雅思阅读真题Colorblindness

admin管理员组

文章数量:1530518

2024年5月17日发(作者：)

 Reading Practice

Colorblindness

A Myths related to the causes and symptoms of "colorblindness" abound throughout

the world. The term itself is misleading, since it is extremely rare for anyone to have a

complete lack of color perception. By looking into the myths related to color

blindness, one can learn many facts about the structure and genetics o the human eye.

It is a myth that colorblind people see the world as if it were a black and white movie.

There are very few cases of complete colorblindness. Those who have a complete lack

of color perception are referred to as monochromatics, and usually have a serious

problem with their overall vision as well as an inability to see colors. The fact is that

in most cases of colorblindness, there are only certain shades that a person cannot

distinguish between. These people are said to be dichromatic. They may not be able to

tell the difference between red and green, or orange and yellow. A person with normal

color vision has what is called trichromatic vision. The differences between the three

levels of color perception have to do with the cones in the human eye. A normal

human eye has three cones located inside the retina: the red cone, the green cone, and

the yellow cone. Each cone contains a specific pigment whose function is to absorb

the light of these colors and the combinations of them. People with trichromatic vision

have all three cones in working order. When one of the three cones does not function

properly, dichromatic vision occurs.

B Some people believe that only men can be colorblind. This is also a myth, though it

is not completely untrue. In an average population, 8% of males exhibit some form of

colorblindness, while only 0.5% of women do. While there may be some truth to the

idea that more men have trouble matching their clothing than women, the reason that

color vision deficiency is predominant in males has nothing to do with fashion. The

fact is that the gene for color blindness is located on the X chromosome, which men

only have one of. Females have two X chromosomes, and if one carries the defective

gene, the other one naturally compensates. Therefore, the only way for a female to

inherit colorblindness is for both of her X chromosomes to carry the defective gene.

This is why the incidence of color deficiency is sometimes more prevalent in

extremely small societies that have a limited gene pool.

C It is true that all babies are born colorblind. A baby's cones do not begin to

differentiate between many different colors until he is approximately four months old.

This is why many of the modern toys for very young babies consist of black and white

patterns or primary colors, rather than traditional soft pastels. However, some current

research points to the importance of developing an infant's color visual system. In

2004, Japanese researcher Yoichi Sugita of the Neuroscience Research Institute

performed an experiment that would suggest that color vision deficiency isn't entirely

genetic. In his experiment, he subjected a group of baby monkeys to monochromatic

lighting for one year. He later compared their vision to normal monkey who had

experienced the colorful world outdoors. It was found that the test monkeys were

1

unable to perform the color-matching tasks that the normal monkeys could.

Nevertheless, most cases of colorblindness are attributed to genetic factors that are

present at birth.

D Part of the reason there are so many inconsistencies related to colorblindness, or

"color vision deficiency" as it is called in the medical world, is that it is difficult to

know exactly which colors each human can see. Children are taught from a very

young age that an apple is red. Naming colors allows children to associate a certain

shade with a certain name, regardless of a color vision deficiency. Someone who

never takes a color test can go through life thinking that what they see as red is called

green. Children are generally tested for colorblindness at about four years of age. The

Ishihara Test is the most common, though it is highly criticized' because it requires

that children have the ability to recognize numerals. In the Ishihara Test, a number

made up of colored dots is hidden inside a series of dots of a different shade. Those

with normal vision can distinguish the number from the background, while those with

color vision deficiency will only see the dots.

E While many of the myths related to colorblindness have been busted by modern

science, there are still a few remaining beliefs that require more research in order to

be labeled as folklore. For example, there is a long-standing belief that colorblindness

can aid military soldiers because it gives them the ability to see through camouflage.

Another belief is that everyone becomes colorblind in an emergency situation. The

basis of this idea is that a catastrophic event can overwhelm the brain, causing it to

utilize only those receptors needed to perform vital tasks. In general, identifying color

is not considered an essential task in a life or death situation.

2

Read the passage and answer the questions. Use your predicting skills. Note the type

of questions.

Questions 1-5

Choose the correct heading for each section from the list of headings. There are more

headings than sections, so you will not use them all.

1

i

Section A 2 Section B 3 Section C 4 Section D 5 Section E

Colorblindness' in different countries ii Diagnosing colorblindness

iii What is colorblindness? iv Curing colorblindness

v Unsolved myths vi Animals and colorblindness

vii Developing the ability to see color viii Colorblindness and the sexes

Questions 6-8 Choose the correct letter, A, B, C, or D.

6 People who see color normally are called

A monochromatic. B dichromatic.

C tichromatic. D colorblind.

7 Children usually begin to see a variety of colors by the age of

A one month. B four months.

C one year. D four years.

8 Children who take the Ishihara Test must be able to

A distinguish letters. B write their names.

C read numbers. D name colors.

Questions 6-8 Completing a Summary

There are more answers than spaces, so you will not use them all.

It is a common 9 that only men suffer from colorblindness. On average

10 than ten percent of men have this problem. Women have two 11 .

For this reason it is 12 for a woman to suffer from colorblindness.

(myth a little less X chromosomes defective genes

fact slightly more exactly less likely more probable)

3

本文标签： 阅读真题