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Saturday, December 18, 2010

Does Your Language Shape How You Think?

Does Your Language Shape How You Think?

Horacio Salinas for The New York Times
Seventy years ago, in 1940, a popular science magazine published a short article that set in motion one of the trendiest intellectual fads of the 20th century. At first glance, there seemed little about the article to augur its subsequent celebrity. Neither the title, “Science and Linguistics,” nor the magazine, M.I.T.’s Technology Review, was most people’s idea of glamour. And the author, a chemical engineer who worked for an insurance company and moonlighted as an anthropology lecturer at Yale University, was an unlikely candidate for international superstardom. And yet Benjamin Lee Whorf let loose an alluring idea about language’s power over the mind, and his stirring prose seduced a whole generation into believing that our mother tongue restricts what we are able to think.

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Horacio Salinas for The New York Times
In particular, Whorf announced, Native American languages impose on their speakers a picture of reality that is totally different from ours, so their speakers would simply not be able to understand some of our most basic concepts, like the flow of time or the distinction between objects (like “stone”) and actions (like “fall”). For decades, Whorf’s theory dazzled both academics and the general public alike. In his shadow, others made a whole range of imaginative claims about the supposed power of language, from the assertion that Native American languages instill in their speakers an intuitive understanding of Einstein’s concept of time as a fourth dimension to the theory that the nature of the Jewish religion was determined by the tense system of ancient Hebrew.
Eventually, Whorf’s theory crash-landed on hard facts and solid common sense, when it transpired that there had never actually been any evidence to support his fantastic claims. The reaction was so severe that for decades, any attempts to explore the influence of the mother tongue on our thoughts were relegated to the loony fringes of disrepute. But 70 years on, it is surely time to put the trauma of Whorf behind us. And in the last few years, new research has revealed that when we learn our mother tongue, we do after all acquire certain habits of thought that shape our experience in significant and often surprising ways.
Whorf, we now know, made many mistakes. The most serious one was to assume that our mother tongue constrains our minds and prevents us from being able to think certain thoughts. The general structure of his arguments was to claim that if a language has no word for a certain concept, then its speakers would not be able to understand this concept. If a language has no future tense, for instance, its speakers would simply not be able to grasp our notion of future time. It seems barely comprehensible that this line of argument could ever have achieved such success, given that so much contrary evidence confronts you wherever you look. When you ask, in perfectly normal English, and in the present tense, “Are you coming tomorrow?” do you feel your grip on the notion of futurity slipping away? Do English speakers who have never heard the German word Schadenfreude find it difficult to understand the concept of relishing someone else’s misfortune? Or think about it this way: If the inventory of ready-made words in your language determined which concepts you were able to understand, how would you ever learn anything new?
SINCE THERE IS NO EVIDENCE that any language forbids its speakers to think anything, we must look in an entirely different direction to discover how our mother tongue really does shape our experience of the world. Some 50 years ago, the renowned linguist Roman Jakobson pointed out a crucial fact about differences between languages in a pithy maxim: “Languages differ essentially in what they must convey and not in what they may convey.” This maxim offers us the key to unlocking the real force of the mother tongue: if different languages influence our minds in different ways, this is not because of what our language allows us to think but rather because of what it habitually obliges us to think about.
Consider this example. Suppose I say to you in English that “I spent yesterday evening with a neighbor.” You may well wonder whether my companion was male or female, but I have the right to tell you politely that it’s none of your business. But if we were speaking French or German, I wouldn’t have the privilege to equivocate in this way, because I would be obliged by the grammar of language to choose between voisin or voisine;Nachbar or Nachbarin. These languages compel me to inform you about the sex of my companion whether or not I feel it is remotely your concern. This does not mean, of course, that English speakers are unable to understand the differences between evenings spent with male or female neighbors, but it does mean that they do not have to consider the sexes of neighbors, friends, teachers and a host of other persons each time they come up in a conversation, whereas speakers of some languages are obliged to do so.
On the other hand, English does oblige you to specify certain types of information that can be left to the context in other languages. If I want to tell you in English about a dinner with my neighbor, I may not have to mention the neighbor’s sex, but I do have to tell you something about the timing of the event: I have to decide whether we dinedhave been diningare diningwill be dining and so on. Chinese, on the other hand, does not oblige its speakers to specify the exact time of the action in this way, because the same verb form can be used for past, present or future actions. Again, this does not mean that the Chinese are unable to understand the concept of time. But it does mean they are not obliged to think about timing whenever they describe an action.
When your language routinely obliges you to specify certain types of information, it forces you to be attentive to certain details in the world and to certain aspects of experience that speakers of other languages may not be required to think about all the time. And since such habits of speech are cultivated from the earliest age, it is only natural that they can settle into habits of mind that go beyond language itself, affecting your experiences, perceptions, associations, feelings, memories and orientation in the world.
BUT IS THERE any evidence for this happening in practice?
