Steven Pinker: Linguistics as a Window to Understanding the Brain

{“en”:”My name is Steve Pinker, and Iu2019m Professor of Psychology at Harvard University.  And today Iu2019m going to speak to you about language.  ufeffIu2019m actually not a linguist, but a cognitive scientist.  Iu2019m not so much interested as language as an object in its own right, but as a window to the human mind.ufeff Language is one of the fundamental topics in the human sciences.

 Itu2019s the trait that most conspicuously distinguishes humans from other species, itu2019s essential to human cooperation; we accomplish amazing things by sharing our knowledge or coordinating our actions by means of words.  It poses profound scientific mysteries such as, how did language evolve in this particular species?  How does the brain compute language? But also, language has many practical applications not surprisingly given how central it is to human life. ufeff Language comes so naturally to us that weu2019re apt to forget what a strange and miraculous gift it is.

 But think about what youu2019re doing for the next hour.   Youu2019re going to be listening patiently as a guy makes noise as he exhales.  Now, why would you do something like that?  Itu2019s not that I can claim that the sounds Iu2019m going to make are particularly mellifluous, but rather Iu2019ve coded information into the exact sequences of hisses and hums and squeaks and pops that Iu2019ll be making.  You have the ability to recover the information from that stream of noises allowing us to share ideas. Now, the ideas we are going to share are about this talent, language, but with a slightly different sequence of hisses and squeaks, I could cause you to be thinking thoughts about a vast array of topics, anything from the latest developments in your favorite reality show to theories of the origin of the universe.

 This is what I think of as the miracle of language, its vast expressive power, and itu2019s a phenomenon that still fills me with wonder, even after having studied language for 35 years.  And it is the prime phenomenon that the science of language aims to explain.  ufeff Not surprisingly, language is central to human life.  The Biblical story of the Tower of Babel reminds us that humans accomplish great things because they can exchange information about their knowledge and intentions via the medium of language.  Language, moreover, is not a peculiarity of one culture, but it has been found in every society ever studied by anthropologists.ufeff Thereu2019s some 6,000 languages spoken on Earth, all of them complex, and no one has ever discovered a human society that lacks complex language.  For this and other reasons, Charles Darwin wrote, u201cMan has an instinctive tendency to speak as we see in the babble of our young children while no child has an instinctive tendency to bake, brew or write.u201d ufeff Language is an intricate talent and itu2019s not surprising that the science of language should be a complex discipline.

ufeffIt includes the study of how language itself works including:  grammar, the assembly of words, phrases and sentences; phonology, the study of sound; semantics, the study of meaning; and pragmatics, the study of the use of language in conversation. ufeff ufeffScientists interested in language also study how it is processed in real time, a field called psycholinguistics; how is it acquired by children, the study of language acquisition.  And how it is computed in the brain, the discipline called neurolinguistics. ufeffu2028 Now, before we begin, itu2019s important to not to confuse language with three other things that are closely related to language.  One of them is written language.  Unlike spoken language, which is found in all human cultures throughout history, writing was invented a very small number of times in human history, about 5,000 years ago.

 ufeff And alphabetic writing where each mark on the page stands for a vowel or a consonant, appears to have been invented only once in all of human history by the Canaanites about 3,700 years ago.  And as Darwin pointed out, children have no instinctive tendency to write, but have to learn it through construction and schooling.ufeff A second thing not to confuse language with is proper grammar.

 Linguists distinguish between descriptive grammar – the rules, that characterize how people to speak – and prescriptive grammar – rules that characterize how people ought to speak if they are writing careful written prose.  ufeff A dirty secret from linguistics is that not only are these not the same kinds of rules, but many of the prescriptive rules of language make no sense whatsoever.  Take one of the most famous of these rules, the rule not to split infinitives.  ufeff According to this rule, Captain Kirk made a grievous grammatical error when he said that the mission of the Enterprise was u201cto boldly go where no man has gone before.u201d  He should have said, according to these editors, u201cto go boldly where no man has gone before,u201d which immediately clashes with the rhythm and structure of ordinary English.  In fact, this prescriptive rule was based on a clumsy analogy with Latin where you canu2019t splint an infinitive because itu2019s a single word, as in facary[ph] to do.

