The Language Instinct: How the Mind Creates Language

by Steven Pinker

  Linguistically, most left-handers are not mirror images of the righty majority. The left hemisphere controls language in virtually all right-handers (97%), but the right hemisphere controls language in a minority of left-handers, only about 19%. The rest have language in the left hemisphere (68%) or redundantly in both. In all of these lefties, language is more evenly distributed between the hemispheres than it is in righties, and thus the lefties are more likely to withstand a stroke on one side of the brain without suffering from aphasia. There is some evidence that left-handers, though better at mathematical, spatial, and artistic activities, are more susceptible to language impairment, dyslexia, and stuttering. Even righties with left-handed relatives (presumably, those righties possessing only one copy of the dominant right-bias gene) appear to parse sentences in subtly different ways than pure righties.

  Language, of course, does not use up the entire left half of the brain. Broca observed that Tan’s brain was mushy and deformed in the regions immediately above the Sylvian fissure—the huge cleavage that separates the distinctively human temporal lobe from the rest of the brain. The area in which Tan’s damage began is now called Broca’s area, and several other anatomical regions hugging both sides of the Sylvian fissure affect language when they are damaged. The most prominent are shown as the large gray blobs in the diagram (“Chapter 10”). In about 98% of the cases where brain damage leads to language problems, the damage is somewhere on the banks of the Sylvian fissure of the left hemisphere. Penfield found that most of the spots that disrupted language when he stimulated them were there, too. Though the language areas appear to be separated by large gulfs, this may be an illusion. The cerebral cortex (gray matter) is a large sheet of two-dimensional tissue that has been wadded up to fit inside the spherical skull. Just as crumpling a newspaper can appear to scramble the pictures and text, a side view of a brain is a misleading picture of which regions are adjacent. Gazzaniga’s coworkers have developed a technique that uses MRI pictures of brain slices to reconstruct what the person’s cortex would look like if somehow it could be unwrinkled into a flat sheet. They found that all the areas that have been implicated in language are adjacent in one continuous territory. This region of the cortex, the left perisylvian region, can be considered to be the language organ.

  Let us zoom in closer. Tan and Mr. Ford, in whom Broca’s area was damaged, suffered from a syndrome of slow, labored, ungrammatical speech called Broca’s aphasia. Here is another example, from a man called Peter Hogan. In the first passage he describes what brought him into the hospital; in the second, his former job in a paper mill:

  Yes…ah…Monday…ah…Dad and Peter Hogan, and

  Dad…ah…hospital…and ah…Wednesday…Wednesday nine o’clock and ah Thursday…ten o’clock ah doctors…two…two…an doctors and…ah…teeth…yah…And a doctor an girl…and gums, an I.

  Lower Falls…Maine…Paper. Four hundred tons a day! And ah…sulphur machines, and ah…wood…Two weeks and eight hours. Eight hours…no! Twelve hours, fifteen hours…workin…workin…workin! Yes, and ah…sulphur. Sulphur and…Ah wood. Ah…handlin! And ah sick, four years ago.

  Broca’s area is adjacent to the part of the motor-control strip dedicated to the jaws, lip, and tongue, and it was once thought that Broca’s area is involved in the production of language (though obviously not speech per se, because writing and signing are just as affected). But the area seems to be implicated in grammatical processing in general. A defect in grammar will be most obvious in the output, because any slip will lead to a sentence that is conspicuously defective. Comprehension, on the other hand, can often exploit the redundancy in speech to come up with sensible interpretations with little in the way of actual parsing. For example, one can understand The dog bit the man or The apple that the boy is eating is red just by knowing that dogs bite men, boys eat apples, and apples are red. Even The car pushes the truck can be guessed at because the cause is mentioned before the effect. For a century, Broca’s aphasics fooled neurologists by using shortcuts. Their trickery was finally unmasked when psycholinguists asked them to act out sentences that could be understood only by their syntax, like The car is pushed by the truck or The girl whom the boy is pushing is tall. The patients gave the correct interpretation half the time and its opposite half the time—a mental coin flip.