Let’s take genders again. Languages like Spanish, French, German and Russian not only oblige you to think about the sex of friends and neighbors, but they also assign a male or female gender to a whole range of inanimate objects quite at whim. What, for instance, is particularly feminine about a Frenchman’s beard (la barbe)? Why is Russian water a she, and why does she become a he once you have dipped a tea bag into her? Mark Twainfamously lamented such erratic genders as female turnips and neuter maidens in his rant “The Awful German Language.” But whereas he claimed that there was something particularly perverse about the German gender system, it is in fact English that is unusual, at least among European languages, in not treating turnips and tea cups as masculine or feminine. Languages that treat an inanimate object as a he or a she force their speakers to talk about such an object as if it were a man or a woman. And as anyone whose mother tongue has a gender system will tell you, once the habit has taken hold, it is all but impossible to shake off. When I speak English, I may say about a bed that “it” is too soft, but as a native Hebrew speaker, I actually feel “she” is too soft. “She” stays feminine all the way from the lungs up to the glottis and is neutered only when she reaches the tip of the tongue.
In recent years, various experiments have shown that grammatical genders can shape the feelings and associations of speakers toward objects around them. In the 1990s, for example, psychologists compared associations between speakers of German and Spanish. There are many inanimate nouns whose genders in the two languages are reversed. A German bridge is feminine (die Brücke), for instance, but el puente is masculine in Spanish; and the same goes for clocks, apartments, forks, newspapers, pockets, shoulders, stamps, tickets, violins, the sun, the world and love. On the other hand, an apple is masculine for Germans but feminine in Spanish, and so are chairs, brooms, butterflies, keys, mountains, stars, tables, wars, rain and garbage. When speakers were asked to grade various objects on a range of characteristics, Spanish speakers deemed bridges, clocks and violins to have more “manly properties” like strength, but Germans tended to think of them as more slender or elegant. With objects like mountains or chairs, which are “he” in German but “she” in Spanish, the effect was reversed.
In a different experiment, French and Spanish speakers were asked to assign human voices to various objects in a cartoon. When French speakers saw a picture of a fork (la fourchette), most of them wanted it to speak in a woman’s voice, but Spanish speakers, for whom el tenedor is masculine, preferred a gravelly male voice for it. More recently, psychologists have even shown that “gendered languages” imprint gender traits for objects so strongly in the mind that these associations obstruct speakers’ ability to commit information to memory.
Of course, all this does not mean that speakers of Spanish or French or German fail to understand that inanimate objects do not really have biological sex — a German woman rarely mistakes her husband for a hat, and Spanish men are not known to confuse a bed with what might be lying in it. Nonetheless, once gender connotations have been imposed on impressionable young minds, they lead those with a gendered mother tongue to see the inanimate world through lenses tinted with associations and emotional responses that English speakers — stuck in their monochrome desert of “its” — are entirely oblivious to. Did the opposite genders of “bridge” in German and Spanish, for example, have an effect on the design of bridges in Spain and Germany? Do the emotional maps imposed by a gender system have higher-level behavioral consequences for our everyday life? Do they shape tastes, fashions, habits and preferences in the societies concerned? At the current state of our knowledge about the brain, this is not something that can be easily measured in a psychology lab. But it would be surprising if they didn’t.
The area where the most striking evidence for the influence of language on thought has come to light is the language of space — how we describe the orientation of the world around us. Suppose you want to give someone directions for getting to your house. You might say: “After the traffic lights, take the first left, then the second right, and then you’ll see a white house in front of you. Our door is on the right.” But in theory, you could also say: “After the traffic lights, drive north, and then on the second crossing drive east, and you’ll see a white house directly to the east. Ours is the southern door.” These two sets of directions may describe the same route, but they rely on different systems of coordinates. The first uses egocentric coordinates, which depend on our own bodies: a left-right axis and a front-back axis orthogonal to it. The second system uses fixed geographic directions, which do not rotate with us wherever we turn.
We find it useful to use geographic directions when hiking in the open countryside, for example, but the egocentric coordinates completely dominate our speech when we describe small-scale spaces. We don’t say: “When you get out of the elevator, walk south, and then take the second door to the east.” The reason the egocentric system is so dominant in our language is that it feels so much easier and more natural. After all, we always know where “behind” or “in front of” us is. We don’t need a map or a compass to work it out, we just feel it, because the egocentric coordinates are based directly on our own bodies and our immediate visual fields.
But then a remote Australian aboriginal tongue, Guugu Yimithirr, from north Queensland, turned up, and with it came the astounding realization that not all languages conform to what we have always taken as simply “natural.” In fact, Guugu Yimithirr doesn’t make any use of egocentric coordinates at all. The anthropologist John Haviland and later the linguist Stephen Levinson have shown that Guugu Yimithirr does not use words like “left” or “right,” “in front of” or “behind,” to describe the position of objects. Whenever we would use the egocentric system, the Guugu Yimithirr rely on cardinal directions. If they want you to move over on the car seat to make room, they’ll say “move a bit to the east.” To tell you where exactly they left something in your house, they’ll say, “I left it on the southern edge of the western table.” Or they would warn you to “look out for that big ant just north of your foot.” Even when shown a film on television, they gave descriptions of it based on the orientation of the screen. If the television was facing north, and a man on the screen was approaching, they said that he was “coming northward.”