 Julius Caesar couldnu2019t have split an infinitive if he wanted to.  That rule was translated literally over into English where it really should not apply.  ufeff Another famous prescriptive rule is that, one should never use a so-called double negative.  Mick Jagger should not have sung, u201cI canu2019t get no satisfaction,u201d he really should have sung, u201cI canu2019t get any satisfaction.u201d  Now, this is often promoted as a rule of logical speaking, but u201ccanu2019tu201d and u201canyu201d is just as much of a double negative as u201ccanu2019tu201d and u201cno.u201d  The only reason that u201ccanu2019t get any satisfactionu201d is deemed correct and u201ccanu2019t get no satisfactionu201d is deemed ungrammatical is that the dialect of English spoken in the south of England in the 17th century used u201ccanu2019tu201d u201canyu201d rather than u201ccanu2019tu201d u201cno.u201d  ufeff If the capital of England had been in the north of the country instead of the south of the country, then u201ccanu2019t get no,u201d would have been correct and u201ccanu2019t get any,u201d would have been deemed incorrect.

ufeff Thereu2019s nothing special about a language that happens to be chosen as the standard for a given country.  In fact, if you compare the rules of languages and so-called dialects, each one is complex in different ways.  Take for example, African-American vernacular English, also called Black English or Ebonics.  There is a construction in African-American where you can say, u201cHe be workin,u201d which is not an error or bastardization or a corruption of Standard English, but in fact conveys a subtle distinction, one thatu2019s different than simply, u201cHe workin.u201d  u201cHe be workin,u201d means that he is employed; he has a job, u201cHe workin,u201d means that he happens to be working at the moment that you and I are speaking.  ufeff Now, this is a tense difference that can be made in African-American English that is not made in Standard English, one of many examples in which the dialects have their own set of rules that is just as sophisticated and complex as the one in the standard language.

 ufeff Now, a third thing, not to confuse language with is thought.  Many people report that they think in language, but commune of psychologists have shown that there are many kinds of thought that donu2019t actually take place in the form of sentences.  ufeff (1.) Babies (and other mammals) communicate without speech ufeffFor example, we know from ingenious experiments that non-linguistic creatures, such as babies before theyu2019ve learned to speak, or other kinds of animals, have sophisticated kinds of cognition, they register cause and effect and objects and the intentions of other people, all without the benefit of speech.  ufeff (2.) Types of thinking go on without language–visual thinkingufeff We also know that even in creatures that do have language, namely adults, a lot of thinking goes on in forms other than language, for example, visual imagery.  If you look at the top two three-dimensional figures in this display, and I would ask you, do they have the same shape or a different shape?  People donu2019t solve that problem by describing those strings of cubes in words, but rather by taking an image of one and mentally rotating it into the orientation of the other, a form of non-linguistic thinking.

 ufeff (3.) We use tacit knowledge to understand language and remember the gistufeff For that matter, even when you understand language, what you come away with is not in itself the actual language that you hear.  Another important finding in cognitive psychology is that long-term memory for verbal material records the gist or the meaning or the content of the words rather than the exact form of the words.  ufeff For example, I like to think that you retain some memory of what I have been saying for the last 10 minutes.

 But I suspect that if I were to ask you to reproduce any sentence that I have uttered, you would be incapable of doing so.  What sticks in memory is far more abstract than the actual sentences, something that we can call meaning or content or semantics.  ufeff In fact, when it even comes to   understanding a sentence, the actual words are the tip of a vast iceberg of a very rapid, unconscious, non-linguistic processing thatu2019s necessary even to make sense of the language itself.  And Iu2019ll illustrate this with a classic bit of poetry, the lines from the shampoo bottle.

 u201cWet hair, lather, rinse, repeat.u201d  ufeff Now, in understanding that very simple snatch of language, you have to know, for example, that when you repeat, you donu2019t wet your hair a second time because its already wet, and when you get to the end of it and you see u201crepeat,u201d you donu2019t keep repeating over and over in infinite loop, repeat here means, u201crepeat just once.u201d  Now this tacit knowledge of what the writers **** of language had in mind is necessary to understand language, but it, itself, is not language. ufeff (4.) If language is thinking, then where did it come from?ufeff Finally, if language were really thought, it would raise the question of where language would come from if it were incapable of thinking without language.  After all, the English language was not designed by some committee of Martians who came down to Earth and gave it to us.  Rather, language is a grassroots phenomenon.  Itu2019s the original wiki, which aggregates the contributions of hundreds of thousands of people who invent jargon and slang and new constructions, some of them get accumulated into the language as people seek out new ways of expressing their thoughts, and thatu2019s how we get a language in the first place.

 ufeff Now, this not to deny that language can affect thought and linguistics has long been interested in what has sometimes been called, the linguistic relativity hypothesis or the Sapir-Whorf Hypothesis (note correct spelling, named after the two linguists who first formulated it, namely that language can affect thought.  Thereu2019s a lot of controversy over the status of the linguistic relativity hypothesis, but no one believes that language is the same thing as thought and that all of our mental life consists of reciting sentences.

