Humor isn't the only trigger of human laughter

Laughter is almost universal. It's an expression that is seen across all human cultures; babies begin to laugh within the first few months of life, and animals such as apes and even rats exhibit forms of laughter.

The ubiquity of laughter suggests that it's a behavior that dates far back in human cultural history and evolution - and that you might be able to trace laughter to some of the most basic parts of the brain.

The neurobiological roots of laughter will be the focus of a lecture this Saturday by Steven Small, Professor in Neurology and Psychology, built from the latest discoveries in brain imaging research. But Small's lecture won't be happening at the big Neuroscience meeting at McCormick Place, but as a special part of the Chicago Humanities Festival.

Small, appearing from 10 to 11 a.m. Saturday at the Max Palevsky Cinema in Ida Noyes Hall, 1212 E. 59th St., said he will give a talk for non-scientists on the strange but primal act of laughing, including where it appears to be localized in the brain and what can happen to make this simple act go awry.

Small, whose research focuses on the neurobiology of language, said he has not studied laughter himself, but found the behavior to be an intriguing example of the brain at work. Gathering material for his talk led him to discover popular 1920's novelty records of people laughing, medical case studies of uncontrollable laughter caused by neurological diseases and tales of a contagious laughing epidemic in Tanzania that lasted as long as one week in some children.

For his lecture, titled "Humor Humours, Laughter and the Brain", Small said he will focus on laughter and its relation to emotional expression, which is not always related to what people find funny - a distinction that actually makes neurobiological sense.

"Laughter as a response to humor is what we think of, but that's not what laughter is. It's a reflex." Small said. "It's a motor sequence and a sound sequence, and it can be produced by a mechanism that doesn't even have to be controlled by the cerebral cortex. You don't need to have a cognitive stimulus: I could tickle you, and you would laugh. It doesn't have to have humor involved at all.

"Of course, its association with emotion, social exchange and humor is what makes laughter in humans different from laughter in other animals."

As a demonstration of how laughter and humor can be dissociated, Small will show footage (acquired from neurologist colleagues) of patients who suffer from laughing spells. This uncontrollable laughter can be seen in patients suffering from epilepsy, neurodegenerative diseases such as amyotrophic lateral sclerosis or after a stroke, Small said. But while brain lesion studies indicate that the act of laughing is mediated by regions in the brainstem, where reflexive actions like breathing and sweating are controlled, damage to almost any part of the brain can cause involuntary laughing spells.

"It's a big enigma, when you look at lesions," Small said. "Some of the diseases that you get when you have laughter in fact are diseases in which people laugh without any emotional feeling whatsoever."

Another mysterious phenomenon of laughter is its ability to spread between people, a feature that television shows notably try to exploit by running laugh tracks after sitcom punch lines. Small will argue that laughter's contagious property is evidence for the existence of mirror neurons, brain cells that become active when an organism is watching an expression or behavior that they themselves can perform.

"When you smile or when you see someone smiling, the same regions of the brain are active," Small said. "If you see two people laughing at a joke you didn't hear, you may laugh anyway. There's a real imitative aspect of it that's been demonstrated. There are overlapping areas for laughing and seeing laughter."

Hence, Small's alternative title for the talk: "Laugh, and the Whole World Laughs with You." And as a scientific test during his lecture, you can try your hardest not to laugh as he shows video and plays audio of other people laughing - it's incredibly hard to do.

By Robert Mitchum