When these peculiarities of Guugu Yimithirr were uncovered, they inspired a large-scale research project into the language of space. And as it happens, Guugu Yimithirr is not a freak occurrence; languages that rely primarily on geographical coordinates are scattered around the world, from Polynesia to Mexico, from Namibia to Bali. For us, it might seem the height of absurdity for a dance teacher to say, “Now raise your north hand and move your south leg eastward.” But the joke would be lost on some: the Canadian-American musicologist Colin McPhee, who spent several years on Bali in the 1930s, recalls a young boy who showed great talent for dancing. As there was no instructor in the child’s village, McPhee arranged for him to stay with a teacher in a different village. But when he came to check on the boy’s progress after a few days, he found the boy dejected and the teacher exasperated. It was impossible to teach the boy anything, because he simply did not understand any of the instructions. When told to take “three steps east” or “bend southwest,” he didn’t know what to do. The boy would not have had the least trouble with these directions in his own village, but because the landscape in the new village was entirely unfamiliar, he became disoriented and confused. Why didn’t the teacher use different instructions? He would probably have replied that saying “take three steps forward” or “bend backward” would be the height of absurdity.
So different languages certainly make us speak about space in very different ways. But does this necessarily mean that we have to think about space differently? By now red lights should be flashing, because even if a language doesn’t have a word for “behind,” this doesn’t necessarily mean that its speakers wouldn’t be able to understand this concept. Instead, we should look for the possible consequences of what geographic languages obligetheir speakers to convey. In particular, we should be on the lookout for what habits of mind might develop because of the necessity of specifying geographic directions all the time.
In order to speak a language like Guugu Yimithirr, you need to know where the cardinal directions are at each and every moment of your waking life. You need to have a compass in your mind that operates all the time, day and night, without lunch breaks or weekends off, since otherwise you would not be able to impart the most basic information or understand what people around you are saying. Indeed, speakers of geographic languages seem to have an almost-superhuman sense of orientation. Regardless of visibility conditions, regardless of whether they are in thick forest or on an open plain, whether outside or indoors or even in caves, whether stationary or moving, they have a spot-on sense of direction. They don’t look at the sun and pause for a moment of calculation before they say, “There’s an ant just north of your foot.” They simply feel where north, south, west and east are, just as people with perfect pitch feel what each note is without having to calculate intervals. There is a wealth of stories about what to us may seem like incredible feats of orientation but for speakers of geographic languages are just a matter of course. One report relates how a speaker of Tzeltal from southern Mexico was blindfolded and spun around more than 20 times in a darkened house. Still blindfolded and dizzy, he pointed without hesitation at the geographic directions.
How does this work? The convention of communicating with geographic coordinates compels speakers from the youngest age to pay attention to the clues from the physical environment (the position of the sun, wind and so on) every second of their lives, and to develop an accurate memory of their own changing orientations at any given moment. So everyday communication in a geographic language provides the most intense imaginable drilling in geographic orientation (it has been estimated that as much as 1 word in 10 in a normal Guugu Yimithirr conversation is “north,” “south,” “west” or “east,” often accompanied by precise hand gestures). This habit of constant awareness to the geographic direction is inculcated almost from infancy: studies have shown that children in such societies start using geographic directions as early as age 2 and fully master the system by 7 or 8. With such an early and intense drilling, the habit soon becomes second nature, effortless and unconscious. When Guugu Yimithirr speakers were asked how they knew where north is, they couldn’t explain it any more than you can explain how you know where “behind” is.
But there is more to the effects of a geographic language, for the sense of orientation has to extend further in time than the immediate present. If you speak a Guugu Yimithirr-style language, your memories of anything that you might ever want to report will have to be stored with cardinal directions as part of the picture. One Guugu Yimithirr speaker was filmed telling his friends the story of how in his youth, he capsized in shark-infested waters. He and an older person were caught in a storm, and their boat tipped over. They both jumped into the water and managed to swim nearly three miles to the shore, only to discover that the missionary for whom they worked was far more concerned at the loss of the boat than relieved at their miraculous escape. Apart from the dramatic content, the remarkable thing about the story was that it was remembered throughout in cardinal directions: the speaker jumped into the water on the western side of the boat, his companion to the east of the boat, they saw a giant shark swimming north and so on. Perhaps the cardinal directions were just made up for the occasion? Well, quite by chance, the same person was filmed some years later telling the same story. The cardinal directions matched exactly in the two tellings. Even more remarkable were the spontaneous hand gestures that accompanied the story. For instance, the direction in which the boat rolled over was gestured in the correct geographic orientation, regardless of the direction the speaker was facing in the two films.
