RECURSION AND HUMAN THOUGHT: WHY THE PIRAHÃ DON'T HAVE NUMBERS

The research question that has motivated my work for the last 25–30 years has been, what is the nature of language. This is the question that motivates most linguistics research. But I started off asking it one way and came to the conclusion that asking it that way was probably wrong and I now have a different way of approaching the problem.

My original concern was to think about Language with a capital "L." Human Language, what it's like in the brain, what the brain has to be like to sustain the capacity for Language. The most influential ideas for me in my early research were the ideas of Noam Chomsky, principally the proposal that there is an innate capacity for grammar in our genes, and that the acquisition of any given language is simply learning what the different parameter-settings are. What is a parameter?

Here's an example, called the "pro-drop" parameter. In English we always have to have a subject, even when it doesn't mean anything, like in "it rains"—"it" doesn't really refer to anything. "It" just is necessary because English has to have subjects. But in a language like Spanish or Portuguese, I don't say "it rains," I say just "rains"—chuva—in Portuguese, because Portuguese has a positive setting for the pro-drop parameter identified in Chomskyan research. All languages have either a positive (as Portuguese) or negative (as English) setting for this parameter. And it has other effects as well in addition to allowing a language to drop subjects; it entails a number of other characteristics.

It's a very attractive idea that people are born with a genetic pre-specification to set parameters in different ways, the environment serving as a "trigger." As Pinker put it, we have an instinct to learn language, and the environment triggers and shapes that instinct. But the environment is nothing more than that in this view—a shaper and a trigger; it is not fundamental to the actual final product in the Pinker-Chomsky view in the way that I have to come to think it actually is. Parameters and language as an instinct are very attractive ideas. Yet at the same time there are a number of components of languages that I've looked at that just don't seem to follow from these ideas.

The essence of human language is, according to Chomsky, the ability of finite brains to produce what he considers to be infinite grammars. By this he means not only that there is no upper limit on what we can say, but that there is no upper limit on the number of sentences our language has, there's no upper limit on the size of any particular sentence. Chomsky has claimed that the fundamental tool that underlies all of this creativity of human language is recursion: the ability for one phrase to reoccur inside another phrase of the same type. If I say "John's brother's house," I have a noun, "house," which occurs in a noun phrase, "brother's house," and that noun phrase occurs in another noun phrase, "John's brother's house." This makes a lot of sense, and it's an interesting property of human language.

But what if a language didn't show recursion? What would be the significance of that? First of all, it would mean that the language is not infinite—it would be a finite language, there could only be limited number of sentences in that language. It would also mean that you could specify the upper size of a particular sentence in that language. That sounds bizarre, until we think of something like chess, which has also got a finite number of moves, but chess is an enormously productive game, it can be played and has been played for centuries, and many of these moves are novel, and the fact that it's finite really doesn't tell us much about its richness, or its importance.

If there were a finite language, because of the lack of recursion, that wouldn't mean that it wasn't spoken by normal humans, nor would it mean that it wasn't a very rich source of communication. But if you lived in an environment in which culture restricted the topics that you talked about, and not only just your general environmental limitations on the topics you talked about, but if there were a value in the culture that said, don't talk about topics that go beyond, say, immediate experience—in other words, don't talk about anything that you haven't seen or that hasn't been told to you by an eyewitness—this would severely limit what you could talk about. If that's the case, then that language might be finite, but it wouldn't be a poor language; it could be a very rich language. The fact that it's finite doesn't mean it's not a very rich language. And if that's the case, then you would look for evidence that this language lacked recursion.

So in the case of Pirahã, the language I've worked with the longest of the 24 languages I've worked with in the Amazon, for about 30 years, Pirahã doesn't have expressions like "John's brother's house." You can say "John's house," you can say "John's brother," but if you want to say "John's brother's house," you have to say "John has a brother. This brother has a house." They have to say it in separate sentences.

As I look through the structure of the words and the structure of the sentences, it just becomes clear that they don't have recursion. If recursion is what Chomsky and Mark Hauser and Tecumseh Fitch have called "the essential property of language," the essential building block—in fact they've gone so far as to claim that that might be all there really is to human language that makes it different from other kinds of systems—then, the fact that recursion is absent in a language—Pirahã—means that this language is fundamentally different from their predictions.

