experimenters could observe what happened as things got more complicated. At the earlier stages, there were a number of different noncompositional grammars used, and all of them were chucked when things got complicated.

But still, in a majority of cases, the pairs of players still didn't arrive at a single code by the end of the trials. The researchers were interested that compositional grammars were successful in this phase of the experiment, which they interpreted as involving "novelty" since each icon was presented only once. Clearly there was a premium on a system that could get things right that hadn't been practiced, and only the "compositional" alternative really allowed that to happen in this context. The authors conclude:

(iii) In stable environments as those considered in point ii, grammar does not matter much, and efficient arbitrary codes often do better. However, compositional grammars have the advantage of being more easily extendable to broader environmental demands. Noncompositional grammars are more fragile and are easily lost if new conditions have to be met.

(iv) In an environment with novelty, in the sense that often the need arises to express something that never has been expressed before, compositional grammars offer considerable coordination advantages. Therefore, under such circumstances, compositional grammars are more likely to arise. In this respect, our findings parallel and complement hypotheses proposed in the literature on language evolution (28, 29). In our experiments, all subjects have grammatical competence but they make relatively little use of it unless pressure of novelty gives them an incentive to do so (Selten and Warglien 2007:7365).

Well, this experiment isn't enough to demonstrate all that, but the cost and incentive structure makes it an interesting addition to theoretical arguments favoring these points.

References:

Selten R, Warglien M. 2007. The emergence of simple languages in an experimental coordination game. Proc Nat Acad Sci USA 104:7361-7366. doi:10.1073/pnas.0702077104

I think this is just cool:

Shakespeare uses a linguistic technique known as functional shift that involves, for example using a noun to serve as a verb. Researchers found that this technique allows the brain to understand what a word means before it understands the function of the word within a sentence. This process causes a sudden peak in brain activity and forces the brain to work backwards in order to fully understand what Shakespeare is trying to say.

Professor Philip Davis, from the University's School of English, said: "The brain reacts to reading a phrase such as 'he godded me' from the tragedy of Coriolanus, in a similar way to putting a jigsaw puzzle together. If it is easy to see which pieces slot together you become bored of the game, but if the pieces don't appear to fit, when we know they should, the brain becomes excited. By throwing odd words into seemingly normal sentences, Shakespeare surprises the brain and catches it off guard in a manner that produces a sudden burst of activity - a sense of drama created out of the simplest of things."

Experts believe that this heightened brain activity may be one of the reasons why Shakespeare's plays have such a dramatic impact on their readers.

I wonder if there is a threshold involving people who can manage to get these quirks and others who can't. For that matter, you have to be fairly deep into the interpretation of a long-past culture in order to feel "in the world" of Shakespeare's plays to begin with. Your mind has to be willing to go a long way out of its usual experience to be ready to perceive Shakespearean prose. There are surely a lot of high school seniors who can't, or don't want to, go there. The idea that the prose itself contains features that reward this effort is no surprise, but it does help to explain the unique resonance. I wonder if Molière has the same effect on the French mind?

OK, maybe not mixmasters, exactly, but Mixing Memory does review this paper on marmoset reactions to human music by McDermott and Hauser, so I don't have to!

It's a good follow-up to my post from earlier this week, if you're interested in current research on the neuroscience and evolution of music abilities in humans.

Here's a quote from the conclusion of the paper to give an impression of why it is interesting.

However, despite the apparently aversive response monkeys have to many musical stimuli, we found for the first time evidence that they do have nontrivial preferences for some musical stimuli over others, and our results suggest that tempo is a critical variable.

Is the monkey response to tempo homologous to the human response to tempo? Further work is needed on this topic, but our results at least leave this possibility open. Humans obviously do not always prefer slow tempos to fast, but differences in temperament could cause tamarins and marmosets to find arousing stimuli aversive, whereas to humans they would merely be stimulating. Many stressful events in the natural environment, such as fights and storms, feature rapid sequences of acoustic events, and it is thus conceivable that animals have come to associate such stimuli with high levels of arousal. Future work using direct measures of arousal could provide further support for this hypothesis. It is also interesting to note that the alarm calls of tamarins and marmosets consist of short broadband bursts repeated at very high rates (Fig. 7 shows one such call from a tamarin). This acoustic structure is common to certain types of alarm calls in species ranging from monkeys and squirrels to birds (Marler, 1955), and could be related to the response nonhuman animals have to fast-tempo stimuli. Taken as a whole, however, the body of work on music perception in nonhuman primates suggests fundamental differences in the way they respond to musical stimuli compared to humans (McDermott and Hauser 2006:9-10).