Psychological experiments have also shown that under certain circumstances, speakers of Guugu Yimithirr-style languages even remember “the same reality” differently from us. There has been heated debate about the interpretation of some of these experiments, but one conclusion that seems compelling is that while we are trained to ignore directional rotations when we commit information to memory, speakers of geographic languages are trained not to do so. One way of understanding this is to imagine that you are traveling with a speaker of such a language and staying in a large chain-style hotel, with corridor upon corridor of identical-looking doors. Your friend is staying in the room opposite yours, and when you go into his room, you’ll see an exact replica of yours: the same bathroom door on the left, the same mirrored wardrobe on the right, the same main room with the same bed on the left, the same curtains drawn behind it, the same desk next to the wall on the right, the same television set on the left corner of the desk and the same telephone on the right. In short, you have seen the same room twice. But when your friend comes into your room, he will see something quite different from this, because everything is reversed north-side-south. In his room the bed was in the north, while in yours it is in the south; the telephone that in his room was in the west is now in the east, and so on. So while you will see and remember the same room twice, a speaker of a geographic language will see and remember two different rooms.
It is not easy for us to conceive how Guugu Yimithirr speakers experience the world, with a crisscrossing of cardinal directions imposed on any mental picture and any piece of graphic memory. Nor is it easy to speculate about how geographic languages affect areas of experience other than spatial orientation — whether they influence the speaker’s sense of identity, for instance, or bring about a less-egocentric outlook on life. But one piece of evidence is telling: if you saw a Guugu Yimithirr speaker pointing at himself, you would naturally assume he meant to draw attention to himself. In fact, he is pointing at a cardinal direction that happens to be behind his back. While we are always at the center of the world, and it would never occur to us that pointing in the direction of our chest could mean anything other than to draw attention to ourselves, a Guugu Yimithirr speaker points through himself, as if he were thin air and his own existence were irrelevant.
IN WHAT OTHER WAYS might the language we speak influence our experience of the world? Recently, it has been demonstrated in a series of ingenious experiments that we even perceive colors through the lens of our mother tongue. There are radical variations in the way languages carve up the spectrum of visible light; for example, green and blue are distinct colors in English but are considered shades of the same color in many languages. And it turns out that the colors that our language routinely obliges us to treat as distinct can refine our purely visual sensitivity to certain color differences in reality, so that our brains are trained to exaggerate the distance between shades of color if these have different names in our language. As strange as it may sound, our experience of a Chagall painting actually depends to some extent on whether our language has a word for blue.
In coming years, researchers may also be able to shed light on the impact of language on more subtle areas of perception. For instance, some languages, like Matses in Peru, oblige their speakers, like the finickiest of lawyers, to specify exactly how they came to know about the facts they are reporting. You cannot simply say, as in English, “An animal passed here.” You have to specify, using a different verbal form, whether this was directly experienced (you saw the animal passing), inferred (you saw footprints), conjectured (animals generally pass there that time of day), hearsay or such. If a statement is reported with the incorrect “evidentiality,” it is considered a lie. So if, for instance, you ask a Matses man how many wives he has, unless he can actually see his wives at that very moment, he would have to answer in the past tense and would say something like “There were two last time I checked.” After all, given that the wives are not present, he cannot be absolutely certain that one of them hasn’t died or run off with another man since he last saw them, even if this was only five minutes ago. So he cannot report it as a certain fact in the present tense. Does the need to think constantly about epistemology in such a careful and sophisticated manner inform the speakers’ outlook on life or their sense of truth and causation? When our experimental tools are less blunt, such questions will be amenable to empirical study.
For many years, our mother tongue was claimed to be a “prison house” that constrained our capacity to reason. Once it turned out that there was no evidence for such claims, this was taken as proof that people of all cultures think in fundamentally the same way. But surely it is a mistake to overestimate the importance of abstract reasoning in our lives. After all, how many daily decisions do we make on the basis of deductive logic compared with those guided by gut feeling, intuition, emotions, impulse or practical skills? The habits of mind that our culture has instilled in us from infancy shape our orientation to the world and our emotional responses to the objects we encounter, and their consequences probably go far beyond what has been experimentally demonstrated so far; they may also have a marked impact on our beliefs, values and ideologies. We may not know as yet how to measure these consequences directly or how to assess their contribution to cultural or political misunderstandings. But as a first step toward understanding one another, we can do better than pretending we all think the same.
Guy Deutscher is an honorary research fellow at the School of Languages, Linguistics and Cultures at the University of Manchester. His new book, from which this article is adapted, is “Through the Language Glass: Why the World Looks Different in Other Languages,” to be published this month by Metropolitan Books.

Genes Take Charge, and Diets Fall by the Wayside

Genes Take Charge, and Diets Fall by the Wayside

Published: May 8, 2007
Correction AppendedIt was 1959. Jules Hirsch, a research physician at Rockefeller University, had gotten curious about weight loss in the obese. He was about to start a simple experiment that would change forever the way scientists think about fat.