One answer that's been given when I claim that Pirahã lacks recursion, is that recursion is a tool that's made available by the brain, but it doesn't have to be used. But then that's very difficult to reconcile with the idea that it's an essential property of human language—if it doesn't have to appear in a given language then, in principle, it doesn't have to appear in any language. If it doesn't have to appear in one part of a language, it doesn't have to appear in any part of a language.

It's not clear what causes recursion; in fact, just two weeks ago, at Illinois State University, we held an international conference on recursion in human language, which was the first conference of its kind ever held, and we had researchers from all around the world come and talk about recursion. One interesting thing that emerged from this is that the linguists, mathematicians and computer scientists disagree on what recursion is, and how significant it is. Also, there are many examples of recursion lacking in a number of structures in languages where we otherwise would expect it. So recursion as the essential building block of human language, if Chomsky's correct, is difficult for me to apply as an intellectual trying to build a theory of human language, because it's not clear what it is, and it's not clear that it is in fact essential to different languages.

So as an alternative, what might we say? Well, recursion could occur because human beings are just smarter than species without it. In fact, the Nobel Prize winning economist, Herbert Simon, who taught psychology for many years at Carnegie Mellon University, wrote an important article in 1962 called "The Architecture of Complexity," and in effect, although he doesn't use this word, he argued that recursive structures are fundamental to information processing. He argued that these are just part of the human brain, and we use them not just in language, but in economy, and discussion of problem-solving, and the stories that we tell.

If you go back to the Pirahã language, and you look at the stories that they tell, you do find recursion. You find that ideas are built inside of other ideas, and one part of the story is subordinate to another part of the story. That's not part of the grammar per se, that's part of the way that they tell their stories. So my idea is that recursion is absolutely essential to the human brain, and it's a part of the fact that humans have larger brains than other species. In fact, one of the papers at the recursion conference was on recursion in other species, and it talked about how when deer look for food in the forest, they often use recursive strategies to map their way across the forest and back, and take little side paths that can be analyzed as recursive paths. So it's not clear, first of all that recursion is unique to humans, and it's certainly not clear that recursion is part of language as opposed to part of the brain's general processing.

I am engaging in ongoing research on Pirahã, along with other researchers, including some from MIT's Brain and Cognitive Sciences department, led by Professor Ted Gibson, and other researchers from the University of Manchester. But my research is also part of a larger project funded by the European Commission, on characterizing human language by structural complexity, and the question we seek to answer there, with a number of researchers from Holland, Germany, and England, is, what is it that makes humans so smart, compared to other species? Is it just bigger brains? That might be the case. Or, are there particular ways that our brain operates that makes it very different from the way that other kinds of brains operate?

Recursion has been proposed in human thinking to be the way that we think that other animals don't. That's very much an open empirical question, but let's say that it's right, in which case recursion once again underlies human thought, but doesn't have to make the jump into human language. You could in principle have a human language that is constrained by the culture, so that the language proper lacks recursion, but the brain has recursion. And that's very difficult to reconcile with Chomsky's ideas on where recursion comes from. Chomsky's absolutely correct to recognize the importance of recursion, but the role that he gives it, and the role that Hauser and Tecumseh Fitch give it, to me has got things backwards. In other words, rather than going from language to the brain, we have to have recursion in language, and then it starts to make its manifestation in other thought processes. It starts in the thought processes and it might or might not jump to language. It does not seem to be an essential property of language, certainly not the essential property of language.

One prediction that this makes in Pirahã follows from the suggestions of people who worked on number theory and the nature of number in human speech: that counting systems—numerical systems—are based on recursion, and that this recursion follows from recursion in the language. This predicts in turn that if a language lacked recursion, then that language would also lack a number system and a counting system. I've claimed for years that the Pirahã don't have numbers or accounting, and this has been verified in two recent sets of experiments, one of which was published in Sciencethree years ago by Peter Gordon, arguing that the Pirahã don't count, and then a new set of experiments which was just carried out in January by people from Brain and Cognitive Sciences at MIT, which establishes pretty clearly that the Pirahã have no numbers, and, again, that they don't count at all.

