Unit 8 Nature and Nurture新編大學(xué)英語(yǔ)第二版第三冊(cè)課文翻譯

1、Unit 8 Nature and NurtureTwins, Genes, and EnvironmentHeredity or environment: which is stronger? The potentials which a person is born with determine in some way what he will do in life. Therefore heredity is fate, a kind of predestination. However, genes do not work in a vacuum; as soon as we begi

2、n considering the role that they play in the development of the individual, we see that there can be no development without the interacting environment. No characteristic is caused exclusively by either environment or genes. The relative effects of heredity and environment are most clearly observabl

3、e in identical twins. Most identical twins are raised together and are remarkably alike in both appearance and behavior. These cases demonstrate that individuals with the same genes, when raised in the same environment, will respond to it in much the same way. They do not indicate what would happen

4、if these identical individuals were raised separately. A number of studies have been made of identical twins raised apart. The twins who were the subjects of these studies lived in America, were raised in much the same physical environments, and experienced much the same nutritional histories. There

5、fore, as one might expect, they maintained the closest resemblance to each other in physical appearance, height, and weight. Exceptions occurred when one twin had developed a rather severe illness and the other had not; but on the whole everyone is impressed by the great psychological and physical l

6、ikenesses that exist between identical twins, even those who have been separated from infancy. In a study of nineteen sets of twins who had been separated from birth, investigators found that in approximately two thirds of the sets there were no more significant differences than existed among unsepa

7、rated pairs of twins. This strongly suggests the power of the genes and the limitation of the effect of environment. However, it must be remembered that, although the identical twins who were studied lived in different families far removed from each other, the environments in those families were not

8、, on the whole, substantially different. Usually every effort would be made to put each child in a home with a background similar to that of its own family, and therefore it should not be surprising to find that the twins developed similarly. But in those cases in which there had been a greater diff

9、erence in the environments of the separated twins, the differences between the twins were more substantial. The following case illustrates what happens to identical twins when they are brought up in contrasting environments. Gladys and Helen were born in a small Ohio town and were separated at about

10、 eighteen months of age. They did not meet again until they were twenty-eight years old. Helen had been adopted twice. Her first foster parents had proved to be unstable, and Helen had been returned to the orphanage after a couple of years; after several months she was again adopted, by a farmer and

11、 his wife who lived in southeastern Michigan. This was her home for the next twenty-five years. Her second foster-mother, though she had had few educational advantages herself, was determined that Helen should receive a good education; Helen eventually graduated from college, taught school for twelv

12、e years, married at twenty-six, and had a daughter. Gladys was adopted by a Canadian railroad conductor and his wife. When she was in the third grade, the family moved to a rather isolated part of the Canadian Rockies, where there were no schools, and Gladys' formal education came to an end, and

13、 was not resumed until the family moved to Ontario. She stayed at home and did housework until she was seventeen, and then went to work in a knitting mill. She went to Detroit at nineteen, got a job, and married when she was twenty-one. Helen had been healthier than Gladys, in childhood and adulthoo

14、d, but other than that, their environments had been very similar except for their educations. Their weight, height, hair color, and teeth were very similar. The differences that distinguished them were obviously associated with the different social lives they had led. Helen was confident, graceful,

15、made the most of her personal appearance, and showed considerable polish and ease in social relationships. Gladys was shy, self-conscious, quiet and without charming or graceful manners. A scientist who studied them remarked, "As an advertisement for a college education the contrast between the

16、se two twins should be quite effective." Considering the nature of their environmental experiences, the differences in Helen and Gladys are not surprising. Since psychological traits depend so much upon experience, it is to be expected that they will reflect it. On the other hand, traits that a

17、re not liable to be influenced by the environment are more likely to exhibit a high degree of similarity in identical twins. Important as they are, genes alone are never absolutely responsible for any trait. What we can do is set by the genes, but what we actually do is largely determined by the env

18、ironment. 基因、環(huán)境與雙胞胎遺傳與環(huán)境究竟哪一個(gè)影響更大呢？從某種程度上講，一個(gè)人生來(lái)具有的潛力將決定他一生的作為。因此遺傳即命運(yùn)，是命中注定的東西。然而，基因并不是在真空中發(fā)揮作用的；一旦我們開(kāi)始認(rèn)識(shí)到基因在個(gè)人發(fā)展中所起的作用，我們就會(huì)明白，沒(méi)有與其相互作用的環(huán)境，就不可能有任何個(gè)人的發(fā)展。沒(méi)有一個(gè)特點(diǎn)是完全由環(huán)境或者完全由基因造成的。遺傳和環(huán)境的相互影響在同卵雙胞胎中最易觀察到。大多數(shù)的同卵雙胞胎是在一起撫養(yǎng)長(zhǎng)大的，因而無(wú)論在外表還是行為上都驚人的相像。這些實(shí)例說(shuō)明，若在同樣的環(huán)境中撫養(yǎng)長(zhǎng)大，具有相同基因的個(gè)體就會(huì)以幾乎同樣的方式對(duì)環(huán)境做出反應(yīng)。但這些例子并不能說(shuō)明如果把這些同

