Practical Joking

/ by Maggie Wittlin /

Researchers examine how laughter may have evolved.

Secretary of Defense Donald H. Rumsfeld (right) shares a laugh with South Korean Minister of National Defense Yoon Kwang-woong, (left) and Singapore Minister for Defense Teo Chee Hean (center). Credit: Tech. Sgt. Cherie A. Thurlby, U.S. Air Force

No character sketch of a movie villain is complete without a signature evil laugh: There’s the sharp cackle of the Wicked Witch of the West, the sweet baritone of Audrey II in Little Shop of Horrors and the gradually-erupting pneumatic chuckle of Doctor Evil, to name a few. While each character’s style is unique, every evil snicker tells the viewer that these villains are not just laughing because they’re being tickled; they’re laughing to reveal their devious motivations or they’re laughing to scare us…and our hero.

There is a real distinction between authentic laughter, that which is caused by a stimulus, and laughter used to manipulate social situations, say Binghamton University researchers. In fact, these two kinds of laughter may have evolved millions of years apart.

In a paper published in the December, 2005 issue of the Quarterly Review of Biology, Binghamton undergrad Matthew Gervais and Professor, Departments of Biology and Anthropology David Sloan Wilson propose an evolutionary theory of laughter based on a review of relevant research. “The ‘lighter’ side of life deserves to be taken seriously when considering the facilitation of human success and development,” Gervais said via email.

Robert Provine, a psychology professor at the University of Maryland, Baltimore County and author of Laughter: A Scientific Investigation, agrees, noting that Gervais and Wilson have done good work in parsing other research, especially in distinguishing laughter from humor. “If you do a literature search on laughter, a lot of the material you’re going to come up with is really about humor,” Provine said. “But humor is really a sort of subcategory of the topic of laughter, instead of vice versa, because laughter is ancient and instinctive, while humor is something of relatively modern origin. So there was laughter long before there was humor.”

The authors begin their evolutionary tale of laughter well before humor came into the mix, arguing that laughter is a more basic function than even language. “Not only does it precede language developmentally…it probably preceded language in terms of evolution,” Wilson said. “So, there was a time in our history when we were laughing before we were talking.”

Laughter-like behavior started before we split from apes, the researchers say. As they tickle each other and horse around, apes give a pant-grunt, which Wilson said is a clear precursor to laughter. Wilson added that neural activity associated with laughter occurs in an ancient part of the brain, further demonstrating that laughter developed long ago. The Binghamton team estimates that laughter evolved into its modern form somewhere between two- and four-million years ago, after our transition to two-footed walking but before the beginning of human language.

Wilson and Gervais believe laughter allowed hominids living on the savanna to create a unified feeling of safety and comfort within a group. “It only takes place in a safe context,” Wilson said. “If you tickle a baby and it’s a safe context, then the baby laughs. But if it becomes menacing, then the baby cries. And whenever things get serious—if you’re really hungry, if you’re really scared—you don’t laugh.”

The stimuli that trigger laughter are reliable indications of safety, Gervais said. As laughter only occurs in these safe conditions, it communicates a sense of security to other members of a group, bringing everyone into an emotional state conducive to bonding. This may have given groups an evolutionary advantage. “Laughter could have evolved—at least in part—via a process of group selection, whereby groups with more laughter and social play were able to out-compete groups with less laughter and social play,” Gervais said.

The researchers say different kinds of laughter, those not of the “genuine” variety, evolved with other sophisticated cognitive traits, sometime within the last two-million years. Genuine laughter is innate, whereas forced laughter is learned; genuine laughter is stimulus driven, whereas forced laughter is self-initiated. When people developed language and learned to infer the beliefs and desires of others, they co-opted genuine laughter. “Conversational, embarrassed, nervous and aggressive laughter are all derived forms of laughter distinct from stimulus-driven, emotional laughter,” Gervais said. He added that genuine laughter and its conscious counterpart occur in different parts of the brain.

Researchers have previously proposed a distinction between these two types of laughter, but, prior to this paper, it wasn’t taken into serious consideration. “It’s strange because everyone intuitively knows that laughter is not always genuine but scientists had somehow not taken this intuition seriously,” Gervais said.

Laughter author Provine said Gervais and Wilson’s distinction between these two types of laughter is important. He adds to the separation a theory that our ability to easily recognize a self-initiated laugh may have led to our ability to smile. “An impetus for the evolution of smiling is the greater control you have over the act,” he said. “It’s difficult to laugh convincingly on command; it’s easier to smile convincingly on command. So smiling is a much more versatile and subtle instrument of expression than laughter, which is a kind of all-or-none thing.”

Gervais said researchers have often considered laughter to be an extreme form of smiling, not a distinct phenomenon. “We tried to treat laughter like a distinct emotional system,” he said. “This actually lent insight to our approach and revealed the importance of laughter in human evolution.”

Originally published January 12, 2006

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