So the evidence is still being collected, the claims that I have made about Pirahã lacking recursion and the fact that Pirahã is an evidence that there probably isn't a need for universal grammar. Contrary to Chomsky's proposal that universal grammar is the best way to think about where language comes from, another possibility is just that humans have different brains that are different globally from those of other species, that they have a greater general intelligence that can be exploited for all sorts of purposes in human thinking and human problem-solving. And one of the biggest problems we have to solve is how to communicate with other people—our conspecifics—and communication with our conspecifics is a problem that's often solved by recursion, but it doesn't have to be solved that way, it can be solved in other ways, especially in very small societies where so much information is implicit and held in common.

The ongoing investigation of these claims and alternatives to universal grammar, an architectonic effect of culture on grammar as whole, and the implications of this for the way that we've thought about language for the last 50 years are serious. If I am correct then the research so ably summarized in Steve Pinker's book The Language Instinct might not be the best way to think about things. Maybe there is no language instinct. So this is very controversial, and a lot more research has to be done. My colleagues and I are writing grants to test these claims. The only way that you can check out what I am saying is just to test the claims. Clearly formulate the claims and counterproposals, and go out and test them. If Everett's right, they ought to have this; and if he's wrong, we ought to find this. It's very simple conceptually to test the claims; you just have the logistical problems of the Amazon and a group that's monolingual and speaks no language but their own.

I don't think Pirahã is the only language that exhibits these qualities. What I think is that a lot of people are just like me in my beginning years of work there; they are given a set of categories to work with from their theories, and are told, these are the categories that languages have. So if you don't find a certain category, you just have to keep looking according to the theory. It takes a lot of courage, or, as in my case, frustration more than courage to say, Look, I'm not finding these things, so I'm just going to say they don't have the categories the theory predicts. Period. Say I am right about this. What are the implications?

I think that if we look at other groups—maybe groups in New Guinea and Australia, and some groups in Africa—what we have to find are groups that have been isolated, for various reasons, from larger cultures. The Pirahã's isolation is due to their very strong sense of superiority, and disdain for other cultures. Far from thinking of themselves as inferior because they lack counting, they consider their way of life the best possible way of life, and so they're not interested in assimilating other values.

They have another interesting value, which is "no coercion." That's one of the strongest Pirahã values; no coercion; you don't tell other people what to do.

I originally went to the Amazon to convert the Pirahã, to see them all become Christians, to translate the New Testament into their language. My only degree was an undergraduate degree from Moody Bible Institute in Chicago, and I went down there with the knowledge of New Testament Greek and a little bit of anthropology and linguistics.

When I first started working with the Pirahã, I realized that I needed more linguistics if I was going to understand their language. When I began to tell them the stories from the Bible, they didn't have much of an impact. I wondered, was I telling the story incorrectly? Finally one Pirahã asked me one day, well, what color is Jesus? How tall is he? When did he tell you these things? And I said, well, you know, I've never seen him, I don't know what color he was, I don't know how tall he was. Well, if you have never seen him, why are you telling us this?

I started thinking about what I had been doing all along, which was, give myself a social environment in which I could say things that I really didn't have any evidence for—assertions about religion and beliefs that I had in the Bible. And because I had this social environment that supported my being able to say these things, I never really got around to asking whether I knew what I was talking about. Whether there was any real empirical evidence for these claims.

The Pirahã, who in some ways are the ultimate empiricists—they need evidence for every claim you make—helped me realize that I hadn't been thinking very scientifically about my own beliefs. At the same time, I had started a Ph.D. program in linguistics at the University of Campinas in southern Brazil, and I was now in the middle of a group of very intelligent Brazilian intellectuals, who were always astounded that someone at a university doing a Ph.D. in linguistics could believe in the things I claimed to believe in at the time. So it was a big mixture of things involving the Pirahã, and at some point I realized that not only do I not have any evidence for these beliefs, but they have absolutely no applicability to these people, and my explanation of the universe.

