The Science of Laughter

By Ellen Kuwana
Neuroscience for Kids Staff Writer
October 15, 2001

Your biology teacher may insist that science is not a laughing matter, but scientists at Vanderbilt University in Tennessee would argue that laughter is a scientific matter. These scientists have found a basic difference in how men and women laugh...the actual sounds males and females make in response to a joke is different.

Men and Women Laugh Differently

Jo-Anne Bachorowski and her research team recorded the laughter of 97 volunteers. The volunteers watched clips from funny movies like Monty Python and When Harry Met Sally. The scientists were surprised at the variety of sounds people made when they laughed. Rarely did they hear sounds that we stereotype as laughter such as "tee hee hee" or "ho ho ho." More often they heard vowel sounds such as those heard in "car" (aah) or "glow" (ooh). What's more, men and women laughed differently.

Women tended to laugh in a more sing-song way, while men more often grunted or snorted. Women produced sing-song laughter 50% of the time, whereas men grunted or snorted as often as they made sing-song laughter (see table below).

TYPE OF LAUGHTERWOMENMEN
Sing-song ("voiced")50%33%
Grunt (exhaling through mouth25%33%
Snort (exhaling through nose)25%33%

The researchers caution that this work was limited to people in the United States, so the results may not be universal. Bachorowski predicts that cultural influences may affect what CAUSES people to laugh, but it probably does not change how we laugh.

When Do We Laugh?

Although we do laugh at jokes and funny movies, 80% of our laughter occurs during everyday comments in everyday social situations. Robert Provine, a neurobiologist who studies laughter, with help from three graduate students, went to places such as shopping malls and eavesdropped on more than 1200 conversations. They noted who was speaking, who was listening, who laughed and when, and whether the speaker and listeners were female or male. They found that the person speaking laughed 46% more than the listeners and that women laughed more often than men. Furthermore, the response to the speaker depended on the speaker's gender. People, whether male or female, laughed more readily in response to a male speaker. The researchers also observed that laughter rarely interrupted speech. Instead, laughter came at the end of a phrase, much as punctuation follows a written sentence.

Laughter and the Brain?

Research has shown that parts of the limbic system are involved in laughter. The limbic system is a primitive part of the brain that is involved in emotions and helps us with basic functions necessary for survival. Two structures in the limbic system have been shown to play a role in laughter: the amygdala and the hippocampus.

Humans may be "tuned" for laughter much in the same way that songbirds are "tuned" for song -- especially their own specific family song. (While birdsong of one species may sound the same to you and me, there are subtle differences among the birds' songs.) Certain nerve cells in the songbird's brain "fire" in response to hearing his song. Perhaps humans have specialized nerve cells that respond to laughter. After all, laughter is a specialized vocalization, and we are "tuned" to respond to vocalizations with language.

Researchers frequently learn about how the brain functions by studying what happens when something goes wrong. People with certain types of brain damage produce abnormal laughter. This is found most often in people with pseudobulbar palsy, gelastic epilepsy, and to a lesser degree, with multiple sclerosis, ALS, and some brain tumors. In one particular case, doctors attempted to control seizures of a 16-year-old girl with epilepsy by electrically stimulating her brain. When they stimulated an area of her cerebral cortex (the supplementary motor area), she smiled (low voltage) and laughed (higher voltage).

We use our brain for many things. Laughter is yet another part of human behavior that the brain regulates. It helps us clarify our intentions and provides an emotional context to our conversations. Laughter, then, is used as a signal for being part of a group--it signals acceptance and positive interactions. It clues the listener in to the emotional tone of the conversation and the speaker's intentions. This may be one reason it is more difficult to interpret the meaning of an e-mail or letter--emotional clues about the sender's tone are missing.

Did You Know?
Laughter is contagious. Since 1950, TV has exploited this by adding "laugh tracks" to sitcoms. People laugh more readily upon hearing others laugh. When you hear others laugh, you actually think the TV show is more humorous.

Babies start to laugh at about 4 months of age. Babies who are born blind and deaf can laugh, so the ability to see or hear is not required for laughter.

References:

  1. New Scientist article "Girls Giggle and Guys Grunt" by Ben Longstaff, September 27, 2001.
  2. Hear Samples of Laughter from the Study
  3. Bachorowski, J.-A., Smoski, M.J., & Owren, M.J. The acoustic features of human laughter. Journal of the Acoustical Society of America, 110 (1581) 2001.
  4. Laughter and the Brain
  5. Laughter by R. Provine, in American Scientist, 1996.
  6. Fried, I., Wilson, C.L., MacDonald, K.A., and Behnke EJ. Electric current stimulates laughter. Nature, 391:650, 1998.


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