Much research has been conducted about why humans laugh and what they laugh at—not only by psychologists, but also by philosophers, for the study of laughter crosses many disciplines. So, why do we laugh? 

The general belief is that humans laugh as a social bonding mechanism. Studies have shown that humans are over 30 times more likely to laugh with others than alone. Even " laughing gas" works more effectively on a group of people than on a single person. We all know that laughter can be very infectious. 

Some researchers believe that laughter in humans was born out of the relief our ancestors felt after danger had passed. If smiling in humans is considered an extension of the " fear" face in primates (灵长类动物), then laughter is a signal that the fear has gone. When we laugh, our " fight or flight" reaction to danger is temporarily switched off, further indicating that we now feel relaxed. So laughter is a way of discharging stress and anxiety. 

Although laughter is universal, people don't always laugh at the same things, and what people find funny often changes as they get older. Children find a lot to laugh about, as they are encountering so many things for the first time, which offers constant surprises. Teenagers often like jokes that adults find annoying, while adults often laugh at jokes about funny things in their own everyday lives. Furthermore, because a lot of our humor comes from a shared cultural background, countless jokes don't cross language and cultural barriers, with the result that what's funny in Australia may well not be in Austria.

Regardless of what different people find funny, people ought to laugh as much as they can. While we're laughing, we increase the killer cells that destroy viruses. So, the next time someone tells you they nearly died laughing, tell them it's far from the truth!