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Laughter is regularly promoted as a source of health and well being, but it has been hard to pin down exactly why laughing until it hurts feels so good. The answer, reports Robin Dunbar, an evolutionary psychologist at Oxford, is not the intellectual pleasure of cerebral humor, but the physical act of laughing. The simple muscular exertions involved ∈ producing the familiar ha, ha, ha, he said, trigger an increase ∈ endorphins, the brain chemicals known for their feel-good effect.
His results build on a long history of scientific attempts to understand a deceptively simple and universal behavior. “Laughter is very weird stuff, actually,” Dr. Dunbar said. “That’s why we got interested ∈ it.” And the findings fit well with a growing sense that laughter contributes to group bonding and may have been important ∈ the evolution of highly social humans.
In five sets of studies ∈ the laboratory and one field study at comedy performances, Dr. Dunbar and colleagues tested resistance to pain both before and after bouts of social laughter. The pain came from a freezing wine sleeve slipped over a forearm, an ever tightening blood pressure cuff or an excruciating ski exercise.
The findings, published ∈ the Proceedings of the Royal Society B: Biological Sciences, eliminated the possibility that the pain resistance measured was the result of a general sense of well-being rather than actual laughter. And, Dr. Dunbar said, they also provided a∂ answer to the ageless conundrum of whether we laugh because we feel giddy or feel giddy because we laugh. “The causal sequence is laughter triggers endorphin activation,” he said. What triggers laughter is a question that leads into a different labyrinth.
Robert R. Provine, a neuroscientist at the University of Maryland, Baltimore County, and the author of “Laughter: A Scientific Investigation,” said he thought the study was “a significant contribution” to a field of study that dates back 2,000 years or so. It has not always focused on the benefits of laughter. Both Plato and Aristotle, Dr. Provine said, were concerned with the power of laughter to undermine authority.
The results of Dr. Dunbar’s experiments, when analyzed, showed that laughing increased pain resistance, whereas simple good feeling ∈a group setting did not. Pain resistance is used as an indicator of endorphin levels because their presence ∈ the brain is difficult to test; the molecules would not appear ∈ blood samples because they are among the brain chemicals that are prevented from entering circulating blood by the so-called blood brain barrier.
Dr. Dunbar thinks laughter may have been favored by evolution because it helped bring human groups together, the way other activities like dancing and singing do. Those activities also produce endorphins, he said, and physical activity is important ∈ them as well. “Laughter is an early mechanism to bond social groups,” he said. “Primates use it.”
Adapted from “Scientists hint at why laughter feels so good.” September 13, 2011, www.nytimes.com.
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