19、卵雙胞胎分開(kāi)撫養(yǎng)會(huì)發(fā)生什么情況。對(duì)分開(kāi)撫養(yǎng)的同卵雙胞胎已進(jìn)行了許多研究。被研究的這些雙胞胎都生活在美國(guó)，成長(zhǎng)的自然環(huán)境幾乎相同，并且具有幾乎相同的營(yíng)養(yǎng)史。因而，正如所料，他們?cè)谕獗?、身高和體重上極其相似。但也有例外：一對(duì)雙胞胎中的一個(gè)患了相當(dāng)嚴(yán)重的疾病而另一個(gè)卻沒(méi)生病；但是總體而言，同卵雙胞胎，甚至從嬰兒時(shí)就分離的同卵雙胞胎，在心理和身體上會(huì)如此相似，給每個(gè)人留下了深刻的印象。在對(duì)從一出生就分離的19對(duì)雙胞胎的研究中，研究者發(fā)現(xiàn)，其中約三分之二的雙胞胎之間的差異與一起長(zhǎng)大的雙胞胎之間的差異一樣不明顯。這有力地說(shuō)明了基因的影響力和環(huán)境作用的局限性。然而，必須記住的是，盡管被研究的同卵雙胞胎生活在

20、不同家庭里且相距甚遠(yuǎn)，但總體而言，那些家庭的環(huán)境基本上沒(méi)有什么差異。人們通常都會(huì)千方百計(jì)地將每個(gè)孩子安置在和他自己原來(lái)的家庭背景相同的家庭里，因而發(fā)現(xiàn)這些雙胞胎成長(zhǎng)中有不少相似之處就不足為奇了。但是在那些分開(kāi)撫養(yǎng)的雙胞胎的生長(zhǎng)環(huán)境有較大差異的實(shí)例中，雙胞胎之間的差異就很大了。下面的例子說(shuō)明了在對(duì)比度很大的環(huán)境中成長(zhǎng)的同卵雙胞胎的情況。格拉迪斯和海倫出生于俄亥俄州的一個(gè)小鎮(zhèn)，在大約18個(gè)月大時(shí)被分開(kāi)撫養(yǎng)。她們直到18歲才再次相遇。海倫被領(lǐng)養(yǎng)了兩次。由于她最初的養(yǎng)父母靠不住，兩年后海倫又被送回到孤兒院。過(guò)了幾個(gè)月，她再一次被住在密歇根東南部的一對(duì)農(nóng)場(chǎng)主夫婦領(lǐng)養(yǎng)。此后25年她一直住在那里。她的第二個(gè)

21、仰慕盡管本身沒(méi)受過(guò)什么教育，卻下決心要讓海倫得到良好的教育；海倫最終大學(xué)畢業(yè)，教了12年的書(shū)，26歲時(shí)結(jié)婚，并有了一個(gè)女兒。格拉迪斯被加拿大的一個(gè)列車乘務(wù)員及其妻子領(lǐng)養(yǎng)。她讀三年級(jí)的那一年，全家搬到了加拿大落基山脈一帶一個(gè)相當(dāng)偏僻的地方，那兒沒(méi)有學(xué)校，格拉迪斯的正是教育也就此結(jié)束，知道全家搬到安大略省后才得以繼續(xù)。于是格拉迪斯就呆在家里干家務(wù)，一直到她17歲，隨后在一家針織廠工作。19歲那年她去了底特律，找到了一份工作，21歲時(shí)結(jié)了婚。海倫在兒童和成年時(shí)期都一直比格拉迪斯健康，但除了這一點(diǎn)以及各自所受的教育不同之外，她們的生活環(huán)境十分相似。她們的體重、身高、發(fā)色和牙齒都十分相似。她們之間的區(qū)別

