Question

The scientists observed that the more junk food the rats ate, the more they wanted to eat – a behavior very similar to that of rats addicted(上了癮的) to heroin, a dangerous drug. Johnson said the experiment shows that the brain chemistry of obesity(肥胖) and drug addiction may be quite similar.
In their experiment, Johnson and his team studied the “pleasure center” of rats’ brains. The pleasure center is a complicated network of nerve cells. If the animal exercises or eats, the cells reward the animal by releasing chemicals into the body that make it feel good. And when the body feels good, the animal – or person – will want to do the behavior again.
For the experiment, Johnson fed foods like cheesecake to one group of rats. Food like this is high in calories and fat. Another group of rats got a regular diet. The rats that ate junk food started to eat more and more.
“They’re taking in twice the amount of calories as the control rats,” says Paul Kenny, one of Johnson’s colleagues.
Kenny and Johnson wanted to know what was going on in the brains of these rats. They first designed a way to deliver a small electrical charge to the rats’ brains. This electrical charge would stimulate the pleasure centers to release pleasure-causing chemicals. The rats could control how much stimulation – and how much pleasure – they received by running on a wheel. The more the rat ran, the more pleasure it received.
The rats that had been eating junk food started running more and more. This behavior suggested that the junk-food-eating rats needed more brain stimulation to feel good compared with rats on a normal diet. In other words, their pleasure centers were becoming less sensitive and the junk food didn’t make them feel good unless they ate more and more.
Experiments like this one could help scientists understand how chemicals in the brain contribute to obesity. With that information, they may be able to help people avoid obesity in the first place.
(Note: Answer the questions or complete the statements in NO MORE THAN TEN WORDS.)
小題1: The scientists suggested it was actually ___________________ that made the rats feel good.
小題2: How did the scientist know what was happening in the brains of the junk-food-eating rats?
小題3:What was the purpose of the experiment mentioned in the article?

Answer 1

小題1:chemicals in the brain
小題2: By delivering a small electrical charge to the rats’ brains.
小題3:To understand how chemicals in the brain contribute to obesity.

試題分析：本文主要敘述的是一項研究，研究人腦中的化學物質是如何控制我們的行為的，尤其是如何控制我們的肥胖的。
小題1:chemicals in the brain
細節題。根據第二段2,3行If the animal exercises or eats, the cells reward the animal by releasing chemicals into the body that make it feel good.可知正是老鼠釋放的化學物質讓它感覺很好。
小題2: By delivering a small electrical charge to the rats’ brains.
細節題。根據文章第五段2,3行They first designed a way to deliver a small electrical charge to the rats’ brains. This electrical charge would stimulate the pleasure centers to release pleasure-causing chemicals.可知他們向老鼠的大腦里投放了一定數量的化學物質。以此來研究具體的反應。
小題3: To understand how chemicals in the brain contribute to obesity.
推理題。根據文章主體段第一段最后2行Johnson said the experiment shows that the brain chemistry of obesity(肥胖) and drug addiction may be quite similar.可知這個研究的目的在于理解頭腦中的化學物質是如何導致我們的肥胖的。