 ufeff Now that we have set aside what language is not, letu2019s turn to what language is beginning with the question of how language works. In a nutshell, you can divide language into three topics.  ufeff There are the words that are the basic components of sentences that are stored in a part of long-term memory that we can call the mental lexicon or the mental dictionary.  There are rules, the recipes or algorithms that we use to assemble bits of language into more complex stretches of language including syntax, the rules that allow us to assemble words into phrases and sentences; Morphology, the rules that allow us to assemble bits of words, like prefixes and suffixes into complex words; Phonology, the rules that allow us to combine vowels and consonants into the smallest words.

 And then all of this knowledge of language has to connect to the world through interfaces that allow us to understand language coming from others to produce language that others can understand us, the language interfaces.ufeff Letu2019s start with words.ufeff The basic principle of a word was identified by the Swiss linguist, Ferdinand de Saussure, more than 100 years ago when he called attention to the arbitrariness of the sign.  Take for example the word, u201cduck.u201d  The word, u201cducku201d doesnu2019t look like a duck or walk like a duck or quack like a duck, but I can use it to get you to think the thought of a duck because all of us at some point in our lives have memorized that brute force association between that sound and that meaning, which means that it has to be stored in memory in some format, in a very simplified form and an entry in the mental lexicon might look something like this.

 There is a symbol for the word itself, there is some kind of specification of its sound and thereu2019s some kind of specification of its meaning.  ufeff Now, one of the remarkable facts about the mental lexicon is how capacious it is.  Using dictionary sampling techniques where you say, take the top left-hand word on every 20th page of the dictionary, give it to people in a multiple choice test, correct for guessing, and multiply by the size of the dictionary, you can estimate that a typical high school graduate has a vocabulary of around 60,000 words, which works out to a rate of learning of about one new word every two hours starting from the age of one.  When you think that every one of these words is arbitrary as a telephone number of a date in history, youu2019re reminded about the remarkable capacity of human long-term memory to store the meanings and sounds of words.

 ufeff But of course, we donu2019t just blurt out individual words, we combine them into phrases and sentences.  And that brings up the second major component of language; namely, grammar.  ufeff Now the modern study of grammar is inseparable to the contributions of one linguist, the famous scholar, Noam Chomsky, who set the agenda for the field of linguistics for the last 60 years. ufeff To begin with, Chomsky noted that the main puzzle that we have to explain in understanding language is creativity or as linguists often call it productivity, the ability to produce and understand new sentences.  ufeff Except for a small number of clichu00e9d formulas, just about any sentence that you produce or understand is a brand new combination produced for the first time perhaps in your life, perhaps even in the history of the species.

 We have to explain how people are capable of doing it.  It shows that when we know a language, we havenu2019t just memorized a very long list of sentences, but rather have internalized a grammar or algorithm or recipe for combining elements into brand new assemblies.  For that reason, Chomsky has insisted that linguistics is really properly a branch of psychology and is a window into the human mind. ufeff A second insight is that languages have a syntax which canu2019t be identified with their meaning.  Now, the only quotation that I know of, of a linguist that has actually made it into Bartlettu2019s Familiar Quotations, is the following sentence from Chomsky, from 1956, u201cColorless, green ideas sleep furiously.u201d  Well, whatu2019s the point of that sentence?  The point is that it is very close to meaningless.

 On the other hand, any English speaker can instantly recognize that it conforms to the patterns of English syntax.  Compare, for example, u201cfuriously sleep ideas dream colorless,u201d which is also meaningless, but we perceive as a word salad.  ufeff A third insight is that syntax doesnu2019t consist of a string of word by word associations as in stimulus response theories in psychology where producing a word is a response which you then hear and it becomes a stimulus to producing the next word, and so on.  Again, the sentence, u201ccolorless green ideas sleep furiously,u201d can help make this point.  Because if you look at the word by word transition probabilities in that sentence, for example, colorless and then green; how often have you heard colorless and green in succession.  Probably zero times.  Green and ideas, those two words never occur together, ideas and sleep, sleep and furiously.  Every one of the transition probabilities is very close to zero, nonetheless, the sentence as a whole can be perceived as a well-formed English sentence.

 ufeff Language in general has long distance dependencies.  The word in one position in a sentence can dictate the choice of the word several positions downstream.  For example, if you begin a sentence with u201ceither,u201d somewhere down the line, there has to be an u201cor.u201d  If you have an u201cif,u201d generally, you expect somewhere down the line there to be a u201cthen.u201d  Thereu2019s a story about a child who says to his father, u201cDaddy, why did you bring that book that I donu2019t want to be read to out of, up for?u201d  Where you have a set of nested or embedded long distance dependencies.