That doesn't say too much about the necessary cognitive and perceptual processes that go into this kind of reaction -- whether aversive or not -- but it does suggest some relevant environmental noise analogues that might influence or constrain the reactions. One wonders whether playing their own chirps at a much higher tempo (part of the experiment) would be perceived in a threatening manner because of the combination of alienness and familiarity. Appropriate vocalizations themselves might change over time in natural groups, but they would in all cases be under selection to maintain appropriateness in constrast with their surroundings. So startlingly inappropriate vocalizations might be scary, even if their components were familiar -- sort of like seeing somebody on the street corner chanting gibberish.

So maybe studying these reactions in monkeys is question-begging. The real question is what about the human mind makes music compelling or attractive for people? We can say that whatever that is, these primates either don't have it or differ from humans sufficiently to make them not react the same way as humans to human music. But then, humans react quite differently to different brands of human music, in a way that is clearly culturally influenced if not completely culturally determined (and the balance between these alternatives is indeterminate).

Maybe it would be helpful to know if different populations of primates exhibit reactions that are comparably different to the differences in reactions to music among humans. We may not share the same affinities, but maybe we share similar dimensions of variability.

References:

McDermott J, Hauser MD. 2006 Nonhuman primates prefer slow tempos but dislike music overall. Cognition (in press) Preprint

Semenza et al. (2006) examined the mathematical abilities of aphasics with hemispheral dominance to determine which side of the brain is used for mathematical abilities. They found that the side with the language capability was always (at least in their sample) the one with math -- even when the language functions were lateralized on the right instead of the left side:

The main purpose of the present study was however to learn how mathematical functions are located in the brain with respect to language. Right hemisphere aphasia is a rare phenomenon and eight cases, including all the most classic varieties, represent a considerable sample. The assessment of language and calculation in this case series seems to suggest that, as a rule, the two functions share the same hemisphere. According to a more cautious interpretation, these data may just reveal that in case of right brain lateralisation of language some math sub-processes migrate with the language functions, whereas others remain located in the left hemisphere. How this would happen could be demonstrated only by studying cases of right hemisphere aphasia, in unambiguously right handers, fully assessed on math functions, suffering a further injury to the left hemisphere or submitted to a Wada test: the possibility of carrying out such study is obviously remote and the results would be only partially revealing. The present study shows however an incidence of numerical and calculation disorders in right hemisphere aphasia that is similar to that expected in aphasia resulting from left hemisphere damage. This seems enough evidence to suggest that, in right lateralisation for language, a considerable amount of math functions migrate to the same side. The reason for this anatomical proximity may lie in the fact that, as recently suggested [13], a primitive computational mechanism capable of recursion, thus constituting an open-ended and limitless system of communication needed for language and calculation, has evolved in the dominant hemisphere for reasons independent of both functions.

They argue that this connection is not merely because language itself is necessary for math:

[L]anguage and calculation abilities have been shown to dissociate at several levels, even though aphasia is most often accompanied by acalculic disorders [1], [8] and [12].

So they suggest that the two require common neural substrates that allow recursion. Personally, I'm guessing there is more to it than "recursion" for this connection with the linguistic areas to hold in this way. But then, I think "recursion" has become a bit of a catchall term for "syntax-ordering functions".

References:

Semenza C and 10 others. 2006. Is math lateralised on the same side as language? Right hemisphere aphasia and mathematical abilities. Neurosci Lett (in press) DOI link

Just taking some notes on a paper from last year by Helga Andresen, on the ways that role playing by preschool-age children can illuminate language and metacommunication development. I recognized a lot of my own children in the descriptions and examples.

Bateson (1955) postulates the existence of metalinguistic rules which determine how linguistic signs are related to non-linguistic entities like objects, persons, actions and places. These rules themselves, of course, cannot be linguistic in nature.

Bruner [1983] analyzed the development of mother-child interaction within the formats over many months and showed that the child constructs knowledge and anticipation of the interaction sequences and thus successively internalizes the structure of the format. This happens during the second half of the first year. First, the child adjusts his own vocalizations, miming and gestures to this structure until, more and more, he takes over the active part of the ongoing communication. Ritualization and repetition of the interaction make it possible for the child to recognize its structure. Above all, it is the close and fixed relations between verbal utterances and the non-verbal context that give children the chance to realize that the vocal activity of the mother refers to something beyond it and to realize the meanings of the utterances. Therefore the formats may be taken as an instantiation of those metalinguistic, non-verbal rules postulated by Bateson.

