新編大學(xué)英語(yǔ)第二冊(cè)u(píng)nit6 Text B: Science Looks Twice at Twins
UNIT 6 AFTER-CLASS READING 1; New College English (II)
Science Looks Twice at Twins
1 If twins interest you, Twinsburg will fascinate you.
2 Every summer since 1976, this little town outside Cleveland, Ohio, has been invaded by twins. Last summer 2,356 sets of twins showed up from around the world to watch and take part in parades, fireworks, magic acts, a 5K race, and more than 100 contests: contests to honor the oldest twins, the youngest, the most alike, the least alike, the twins with the widest combined smile.
3 Had you been there, you might have noticed a large group of scientists who also attend the festival. Some come seeking clues to the causes of health problems skin diseases, cancer, and heart attack, for example. Others are interested in how it feels to be a twin. But of all the scientists, perhaps the ones doing the most important and most controversial work are those who study nature and nurture, that age-old question of how we come to be the kind of people we are.
4 Why are some of us good at math, or writing, while others excel at art or basketball? What causes the differences in our intelligence, talents, and tastes? Are they largely determined by the genes we inherit from our parents (nature)? How much do our experiences in life (nurture) the social environment we grow up in have to do with it?
5 If you were a scientist interested in this question, wouldn't you love to study identical twins? Just think of it: two people who developed from the same fertilized egg. That is, two people with the exact same set of genes. Any differences between such identical twins would have to be the result of differences in their environment. But could you also say that any similarities were the result of having the same genes?
6 Not really. Remember, most twins share a similar environment same house, food, relatives, and so on. The only way you could accurately measure the effects of nature and nurture would be to study identical twins raised apart, in different environments.
7 Over the last ten years, a team of scientists led by psychologist Thomas J. Bouchard Jr. has studied about 65 pairs of identical twins who were raised apart. They've also studied about 45 fraternal twins who were raised apart.
8 The scientists bring each pair of twins to the University of Minnesota for a week of intensive testing. Doctors and dentists on the team give the twins thorough physical examinations. They record the twins' height, weight, eye color, ear shape, and head length.
9 Meanwhile, psychologists give the twins 1Q and personality tests. To measure personality, the psychologists try to determine things like how much the twins worry, whether they are cautious or reckless, and how creative they are. They measure these and other traits by the twins' responses to statements such as "I rarely, if ever, do anything reckless" and "The flames of a wood fire stimulate my imagination". By the end of the week, each twin has answered about 15,000 questions.
10 Bouchard's team has been startled by the similarities between twins raised apart. The twins often have surprisingly similar gestures and postures, for instance. In pictures, many of the twins strike nearly identical poses. And some of the identical twins discover they have led remarkably similar lives.
11 The first set of identical twins Bouchard studied, the "Jim twins", were adopted by different families four weeks after they were born. They grew up in Ohio, 45 miles away from each other. When they were reunited at the age of 39, they discovered a series of striking similarities. Both were named Jim. Both drove the same model blue Chevrolet, liked woodworking, chewed their fingernails, and owned dogs named Toy. Both started having late-afternoon headaches at the age of 18.
12 The sort of similarities the Jim twins discovered are common with the twins the Minnesota team has studied. Some critics of the Minnesota study say the coincidences are not surprising. They argue that everyone's life has enough details that a number of coincidences are bound to exist. What's more, for every coincidence discovered by a pair of identical twins raised apart, a skeptic could point to a vast number of undiscovered differences. The same two twins might have different model television sets and support different football teams. But the differences would go unreported since they would not surprise anyone.
13 But beyond the coincidences, the Minnesota scientists have gathered and analyzed a mountain of data about the twins' health, intelligence, and personalities. And according to Bouchard, the data on the identical twins raised apart show clearly that nature the genes we inherit exerts a notably strong influence over our lives. The Minnesota team has found that these identical twins are remarkably similar in physical traits such as height, fingerprints and heart rates. Adult identical twins also tend to have similar medical histories, developing the eye disease glaucoma at the same time, for example.
14 The Minnesota team has reported that intelligence also seems to be influenced much more by genes than by environment. Despite being raised by different families, separated identical twins studied by Bouchard's team earned identical or nearly identical scores on adult intelligence tests.
15 But most surprisingly, the Minnesota team finds that genes play a big part in shaping our personalities helping to determine whether we respect tradition and like to follow rules, for example, or whether we're dedicated nonconformists. According to Bouchard, the genes you were born with have a lot to do with whether you are confident, cheerful, and optimistic, or whether you have a negative view of the world. "The study shows in a very persuasive way that genes influence every aspect of behavior," says Nancy Segal, a psychologist with the Minnesota team.
16 Other scientists disagree. How can you study whether intelligence is inherited, they ask, when there are so many different ways just to define intelligence? The same problem applies to other traits, they say.
17 Bouchard himself makes the point that even the most closely matched twins he has studied are different from each other. So even though genes may have a strong influence over our lives, they're not the only influence. Our day-to-day experiences help to mold us too.
18 You know what that means: you still have to study for tests!
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