Other primates maintain their bonds by grooming, which takes physical contact and therefore time. Human social networks are much larger than grooming could sustain, so something cheaper must be doing the work. One proposal is that laughter triggers the same opioid release that grooming does. That had no direct neurophysiological support. So 12 healthy men were scanned after laughing with close friends. What was released?
Laughter released the body’s own opioids. scanning with a receptor-specific tracer found release in the thalamus, the caudate nucleus and the after half an hour of comedy with close friends, alongside raised pleasurable sensations. Baseline receptor availability in the cingulate and orbitofrontal cortices tracked how much each person laughed. A separate experiment found rose after group comedy.
Primates maintain their social bonds largely by grooming, which requires touching one animal at a time. That sets a ceiling on how many relationships an individual can sustain. Human social networks significantly exceed what grooming could support, so the question is what humans use instead.
One proposal holds that endogenous opioid release after social laughter opens a neurochemical pathway, doing the job grooming does without the physical cost. It is an appealing idea that lacked direct neurophysiological support, which is what this study set out to supply.
PET imaging with the mu-opioid-receptor-specific ligand carfentanil was used to quantify laughter-induced opioid release in 12 healthy males. Before the social laughter scan the subjects watched laughter-inducing comedy clips with their close friends for 30 minutes. Before the baseline scan they spent 30 minutes alone in the testing room.
Social laughter increased pleasurable sensations and triggered endogenous opioid release in the thalamus, the caudate nucleus and the anterior insula. Baseline receptor availability in the cingulate and orbitofrontal cortices was associated with how much a person laughed. A behavioral control experiment then showed pain threshold, a proxy for opioid activation, rising significantly more after group comedy than after group drama, in both male and female volunteers. The imaging arm is twelve men, so the mechanism rests on a very small sample.
wat. Half an hour of laughing with friends released the brain’s own opioids, in the same system other primates engage by grooming each other.
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It supplies a mechanism for something sociology could only describe. If laughter buys the same neurochemical reward as grooming without the time cost, that is a plausible route to networks larger than any other primate maintains.
How do we know?
Manninen and colleagues used PET with the mu-opioid-receptor ligand carfentanil in 12 healthy males, scanning after 30 minutes of comedy with close friends and after 30 minutes alone. A behavioral pain-threshold experiment included men and women.
What is still unknown
Twelve healthy males in the imaging arm, which is small even by PET standards. The pain-threshold experiment included women, and the direct neurochemical evidence does not.
Learn something?
Where to next
What brings dancers closer, moving together or working hard together?social bonds
Can you hear how good a relationship is from when the couple laughs?laughter