Fred R. Conrad/The New York Times
Jules Hirsch, a research physician at Rockefeller University, conducted a simple but groundbreaking experiment on obesity nearly 50 years ago, changing the way scientists think about fat.

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Gina Kolata answered readers' questions about this article.Read her answers.
Obese people, he knew, had huge fat cells, stuffed with glistening yellow fat. What happened to those cells when people lost weight, he wondered. Did they shrink or did they go away? He decided to find out.
It seemed straightforward. Dr. Hirsch found eight people who had been fat since childhood or adolescence and who agreed to live at the Rockefeller University Hospital for eight months while scientists would control their diets, make them lose weight and then examine their fat cells.
The study was rigorous and demanding. It began with an agonizing four weeks of a maintenance diet that assessed the subjects’ metabolism and caloric needs. Then the diet began. The only food permitted was a liquid formula providing 600 calories a day, a regimen that guaranteed they would lose weight. Finally, the subjects spent another four weeks on a diet that maintained them at their new weights, 100 pounds lower than their initial weights, on average.
Dr. Hirsch answered his original question — the subjects’ fat cells had shrunk and were now normal in size. And everyone, including Dr. Hirsch, assumed that the subjects would leave the hospital permanently thinner.
That did not happen. Instead, Dr. Hirsch says, “they all regained.” He was horrified. The study subjects certainly wanted to be thin, so what went wrong? Maybe, he thought, they had some deep-seated psychological need to be fat.
So Dr. Hirsch and his colleagues, including Dr. Rudolph L. Leibel, who is now at Columbia University, repeated the experiment and repeated it again. Every time the result was the same. The weight, so painstakingly lost, came right back. But since this was a research study, the investigators were also measuring metabolic changes, psychiatric conditions, body temperature and pulse. And that led them to a surprising conclusion: fat people who lost large amounts of weight might look like someone who was never fat, but they were very different. In fact, by every metabolic measurement, they seemed like people who were starving.
Before the diet began, the fat subjects’ metabolism was normal — the number of calories burned per square meter of body surface was no different from that of people who had never been fat. But when they lost weight, they were burning as much as 24 percent fewer calories per square meter of their surface area than the calories consumed by those who were naturally thin.
The Rockefeller subjects also had a psychiatric syndrome, called semi-starvation neurosis, which had been noticed before in people of normal weight who had been starved. They dreamed of food, they fantasized about food or about breaking their diet. They were anxious and depressed; some had thoughts of suicide. They secreted food in their rooms. And they binged.
The Rockefeller researchers explained their observations in one of their papers: “It is entirely possible that weight reduction, instead of resulting in a normal state for obese patients, results in an abnormal state resembling that of starved nonobese individuals.”
Eventually, more than 50 people lived at the hospital and lost weight, and every one had physical and psychological signs of starvation. There were a very few who did not get fat again, but they made staying thin their life’s work, becoming Weight Watchers lecturers, for example, and, always, counting calories and maintaining themselves in a permanent state of starvation.
“Did those who stayed thin simply have more willpower?” Dr. Hirsch asked. “In a funny way, they did.”
One way to interpret Dr. Hirsch and Dr. Leibel’s studies would be to propose that once a person got fat, the body would adjust, making it hopeless to lose weight and keep it off. The issue was important, because if getting fat was the problem, there might be a solution to the obesity epidemic: convince people that any weight gain was a step toward an irreversible condition that they most definitely did not want to have.
But another group of studies showed that that hypothesis, too, was wrong.
It began with studies that were the inspiration of Dr. Ethan Sims at the University of Vermont, who asked what would happen if thin people who had never had a weight problem deliberately got fat.
His subjects were prisoners at a nearby state prison who volunteered to gain weight. With great difficulty, they succeeded, increasing their weight by 20 percent to 25 percent. But it took them four to six months, eating as much as they could every day. Some consumed 10,000 calories a day, an amount so incredible that it would be hard to believe, were it not for the fact that there were attendants present at each meal who dutifully recorded everything the men ate.
Once the men were fat, their metabolisms increased by 50 percent. They needed more than 2,700 calories per square meter of their body surface to stay fat but needed just 1,800 calories per square meter to maintain their normal weight.
When the study ended, the prisoners had no trouble losing weight. Within months, they were back to normal and effortlessly stayed there.
The implications were clear. There is a reason that fat people cannot stay thin after they diet and that thin people cannot stay fat when they force themselves to gain weight. The body’s metabolism speeds up or slows down to keep weight within a narrow range. Gain weight and the metabolism can as much as double; lose weight and it can slow to half its original speed.
That, of course, was contrary to what every scientist had thought, and Dr. Sims knew it, as did Dr. Hirsch.
The message never really got out to the nation’s dieters, but a few research scientists were intrigued and asked the next question about body weight: Is body weight inherited, or is obesity more of an inadvertent, almost unconscious response to a society where food is cheap, abundant and tempting? An extra 100 calories a day will pile on 10 pounds in a year, public health messages often say. In five years, that is 50 pounds.