I sat with a Pirahã once and he said, what does your god do? What does he do? And I said, well, he made the stars, and he made the Earth. And I asked, what do you say? He said, well, you know, nobody made these things, they just always were here. They have no concept of God. They have individual spirits, but they believe that they have seen these spirits, and they believe they see them regularly. In fact, when you look into it, these aren't sort of half-invisible spirits that they're seeing, they just take on the shape of things in the environment. They'll call a jaguar a spirit, or a tree a spirit, depending on the kinds of properties that it has. "Spirit" doesn't really mean for them what it means for us, and everything they say they have to evaluate empirically. This is what I hadn't been doing, and this challenged the faith that I thought I had, to the extent that I realized that it wasn't honest for me to continue to claim to believe these things when I realized how little investigation I had done into the nature of the things I claimed to believe.

I went to Brazil in 1977 as a missionary. I started my graduate program in 1979. By 1982, I was pretty sure that I didn't believe in the tenets of Christianity or any other religion or creeds based on the supernatural. But there's a social structure when you're a missionary, one that includes the income for you and your entire family as well as all of the relationships you've built up over the years. All the people you know and like and depend on are extremely religious and fundamentalist in their religion. It's very difficult to come out and say, "I don't believe this stuff any more." When I did say that, which was probably 13 years later, it had severe consequences for me personally. It's a difficult decision for anyone. I have a couple of friends whom I've told that it must be something like what it's like to come out as gay, to finally admit to your family that your values are just very very different from theirs.

My wife is still a missionary in Brazil to the Pirahã, and we've been separated for three years, and my view is pretty much irreconcilable with hers. It's difficult—it means that I don't go to that village when she's there. I don't go there and tell the Pirahãs not to believe in Jesus or anything like that. Actually I don't need to tell them that, because there's no danger that they ever will. They just find the entire concept—our beliefs—useless for them.

They wouldn't find the Pope remotely impressive; they would find his clothes very impractical, and they would find it very funny. I took a Pirahã to Brasilia, the capital of Brazil, for health reasons once, to go to a hospital, and I took him to the Presidential Palace. As the president of Brazil was coming out, there was all this fanfare and I said, That's the chief of all Brazilians. Uh huh. Can we go eat now? He was totally uninterested; the whole concept just sounds silly to them.

The first time I took a Pirahã on an airplane, I got a similar reaction. I was flying a man out for health reasons; he had a niece who needed surgery and he was accompanying her. We're flying above the clouds, and I know that he's never seen clouds from the top before, so I point down and I say, those are clouds down there. Uh huh. He was completely uninterested; he acted like he flew in planes every day. The Pirahã are not that curious about what we have. They haven't shown interest in a number of things that other indigenous groups, even Amazonian groups, that have come out and had contact with in civilization for the first time are curious about. The Pirahã have been in regular contact for a couple of hundred years now, and they have assimilated almost nothing. It's very unusual.

The reason that I believe that the Pirahã are like this is because of the strong cultural values that they have—a series of cultural values. One principle is immediacy of experience; they aren't interested in things if they don't know the history behind them. If they haven't seen it done. But there's also just a strong conservative core to the culture; they don't change, and they don't change the environment around them much either. They don't make canoes. They live on the river, and they depend on canoes for their daily existence—someone's always fishing, someone's always crossing the river to hunt and gather—but they don't make canoes. If there are no Brazilian canoes, they'll take the bark off a tree and just sit in that and paddle across. And that's only good for one or two uses.

I brought in a Brazilian canoe master, and spent days with them and him in the jungle; we selected the wood, and made a dugout canoe. The Pirahã did all the labor—so they knew how to make a canoe, and I gave them the tools—but they came to me and they said, we need you to buy us another canoe. I said, well we have the tools now, and you guys can make canoes. But they said, Pirahã don't make canoes. And that was the end of it. They never made a canoe like the Brazilians, even though I know that some of them have the skills to do that.

In the 1700s, the first Catholic mission to the Amazon area made contact with the Pirahã and the related people, the Muras, and abandoned them after a few years as the most recalcitrant group they had ever encountered. Other missionaries have worked with the Pirahã since then. Protestant missionaries have worked with them since about 1958, and there's not a single convert, there's not a single bit of interest.

