The K family, three generations of SLI sufferers, whose members say things like Carol is cry in the church and can not deduce the plural of wug, is currently one of the most dramatic demonstrations that defects in grammatical abilities might be inherited. The attention-grabbing hypothesis about a single dominant autosomal gene is based on the following Mendelian reasoning. The syndrome is suspected of being genetic because there is no plausible environmental cause that would single out some family members and spare their agemates (in one case, one fraternal twin was affected, the other not), and because the syndrome has struck fifty-three percent of the family members but strikes no more than about three percent of the population at large. (In principle, the family could just have been unlucky; after all, they were not randomly selected from the population but came to the geneticists’ attention only because of the high concentration of the syndrome. But it is unlikely.) A single gene is thought to be responsible because if several genes were responsible, each eroding language ability by a bit, there would be several degrees of disability among the family members, depending on how many of the damaging genes they inherited. But the syndrome seems to be all-or-none: the school system and family members all agree on who does and who does not have the impairment, and in most of Gopnik’s tests the impaired members cluster together at the low end of the scale while the normal members cluster at the high end, with no overlap. The gene is thought to be autosomal (not on the X chromosome) and dominant because the syndrome struck males and females with equal frequency, and in all cases the spouse of an impaired parent, whether husband or wife, was normal. If the gene were recessive and autosomal, it would be necessary to have two impaired parents to inherit the syndrome. If it were recessive and on the X chromosome, only males would have it; females would be carriers. And if it were dominant and on the X chromosome, an impaired father would pass it on to all of his daughters and none of his sons, because sons get their X chromosome from their mother, and daughters get one from each parent. But one of the daughters of an impaired man was normal.
This single gene is not, repeat not, responsible for all the circuitry underlying grammar, contrary to the Associated Press, James Kilpatrick, et al. Remember that a single defective component can bring a complex machine to a halt even when the machine needs many properly functioning parts to work. In fact, it is possible that the normal version of the gene does not build grammar circuitry at all. Maybe the defective version manufactures a protein that gets in the way of some chemical process necessary for laying down the language circuits. Maybe it causes some adjacent area in the brain to overgrow its own territory and spill into the territory ordinarily allotted to language.
But the discovery is still quite interesting. Most of the language-impaired family members were average in intelligence, and there are sufferers in other families who are way above average; one boy studied by Gopnik was tops in his math class. So the syndrome shows that there must be some pattern of genetically guided events in the development in the brain (namely, the events disrupted in this syndrome) that is specialized for the wiring in of linguistic computation. And these construction sites seem to involve circuitry necessary for the processing of grammar in the mind, not just the articulation of speech sounds by the mouth or the perception of speech sounds by the ear. Though the afflicted family members as children suffered from difficulties in articulating speech and developed language late, most of them outgrew the articulation problems, and their lasting deficits involve grammar. For example, although the impaired family members often leave off the -ed and -s suffixes, it is not because they cannot hear or say those sounds; they easily discriminate between car and card, and never pronounce nose as no. In other words, they treat a sound differently when it is a permanent part of a word and when it is added to a word by a rule of grammar.
Equally interestingly, the impairment does not wipe out any part of grammar completely, nor does it compromise all parts equally. Though the impaired family members had trouble changing the tense of test sentences and applying suffixes in their spontaneous speech, they were not hopeless; they just performed far less accurately than their unimpaired relatives. These probabilistic deficits seemed to be concentrated in morphology and the features it manipulates, like tense, person, and number; other aspects of grammar were less affected. The impaired members could, for example, detect verb phrase violations in sentences like The nice girl gives and The girl eats a, cookie to the boy, and could act out many complex commands. The lack of an exact correspondence between a gene and a single function is exactly what we would expect, knowing how genes work.
