一个英语句子结构的分析---在线等---高手进

一个英语句子结构的分析---在线等---高手进
Other tests have shown that laughter appears to be capable of reducing the effect of pain on the body.In one experiment doctors produced pain in groups of students who listened to different radio programs.The group,which tolerated the pain for the longest time,was the group,which listened to a funny program.The reason why laughter can reduce pain seems to be that it helps to produce endorphins（内啡肽）in the brain.
分析这个句子结构：The reason why laughter can reduce pain seems to be that it helps to produce endorphins（内啡肽）in the brain.