A lot of people say that I'm a failure as a missionary. A lot of missionaries say I'm a failure—my ex-wife thinks I'm a failure as a missionary—and the reason they give is, I don't have enough faith. If you have enough faith, the story goes, God will overcome all of these things. But if you say that you should know that god is up against some serious cultural barriers. The Pirahã have a cultural taboo against talking about the world in certain ways, and the Christian message violates these.

They have the other cultural value against coercion that I mentioned. Religion is all about coercion—telling people how they should live and giving them a list of rules to live by—and the Pirahã just don't have coercion in that form. If someone were really violent and disrupted the entire life of the community, they would be ostracized; they might even be killed. But that would be a very serious pathological case in the culture. By and large, they tolerate differences, and even children aren't told what they have to do that much. Life is hard enough; if children don't do what they have to do, they'll go hungry. There's just no place for the Western concept of religion in their culture at all.

When a group receives this much publicity; you get different reactions. First of all, you get a lot of people who want to go there and investigate, until they see how difficult it is to get there, and how in fact they don't speak Portuguese and it's going to take a couple of years to be able to communicate with the Pirahã, even at a fairly simple level. This discourages people.

There are also a number of people who are upset that the group that they've been working with for 10 or 15 or 20 years didn't get any publicity. Scientists—linguists and anthropologists in particular—are very reticent to say that one group is somehow more special than another group because if that's the case, then you've made discoveries that they haven't made. I really think that's probably right. I don't think the Pirahã are special in some deep sense. They're certainly very unusual, and they have characteristics that need to be explained, but all of the groups in the Amazon have different but equally interesting characteristics. I think that one reason we fail to notice, when we do field research, the fundamental differences between languages is because linguistic theory over the last 50 years—maybe even longer—has been primarily directed towards understanding how languages are alike, as opposed to how they are different.

If we look at the differences between languages—not exclusively, because what makes them alike is also very very important—the differences can be just as important as the similarities. We have no place in modern linguistic theory for really incorporating the differences and having interesting things to say about the differences. So when you say that this language lacks X, we will say, well, that's just an exotic fact: so they lack it, no big deal. But when you begin to accumulate differences across languages around the world, maybe some of these things that we thought were so unusual aren't as unusual and could in fact turn out to be similarities. Or, the differences could be correlated with different components that we didn't expect before. Maybe there's something about the geography, or something about the culture, or something about other aspects of these people that account for these differences. Looking at differences doesn't mean you throw your hands up and say there's no explanation and that you have nothing more than a catalog of what exists in the world. But it does develop a very different way of looking at culture and looking at language.

Missionaries have gone to the Pirahãs, learned their language more or less, and then left after a few years. There is a Brazilian anthropologist, Marco Antonio Gonçalves, who teaches at the University of Rio. He spent 18 months off and on working with them, and he speaks the language at a very basic level. The tones are part of what make it so difficult for people who haven't had a lot of linguistic training, but it's just like Chinese, or Vietnamese, or Korean, in the fact that the tones are very important to the meanings of the words. This is really difficult for a lot of researchers without a significant linguistic background. I now have two researchers working with me from the University of Manchester: a Ph.D. student who's writing her Ph.D. on recursion or the absence thereof among the Pirahã; and a postdoc on a grant of mine whose research is looking at how well the Pirahã speak Portuguese, and if they do know some Portuguese, what kinds of grammatical characteristics does it have—does their Portuguese show anything that violates what I say about Pirahã itself? Both of these people, Jeanette Sakel and Engenie Stapert, are learning Pirahã, and I've encouraged them to learn the language, and given them some lessons.

What happens is with some people is that they go to the Pirahãs with me and I translate for them and help them get going. For people who do ongoing research of their own—many people have gone to the Pirahã with the idea that they're going to develop a multi-year research program and I'm going to be their partner every time they go.

I don't have the time to go with every researcher who wants to work with the Pirahã; I have my own research agenda. I've tried to help them to start learning the language, and most people sort of disappear after that. Tecumseh Fitch went with me last summer and he would like to go again, and maybe he will. But I think that the best way for anyone to go again is to invest the time to learn enough of the language to do their own research. There's also the fact that if anybody has to go with me, people can then say that my influence is so pervasive that you could never test what I'm saying, because I'm behind every single experiment.