  There are other reasons to believe that the front portion of the perisylvian cortex, where Broca’s area is found, is involved in grammatical processing. When people read a sentence, electrodes pasted over the front of their left hemispheres pick up distinctive patterns of electrical activity at the point in the sentence at which it becomes ungrammatical. Those electrodes also pick up changes during the portions of a sentence in which a moved phrase must be held in memory while the reader awaits its trace, like What did you say (trace) to John? Several studies using PET and other techniques to measure blood flow have shown that this region lights up when people listen to speech in a language they know, tell stories, or understand complex sentences. Various control tasks and subtractions confirm that it is processing the structure of sentences, not just thinking about their content, that engages this general area. A recent and very carefully designed experiment by Karin Stromswold and the neurologists David Caplan and Nat Alpert obtained an even more precise picture; it showed one circumscribed part of Broca’s area lighting up.

  So is Broca’s area the grammar organ? Not really. Damage to Broca’s area alone usually does not produce long-lasting severe aphasia; the surrounding areas and underlying white matter (which connects Broca’s area to other brain regions) must be damaged as well. Sometimes symptoms of Broca’s aphasia can be produced by a stroke or Parkinson’s disease that damages the basal ganglia, complex neural centers buried inside the frontal lobes that are otherwise needed for skilled movement. The labored speech output of Broca’s aphasics may be distinct from the lack of grammar in their speech, and may implicate not Broca’s area but hidden parts of the cortex nearby that tend to be damaged by the same lesions. And, most surprisingly of all, some kinds of grammatical abilities seem to survive damage to Broca’s area. When asked to distinguish grammatical from ungrammatical sentences, some Broca’s aphasics can detect even subtle violations of the rules of syntax, as in pairs like these:

  John was finally kissed Louise.

  John was finally kissed by Louise.

  I want you will go to the store now.

  I want you to go to the store now.

  Did the old man enjoying the view?

  Did the old man enjoy the view?

  Still, aphasics do not detect all ungrammaticalities, nor do all aphasics detect them, so the role of Broca’s area in language is maddeningly unclear. Perhaps the area underlies grammatical processing by converting messages in mentalese into grammatical structures and vice versa, in part by communicating via the basal ganglia with the prefrontal lobes, which subserve abstract reasoning and knowledge.

  Broca’s area is also connected by a band of fibers to a second language organ, Wernicke’s area. Damage to Wernicke’s area produces a very different syndrome of aphasia. Howard Gardner describes his encounter with a Mr. Gorgan:

  “What brings you to the hospital?” I asked the 72-year-old retired butcher four weeks after his admission to the hospital.

  “Boy, I’m sweating, I’m awful nervous, you know, once in a while I get caught up, I can’t mention the tarripoi, a month ago, quite a little, I’ve done a lot well, I impose a lot, while, on the other hand, you know what I mean, I have to run around, look it over, trebbin and all that sort of stuff.”

  I attempted several times to break in, but was unable to do so against this relentlessly steady and rapid outflow. Finally, I put up my hand, rested it on Gorgan’s shoulder, and was able to gain a moment’s reprieve.

  “Thank you, Mr. Gorgan. I want to ask you a few—”

  “Oh sure, go ahead, any old think you want. If I could I would. Oh, I’m taking the word the wrong way to say, all of the barbers here whenever
they stop you it’s going around and around, if you know what I mean, that is tying and tying for repucer, repuceration, well, we were trying the best that we could while another time it was with the beds over there the same thing…”

  Wernickc’s aphasia is in some ways the complement of Broca’s. Patients utter fluent streams of more-or-less grammatical phrases, but their speech makes no sense and is filled with neologisms and word substitutions. Unlike many Broca’s patients, Wernicke’s patients have consistent difficulty naming objects; they come up with related words or distortions of the sound of the correct one:

  table: “chair”

  elbow: “knee”

  clip: “plick”

  butter: “tubber”

  ceiling: “leasing”

  ankle: “ankley, no mankle, no kankle”

  comb: “close, saw it, cit it, cut, the comb, the came”

  paper: “piece of handkerchief, pauper, hand pepper, piece of hand paper”

  fork: “tonsil, teller, tongue, fung”