The assumption was that environment determined weight, but Dr. Albert Stunkard of theUniversity of Pennsylvania wondered if that was true and, if so, to what extent. It was the early 1980s, long before obesity became what one social scientist called a moral panic, but a time when those questions of nature versus nurture were very much on Dr. Stunkard’s mind.
He found the perfect tool for investigating the nature-nurture question — a Danish registry of adoptees developed to understand whether schizophrenia was inherited. It included meticulous medical records of every Danish adoption between 1927 and 1947, including the names of the adoptees’ biological parents, and the heights and weights of the adoptees, their biological parents and their adoptive parents.
Dr. Stunkard ended up with 540 adults whose average age was 40. They had been adopted when they were very young — 55 percent had been adopted in the first month of life and 90 percent were adopted in the first year of life. His conclusions, published in The New England Journal of Medicine in 1986, were unequivocal. The adoptees were as fat as their biological parents, and how fat they were had no relation to how fat their adoptive parents were.
The scientists summarized it in their paper: “The two major findings of this study were that there was a clear relation between the body-mass index of biologic parents and the weight class of adoptees, suggesting that genetic influences are important determinants of body fatness; and that there was no relation between the body-mass index of adoptive parents and the weight class of adoptees, suggesting that childhood family environment alone has little or no effect.”
In other words, being fat was an inherited condition.
Dr. Stunkard also pointed out the implications: “Current efforts to prevent obesity are directed toward all children (and their parents) almost indiscriminately. Yet if family environment alone has no role in obesity, efforts now directed toward persons with little genetic risk of the disorder could be refocused on the smaller number who are more vulnerable. Such persons can already be identified with some assurance: 80 percent of the offspring of two obese parents become obese, as compared with no more than 14 percent of the offspring of two parents of normal weight.”
A few years later, in 1990, Dr. Stunkard published another study in The New England Journal of Medicine, using another classic method of geneticists: investigating twins. This time, he used the Swedish Twin Registry, studying its 93 pairs of identical twins who were reared apart, 154 pairs of identical twins who were reared together, 218 pairs of fraternal twins who were reared apart, and 208 pairs of fraternal twins who were reared together.
The identical twins had nearly identical body mass indexes, whether they had been reared apart or together. There was more variation in the body mass indexes of the fraternal twins, who, like any siblings, share some, but not all, genes.
The researchers concluded that 70 percent of the variation in peoples’ weights may be accounted for by inheritance, a figure that means that weight is more strongly inherited than nearly any other condition, including mental illnessbreast cancer or heart disease.
The results did not mean that people are completely helpless to control their weight, Dr. Stunkard said. But, he said, it did mean that those who tend to be fat will have to constantly battle their genetic inheritance if they want to reach and maintain a significantly lower weight.
The findings also provided evidence for a phenomenon that scientists like Dr. Hirsch and Dr. Leibel were certain was true — each person has a comfortable weight range to which the body gravitates. The range might span 10 or 20 pounds: someone might be able to weigh 120 to 140 pounds without too much effort. Going much above or much below the natural weight range is difficult, however; the body resists by increasing or decreasing the appetite and changing the metabolism to push the weight back to the range it seeks.
The message is so at odds with the popular conception of weight loss — the mantra that all a person has to do is eat less and exercise more — that Dr. Jeffrey Friedman, an obesity researcher at the Rockefeller University, tried to come up with an analogy that would convey what science has found about the powerful biological controls over body weight.
He published it in the journal Science in 2003 and still cites it:
“Those who doubt the power of basic drives, however, might note that although one can hold one’s breath, this conscious act is soon overcome by the compulsion to breathe,” Dr. Friedman wrote. “The feeling of hunger is intense and, if not as potent as the drive to breathe, is probably no less powerful than the drive to drink when one is thirsty. This is the feeling the obese must resist after they have lost a significant amount of weight.”

This is an excerpt from Gina Kolata’s new book, “Rethinking Thin: The New Science of Weight Loss — and the Myths and Realities of Dieting” (Farrar, Straus & Giroux).
Correction: May 12, 2007

An article in Science Times on Tuesday about the role of genes in weight gain misstated the publication date for an article in the journal Science describing the biological controls over body weight. The article was published in 2003, not 2000.

In Studies of Virtual Twins, Nature Wins Again

In Studies of Virtual Twins, Nature Wins Again

Sandy Huffaker for The New York Times
MAMAS AND PAPAS Parents are sometimes surprised by virtual twins. Deborah and Dave Curry, center, learned that Deborah was pregnant with Julie, left, after the birth mother of Sara, right, chose them as parents.
Published: September 3, 2008
Ramona, Calif.
Curry Family
SISTER ACT Sara, left, and Julie Curry, here at about 4, are virtual twins: less than nine months apart, raised together, and unrelated.
Ann Johansson for The New York Times
MOTHER NATURE Dr. Nancy L. Segal studies virtual twins for the material they contribute to the nature-versus-nurture question. She says that evidence suggests nature is winning.