22、顯然與她們各自的社交生活不同有關(guān)。 海倫自信、舉止得體、充分利用了她外表的優(yōu)勢(shì)，在社交中也顯得很從容、有修養(yǎng)。格拉迪斯則害羞、忸怩、沉默寡言，缺乏迷人或優(yōu)雅的風(fēng)度。一位研究她們的科學(xué)家曾經(jīng)說(shuō)過(guò)：“這兩個(gè)雙胞胎之間的懸殊差異真可謂是大學(xué)教育的頗有說(shuō)服力的廣告。”考慮到她們?cè)诃h(huán)境方面的經(jīng)歷的本質(zhì)不同，海倫和格拉迪斯之間的差異也就不足為怪了。由于心理特點(diǎn)在很大程度上取決于經(jīng)歷，可想而知心理特點(diǎn)也反映經(jīng)歷。另一方面，那些不易受環(huán)境影響的特點(diǎn)更有可能在同卵雙胞胎中表現(xiàn)出高度的相似性。盡管基因十分重要，但是基因本身絕不能完全決定任何一個(gè)特點(diǎn)。我們的能力會(huì)達(dá)到什么程度由基因注定，而我們真正做了什么則主要由環(huán)

23、境決定。Science Looks Twice at Twins1   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 para

24、des, fireworks, magic acts, a 5 K 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 fes

25、tival. Some come seeking clues to the causes of health problemsskin 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 importantand most controversialwork are those who study nature and

26、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 inh

27、erit from our parents (nature)? How much do our experiences in life (nurture)the social environment we grow up inhave to do with it?5   If you were a scientist interested in this question, wouldnt you love to study identical twins? Just think of it: two people who developed from

28、the same fertilized egg. That is, two people with the exact same set of genes. Any differences between suchidentical 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.

29、Remember, most twins share a similar environmentsame 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 scientis

30、ts led by psychologist Thomas J. Bouchard Jr. has studied about 65 pairs of identical twins who were raised apart. Theyve 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.

31、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 IQ and personality tests. To measure personality, the psychologists try to determine thing

32、s 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

33、week, each twin has answered about 15,000 questions.10  Bouchards 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 i

34、dentical 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 3

35、9, 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 di

36、scovered 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 everyones life has enough details that a number of coincidences are bound to exist. Whats more, for every coincidence discovered by a pair o

37、f 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 beyon

38、d 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 naturethe genes we inheritexerts a notably strong influence ov

39、er 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 

40、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 Bouchards team earned identical or nearly identical scores on adult intelligence tests.15  But m

41、ost 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 were dedicated nonconformists. According to Bouchard, the genes you were born with have a lot to do w

42、ith 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 yo

43、u study whether intelligence is inherited, they ask, when there are so many different ways just to define intelligence? The problem applies7 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 e

44、ven though genes may have a strong influence over our lives, theyre 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! 科學(xué)再次關(guān)注雙胞胎如果你對(duì)雙胞胎感興趣的話，那么雙胞胎鎮(zhèn)會(huì)使你著迷。從1976年起的每個(gè)夏天，這個(gè)位于俄亥俄州克利夫蘭郊外的小鎮(zhèn)都會(huì)擠滿眾多的雙胞胎。去年夏天，有2356對(duì)

45、雙胞胎從世界各地來(lái)到這里，參加并觀看游行、焰火、魔術(shù)表演、五公里賽跑以及100多項(xiàng)的比賽：評(píng)選出年紀(jì)最大的、年紀(jì)最小的、最像的、最不像的，以及兩人相加笑起來(lái)嘴咧得最大的雙胞胎。你要是去過(guò)那兒的話，你可能會(huì)注意到有很多科學(xué)家也參加了這個(gè)盛會(huì)。有些科學(xué)家是來(lái)尋找引起疾病的緣由例如皮膚病、癌癥、心臟病。另外一些科學(xué)家則對(duì)雙胞胎自身的感受感興趣。但是在所有的科學(xué)家中，從事最重要的也是最有爭(zhēng)議的工作的是這樣一些科學(xué)家，他們專門研究先天遺傳和后天培養(yǎng)這個(gè)由來(lái)已久的問(wèn)題，即研究我們是如何發(fā)展成現(xiàn)在這個(gè)樣子的。為什么我們有些人精通數(shù)學(xué)或擅長(zhǎng)寫作，而另外一些人則在藝術(shù)或籃球上出類拔萃？是什么造成了我們?cè)谥橇Α⒉?/p>

