It's one of our common beliefs that mice areafraid of cats.Scientists have long known that even if a mouse has never seena cat before,it is still able to detect chemical signals released from the catand run away in fear.This has always been thought to be something that ishard-wired into a mouse's brain.
But now Wendy Ingram,a graduate student at theUniversity of California,Berkeley,has challenged this common sense.She hasfound a way to"cure"mice of their inborn fear of cats by infectingthem with a parasite,reported the science journal Nature.
The parasite,called Toxoplasma gondii,might soundunfamiliar to you,but the shocking fact is that up to one-third of peoplearound the world are infected by it.This parasite can cause different diseasesamong humans,especially pregnant women--it is linked to blindness and thedeath of unborn babies.
However,the parasite's effects on mice are unique.Ingram and her team measured how mice reacted to a cat's urine before and afterit was infected by the parasite.They noted that normal mice stayed far awayfrom the urine while mice that were infected with the parasite walked freelyaround the test area.
But that's not all.The parasite was found to bemore powerful than originally thought--even after researchers cured the mice ofthe infection.They no longer reacted with fear to a cat's smell,which couldindicate that the infection has caused a permanent change in mice's brains.
Why does a parasite change a mouse's brain insteadof making it sick like it does to humans?The answer lies inevolution."It's exciting scary to know how a parasite can manipulate amouse's brain this way,"Ingram said.But she also finds it inspiring."Typically if you have a bacterial infection,you go to a doctor and takeantibiotics and the infection is cleared and you expect all the symptoms toalso go away."She said,but this study has proven that wrong."Thismay have huge implications for infectious disease medicine."
The author's attitude towards the experimentis_______.查看材料
- A.positive
- B.subjective
- C.negative
- D.objective
正确答案及解析
正确答案
解析
态度题。在整篇文章中，作者都是在客观地叙述Wendy Ingram的新发现。故本题选D。
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