Unit 6
Nature and Nurture

In-Class Reading
Twins, Genes, and Environment

I. Word List
Directions: Memorize the following words and phrases before class. You will benefit from your effort when you get the passage from your teacher and read it in class.

Proper Names

Detroit
底特律（美国密歇根州东南部港市）

Gladys
（女子名）格莱蒂丝

Ohio
俄亥俄（美国州名）

0ntario
安大略省（位于加拿大中部）

Rockies
落基山脉（Rocky Mountains, 位于北美洲西部）


New Words

approximately *
adv. 大概，大约
e.g. There were approximately 50 people there.

considerable *
adj. fairly large or great 相当大的，相当多的
e.g. There was a considerable amount of memory work.

considering
prep. taking into consideration 考虑到

environmental *
adj. 环境的
e.g. Should we take this boy away because of the bad environmental influences?

exhibit *
v. show a particular quality, feeling, or type of behavior 显示，显出
e.g. The economy continued to exhibit signs of decline in September.

graceful *
adj. behaving in a polite and pleasant way 优雅的
e.g. She finally apologized, but she wasn't graceful about it.

heredity
n. 遗传

illustrate *
v. make the meaning of (something) clearer by giving related examples 阐明，说明
e.g. The lecturer illustrated his point with a diagram (图表) on the blackboard.

infancy
n. 婴儿期，幼儿期

interact *
v. 相互作用，相互影响
e.g. All things are interrelated (互相联系的) and interact on each other.

knit *
v. 编织

liable *
adj. likely 有......的倾向
e.g. We are all liable to make mistakes.

likeness *
n. 相似之处
e.g. All my children share a strong likeness.

mill *
n. 工厂
e.g. a cotton mill

observable *
adj. 看得到的，觉察得到的
e.g. That distant star is observable on a dark night.

orphanage
n. 孤儿院

polish *
n. 优雅，文雅
e.g. Travel with polite people gives polish to a girl's manners.

predestination
n. 命运，造化

remarkably *
adv. unusually, noticeably 不同寻常地，相当地
e.g. She was a remarkably good cook.

resemblance *
n. 相像
e.g. Twins often show great resemblance.

severe *
adj. very serious 严重的
e.g. She said that the pain was becoming increasingly severe.

similarity *
n. 相似，类似
e.g. There is not much similarity between the two brothers.

southeastern *
adj. 东南部的

substantially *
adv. 基本上，在本质上
e.g. Our opinions are substantially the same.

twin *
n. 双胞胎

unseparated *
adj. 未分离的

unstable *
adj. 不稳定的
e.g. I would describe her as emotionally unstable.

vacuum *
n. 真空

Twins, Genes, and Environment

1 Heredity 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 begin 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.
2 The relative effects of heredity and environment are most clearly observable 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 if these identical individuals were raised separately.
3 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. Therefore, 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 likenesses that exist between identical twins, even those who have been separated from infancy.
4 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 unseparated 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, 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 difference 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.
5 Gladys and Helen were born in a small Ohio town and were separated at about 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 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 twelve years, married at twenty-six, and had a daughter.
6 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 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.
7 Helen had been healthier than Gladys, in childhood and adulthood, 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.
8 Helen was confident, graceful, 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 these two twins should be quite effective."
9 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 are 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 environment. (830 words)
Time taken: __________ minutes


Phrases and Expressions

be liable to do something
be likely to do something 可能做某事
e.g. They are liable to run away if you speak to them.

be responsible for
be the cause of 作为......的原因
e.g. The storm was responsible for most of the damage.

bring up
educate and care for a child until he/she is grown up 抚养，养育
e.g. He left her to bring up three young children on her own.

come to an end
finish, end 结束
e.g. The meeting came to an end at last.

make the most of
get the most advantage of a situation 充分利用
e.g. You should be outside making the most of the sunshine.

no more...than...
不比......更......
e.g. You are no more capable of speaking Chinese than I am. 你说汉语的能力并不比我强。(意为两个人都说得不太好。)

on the whole
considering everything 总的来说
e.g. On the whole they got on very well with him.

respond to
do something in reply, react 响应，作出反应
e.g. The government has responded to pressure by moving towards reform.