  A striking symptom of Wernicke’s aphasia is that the patients show few signs of comprehending the speech around them. In a third kind of aphasia, the connection between Wernicke’s area and Broca’s is damaged, and these patients are unable to repeat sentences. In a fourth kind, Broca’s and Wernicke’s and the link between them are intact but they are an island cut off from the rest of the cortex, and these patients eerily repeat what they hear without understanding it or ever speaking spontaneously. For these reasons, and because Wernicke’s area is adjacent to the part of the cortex that processes sound, the area was once thought to underlie language comprehension. But that would not explain why the speech of these patients sounds so psychotic. Wernicke’s area seems to have a role in looking up words and funneling them to other areas, notably Broca’s, that assemble or parse them syntactically. Wernicke’s aphasia, perhaps, is the product of an intact Broca’s area madly churning out phrases without the intended message and intended words that Wernicke’s area ordinarily supplies. But to be honest, no one really knows what either Broca’s area or Wernicke’s area is for.

  Wernicke’s area, together with the two shaded areas adjacent to it in the diagram (the angular and supramarginal gyri), sit at the crossroads of three lobes of the brain, and hence are ideally suited to integrating streams of information about visual shapes, sounds, bodily sensations (from the “somatosensory” strip), and spatial relations (from the parietal lobe). It would be a logical place to store links between the sounds of words and the appearance and geometry of what they refer to. Indeed, damage to this general vicinity often causes a syndrome that is called anomia, though a more mnemonic label might be “no-name-ia,” which is literally what it means. The neuropsychologist Kathleen Baynes describes “HW,” a business executive who suffered a stroke in this general area. He is highly intelligent, articulate, and conversationally adept but finds it virtually impossible to retrieve nouns from his mental dictionary, though he can understand them. Here is how he responded when Baynes asked him to describe a picture of a boy falling from a stool as he reaches into a jar on a shelf and hands a cookie to his sister:

  First of all this is falling down, just about, and is gonna fall down and they’re both getting something to eat…but the trouble is this is gonna let go and they’re both gonna fall down…I can’t see well enough but I believe that either she or will have some food that’s not good for you and she’s to get some for her, too…and that you get it there because they shouldn’t go up there and get it unless you tell them that they could have it. And so this is falling down and for sure there’s one they’re going to have for food and, and this didn’t come out right, the, uh, the stuff that’s uh, good for, it’s not good for you but it, but you love, um mum mum [smacks lips]…and that so they’ve…see that, I can’t see whether it’s in there or not…I think she’s saying, I want two or three, I want one, I think, I think so, and so, so she’s gonna get this one for sure it’s gonna fall down there or whatever, she’s gonna get that one and, and there, he’s gonna get one himself or more, it all depends with this when they fall down…and when it falls down there’s no problem, all they got to do is fix it and go right back up and get some more.

  HW uses noun phrases perfectly but cannot retrive the nouns to put inside them: he uses pronouns, gerunds like falling down, and a few generic nouns like food and stuff, referring to particular objects with convoluted circumlocutions. Verbs tend to pose less of a problem for anomics; they are much harder for Broca’s aphasics, presumably because verbs are intimately linked to syntax.

  There are other indications that these regions in the rear of the pensylvian are implicated in storing and retrieving words. When people read perfectly grammatical sentences and come across a word that makes no sense, like The boys heard Joe’s orange about Africa, electrodes pasted near the back of the skull pick up a change in their EEG’s (although, as I have mentioned, it is only a guess that the blips are coming from below the electrodes). When people put their heads in the PET scanner, this general part of the brain lights up when they hear words (and pseudo-words, like tweal) and even when they read words on a screen and have to decide whether the words rhyme—a task requiring them to imagine the word’s sounds.

