What makes us laugh？ Why do we laugh？Well it's funny you should ask，but this question is a very interesting one to investigate．For what at first seems like a simple question turns out to require a surprisingly complex answer -- one that takes us on a journey into the very heart of trying to understand human nature．
    Most people would guess that we laugh because something is funny．But if you watch when people actually laugh，you'll find this isn't the case．Laughter expert Robert Provine spent hours recording real conversations at shopping malls，classrooms，offices and cocktail parties，and he found that most laughter did not follow what looked like jokes．People laughed at the end of normal sentences，in response to unfunny comments or questions such as "Look，it's Andre"，or "Are you sure？"．Even attempts at humor that provoked laughter didn't sound that funny．
    So if we want to understand laughter，perhaps we need to go deeper，and look at what is going on in the brain．The areas that control laughing lie deep in the sub cortex（下皮層），and in terms of evolutionary development these parts of the brain are ancient，responsible for primal（原始的） behaviors such as breathing and basic reflexes（反射）．This means laughter control mechanisms are located a long way away from brain regions that developed later and control higher functions such as language or even memory．
    Perhaps this explains why it is so hard to control a laugh，even if we know it is inappropriate．Once a laugh is started deep within our brains these "higher function" brain regions have trouble interfering．And the opposite is true，of course．It is difficult to laugh on demand．If you consciously make yourself laugh it will not sound like the real thing - at least initially．
    But this does not fully answer the original question．To answer this，perhaps we need to look outwards，to look at the social factors at play when people laugh．Provine's study suggests that it isn't just some independent process that happens to us while we are talking to someone．He also found that laughter was most common in situations of emotional warmth and so-called "in-groupness"．
    Perhaps "transmission" is another most important feature of laughter．Just listening to someone laugh is funny．You can even catch laughter from yourself．Start with a forced laugh and if you keep it up you will soon find yourself laughing for real．
    What these observations show is that laughter is both fundamentally social，and rooted deep within our brains，part and parcel of ancient brain structures．All these things are true．And biologists say each time we get closer to an answer for a fundamental question，it deepens our appreciation of the challenge remaining to answer the others．And there is a long way to go．

What makes us laugh？
Introduction	Studying laugh is closely （1） related/ relevant related/ relevant to understanding human nature．
（2） Findings Findings	●The popular （3） belief/assumption belief/assumption is not true that we laugh because something is funny． ●The study of real conversations reveals that laughter didn't （4） necessarily necessarily follow funny comments．
Causes	Inside	● Ancient areas （5） responsible responsible for primal behaviors control laughing． ● "Higher function" regions can't （6） interfere interfere with laughing．
	（7） Outside Outside	● Situations of emotional warmth and in-groupness give （8） rise rise to laughing． ●Laughter can be （9） transmitted transmitted ，which is another most important feature．
Conclusion	The origin of laugh is associated with both brain structures and （10） social social factors．