These considerations explain why early language use must be sympraxic; otherwise, children would have no chance to grasp the symbolic function of language (Andresen 2005:394).

Andresen has some fascinating examples where she documents interactions between children during roleplay, showing how much of the communication occurs within the roles and how much is metacommunication about the nature of the roleplay (a surprisingly large proportion).

The finding that older children produce less explicit metacommunication is of special interest. At first glance it may be surprising because from a scientific view it would be suggestive to propose that explicit metacommunication demands complex cognitive and communicative abilities which can be developed only on the basis of complex communicative skills which are beyond the scope of 4-year-old children. But metacommunication does not vanish out of play when children grow older; on the contrary, the pretend play of older children is much more complex than in the earlier years and contains a lot of transformations. Qualitative analyses of the older children's play in the Flensburg corpus show that they produce more implicit metacommunication than the younger ones. So, during the preschool period metacommunication changes from explicit to implicit performance (Andresen 2005:401-402).

A passage follows that discusses the complexity of carrying off implicit metacommunication -- which we may take as deliberately structuring communication in a form that itself more or less unambiguously conveys its context. In other words, implicit metacommunciation takes advantage of certain redundancies available in communication -- such as special same-meaning grammatical structures, gestures, tones, etc. -- to context-mark the communication.

Andresen then connects the progression from explicit to implicit in terms of Vygotsky's model of cognitive development:

According to [Vygotsky], internal mental processes arise out of external, interactive and communicative processes in earlier stages. He formulated this phenomenon as the transition from interpsychic to intrapsychic processes and functions during development (Andresen 2005:402).

And the subsequent section considers the development of egocentric speech along a similar timeline. Egocentric speech is inward-directed and regulatory in nature (with respect to actions); Andresen suggests a similar regulatory role for metacommunication. One might mention that egocentric speech has its own metacommunicative elements -- it being hard to mistake someone talking to herself for someone deliberately trying to communicate to others. In any event, this provides an opportunity to argue against simple word-object associations and in favor of the idea that roleplay indicates the ability to create linguistic (i.e., not here-and-now present) objects:

But an analysis of children's role plays clearly shows that already 4- year-olds are indeed able to create objects and meanings by linguistic means: for example, Aunt Maria, in the play of Hilde and Ingrid, who comes into existence through Hilde's utterance on the metacommunicative level and whose existence afterwards can be presupposed within the play. If the children could not create new meanings and communicate them to each other, role play could not take place at all (Andresen 2005:404).

There is a lot of detail in this article, related to the interchange of parent and child joint attention, the development of metacommunication skills in parent-child interactions, and the emergence of role playing as a way for children to take on adult roles they are normally not permitted. It relates well to Tomasello's work and Gregory Bateson's as well as Vygotsky, who is the model for much of the theory.

References:

Andresen H. 2005. Role play and language development in the preschool years. Culture and Psychology 11:387-414. DOI link

There's a study of handedness in baboon communicative gestures by Meguerditchian and Vauclair. Discovery News has a report about it (via Palanthsci). From the report, you wouldn't realize that these gestures themselves have been known from field studies for forty years. The new part is the evidence for lateralization, which is given as evidence for an ancient role of gestures in communication:

Since the right hand is controlled by the brain’s left hemisphere, which is the source of most linguistic functions, scientists believe communication by hand likely existed in apes 30 million years ago and was a forerunner to spoken and written language among people.

The last few paragraphs of the paper by Meguerditchian and Vauclair have several points to make in relation to communication and gesture. Here's the last, with the summary:

From a comparative viewpoint, regarding our results and the literature, we suggest the existence of a continuity between asymmetries of speech related gestures and asymmetries of communicative gestures in chimpanzees and now in baboons, even though the degree of population-level right-handedness is lower in non-human primates than in humans. From an evolutionary viewpoint, we suggest that the neuroanatomical substrate of manual communication controlled by the left cerebral hemisphere may have existed in their common ancestor at least 30 million years ago and may be considered as the precursor of the human language area. Our results hence bring additional support to the view that lateralization for language in humans may have evolved from a gestural system of communication lateralized in the left hemisphere (Meguerditchian and Vauclair 2006:173).