So for now there is suggestive evidence for grammar genes, in the sense of genes whose effects seem most specific to the development of the circuits underlying parts of grammar. The chromosomal locus of the putative gene is completely unknown, as is its effect on the structure of the brain. But blood samples are being drawn from the family for genetic analysis, and MRI scans of brains from other individuals with Specific Language Impairment have already been found to lack the asymmetry in the perisylvian areas that we find in linguistically normal brains. Other researchers on language disorders, some excited by Gopnik’s claims, others skeptical of them, have begun to screen their patients with careful tests of their grammatical abilities and their family histories. They are seeking to determine how commonly Specific Language Impairment is inherited and how many distinct syndromes of the impairment there might be. You can expect to read about some interesting discoveries about the neurology and genetics of language in the next few years.
In modern biology, it is hard to discuss genes without discussing genetic variation. Aside from identical twins, no two people—in fact, no two sexually reproducing organisms—are genetically identical. If this were not true, evolution as we know it could not have happened. If there are language genes, then, shouldn’t normal people be innately different from one another in their linguistic abilities? Are they? Must I qualify everything I have said about language and its development, because no two people have the same language instinct?
It is easy to get carried away with the geneticists’ discovery that many of our genes are as distinctive as our fingerprints. After all, you can open up any page of Grey’s Anatomy and expect to find a depiction of organs and their parts and arrangements that will be true of any normal person. (Everyone has a heart with four chambers, a liver, and so on.) The biological anthropologist John Tooby and the cognitive psychologist Leda Cosmides have resolved the apparent paradox.
Tooby and Cosmides argue that differences between people must be minor quantitative variations, not qualitatively different designs. The reason is sex. Imagine that two people were really built from fundamentally different designs: either physical designs, like the structure of the lungs, or neurological designs, like the circuitry underlying some cognitive process. Complex machines require many finely meshing parts, which in turn require many genes to build them. But the chromosomes are randomly snipped, spliced, and shuffled during the formation of sex cells, and then are paired with other chimeras at fertilization. If two people really had different designs, their offspring would inherit a mishmash of fragments from the genetic blueprints of each—as if the plans for two cars were cut up with scissors and the pieces taped back together without our caring about which scrap originally came from which car. If the cars are of different designs, like a Ferrari and a jeep, the resulting contraption, if it could be built at all, would certainly not get anywhere. Only if the two designs were extremely similar to begin with could the new pastiche work.
That is why the variation that geneticists tell us about is microscopic—differences in the exact sequence of molecules in proteins whose overall shape and function are basically the same, kept within narrow limits of variation by natural selection. That variation is there for a purpose: by shuffling the genes each generation, lineages of organisms can stay one step ahead of the microscopic, rapidly evolving disease parasites that fine-tune themselves to infiltrate the chemical e
nvironments of their hosts. But above the germ’s-eye view, at the macroscopic level of functioning biological machinery visible to an anatomist or psychologist, variation from one individual to another must be quantitative and minor; thanks to natural selection, all normal people must be qualitatively the same.
But this does not mean that individual differences are boring. Genetic variation can open our eyes to the degree of structure and complexity that the genes ordinarily give to the mind. If genes just equipped a mind with a few general information-processing devices like a short-term memory and a correlation detector, some people might be better than others at holding things in memory or learning contingencies, and that would be about it. But if the genes built a mind with many elaborate parts dedicated to particular tasks, the unique genetic hand that is dealt to each person would give rise to an unprecedented profile of innate cognitive quirks.
I quote from a recent article in Science:
When Oskar Stöhr and Jack Yufe arrived in Minnesota to participate in University of Minnesota psychologist Thomas J. Bouchard, Jr.’s study of identical twins reared apart, they were both sporting blue double-breasted epauletted shirts, mustaches, and wire-rimmed glasses. Identical twins separated at birth, the two men, in their late 40s, had met once before two decades earlier. Nonetheless, Oskar, raised as a Catholic in Germany, and Jack, reared by his Jewish father in Trinidad, proved to have much in common in their tastes and personalities—including hasty tempers and idiosyncratic senses of humor (both enjoyed surprising people by sneezing in elevators).