David Ahntholz for The New York Times
AS sisters only four months apart, Julie and Sara Curry grew up being peppered with questions from confused classmates. Your mom was in labor for four months? asked one friend, said Sara, 19. How is it possible? others inquired.
The Curry sisters, college sophomores who live with their parents in this high desert town on the outskirts of San Diego, are what Dr. Nancy L. Segal, a psychologist who is researching behavioral differences among twins, refers to as virtual twins. By her definition, virtual twins are unrelated children born within nine months of each other who enter a family, through birth or adoption, in the first year of life. Since 1991, Dr. Segal has been studying 137 such sets of siblings, whose average age difference is three months.
As scientific subjects, virtual twins provide a rich pool of material for researchers tackling the nature-versus-nurture question. In Dr. Segal’s studies, as in so many involving biological twins, it seems that nature is winning.
Raised together essentially from birth, or at least since infancy, virtual twins may be genetic strangers, but they share an environment from an early point in life.
A twin herself, Dr. Segal runs the Twin Studies Center atCalifornia State University, Fullerton, and is the author of two books on twins. She said her work has shown that virtual twins have less in common in terms of behavior, intelligence and decision-making than fraternal or identical twins, including those reared apart, or even biological siblings several years apart in age. Her research has appeared in publications like the Journal of Educational Psychology over the last few years.
“I expected the virtual twins to be more alike than they were because they had been raised together all their lives,” said Dr. Segal, who has also studied hundreds of pairs of fraternal and identical twins, including dozens reared apart. “Yet they were so much less alike. It gives us another piece of evidence in the whole nature-versus-nurture puzzle.”
While it is difficult to quantify the phenomenon, researchers say that virtual twins are an increasingly common result of Americans having children later in life, facing fertility issues and forming families through a patchwork of channels: adoptions, surrogate births, natural pregnancies and fertility treatments, which can lead to multiple births. Many parents, having struggled with infertility for years, pursue several avenues at once to increase their chances of having at least one child. If two adoptions or an adoption and apregnancy work out at about the same time, the stage is set for virtual twins.
Peggi Ignagni of Oberlin, Ohio, had been trying to become pregnant for nine years when she and her husband, Tony, applied for a foster-care license, hoping they could adopt an infant after taking him into foster care. They got Nickholas when he was 3 days old but decided to proceed with in vitro fertilization, fearing that they might not be able to keep the boy. The fertility treatment worked, and Ms. Ignagni became pregnant with triplets who were born eight months after Nickholas. She and her husband, who owns a medical device company, now have four 6-year-olds. “At least they were all potty-trained within the same week,” she said.
In the case of the Curry sisters, Sara was adopted at birth by Deborah and Dave Curry, who are both retired from the Navy. The couple had tried having children for almost four years before they arranged for a private adoption. Ms. Curry became pregnant with Julie a month after Sara’s birth mother chose them as parents. When they left the hospital with Sara, they were stopped by a security guard and asked to explain why they were leaving with a newborn when Ms. Curry was obviously still pregnant.
The Currys — he is one of six siblings, she is one of 11 — say the differences between Julie and Sara are striking. They saw fewer differences between themselves and their own siblings, they said. Moreover, the girls became more different as they grew older and were less influenced by their parents, a conclusion that Dr. Segal has drawn through her research on other virtual twins as well. Their genes came to play a larger role in determining their aptitudes and personality traits, Dr. Segal said, adding that the experiences of other virtual twins she has studied provide more evidence of that.
Sara loves horror films but hates extreme sports; Julie likes feel-good films but loves jumping out of planes with a parachute. “I’ll jump off a cliff but I won’t watch ‘Saw,’ ” Julie said, referring to the gore-filled movie.
Sara goes to church; Julie doesn’t. Sara wears six earrings on each ear; Julie rarely wears jewelry. Sara is chatty, Julie quiet. Sara wears glasses, Julie contacts. Sara dresses up; Julie generally dresses down.
The dissimilarities may sound like those that occur among any siblings, but their parents and Dr. Segal, who has studied the sisters at two different times, say the contrast between them seems to go much deeper. In fact, she said the differences she found in general intelligence between the sisters were greater than you would find in most biological siblings, even those of very different ages.
Dr. Segal’s research typically involves interviewing virtual twins when they are at least 4 years old, giving them intelligence tests and having their parents and teachers fill out extensive questionnaires on behavior, their relationship with their sibling and their school, medical and dental histories. So far she has conducted follow-up interviews with 42 of the 137 pairs, including Sara and Julie; there is no age limit for the subjects she is studying.
Unlike some other virtual twins, Sara and Julie were not dressed alike or treated as twins in school. “They are totally different,” Mr. Curry said. “They offset each other.” As the family sat around their dining room table on a recent afternoon, Mr. Curry turned to his daughters and said: “It has to be more nature. You grew up so close, you were together 24-7.” He turned to Sara and said, “She’s a stabilizer to your drama.” And to Julie, “She brings excitement to you.”