The right-handedness angle is, to me at least, much less interesting than the communication aspect. But the two are interrelated, as is made clear by the penultimate paragraph:

We thus suggest that the communicative functions of the hand could imply a different cerebral substrate than that involved in their manipulative functions: a communicatory left-hemisphere system may be involved for the production of gestures. This system would more strongly favor the use of the right hand than bimanual coordinations for object manipulations. Moreover, results from recent studies in chimpanzees that used RMI (magnetic resonance imaging) to investigate the neurobiological basis of handedness are convergent with this argument. In effect, it was found that asymmetries of homologous language areas did not correlate with handedness for non-communicative motor actions [13], but a significant correlation was shown between asymmetries in Brodmann's area 44 (homologous of Broca's area) and hand preferences for communicative gestures [12] (ibid.).

The idea is that brain lateralization for communication initiated hand preferences for communicative functions; these remain separate from manupulative functions in most anthropoids and therefore communicative functions are more highly lateralized.

On the other hand, given recent evidence that Broca's area and its right homologue are involved in all kinds of temporally sequenced hierarchical actions. It may be that communicative actions fit that category more often than manipulative actions for nonhuman primates.

If so, it would be of great interest to see whether complex, temporally sequenced manipulative actions -- like maybe extractive foraging -- require hierarchical temporal organization more than most other kinds of activities. Maybe there are logical connections between food extractive actions that require hierarchicalization and communicative actions. Maybe the anthropoid style of communication has emerged in part from brain functions developed originally for complex motor sequences.

Well, that's a lot of "maybes", and other scenarios could take form instead. For instance, most anthropoid communications themselves aren't very "hierarchical". The baboon hand gestures are not especially long or complex, nor are most vocalizations.

What kinds of communications are hierarchical? Some threat displays are fairly long and complex, and they also may use both vocal and visual channels. These characteristics have a communicative purpose: by emphasizing the threat message through long agonistic rituals and multichannel redundancy, the sender advertises sincerity. A threat that is perceived as insincere or unserious may be worse than no threat at all.

But there is another element to this: threat displays are long and complex in themselves because they are minimally interactive. They represent circumstances under which individuals wish to convey a clear message without interference or feedback. They are multichannel and long in part to dominate the bandwidth available for communications within the group. In other words, they demand attention because they impede other communications and interactions.

This points to a way that communication is always hierarchical -- it generally involves feedback. The sender is interested in whether other individuals receive the message, and may alter his or her further behaviors as a result. This may mean resending a message if there is no sign of its receipt; it may mean some other course of action depending on the signs emitted by the receivers.

That's the kind of context-dependent sequencing indicated by the Broca's area research I cited earlier. And it also would seem like the kind of context-dependent sequencing used for learning and executing complex manipulative sequences, like tool manufacture and use.

References:

Meguerditchian A, Vauclair J. 2006. Baboons communicate with their right hand. Behav Brain Res 171:170-174. DOI link

The lead report in Science this week was this paper by Dmitri Tymoczko, titled "The geometry of musical chords":

A musical chord can be represented as a point in a geometrical space called an orbifold. Line segments represent mappings from the notes of one chord to those of another. Composers in a wide range of styles have exploited the non-Euclidean geometry of these spaces, typically by using short line segments between structurally similar chords. Such line segments exist only when chords are nearly symmetrical under translation, reflection, or permutation. Paradigmatically consonant and dissonant chords possess different near-symmetries and suggest different musical uses (Tymoczko 2006:72).

Like a lot of things mathematical, the mathematical description of this is fairly distant from everyday experience. Cosmic Log provides a pretty good summary of the mathematical connections. This is pithy:

For years, string theorists have used music as a metaphor for fundamental particles, and now Tymoczko is using the mathematics of string theory to understand the fundamentals of music.

The next couple of paragraphs capture the essence of the work:

The math makes it easier to understand objectively what great musicians and composers do in their head. "When you sit down to interact with a piano, you're actually interacting with a non-Euclidean space, because there are many different ways you can play a C-major chord on a piano," Tymoczko said.

He said orbifolds capture the multidimensionality of music: how harmony interacts with counterpoint, how chords are connected with each other, even how notes are arranged "to minimize the amount of effort that musicians have to make when moving from chord to chord."

