Why laughing feels so good...

Robin Dunbar, the evolutionary psychologist at Oxford who has correlated social group size with brain size in evolution, and also argued for the importance of grooming as a group bonding mechanism, has come up with a simple and fascinating observation: social laughter increases pain resistance, suggesting that moving the muscles that are involved in a laugh causes the release of endorphins (Pain thresholds are taken to be a proxy for endorphin release). Here is the abstract from Dunbar et al.:

Although laughter forms an important part of human non-verbal communication, it has received rather less attention than it deserves in both the experimental and the observational literatures. Relaxed social (Duchenne) laughter is associated with feelings of wellbeing and heightened affect, a proximate explanation for which might be the release of endorphins. We tested this hypothesis in a series of six experimental studies in both the laboratory (watching videos) and naturalistic contexts (watching stage performances), using change in pain threshold as an assay for endorphin release. The results show that pain thresholds are significantly higher after laughter than in the control condition. This pain-tolerance effect is due to laughter itself and not simply due to a change in positive affect. We suggest that laughter, through an endorphin-mediated opiate effect, may play a crucial role in social bonding.

In a review James Gorman quotes Dunbar:

“Laughter is very weird stuff, actually,” Dr. Dunbar said. “That’s why we got interested in it.” And the findings fit well with a growing sense that laughter contributes to group bonding and may have been important in the evolution of highly social humans....Social laughter, Dr. Dunbar suggests, relaxed and contagious, is “grooming at a distance,” an activity that fosters closeness in a group the way one-on-one grooming, patting and delousing promote and maintain bonds between individual primates of all sorts.