When you hear someone laugh behind you, you probably picture them on the phone or with a friend – smiling and experiencing a warm, fuzzy feeling inside. Chances are just the sound of the laughter could make you smile or even laugh along. But imagine that the person laughing is just walking around alone in the street, or sitting behind you at a funeral. Suddenly, it doesn’t seem so inviting.
The truth is that laughter isn’t always positive or healthy. According to science, it can be classified into different types, ranging from genuine and spontaneous to simulated (fake), stimulated (for example by tickling), induced (by drugs) or even pathological. But the actual neural basis of laughter is still not very well known – and what we do know about it largely comes from pathological clinical cases.
Laughter and the appreciation of humor are vital components of adaptive social, emotional and cognitive function. Surprisingly, they are not uniquely human. Primates and apes also enjoy a good chuckle. This may have evolved because it helps them survive. Laughter is, after all, a communal activity which promotes bonding, diffuses potential conflict and eases stress and anxiety. But it loses its momentum quickly when indulged in alone (solitary laughter can have ominous connotations).