And both flushed the toilet both before and after using it, kept rubber bands around their wrists, and dipped buttered toast in their coffee.
Many people are skeptical of such anecdotes. Are the parallels just coincidences, the overlap that is inevitable when two biographies are scrutinized in enough detail? Clearly not. Bouchard and his behavior geneticist colleagues D. Lykken, M. McGue, and A. Tellegen are repeatedly astonished by the spooky similarities they discover in their identical twins reared apart but that never appear in their fraternal twins reared apart. Another pair of identical twins meeting for the first time discovered that they both used Vademecum toothpaste, Canoe shaving lotion, Vitalis hair tonic, and Lucky Strike cigarettes. After the meeting they sent each other identical birthday presents that crossed in the mail. One pair of women habitually wore seven rings. Another pair of men pointed out (correctly) that a wheel bearing in Bouchard’s car needed replacing. And quantitative research corroborates the hundreds of anecdotes. Not only are very general traits like IQ, extroversion, and neuroticism partly heritable, but so are specific ones like degree of religious feeling, vocational interests, and opinions about the death penalty, disarmament, and computer music.
Could there really be a gene for sneezing in elevators? Presumably not, but there does not have to be. Identical twins share all their genes, not just one of them. So there are fifty thousand genes for sneezing in elevators—which are also fifty thousand genes for liking blue double-breasted epauletted shirts, using Vitalis hair tonic, wearing seven rings, and all the rest. The reason is that the relationship between particular genes and particular psychological traits is doubly indirect. First, a single gene does not build a single brain module; the brain is a delicately layered soufflé in which each gene product is an ingredient with a complex effect on many properties of many circuits. Second, a single brain module does not produce a single behavioral trait. Most of the traits that capture our attention emerge out of unique combinations of kinks in many different modules. Here is an analogy. Becoming an all-star basketball player requires many physical advantages, like height, large hands, excellent aim, good peripheral vision, lots of fast-twitch muscle tissue, efficient lungs, and springy tendons. Though these traits are probably genetic to a large degree, there does not have to be a basketball gene; those men for whom the genetic slot machine stopped at three cherries play in the NBA, while the more numerous seven-foot klutzes and five-foot sharpshooters go into some other line of work. No doubt the same is true of any interesting behavioral trait like sneezing in elevators (which is no odder than an aptitude for shooting a ball through a hoop with someone’s hand in your face). Perhaps the sneezing-in-elevators gene complex is the one that specifies just the right combination of thresholds and cross-connections among the modules governing humor, reactions to enclosed spaces, sensitivity to the mental states of others such as their anxiety and boredom, and the sneezing reflux.
No one has ever studied heritable variation in language, but I have a strong suspicion of what it is like. I would expect the basic design of language, from X-bar syntax to phonological rules and vocabulary structure, to be uniform across the species; how else could children learn to talk and adults understand one another? But the complexity of language circuitry leaves plenty of scope for quantitative variation to combine into unique linguistic profiles. Some module might be relatively stunted or hypertrophied. Some normally unconscious representation of sound or meaning or grammatical structure might be more accessible to the rest of the brain. Some connection between language circuitry and the intellect or emotions might be faster or slower.
Thus I predict that there are idiosyncratic combinations of genes (detectable in identical twins reared apart) behind the raconteur, the punster, the accidental poet, the sweet-talker, the rapier-like wit, the sesquipedalian, the word-juggler, the owner of the gift of gab, the Reverend Spooner, the Mrs. Malaprop, the Alexander Haig, the woman (and her teenage son!) I once tested who can talk backwards, and the student at the back of every linguistics classroom who objects that Who do you believe the claim that John saw? doesn’t sound so bad. Between 1988 and 1992, many people suspected that the chief executive of the United States and his second-in-command were not playing with a full linguistic deck:
I am less interested in what the definition is. You might argue technically, are we in a recession or not. But when there’s this kind of sluggishness and concern—definitions, heck with it.
