(单词翻译:单击)
Tetrachromacy is a rare genetic condition that causes some people to see more colours than usual.
四色视觉是一种罕见的遗传病，它能使人看到更多颜色。
Most people have three types of cones in their eyes, which are sensitive to red, green, and blue light.
大多数人的眼睛里有三种视锥细胞，对红色、绿色和蓝色的光很敏感。
However, tetrachromats have four.
然而，四色视者有四种视锥细胞。
This allows them to see millions of colours that the average person can’t distinguish.
这使得他们能够看到普通人无法分辨的数百万种颜色。
So far, very few true tetrachromats have been identified, and all of them are female.
到目前为止，人们仅发现了几个四色视者，而且都是女性。
This is because the gene for an extra cone is found on the X chromosome.
这是因为第四种视锥细胞的基因位于X染色体上。
If men experience the same mutation, they are likely to become colourblind instead.
如果男性X染色体上也有这种基因，他们很可能会变成色盲。
Scientists test for tetrachromacy by asking people to sort nearly identical colours by similarity.
科学家让人们根据相似度对几乎相同的颜色进行分类，来测试其是否具有四色视觉。
The average person will likely change their answer, but a tetrachromat will always sort these colours the same way.
一般人很可能会改变自己的答案，但四色视者总是以相同的方式对这些颜色进行分类。