I think it helps to read a few different descriptions, and so I'm also linking the perspective in Science by Julian Hook, which includes some history, showing why Tymoczko's paper is part of a long tradition of mathematical application to music:

Mathematical music theory, although terra incognita to practicing musicians and even to many professional music theorists, has in recent years blossomed into a sizable and multifaceted industry. Pitch-class set theory (3), the study of a discrete 12-note quotient space, was developed as a means of confronting the analytical challenges posed by "post-tonal" music of the 20th century, whose harmonic materials are more varied and complex than those in most earlier music. Diatonic set theory (4, 5) investigates the subtle and beautiful relationship between the 12-note chromatic scale and diatonic scales such as the C major scale, with seven unequally spaced notes per octave (a scale type of great importance in many styles of music). Scale theory (6, 7) studies structural properties of scales and their subscales more broadly, allowing variation in both chromatic and diatonic cardinalities and occasionally engaging considerations of tuning and acoustics.

...

A particularly active area is neo-Riemannian theory, which synthesizes modern group-theoretic techniques with inspiration drawn from the work of the prolific German musicologist Hugo Riemann (1849-1919) and his contemporaries. In its basic form (9, 10), neo-Riemannian theory investigates certain transformational relationships among the 12 major and 12 minor triads in ways that are algebraically elegant, musically suggestive, and readily visualized in various forms of a graph known as a Tonnetz (tone network), in which the harmonic path traced by a musical composition may be plotted (Hook 2006:49-50).

In other words, musical progressions form paths or shapes in multidimensional spaces. Music that is part of the classical Western tradition actually falls within a fairly restricted set of possible paths; other musical traditions also form paths that to a greater or lesser extent overlap (although the dimensionality of the spaces may be different for different systems).

This seems very interesting from the perspective of how musical abilities emerged in the brain, and what relationship music may have to other mental functions or abilities. Whether by training or innate preference, human minds perceive certain classes of mathematical relationships among chords and note sequences as "special". We may describe this "specialness" in many different terms: "harmonic", "melodic", "musical", "cool", etc. Some of these paths have emotional resonance. Some of them have become loaded with cultural significance. Some of them communicate, either directly (through encoding) or indirectly (through redundantly providing additional context or mnemonics for texts of various kinds, including lyrics).

In all cases, the carriers for these cultural, emotional, or communicative aspects of music are the sequences of sounds themselves, which our minds apparently distinguish in accordance with their mathematical properties.

Science has visited this issue before, with a 2002 paper by Petr Janata and colleagues that attempted to localize the geometry of musical tonal structures in the prefrontal cortex:

Western tonal music relies on a formal geometric structure that determines distance relationships within a harmonic or tonal space. In functional magnetic resonance imaging experiments, we identified an area in the rostromedial prefrontal cortex that tracks activation in tonal space. Different voxels in this area exhibited selectivity for different keys. Within the same set of consistently activated voxels, the topography of tonality selectivity rearranged itself across scanning sessions. The tonality structure was thus maintained as a dynamic topography in cortical areas known to be at a nexus of cognitive, affective, and mnemonic processing.

Reading over that paper, they didn't really have anything concrete about how these brain areas may have functioned to facilitate this ultimately geometric processing, but they apply an explicitly geometric model (this one less string-theory-related!).

There has been quite a bit of work in the last few years attempting to relate these musical abilities (mostly without considering their geometric nature) to the processing of other functions -- particularly language and mathematics. This paper from last year by Koelsch and colleagues relates this point to how syntactic sequences in both music and language are processed in the brain:

Results demonstrate that processing of musical syntax (as reflected in the ERAN) interacts with the processing of linguistic syntax (as reflected in the LAN), and that this interaction is not due to a general effect of deviance-related negativities that precede an LAN. Findings thus indicate a strong overlap of neural resources involved in the processing of syntax in language and music.

Another study by Koelsch et al. last year examined which areas of the brain are associated with music processing in both adults and children, musically trained vs. not musically trained:

Subjects made judgements on sequences that ended on chords that were music-syntactically either regular or irregular. In adults, irregular chords activated the inferior frontal gyrus, orbital frontolateral cortex, the anterior insula, ventrolateral premotor cortex, anterior and posterior areas of the superior temporal gyrus, the superior temporal sulcus, and the supramarginal gyrus. These structures presumably form different networks mediating cognitive aspects of music processing (such as processing of musical syntax and musical meaning, as well as auditory working memory), and possibly emotional aspects of music processing. In the right hemisphere, the activation pattern of children was similar to that of adults. In the left hemisphere, adults showed larger activations than children in prefrontal areas, in the supramarginal gyrus, and in temporal areas. In both adults and children, musical training was correlated with stronger activations in the frontal operculum and the anterior portion of the superior temporal gyrus.

