什么能让你发笑？能让我们笑出声的原因有很多，其中一个主要原因是为了建立和维持社会联系。你觉得和朋友在一起的时候更容易笑吗？

What things make you laugh? There are many things that make us chuckle or burst into laughter. This natural show of emotion gives off signals that we are happy, we find something humorous or even that we're just a barrel of laughs! Gelotologists have been looking at why we do it and what the benefits are.

Laughter is a very primitive way of making a sound. When we do it, we make very strange noises – from wheezes and squeaks to gasps and snorts – and each sound simply reflects the muscles in the chest squeezing out air from our ribcages under very high pressure.

Most of the time our laughter is involuntary and contagious, particularly between friends. Neuroscientist, Sophie Scott, told the BBC that it's "a social emotion. It's better to laugh with people we like." She defines two types of laughter – spontaneous laughter, where we laugh instantly and uncontrollably, and conversational laughter – where we laugh together with friends. Research found, on average, people laugh seven times for every ten minutes of conversation.

The BBC World Service programme Crowd Science examined the science of laughter. It wanted to know what caused this highly infectious repetitive action. It found we use laughter to show others that we're being playful and non-threatening, and this serves to make and maintain social bonds. Also, people outside of our social group can understand the relationship between the laughers by the sound of our chuckles.

While our health is no laughing matter, research has found a good guffaw can help our body and mind – it can make us feel good and relax our bodies. It also helps us manage pain and improve our immune system. That's why laughter therapy is being used as an alternative to conventional treatments. But generally, our ability to laugh is out of our control. When you start doing it, just go with the flow and others will join in.