46、能和品味上的差異？這些主要是由我們從父母那里繼承來(lái)的基因（先天遺傳）決定的嗎？同我們的生活經(jīng)歷（后天培養(yǎng)），也就是我們成長(zhǎng)的社會(huì)環(huán)境又有多大關(guān)系呢？如果你是一個(gè)對(duì)這個(gè)問(wèn)題感興趣的科學(xué)家，你難道不想研究一下同卵雙胞胎嗎？想一想，從同一受精卵發(fā)育出來(lái)了兩個(gè)人。也就是說(shuō)，兩個(gè)人有完全相同的基因。同卵雙胞胎之間存在的任何不同都只能是他們成長(zhǎng)環(huán)境不同的結(jié)果。但是你能說(shuō)他們之間的任何相同點(diǎn)都是基因相同的緣故嗎？不一定吧。記住，大多數(shù)雙胞胎都有相似的成長(zhǎng)環(huán)境同樣的房子，同樣的飲食，同樣的親戚等等。研究在不同環(huán)境下?lián)狃B(yǎng)的同卵雙胞胎，或許是你能準(zhǔn)確衡量先天遺傳和后天培養(yǎng)所起的作用的唯一方法。在過(guò)去的10年間，由

47、心理學(xué)家小托馬斯·J·布沙爾帶領(lǐng)的一組科學(xué)家研究了大約65對(duì)分開(kāi)撫養(yǎng)的同卵雙胞胎。他們還研究了大約45對(duì)分開(kāi)撫養(yǎng)的異卵雙胞胎。科學(xué)家們把每對(duì)雙胞胎帶到明尼蘇達(dá)大學(xué)進(jìn)行為期一周、深入細(xì)致的檢測(cè)。小組里的醫(yī)生和牙醫(yī)們給這些雙胞胎進(jìn)行了全面的體檢。他們記錄了雙胞胎的身高、體重、眼睛顏色、耳朵的形狀和頭圍。同時(shí)，心理學(xué)家們還對(duì)雙胞胎進(jìn)行了智商和性格測(cè)試。為了測(cè)試性格，心理學(xué)家們?cè)O(shè)法測(cè)定了：雙胞胎們對(duì)事情擔(dān)憂的程度，他們是謹(jǐn)慎型的還是魯莽型的，以及他們的創(chuàng)造力如何。他們根據(jù)雙胞胎們對(duì)一些陳述的回答來(lái)衡量這些方面以及其他一些性格特征，這些陳述包括“我很少魯莽行事”，“木柴燃燒的火焰激發(fā)

48、我的想象力”等。一周結(jié)束時(shí)，每個(gè)雙胞胎都回答了大約15000個(gè)問(wèn)題。布沙爾小組對(duì)分開(kāi)撫養(yǎng)的雙胞胎之間的相似之處感到非常吃驚。例如他們的手勢(shì)和姿勢(shì)經(jīng)常很相似，真是令人驚奇。在照片上，很多雙胞胎擺出的姿勢(shì)幾乎一模一樣。有些同卵雙胞胎還發(fā)現(xiàn)他們的生活方式極其相似。“吉姆兄弟”是布沙爾研究的第一對(duì)同卵雙胞胎，他們出生四周后就被不同的家庭領(lǐng)養(yǎng)。他們都在俄亥俄州長(zhǎng)大，彼此相隔45英里。當(dāng)他們?cè)?9歲重逢時(shí)，發(fā)現(xiàn)了一系列驚人的相同之處：兩個(gè)人都叫吉姆，都開(kāi)同一型號(hào)的藍(lán)色雪佛蘭，都喜歡做木工，都有啃手指甲的習(xí)慣，養(yǎng)的狗都叫“Toy”。兩個(gè)人都有傍晚頭痛的毛病，都是在18歲時(shí)開(kāi)始的。在吉姆兄弟之間所發(fā)現(xiàn)的相同點(diǎn)

49、在明尼蘇達(dá)小組研究的雙胞胎身上都普遍存在的。有些對(duì)明尼蘇達(dá)小組研究工作持批評(píng)態(tài)度的人說(shuō)“這些巧合沒(méi)什么可奇怪的”。他們認(rèn)為每個(gè)人的生活里都有很多的細(xì)節(jié)，因此必然會(huì)有巧合。而且，對(duì)于異地?fù)狃B(yǎng)的同卵雙胞胎之間發(fā)現(xiàn)的任何一個(gè)巧合，持懷疑態(tài)度者都能指出大量未被發(fā)現(xiàn)的不同點(diǎn)。同一對(duì)雙胞胎可能有不同型號(hào)的電視機(jī)，支持不同的足球隊(duì)。但不同點(diǎn)是不會(huì)被報(bào)道的，因?yàn)樗鼈儾粫?huì)使人吃驚。但是除了巧合之外，明尼蘇達(dá)的科學(xué)家們收集并分析了有關(guān)雙胞胎的健康、智力和個(gè)性方面的大量數(shù)據(jù)。布沙爾認(rèn)為，有關(guān)異地?fù)狃B(yǎng)的同卵雙胞胎的數(shù)據(jù)清楚地顯示了：先天遺傳，即我們所繼承的基因，對(duì)我們的生活有顯著的影響。該小組發(fā)現(xiàn)，這些同卵雙胞胎在身