These studies both make use of the regular structure of music to elicit reactions in subjects to expected vs. nonexpected transitions. This is directly using those multidimensional geometric relationships, and probing which parts of the brain are sensitive to them, in a sense.

Music is not an isolated function, in exhibiting temporal structure. For example, there is this paper by Levitin and Menon:

The neuroanatomical correlates of musical structure were investigated using functional magnetic neuroimaging (fMRI) and a unique stimulus manipulation involving scrambled music. The experiment compared brain responses while participants listened to classical music and scrambled versions of that same music. Specifically, the scrambled versions disrupted musical structure while holding low-level musical attributes constant, including the psychoacoustic features of the music such as pitch, loudness, and timbre. Comparing music to its scrambled counterpart, we found focal activation in the pars orbitalis region (Brodmann Area 47) of the left inferior frontal cortex, a region that has been previously closely associated with the processing of linguistic structure in spoken and signed language, and its right hemisphere homologue. We speculate that this particular region of inferior frontal cortex may be more generally responsible for processing fine-structured stimuli that evolve over time, not merely those that are linguistic.

And as long as I am abstract-quoting, there is this paper investigating how musically-trained people may differ from non-musically-trained people in math processing:

The neural correlates of the previously hypothesized link between formal musical training and mathematics performance are investigated using functional magnetic resonance imaging (fMRI). FMRI was performed on fifteen normal adults, seven with musical training since early childhood, and eight without, while they mentally added and subtracted fractions. Musical training was associated with increased activation in the left fusiform gyrus and prefrontal cortex, and decreased activation in visual association areas and the left inferior parietal lobule during the mathematical task. We hypothesize that the correlation between musical training and math proficiency may be associated with improved working memory performance and an increased abstract representation of numerical quantities.

It's not clear to me from this reading whether there is a good case for music being secondary to other related functions like language -- although the commonality between the interpretation of syntactic structures of language and music suggests that one may have followed the other. That raises the interesting possibility that there may be an underlying geometric arrangement to phonetic information. The brain recognizes phonemes by contrast just as these musical sequences are defined by contrasts with each other, so it is plausible that there is a fundamental multidimensional model that includes both. Finding such commonalities would certainly clarify how the brain must handle such information, and would thereby provide much evidence about linguistic and musical (and possibly mathematical) evolution.

I am really less bullish on the possibility that our ostensive mathematical abilities may be related to language or music. There appears to be little in the way of mathematics that is basic to human cognition (such as might be shared cross-culturally, for instance), and much of what is there falls sort of generally into geometry, short counting sequences, and pattern-matching of various kinds. Music might certainly facilitate the learning of patterns -- and I could conceive this may underlie the so-called "Mozart effect" of greater math skills following musical exposure (although the effect itself may be a myth, see Bangerter and Heath 2004; Talero-Gutierrez et al. 2004). But I don't imagine that analytic geometry and music make more than incidental use of the same brain functions.

With music and language, on the other hand, I expect we'll hear a lot more about the connection between them.

References:

Bangerter A, Heath C. 2004. The Mozart effect: tracking the evolution of a social legend. Br J Soc Psych 43:605-623. DOI link

Hook J. 2006. Exploring musical space. Science 313:49-50. DOI link

Janata P, Birk JL, Van Horn JD, Leman M, Tillmann B, Bharucha JJ. 2002. The cortical topography of tonal structures underlying Western music. Science 298:2167-2170. DOI link

Koelsch S, Fritz T, Schulze K, Alsop D, Schlaug G. 2005. Adults and children processing music: an fMRI study. Neuroimage 25:1068-1076. PubMed

Koelsch S, Gunter TC, Wittfoth M, Sammler D. 2005. Interaction between syntax processing in language and in music: an ERP study. J Cogn Neurosci 17:1565-1577. PubMed

Schmithorst VJ, Holland SK. 2004. The effect of musical training on the neural correlates of math processing: a functional magnetic resonance imaging study in humans. Neurosci Lett 16:193-196. PubMed

Talero-Gutierrez C, Zarruk-Serrano JG, Espinosa-Bode A. 2004. Musical perception and cognitive functions: is there such a thing as the Mozart effect? Rev Neurol 39:1167-1173. PubMed

Tymoczko D. 2006. The geometry of musical chords. Science 313:72-74. DOI link

Jesper Hoffmeyer, in Signs of Meaning in the Universe (translated by Barbara Haveland):

When we became human beings, language ran its hyphae far into the nervous system allowing, today, no hope of excision -- not even in theory.