 ufeff Indeed, one of the applications of linguistics to the study of good prose style is that sentences can be rendered difficult to understand if they have too many long distance dependencies because that could put a strain on the short-term memory of the reader or listener while trying to understand them.  ufeff Rather than a set of word by word associations, sentences are assembled in a hierarchical structure that looks like an upside down tree.  Let me give you an example of how that works in the case of English.  One of the basic rules of English is that a sentence consists of a noun phrase, the subject, followed by a verb phrase, the predicate.ufeff A second rule in turn expands the verb phrase.  A very phrase consists of a verb followed by a noun phrase, the object, followed by a sentence, the complement as, u201cI told him that it was sunny outside.u201d  ufeff ufeff Now, why do linguists insist that language must be composed out of  phrase structural rules?  ufeff (1.) Rules allow for open-ended creativity ufeffWell for one thing, that helps explain the main phenomenon that we want to explain, mainly the open-ended creativity of language.

 ufeff (2.) Rules allow for expression of unfamiliar meaningufeff It allows us to express unfamiliar meanings.  Thereu2019s a clichu00e9 in journalism for example, that when a dog bites a man, that isnu2019t news, but when a man bites a dog, that is news.  The beauty of grammar is that it allows us to convey news by assembling into familiar word in brand new combinations.  Also, because of the way phrase structure rules work, they produce a vast number of possible combinations. ufeff (3.) Rules allow for production of vast numbers of combinationsufeff Moreover, the number of different thoughts that we can express through the combinatorial power of grammar is not just humongous, but in a technical sense, itu2019s infinite.  Now of course, no one lives an infinite number of years, and therefore can shell off their ability to understand an infinite number of sentences, but you can make the point in the same way that a mathematician can say that someone who understands the rules of arithmetic knows that there are an infinite number of numbers, namely if anyone ever claimed to have found the longest one, you can always come up with one thatu2019s even bigger by adding a one to it.

 And you can do the same thing with language.  ufeff Let me illustrate it in the following way.  As a matter of fact, there has been a claim that there is a worldu2019s longest sentence.  ufeff Who would make such a claim?  Well, who else?  The Guinness Book of World Records.  You can look it up.  There is an entry for the Worldu2019s Longest Sentence.  It is 1,300 words long.  And it comes from a novel by William Faulkner.  Now I wonu2019t read all 1,300 words, but Iu2019ll just tell you how it begins.

 ufeff u201cThey both bore it as though in deliberate flatulent exaltationu2026u201d and it runs on from there. ufeff But Iu2019m here to tell you that in fact, this is not the worldu2019s longest sentence.  And Iu2019ve been tempted to obtain immortality in Guinness by submitting the following record breaker.  “Faulkner wrote, they both bore it as though in deliberate flatulent exaltation.u201d  But sadly, this would not be immortality after all but only the proverbial 15 minutes of fame because based on what you now know, you could submit a record breaker for the record breaker namely, “Guinness noted that Faulkner wrote” or “Pinker mentioned that Guinness noted that Faulkner wrote”, or “who cares that Pinker mentioned that Guinness noted that Faulkner wroteu2026”  ufeff Take for example, the following wonderfully ambiguous sentence that appeared in TV Guide.

 u201cOn tonightu2019s program, Conan will discuss sex with Dr. Ruth.u201d  ufeff Now this has a perfectly innocent meaning in which the verb, u201cdiscussu201d involves two things, namely the topic of discussion, u201csexu201d and the person with who itu2019s being discussed, in this case, with Dr. Ruth.  But is has a somewhat naughtier meaning if you rearrange the words into phrases according to a different structure in which case u201csex with Dr. Ruthu201d is the topic of conversation, and thatu2019s whatu2019s being discussed.  ufeff Now, phrase structure not only can account for our ability to produce so many sentences, but itu2019s also necessary for us to understand what they mean.  The geometry of branches in a phrase structure is essential to figuring out who did what to whom.ufeff Another important contribution of Chomsky to the science of language is the focus on language acquisition by children.