50、高、指紋和心率等生理特征方面極其相似。成年的同卵雙胞胎還往往有相似的病史，例如同時(shí)得了青光眼。明尼蘇達(dá)小組報(bào)告說(shuō)智力似乎也更受基因的影響而不是環(huán)境。盡管由不同的家庭撫養(yǎng)長(zhǎng)大，布沙爾小組研究的同卵雙胞胎在成人智力測(cè)驗(yàn)中所得的分?jǐn)?shù)完全相同或幾乎相同。但是最令人吃驚的是，明尼蘇達(dá)小組發(fā)現(xiàn)基因?qū)τ趥€(gè)性的形成起著重要作用，例如，會(huì)決定我們是尊重傳統(tǒng)、循規(guī)蹈矩，還是會(huì)成為堅(jiān)定的離經(jīng)叛道者。根據(jù)布沙爾的看法，你與生俱來(lái)的基因?qū)δ闶欠褡孕?、快?lè)、樂(lè)觀或者對(duì)世界上的事是否持消極態(tài)度有很大影響。明尼蘇達(dá)小組的一位心理學(xué)家南希·西格爾說(shuō)：“這項(xiàng)研究令人信服地表明：基因影響人們行為的每個(gè)方面?！绷硪恍┛茖W(xué)家

51、不同意這個(gè)說(shuō)法。他們質(zhì)問(wèn)：既然光是對(duì)智力的定義就多種多樣，你們又怎么能夠去研究智力是否是遺傳的呢？他們認(rèn)為同樣的問(wèn)題也存在于其它的性格特征中。布沙爾本人表示了這樣的觀點(diǎn)：即使是他所研究過(guò)的最相似的雙胞胎也是彼此不同的。因此即便基因?qū)ξ覀兊纳钣泻艽蟮挠绊?，它們也不是唯一起影響作用的因素。我們的日常?jīng)歷也有助于塑造我們。你知道這意味著什么：為了考試，你還得學(xué)習(xí)！Talkative Parents Make Kids SmarterAn exhaustive study of how "typical" parents talk with their children duri

52、ng the first few years of their life has yielded a mountain of valuable data and some initial findings with serious social implications. There are striking class differences in the nature and extent of parental interaction with children between the age of 9 months and 3 years. This results in a cons

53、iderable intellectual boost for kids in white-collar families, a modest lift for those in blue-collar households, and a disturbingly weak assist for children in welfare families. Young children whose parents talk extensively to them score much higher on later IQ tests than those exposed to minimal a

54、mounts of parental talk, assert study codirectors Betty Hart of the University of Kansas and Todd Risley of the University of Alaska. "The more parents talk with their young children, the more good things happen intellectually to those kids later on," Risley contends. "But the massive

55、 class differences in this parental behavior surprised us and suggest that children in welfare families face problems that cannot be reversed by a few hours of Head Start classes every week." Hart and Risley presented their findings, based on observations of forty-two families in their homes lo

56、cated in the Kansas City area, at the annual meeting of the American Psychological Association in Toronto last week. The study has intensified an already intense debate over the relative influence of genes and environment on IQ and intellectual potential, both in individuals and racial groups. The 2

57、.5-year investigation, followed by 3 years during which researchers analyzed a mountain of written and tape-recorded observations, adds a new dimension to the nurture side of the controversy. Families in Hart and Risley's study functioned well and exhibited no serious problems, such as child abu

58、se or psychiatric illness. Thirteen professional families included at least one parent who worked in a white-collar occupation; in twenty-three working-class families, jobs included electrician and plumber; six families subsisted mainly on welfare. The families represented a range of racial and ethn

59、ic groups; eight were single-parent families. The families ranged in size from a single child to seven children. Trained observers spent 1 hour every 2 months tape-recording and writing down the nature of all at-home interactions with a designated child in each family beginning at 9 months of age. O

60、bservers focused only on that child and whoever talked or interacted with him or her. They never offered advice to parents, even when asked. The parent or parents in each family displayed a characteristic level of talk with their young children, month after month, Risley asserts. Overall, parents in professional families prov