We all have experienced the positive effects of laughter. It induces a deep state of relaxation and a sense of well-being. It is also an important form of non-verbal communication that allows others to know we agree that something is funny. In this way, laughter strengthens social bonds because when we laugh we lower our guard and do not perceive the other person as a potential threat. Some have proposed that the positive emotions associated with laughter help us learn new things from others and promote cooperation. But what are the mechanisms behind all of this? How does laughter make us feel good? Robin Dunbar from the University of Oxford and his team of collaborators proposed that endorphins might be responsible for many of the beneficial effects of laughter. Endorphins are internally produced opioids that have an important role in social bonding in primates, as well as having an analgesic effect. Dunbar and his colleagues proposed that the physical action of laughing induces the release of these endorphins, just as any form of physical exercise does, causing the positive feelings we are all familiar with.

Because of the analgesic effect of endorphins, it is common practice for scientists to use pain thresholds to assess individual endorphin levels. Using this technique, Dunbar and his colleagues performed a series of experiments in which they evaluated the effect of laughter on endorphin release. During some of the experiments, volunteers were tested in groups whereas other experiments were performed on individuals. The participants were shown either funny videos, such as ‘America's Funniest Home Videos’ or other comedy shows, or videos with neutral emotional content, such as a documentary. To rule out any effects that positive feelings alone might have on their endorphin levels, the scientists also showed a group of participants non-humorous ‘feel-good’ videos of beautiful scenery. The researchers recorded the participants' laughter throughout the experiments and tested each participant's pain tolerance before and after they had watched the videos. They did this either by touching a frozen wine cooler sleeve to a participant's skin and measuring the time at which they could not tolerate it anymore or, in a separate set of experiments, by inflating a pressure cuff around the participant's arm until they could no longer stand the pain (ouch!).

Not surprisingly, the people who watched the comedy videos spent much more time laughing than those who saw the documentaries or the videos of nice scenery. Furthermore, those who watched the funny videos in a group laughed much more than those who watched the same videos alone. More interestingly, the participants increased their pain tolerance in a laughter dose-dependent fashion: the more they laughed, the more their pain threshold increased.

The team proposes that the physical exertion of sustained laughter triggers the release of endorphins, in a way similar to other types of exercise. Because humans, in contrast to other laughing apes, are capable of sustaining laughter for several minutes, the opioid effects of a good chuckle might be particularly enhanced in our species, increasing not only our pain thresholds but also strengthening social bonds and promoting collaboration and altruistic behaviour. So it seems that laughter really is the best medicine after all!

R. I. M.
van Leeuwen
E. J. C.
van Vugt
Social laughter is correlated with an elevated pain threshold
Proc. R. Soc. B