This is actually a more complicated question than might first be thought. The answer is not because someone tickled me or I heard a funny story. Both of these examples of course can trigger laughter depending on how ticklish we are and our sense of humour. But there is more to it than that. To begin, let us look at the anatomical mechanism that allows us to laugh. Put simply, it is the epiglottis constricting the larynx.
But why should certain triggers cause this to happen? Research has been carried out in this area and some of the results indicate that we often laugh when there is nothing obvious to have made us do so. Analysis of the behaviour of bonobo apes shows that they also laugh when tickled. Therefore, we can perhaps assume that the ability to laugh goes back to ancient times. It has also been suggested that it was a form of communicating before language was developed.
Like most of our systems, they originate in the brain. So, where in the brain is our laughter centre? The answer supports the idea that laughter has been a part of us since ancient times. It lies deep within our subcortex which is also an ancient part of our brains. Since it is located away from later parts of our brains which are responsible for language and other higher functions, laughter has been around for a long time. Now and again, we might laugh or want to laugh when we should not; when the situation is serious. The reason for this is that once a laugh has been initiated, our higher reasoning finds it difficult to stop it from happening.
So, it appears that laughter is its own master. When it wants to initiate, there is little we can do to stop it. But, as said above, we believe laughter is also about communication. Laughter within a group helps to tell others that things are good or that we can relax. It is contagious and therefore may alleviate any aggressive feelings in the group. It usually puts people at ease.
Finally, let’s test this out. Here is a joke I made up…. Nah, it will be the exception that proves the rule!
John Pullen 