Now, children canu2019t memorize sentences because knowledge of language isnu2019t just one long list of memorized sentences, but somehow they must distill out or abstract out the rules that goes into assembling sentences based on what they hear coming out of their parentu2019s mouths when they were little.  And the talent of using rules to produce combinations is in evidence from the moment that kids begin to speak.  ufeff Children create sentences unheard from adultsufeff At the two-word stage, which you typically see in children who are 18 months or a bit older, kids are producing the smallest sentences that deserve to be counted as sentences, namely two words long.  But already itu2019s clear that they are putting them together using rules in their own mind.  To take an example, a child might say, u201cmore outside,u201d meaning, take them outside or let them stay outside.  Now, adults donu2019t say, u201cmore outside.u201d  So itu2019s not a phrase that the child simply memorized by rote, but it shows that already children are using these rules to put together new combinations.

 ufeff Another example, a child having jam washed from his fingers said to his mother ‘all gone sticky’.ufeff Again, not a phrase that you could ever have copied from a parent, but one that shows the child producing new combinations.  ufeff Past tense ruleufeff An easy way of showing that children assimilate rules of grammar unconsciously from the moment they begin to speak, is the use of the past tense rule. ufeff For example, children go through a long stage in which they make errors like, u201cWe holded the baby rabbitsu201d or u201cHe teared the paper and then he sticked it.u201d  Cases in which they over generalize the regular rule of forming the past tense, add u2018edu2019 to irregular verbs like u201chold,u201d u201csticku201d or u201ctear.u201d  And itu2019s easy to showu2026 itu2019s easy to get children to flaunt this ability to apply rules productively in a laboratory demonstration called the Wug Test.

 You bring a kid into a lab.  You show them a picture of a little bird and you say, u201cThis is a wug.u201d  And you show them another picture and you say, u201cWell, now there are two of them.u201d  There are two and children will fill in the gap by saying u201cwugs.u201d  Again, a form they could not have memorize because itu2019s invented for the experiment, but it shows that they have productive mastery of the regular plural rule in English.  ufeff And famously, Chomsky claimed that children solved the problem of language acquisition by having the general design of language already wired into them in the form of a universal grammar.  ufeff A spec sheet for what the rules of any language have to look like.  ufeff What is the evidence that children are born with a universal grammar?  Well, surprisingly, Chomsky didnu2019t propose this by actually studying kids in the lab or kids in the home, but through a more abstract argument called, u201cThe poverty of the input.u201d  Namely, if you look at what goes into the ears of a child and look at the talent they end up with as adults, there is a big chasm between them that can only be filled in by assuming that the child has a lot of knowledge of the way that language works already built in.

 ufeff Hereu2019s how the argument works.  One of the things that children have to learn when they learn English is how to form a question.  Now, children will get evidence from parentu2019s speech to how the question rule works, such as sentences like, u201cThe man is here,u201d ufeffand the corresponding question, u201cIs the man here?u201dufeff   Now, logically speaking, a child getting that kind of input could posit two different kinds of rules.

ufeffThereu2019s a simple word by word linear rule.  In this case, find the first u201cisu201d in the sentence and move it to the front.  u201cThe man is here,u201d u201cIs the man here?u201d Now thereu2019s a more complex rule that the child could posit called a structure dependent rule, one that looks at the geometry of the phrase structure tree.  In this case, the rule would be:  find the first u201cisu201d after the subject noun phrase and move that to the front of the sentence.  A diagram of what that rule would look like is as follows:  you look for the u201cisu201d that occurs after the subject noun phrase and thatu2019s what gets moved to the front of the sentence.  Now, whatu2019s the difference between the simple word-by-word rule and the more complex structured dependent rule?  Well, you can see the difference when it comes to performing the question from a slightly more complex sentence like, u201cThe man who is tall is in the room.u201d  ufeff But how is the child supposed to learn that?  How did all of us end up with the correct structured dependent of the rule rather than the far simpler word-by-word version of the rule? ufeff u201cWell,u201d Chomsky argues, u201cif you were actually to look at the kind of language that all of us hear, itu2019s actually quite rare to hear a sentence like, u201cIs the man who is tall in the room?  The kind of input that would logically inform you that the word-by-word rule is wrong and the structure dependent rule is right.

 Nonetheless, we all grow up into adults who unconsciously use the structure dependent rule rather than the word-by-word rule.  Moreover, children donu2019t make errors like, u201cis the man who tall is in the room,u201d as soon as they begin to form complex questions, they use the structure dependent rule.  And that,u201d Chomsky argues, u201cis evidence that structure dependent rules are part of the definition of universal grammar that children are born with.u201d  ufeff Now, though Chomsky has been fantastically influential in the science of language that does not mean that all language scientists agree with him.  And there have been a number of critiques of Chomsky over the years.  For one thing, the critics point out, Chomsky hasnu2019t really shown principles of universal grammar that are specific to language itself as opposed to general ways in which the human mind works across multiple domains, language and vision and control of motion and memory and so on.  We donu2019t really know that universal grammar is specific to language, according to this critique. ufeff Secondly, Chomsky and the linguists working with him have not examined all 6,000 of the worldu2019s languages and shown that the principles of universal grammar apply to all 6,000.