Peter Gordon and I were colleagues at the University of Pittsburgh, and Peter did his Ph.D. at MIT in psychology, with a strong concern for numerosity. We were talking, and I said, there's a group that doesn't count—I work with a group that doesn't count—and he found that very difficult to believe, so he wanted to go do experiments. He went, and I helped him get going; he did the experiments, but his explanation for the reason that the Pirahã don't count is that they don't have words for numbers. They only have one to many. I claim that in fact they don't have any numbers. His idea is that the absence of counting in Pirahã has a Whorfian explanation—that there's a linguistic determinism: if you lack numbers, you lack counting—that is, that the absence of the words causes the absence of the concepts. But this really doesn't explain a lot of things. There are a lot of groups that have been known not to have more than one to many—as soon as they got into a relationship where they needed it for trade, they borrowed the numbers from Portuguese or Spanish or English or whatever other language.

The crucial thing is that the Pirahã have not borrowed any numbers—and they want to learn to count. They asked me to give them classes in Brazilian numbers, so for eight months I spent an hour every night trying to teach them how to count. And it never got anywhere, except for a few of the children. Some of the children learned to do reasonably well, but as soon as anybody started to perform well, they were sent away from the classes. It was just a fun time to eat popcorn and watch me write things on the board. So I don't think that the fact that they lack numbers is attributable to the linguistic determinism associated with Benjamin Lee Whorf, i.e. that language determines our thought—I don't really think that goes very far. It also doesn't explain their lack of color words, the simplest kinship system that's ever been documented, the lack of recursion, and the lack of quantifiers, and all of these other properties. Gordon has no explanation for the lack of these things, and he will just say, "I have no explanation, that's all a coincidence."

Some people have suggested that since this a small society it's not unreasonable to hypothesize that there's a lot of inbreeding, and that this has made one particular gene much more prevalent in the society. Maybe Pirahã uniqueness is genetic in origin. People have asked me to do DNA tests, but my research has already been attacked for being borderline racist, because I say that the people are so different. So the last thing that I want to do is be associated with DNA testing. Somebody else can go there and do that. I don't think they have a closed gene pool, even though it's a small group of people. River traders come up frequently, and it's not uncommon for Pirahã to trade sex for different items off the boat that they want. So I don't think that genetics is relevant at all here.

Most inhabitants of the Brazilian Amazon are descended from Brazilian Indians, but now they would just consider themselves Brazilians. The Brazilians the Pirahãs most often see have boats, and they just come up the Pirahãs' river to buy Brazil nuts. In exchange, they bring machetes, gunpowder, powdered milk, sugar, whiskey and so forth. The Pirahãs are usually interested in acquiring these things. They don't accumulate Western goods, but if you've got consumables, the Pirahã might buy, say, two pounds of sugar, pour it in a bowl and eat it all at once. They're not going to put it on the shelf and save it; they'll just eat it when they get it.

It depends on the river trader, but sex is also a very common trade item. So you see these foreign babies being raised among the Pirahã. It's mainly the husband who works out the deal. Single women can negotiate on their own; wives wouldn't make that offer unless their husband negotiated it. In their dealings with outsiders, men take the lead, and the women won't usually come around unless they're called by Pirahã men. But promiscuity is not a problem for the Pirahã. It doesn't violate any values that they have.

I remember one time sitting in a hut with the Pirahã and they came and they said, we understand that you want to tell us about Jesus and that Jesus tells us that we should live certain ways. Since you love Jesus, this is an American thing—but we don't want to live like you. We want to live like Pirahã, and we do lots of other things that you don't do, and we don't want to be like you. They've noticed these characteristics, and they much prefer to have the values that they have.