  A very gross anatomy of the language sub-organs within the perisylvian might be: front of the perisylvian (including Broca’s area), grammatical processing; rear of the perisylvian (including Wernicke’s and the three-lobe junction), the sounds of words, especially nouns, and some aspects of their meaning. Can we zoom in still closer, and locate smaller areas of brain that carry out more circumscribed language tasks? The answer is no and yes. No, there are no smaller patches of brain that one can draw a line around and label as some linguistic module—at least, not today. But yes, there must be portions of cortex that carry out circumscribed tasks, because brain damage can lead to language deficits that are startlingly specific. It is an intriguing paradox.

  Here are some examples. Although impairments of what I have been calling the sixth sense, speech perception, can arise from damage to most areas of the left perisylvian (and speech perception causes several parts of the perisylvian to light up in PET studies), there is a specific syndrome called Pure Word Deafness that is exactly what it sounds like: the patients can read and speak, and can recognize environmental sounds like music, slamming doors, and animal cries, but cannot recognize spoken words; words are as meaningless as if they were from a foreign language. Among patients with problems in grammar, some do not display the halting articulation of Broca’s aphasia but produce fluent ungrammatical speech. Some aphasics leave out verbs, inflections, and function words; others use the wrong ones. Some cannot comprehend complicated sentences involving traces (like The man who the woman kissed (trace) hugged the child) but can comprehend complex sentences involving reflexives (like The girl said that the woman washed herself). Other patients do the reverse. There are Italian patients who mangle their language’s inflectional suffixes (similar to the -ing, -s, and -ed of English) but are almost flawless with its derivational suffixes (similar to -able, -ness, and -er).

  The mental thesaurus, in particular, is sometimes torn into pieces with clean edges. Among anomic patients (those who have trouble using nouns), different patients have problems with different kinds of nouns. Some can use concrete nouns but not abstract nouns. Some can use abstract nouns but not concrete nouns. Some can use nouns for nonliving things but have trouble with nouns for living things; others can use nouns for living things but have trouble with nouns for nonliving things. Some can name animals and vegetables but not foods, body parts, clothing, vehicles, or furniture. There are patients who have trouble with nouns for anything but animals, patients who cannot name body parts, patients who cannot name objects typically found indoors, patients who cannot name colors, and patients who have trouble with proper names. One patient could not name fruits or vegetables: he could name an abacus and a sphinx but not an apple or a peach. The psychologist Edgar Zurif,
jesting the neurologist’s habit of giving a fancy name to every syndrome, has suggested that it be called anomia for bananas, or “banananomia.”

  Does this mean that the brain has a produce section? No one has found one, nor centers for inflections, traces, phonology, and so on. Pinning brain areas to mental functions has been frustrating. Frequently one finds two patients with lesions in the same general area but with different kinds of impairment, or two patients with the same impairment but lesions in different areas. Sometimes a circumscribed impairment, like the inability to name animals, can be caused by massive lesions, brain-wide degeneration, or a blow to the head. And about ten percent of the time a patient with a lesion in the general vicinity of Wernicke’s area can have a Broca-like aphasia, and a patient with lesions near Broca’s area can have a Wernicke-like aphasia.

  Why has it been so hard to draw an atlas of the brain with areas for different parts of language? According to one school of thought, it is because there aren’t any; the brain is a meatloaf. Except for sensation and movement, mental processes are patterns of neuronal activity that are widely distributed, hologram-style, all over the brain. But the meatloaf theory is hard to reconcile with the amazingly specific deficits of many brain-damaged patients, and it is becoming obsolete in this “decade of the brain.” Using tools that are getting more sophisticated each month, neurobiologists are charting vast territories that once bore the unhelpful label “association cortex” in the old textbooks, and are delineating dozens of new regions with their own functions or styles of processing, like visual areas specializing in object shape, spatial layout, color, 3D stereo-vision, simple motion, and complex motion.