 Theyu2019ve posited it based on a small number of languages and the logic of the poverty of the input, but havenu2019t actually come through with the data that would be necessary to prove that universal grammar is really universal.  ufeff Finally, the critics argue, Chomsky has not shown that more general purpose learning models, such as neuro network models, are incapable of learning language together with all the other things that children learn, and therefore has not proven that there has to be specific knowledge how grammar works in order for the child to learn grammar.

  ufeff  Another component of language governs the sound pattern of language, the ways that the vowels and consonants can be assembled into the minimal units that go into words.  Phonology, as this branch of linguistics is called, consists of formation rules that capture what is a possible word in a language according to the way that it sounds.   To give you an example, the sequence, bluk, is not an English word, but you get a sense that it could be an English word that someone could coin a new formu2026 that someone could coin a new term of English that we pronounce u201cbluk.u201d  But when you hear the sound ****, you instantly know thatthat not only isnu2019t it an English word, but it really couldnu2019t be an English word.

 ****, by the way, comes from Yiddish and it means kind of to sigh or to moan.  Oi.  Thatu2019s to ****.  ufeff The reason that we recognize that itu2019s not English is because it has sounds like **** and sequences like ****, which arenu2019t part of the formation rules of English phonology.  But together with the rules that define the basic words of a language, there are also phonological rules that make adjustments to the sounds, depending on what the other words the word appears with.  Very few of us realize, for example, in English, that the past tense suffix u201cedu201d ufeffis actually pronounced in three different ways.  When we say, u201cHe walked,u201d ufeffwe pronounce the u201cedu201d like a u201cta,u201d walked.  When we say u201cjogged,u201d ufeffwe pronounce it as a u201cd,u201d jogged.

 And when we say u201cpatted,u201dufeff we stick in a vowel, pat-ted, showing that the same suffix, u201cedu201d can be readjusted in its pronunciation according to the rules of English phonology.  ufeff Now, when someone acquires English as a foreign language or acquires a foreign language in general, they carry over the rules of phonology of their first language and apply it to their second language.  We have a word for it; we call it an u201caccent.u201d  When a language user deliberately manipulates the rules of phonology, that is, when they donu2019t just speak in order to convey content, they pay attention as to what phonological structures are being used; we call it poetry and rhetoric.  ufeff So far, Iu2019ve been talking about knowledge of language, the rules that go into defining what are possible sequences of language.  But those sequences have to get into the brain during speech comprehension and they have to get out during speech production.

 And that takes us to the topic of language interfaces.  ufeff And letu2019s start with production.  ufeff This diagram here is literally a human cadaver that has been sawn in half.  An anatomist took a saw and [sound] allowing it to see in cross section the human vocal tract.  And that can illustrate how we get out knowledge of language out into the world as a sequence of sounds.  ufeff Now, each of us has at the top of our windpipe or trachea, a complex structure called the larynx or voice box; itu2019s behind your Adamu2019s Apple.  And the air coming out of your lungs have to go passed two cartilaginous flaps that vibrate and produce a rich, buzzy sound source, full of harmonics.

 Before that vibrating sound gets out to the world, it has to pass through a gauntlet or chambers of the vocal tract.  The throat behind the tongue, the cavity above the tongue, the cavity formed by the lips, and when you block off airflow through the mouth, it can come out through the nose.  ufeff Now, each one of those cavities has a shape that, thanks to the laws of physics, will amplify some of the harmonics in that buzzy sound source and suppress others.

 We can change the shape of those cavities when we move our tongue around.  When we move our tongue forward and backward, for example, as in u201ceh,u201d u201caa,u201d u201ceh,u201d u201caa,u201d we change the shape of the cavity behind the tongue, change the frequencies that are amplified or suppressed and the listener hears them as two different vowels.  ufeff Likewise, when we raise or lower the tongue, we change the shape of the resonant cavity above the tongue as in say, u201ceh,u201d u201cah,u201d u201ceh,u201d u201cah.u201d  Once again, the change in the mixture of harmonics is perceived as a change in the nature of the vowel.  ufeff When we stop the flow of air and then release it as in, u201ct,u201d u201cca,u201d u201cba.u201d  Then we hear a consonant rather than a vowel or even when we restrict the flow of air as in u201cf,u201d u201cssu201d producing a chaotic noisy sound.  Each one of those sounds that gets sculpted by different articulators is perceived by the brain as a qualitatively different vowel or consonant.

 ufeff Now, an interesting peculiarity of the human vocal track is that it obviously co-ops structures that evolved for different purposes for breathing and for swallowing and so on.  And itu2019s anu2026 And itu2019s an interesting fact first noted by Darwin that the larynx over the course of evolution has descended in the throat so that every particle of food going from the mouth through the esophagus to the stomach has to pass over the opening into the larynx with some probability of being inhaled leading to the danger of death by choking.