I’m all for Lawrence Welk. Lawrence Welk is a wonderful man. He used to be, or was, or—wherever he is now, bless him.
—George Bush
Hawaii has always been a very pivotal role in the Pacific. It is IN the Pacific. It is a part of the United States that is an island that is right here.
[Speaking to the United Negro College Fund, whose motto is “A mind is a terrible thing to waste”:] What a terrible thing to have lost one’s mind. Or not to have a mind at all. How true that is.
—Dan Quayle
And who knows what unrepeatable amalgam of genes creates the linguistic genius?
If people don’t want to come out to the ballpark, nobody’s going to stop them.
You can observe a lot just by watching.
In baseball, you don’t know nothing.
Nobody goes there anymore. It’s too crowded.
It ain’t over till it’s over.
It gets late early this time of year.
—Yogi Berra
And NUH is the letter I use to spell Nutches
Who live in small caves, known as Nitches, for hutches.
These Nutches have troubles, the biggest of which is
The fact that there are many more Nutches than Nitches.
Each Nutch in a Nitch knows that some other Nutch
Would like to move into his Nitch very much.
So each Nutch in a Nitch has to watch that small Nitch
Or Nutches who haven’t got Nitches will snitch.
—Dr. Seuss
Lolita, light of my life, fire of my loins. My sin, my soul. Lo-lee-ta: the tip of the tongue taking a trip of three steps down the palate to tap, at three, on the teeth. Lo. Lee. Ta.
—Valdimir Nabokov
I have a dream that one day this nation will rise up and live out the true meaning of its creed: “We hold these truths to be self-evident, that all men are created equal.”
I have a dream that one day on the red hills of Georgia the sons of former slaves an
d the sons of former slaveowners will be able to sit down together at the table of brotherhood.
I have a dream that one day even the state of Mississippi, a state sweltering with the people’s injustice, sweltering with the heat of oppression, will be transformed into an oasis of freedom and justice.
I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character.
—Martin Luther King, Jr.
This goodly frame, the earth, seems to me a sterile promontory, this most excellent canopy, the air, look you, this brave o’er-hanging firmament, this majestical roof fretted with golden fire, why, it appears no other thing to me than a foul and pestilent congregation of vapours. What a piece of work is a man! how noble in reason! how infinite in faculty! in form and moving how express and admirable! in action how like an angel! in apprehension how like a god! the beauty of the world! the paragon of animals! And yet, to me, what is this quintessence of dust?
—William Shakespeare
The Big Bang
The elephant’s trunk is six feet long and one foot thick and contains sixty thousand muscles. Elephants can use their trunks to uproot trees, stack timber, or carefully place huge logs in position when recruited to build bridges. An elephant can curl its trunk around a pencil and draw characters on letter-size paper. With the two muscular extensions at the tip, it can remove a thorn, pick up a pin or a dime, uncork a bottle, slide the bolt off a cage door and hide it on a ledge, or grip a cup so firmly, without breaking it, that only another elephant can pull it away. The tip is sensitive enough for a blindfolded elephant to ascertain the shape and texture of objects. In the wild, elephants use their trunks to pull up clumps of grass and tap them against their knees to knock off the dirt, to shake coconuts out of palm trees, and to powder their bodies with dust. They use their trunks to probe the ground as they walk, avoiding pit traps, and to dig wells and siphon water from them. Elephants can walk underwater on the beds of deep rivers or swim like submarines for miles, using their trunks as snorkels. They communicate through their trunks by trumpeting, humming, roaring, piping, purring, rumbling, and making a crumpling-metal sound by rapping the trunk against the ground. The trunk is lined with chemoreceptors that allow the elephant to smell python hidden in the grass or food a mile away.
The Language Instinct: How the Mind Creates Language Page 37