The paper I wrote that has attracted all the attention is "Cultural Constraints on Grammar and Cognition in Pirahã," published in the anthropology journal, Current Anthropology, in 2005. It would have been almost impossible to get this article—for one thing, it was 25,000 words, and for another thing it was so controversial—in a linguistics journal. Also, I chose this journal because it has a much higher circulation than any linguistics journal. And also the anthropology journal Current Anthropology invites commentators, a feature I really like. In my case, they had eight well-known linguists and anthropologists and psychologists comment on the paper. And the press picked up on it. You can never predict, obviously, when the press is going to pick up on something. But it started getting reported in magazines. And a lot of it was twisted; it wasn't exactly what I said, but it got a lot of play on radio, was in a lot of magazines. And everyone had the spin that this was—in fact I say it in the article—that this is a very strong counter-example to the kinds of claims that Chomsky makes. And I knew that there would be a response eventually, as it got more and more press.

David Pesetsky is a professor at MIT, Andrew Nevins was a student at MIT who now holds a temporary appointment in Linguistics at Harvard, and Cilene Rodrigues is a Brazilian linguist who I think is doing her Ph.D. at MIT. They decided that they would write a reply to my article. The interesting thing is that I'm the main source of data on Pirahã. Now, the best way to check out what I'm saying would be to get some research funds to go down there and do experiments and test this stuff. But what they decided to do was to look at my doctoral dissertation, and where I describe the grammar of Pirahã, and find inconsistencies between my doctoral dissertation and what I'm saying now. And there are some. And I say in the Current Anthropology article that there are inconsistencies, and that the 2005 article supersedes my previous work. And all of those decisions to change my mind on this or that analytical point were based on a lot of thought about what I had said previously and how it compared to my current knowledge.

My doctoral dissertation was written when I was using a certain set of grammatical categories common among most linguists, and I did my very best to make Pirahã come out and look like a "normal" language. So there are a couple of small examples of things that look like recursion in my doctoral dissertation. In fact I call them that. So the authors of the rebuttal dwell on these discrepancies. And then they try to counter my claims in the paper. Also, they refer to some unpublished studies by Steven Sheldon in which it is claimed that Pirahã has color words and number words. And they refer to an introduction to a dissertation on Pirahã that says that they speak Portuguese. And you do find these things in the studies they cite. But these are all written by people who either were not professional linguists, or who didn't speak the language. If you take the color words, Sheldon did in fact claim that the Pirahã had color words. But if you look at them, "mii sai," which he translated as "red," means "like blood." All of the color words in fact are just descriptions. This looks like blood, this looks like water, this looks like the sky, or this looks like a fire, or something like this. There can be any number of expressions. With regard to their ability to speak Portuguese, the Pirahã men do understand very simple Portuguese, just enough to trade with the river traders. Now if I went to Paris, I could probably get directions to the nearest bathroom, but that doesn't mean I speak French. I don't. That's roughly the Pirahãs' level of Portuguese.

So Pesetsky, Nevins, and Rodrigues were very careful in their criticisms, they worked very long and hard, they took months to do this. Then they posted it to a Web site called Ling Buzz, and it started being downloaded because of all the press on Pirahã—in the first few days there were 700 downloads. Every day it's getting dozens more downloads. I was actually trying to write something else at the time when I saw the reply, but I reluctantly put that aside to reply to their work. I replied to them point by point. The only part of their article that irritated me was the insinuations that because I focused on negative aspects of Pirahã, I was perhaps racist. They didn't use the term "racist," but they insinuated that I might have a negative view of the Pirahã as a people because I was only focusing on the gaps in the language. But I pointed out that I published over 40 articles on Pirahã, and a book, and that all of those mainly talked about things they did have, not the gaps that they had. I put my reply on Ling Buzz, that's now the top-loaded paper on Ling Buzz, so those two papers are still getting downloaded a lot, and there's a debate going on. I don't know if they're planning a reply to my reply, but the way things go, they probably are.