 And in fact, until the invention of the Heimlich Maneuver, several thousand people every year died of choking because of this maladaptive of the human vocal tract. ufeff Why did we evolve a mouth and throat that leaves us vulnerable to choking?  Well, a plausible hypothesis is that itu2019s a compromise that was made in the course of evolution to allow us to speak.  By giving range to a variety of possibilities for alternating the resonant cavities, for moving the tongue back and forth and up and down, we expanded the range of speech sounds we could make, improve the efficiency of language, but suffered the compromise of an increased risk of choking showing that language presumably had some survival advantage that compensated for the disadvantage in choking.

 ufeff What about the flow of information in the other direction, that is from the world into the brain, the process of speech comprehension?  ufeff Speech comprehension turns out to be an extraordinarily complex computational process, which we’re reminded of every time we interact with a voicemail menu on a telephone or you use a dictation on our computers.  For example, One writer, using the state-of-the-art speech-to-text systems dictated the following words into his computer.  He dictated u201cbook tour,u201d and it came out on the screen as u201cback to work.u201d  Another example, he said, u201cI truly couldnu2019t see,u201d and it came out on the screen as, u201ca cruelly good MC.u201d  Even more disconcertingly, he started a letter to his parents by saying, u201cDear mom and dad,u201d and what came out on the screen, u201cThe man is dead.u201d  ufeff ufeff Now, dictation systems have gotten better and better, but they still have a way to go before they can duplicate a human stenographer.  ufeff What is it about the problem of speech understanding that makes it so easy for a human, ufeffbut so hard for a computer? Well, there are two main contributors.

 One of them is the fact that each phony, each vowel or consonant actually comes out very differently, depending on what comes before and what comes after.  A phenomenon sometimes called co-articulation.  ufeff Let me give you an example.  The place called Cape Cod has two u201ccu201d sounds.  ufeff u2028Each of them symbolized by the letter u201cC,u201d the hard u201cC.u201d  Nonetheless, when you pay attention to the way you pronounce them, you notice that in fact, you pronounce them in very different parts of the mouth.  Try it.  Cape Cod, Cape Codu2026 u201cc,u201d u201ccu201d.  In one case, the u201ccu201d is produced way back in the mouth; the other itu2019s produced much farther forward.

 We donu2019t notice that we pronounce u201ccu201d in two different ways depending whether it comes before an u201cau201d or an u201cah,u201d but that difference forms a difference in the shape of the resonant cavity in our mouth which produces a very different wave form.  And unless a computer is specifically programmed to take that variability into account, it will perceive those two different u201ccu2019s,u201d as a different sound that objectively speaking, they really are:  u201cc-ehu201d u201cc-oau201d.  They really are different sounds, but our brain lumps them together.  ufeff The other reason that speech recognition is such a difficult problem is because of the absence of segmentation.  Now we have an illusion when we listen to speech that consists of a sequence to sounds corresponding to words.  But if you actually were to look at the wave form of a sentence on a oscilloscope, there would not be little silences between the words the way there are little bits of white space in printed words on a page, but rather a continuous ribbon in which the end of one word leads right to the beginning of the next.

 ufeff Itu2019s something that weu2019re aware ofu2026 Itu2019s something that weu2019re aware of when we listen to speech in a foreign language when we have no idea where one word ends and the other one begins.  In our own language, we detect the word boundaries simply because in our mental lexicon, we have stretches of sound that correspond to one word that tell us where it ends.