“Yeah,” Julie said to her sister, “you bring me out of my shell.”
Some virtual twins in the study, however, have been deliberately raised as twins from birth. Julie Dykstra, a former nurse who lives in Belmont, Mich., had two adoptions come through within the same week. Her sons, now 6, were due on May 1 and May 3. Each was born 8 pounds 2 ounces and 21 inches long, she said, 10 days apart. “I never felt like I didn’t have twins,” she said. “I felt like I was immersed in it.”
They have grown up feeling like twins, and the family has told their school that they are twins.
“They have twin language,” Mrs. Dykstra said. “They know what the other is thinking and going to say before he says it. They met at 13 days and 3 days old.”
Dr. Segal said that while “genetics do not tell the whole story,” even if parents treat their virtual twins as biological twins or if the children show similarities early in life, her research has found that environment still has “minimal or no effect” on them in terms of behavior and intelligence. Virtual twins can seem very similar in their early years, she said, but in the long term a shared environment is not “going to have a lasting impact.”
Mrs. Dykstra and her husband, Todd, a pastor at Maranatha Bible Church, later adopted another set of virtual twins, two girls who are 20 days apart and are now 2. One was adopted from China and did not join the family until she was 10 months old. Mrs. Dykstra said she does not feel the girls are twins because one had been in an orphanage in China and came into the family so much later than the other. She added that the girls are still young. Six months ago the couple adopted another girl at birth, the biological sibling of one of their adopted daughters, and Mrs. Dykstra said she was excited to find out how the three sisters will be different. “We are like a little petri dish,” she said.
Some critics and adoption agencies say that having virtual twins (sometimes called pseudo twins or artificial twins) should be avoided by parents when possible, so that each child receives adequate parental attention. Some say that parents are not being truthful or fair when they attempt to arrange more than one adoption from birth mothers who might not choose them if they knew another infant would be brought into the home within the first year.
“People need to be very well counseled,” said Joyce Maguire Pavao, the chief executive and founder of the Center for Family Connections in Cambridge, Mass., which provides counseling and other services to what the center calls blended families.
“Adoption should be about finding families for children, not about finding children for families,” she said. “In many cases parents are doing this without understanding what the ramifications are. I think it’s fine to do it if people are well aware that doing it may be very difficult.”
But Dr. Segal said that in most cases fate, more than parents’ choices, leads to instances of virtual twins, and that those parents cannot be faulted for covering as many bases as possible, given that so much can go wrong with high-risk pregnancies and adoptions. In her work, she said, she found that parents were happy to have children close in age because it offered the siblings companionship.
Several major twin studies over the last 20 years, particularly those following twins raised by different families, have provided what scientists say is clear evidence that genetics play a greater role than environment in intelligence and a range of personality traits. Dr. Segal’s research, believed to be the first to examine virtual twins as a subset of the twin population, has bolstered the prevailing view through another lens.
Over the last 17 years, Dr. Segal and her researchers have tested verbal and nonverbal abilities in intelligence tests of identical, fraternal and virtual twins. More recently they have conducted other tests that evaluate how subjects make decisions, asking them to answer questions based on how they thought they and their sibling would answer together. She found striking differences among the virtual twins. Among the questions: name a book, a movie and an ice cream flavor, and if your twin was lost in the park, where would you look? That research is scheduled for publication this fall in Personality and Individual Differences, a psychological journal.
Dr. Segal has found that identical twins were the most alike in their thinking, fraternal twins somewhat less so, and virtual twins strikingly different. When it comes to intelligence, for example, her research has found that only 25 percent of the differences between twins — virtual, fraternal or identical — can be accounted for by their environment, 75 percent by genetics.
Not all of the virtual twins in Dr. Segal’s study show intellectual or social disparities. Ginger Relyea, a dance and fitness instructor who lives in Encinitas, Calif., with her husband, Steve, a vice chancellor of the University of California, San Diego, has two 11-year-old boys who are 11 weeks apart. One was adopted, the other born to a surrogate. On recent intelligence tests at school, they scored three points apart. The boys, each with a spray of freckles across his nose and cheeks, and each 4 feet 9 1/2 inches tall (though one is 12 pounds heavier), look like fraternal twins.
When they were infants and toddlers, they were often dressed alike, and in early photographs they appear identical. As babies, their personalities were very different: Nathan was a screamer, Dylan quiet. By about a year, they had begun to seem more like twins, Ms. Relyea said, and they reached milestones together, walking within a week of each other, for example.
Until about a year ago, she said, they acted like twins and were treated like twins, but differences have started to emerge. “I prefer freestyle sports, skateboarding and surfing,” said Nathan, the younger of the two. “Dylan tends to be more aggressive. Even though he’s only 3 months older, he takes advantage of the big brother, older, dominant thing.”
Dylan said: “I like the three-month difference. It makes me feel in command.” Nathan concurred: “He likes power,” he said.
But, Nathan added, he stands up to Dylan when he has to. “Some of our biggest arguments are over which is better, shorts or jeans,” he said.