When I saw this, I wrote the three of them, and I said, you've put me in the interesting situation of pitting Dan Everett at 55 against Dan Everett at 26. Because, I said, all the data you use are my data. So I'll just have to explain why when I wrote my doctoral dissertation I didn't know as much about Pirahã as I know now. Their objection is that even though I published extensively, I haven't published on all of these things previously. And so one of the many projects that I'm engaged in right now, along with several other people, mainly this group of researchers at MIT, Brain and Cognitive Sciences, is an experimental grammar of Pirahã, where we basically rewrite the grammar of Pirahã and do experiments to substantiate or test as many points as we can. If I had written all of this before I came out with the claims, I would never have come out with the claims. You have to make the claims and see the controversies, see what people say about them, to be sure you have the data. So I turned over all of my data to other researchers, and they're in the process of digitizing it, and eventually all these data will be on the Web, translated—it'll take a couple of years, but then you won't actually have to go to the Pirahã, you can look at the data, and you can search through the data and see if you can find counter-examples, or find other things that I've missed, and I'm sure people will.

When I was interviewed for Der Spiegel, I was at the Max Planck Institute for Evolutionary Anthropology in Leipzig, and my next-door neighbor was Tecumseh Fitch. We were talking about this quite a bit—he was my next-door neighbor both at the Institute and in the apartment building that we lived in, so we talked quite a bit, and went out a few times—and he made a comment about the fact that he didn't really believe the significance of what I was saying to the Der Spiegel reporter, and so I wrote a reply to him, copying Noam Chomsky and Mark Hauser. And I actually thought that Tecumseh would be the one to respond, because that's who the letter was directed to, but in fact I immediately got a long response from Chomsky, followed by other long emails.

Initially it was a very interesting exchange. I know Noam fairly well, I've known his work most of my career and I've read everything he's ever written in linguistics—I could have written his responses myself. I don't mean to be flippant, but they were re-statements of things that everybody knows that he believes. I think that it's difficult for him to see that there is any alternative to what he's saying. He said to me there is no alternative to universal grammar; it just means the biology of humans that underlies language. But that's not right, because there are a lot of people who believe that the biology of humans underlies language but that there is no specific language instinct. In fact at the Max Planck, Mike Tomasello has an entire research lab and one of the best primate zoos in the world, where he studies the evolution of communication, and human language, without believing in a language instinct or a universal grammar.

I've mainly followed Mike's research there because we talk more or less the same language, and he's more interested in directly linguistic questions than just primatology, but there's a lot of really interesting work in primatology—looking at the acquisition of communication and finding similarities that we might not have thought were there if we believe in a universal grammar.

I think that the way that Chomskyan theories developed over the last 50 years has made it completely untestable now. It's not clear what usefulness there is in the notion of universal grammar. It appeals to the public at large, and it used to appeal to linguists, but as you work more and more with it, there's no way to test it—I can't think of a single experiment—in fact I asked Noam this in an e-mail, what is a single prediction that universal grammar makes that I could falsify? How could I test it? What prediction does it make? And he said, It doesn't make any predictions; it's a field of study, like biology.

Now that is not quite right. No scientist can get by without believing in biology, but it's quite possible to study human language without believing in universal grammar. So UG is really not a field of study in the same sense. I think the history of science shows that the people who develop a theory and who are responsible for the development of the theory are rarely the people who come forward and say: whoops, I was wrong, we need to actually work at it another way, this guy over here had the right idea. It's rare for that to happen. Noam is not likely to say this.

I want to have well-designed experiments to test my claims on recursion; I want to have mores studies of the Pirahã grammar from people working outside my influence. The more people who can look at this independently, the more likely it is that others are going to start to believe this, because I think it's going to be shown to be correct. If it's wrong, that's also important. The tests have to be done, and then if there is evidence that I might be onto something, we have to look at other languages. And other languages in similar situations where they've been cut off for one reason or another from outside influences for long periods of time. And re-examine those languages in light of the possibility that languages can vary more than we thought. And maybe the categories that we have aren't the best categories.

We need more fieldwork. Linguists have gotten away from fieldwork over the last 50 years. There's more interest in endangered languages now than there was a few years ago, but there's just now beginning to be a resurgence of the field work ethic among linguists, and the idea that we can't figure out everything that we need to know just by looking at grammars that have been written, without going and seeing the language in the cultural context.

And that's really the biggest research question that I have for the future: What evidence is there that culture can exercise an architectonic effect on the grammar —that it can actually shape the very nature of grammar, and not simply trigger parameters.