 But you canu2019t get that information from the wave form itself.  ufeff In fact, thereu2019s a whole genre of wordplay that takes advantage of the fact that word boundaries are not physically present in the speech wave.  Novelty songs like Mairzy doats and dozy doats and liddle lamzy diveyufeff u2028A kiddley divey too, wooden shoe? ufeffu2028u2028Now, it turns out that this is actually a grammatical sequence in words in Englishu2026 Mares eat oats and does eat oats and little lambs eat ivy, a kid’ll eat ivy too, wouldnu2019t you?ufeff When it is spoken or sung normally, the boundaries between words are obliterated and so the same sequence of sounds can be perceived either as nonsense or if you know what theyu2019re meant to convey, as sentences.  ufeff Another example familiar to most children, ufeffFuzzy Wuzzy was a bear, Fuzzy Wuzzy had no hair.  Fuzzy Wuzzy wasnu2019t very fuzzy, was he?  And the famous dogroll, I scream, you scream, we all scream for ice cream.

ufeff We are generally unaware of how unambiguous language is.  In context, we effortlessly and unconsciously derive the intended meaning of a sentence, but a poor computer not equipped with all of our common sense and human abilities and just going by the words and the rules is often flabbergasted by all the different possibilities.  Take a sentence as simple as u201cMary had a little lamb,u201d ufeffyou might think that thatu2019s a perfectly simple unambiguous sentence.  But now imagine that it was continued with u201cwith mint sauce.u201d  You realize that u201chaveu201d is actually a highly ambiguous word.ufeff As a result, the computer translations can often deliver comically incorrect results.  ufeff According to legend, one of the first computer systems that was designed to translate from English to Russian and back again did the following given the sentence, u201cThe spirit is willing, but the flesh is weak,u201d it translated it back as u201cThe vodka is agreeable, but the meat is rotten.u201d ufeff So why do people understand language so much better than computers?  What is the knowledge that we have that has been so hard to program into our machines?  Well, thereu2019s a third interface between language and the rest of the mind, and that is the subject matter of the branch of linguistics called Pragmatics, namely, how people understand language in context using their knowledge of the world and their expectation about how other speakers communicate.

 ufeff The most important principle of Pragmatics is called u201cthe cooperative principle,u201d namely; assume that your conversational partner is working with you to try to get a meaning across truthfully and clearly.  And our knowledge of Pragmatics, like our knowledge of syntax and phonology and so on, is deployed effortlessly, but involves many intricate computations.  For example, if I were to say, u201cIf you could pass the guacamole, that would be awesome.u201d  You understand that as a polite request meaning, give me the guacamole.  You donu2019t interpret it literally as a rumination about a hypothetical affair, you just assume that the person wanted something and was using that string of words to convey the request politely.  ufeff Often comedies will use the absence of pragmatics in robots as a source of humor.  As in the old u201cGet Smartu201d situation comedy, which had a robot named, Hymie, and a recurring joke in the series would be that Maxwell Smart would say to Hymie, u201cHymie, can you give me a hand?u201d  And then Hymie would go, {sound}, remove his hand and pass it over to Maxwell Smart not understanding that u201cgive me a hand,u201d in context means, help me rather than literally transfer the hand over to me.

 ufeff Or take the following example of Pragmatics in action.  Consider the following dialogue, Martha says, u201cIu2019m leaving you.u201d  John says, u201cWho is he?u201d  Now, understanding language requires finding the antecedents pronouns, in this case who the u201cheu201d refers to, and any competent English speaker knows exactly who the u201cheu201d is, presumably Johnu2019s romantic rival even though it was never stated explicitly in any part of the dialogue.

 This shows how we bring to bear on language understanding a vast store of knowledge about human behavior, human interactions, human relationships.  And we often have to use that background knowledge even to solve mechanical problems like, who does a pronoun like u201cheu201d refer to.  Itu2019s that knowledge thatu2019s extraordinarily difficult, to say the least to program into a computer.  ufeff Language is a miracle of the natural world because it allows us to exchange an unlimited number of ideas using a finite set of mental tools.  Those mental tools comprise a large lexicon of memorized words and a powerful mental grammar that can combine them.  Language thought of in this way should not be confused with writing, with the prescriptive rules of proper grammar or style or with thought itself.  ufeff Modern linguistics is guided by the questions, though not always the answers suggested by the linguist known as Noam Chomsky, namely how is the unlimited creativity of language possible?  What are the abstract mental structures that relate word to one another? How do children acquire them?  ufeff What is universal across languages?  And what does that say about the human mind?  ufeff The study of language has many practical applications including computers that understand and speak, the diagnosis and treatment of language disorders, the teaching of reading, writing, and foreign languages, the interpreting of the language of law, politics and literature.ufeff But for someone like me, language is eternally fascinating because it speaks to such fundamental questions of the human condition.

 ufeff[Language] is really at the center of a number of different concerns of thought, of social relationships, of human biology, of human evolution, that all speak to whatu2019s special about the human species. ufeff Language is the most distinctively human talent.  Language is a window into human nature, and most significantly,ufeff the vast expressive power of language is one of the wonders of the natural world.  Thank you.ufeff. “}

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