We laugh because it's good for us; mirth is a kind of social glue.
WHEN MOVIE STAR Julia Roberts erupts with her ear-to-ear megawatt laughter, we really love it. We all express ourselves in many ways, but laughter is the most enjoyable, peculiar and mysterious phenomenon.
Sounds of laughter are all around us. They are so pervasive that we tend to dismiss them. It is hard to believe that laughter can be a subject of serious scientific research.
Why do we laugh?
It is commonly understood that we laugh in response to jokes. But that's not absolutely correct.
Based on an analysis of 1,200 laughter episodes, psychology professor Robert Provine, of the University of Maryland, concludes that 80 per cent of laughter has nothing to do with humour.
In fact, we laugh at all occasions: we laugh when we are nervous, excited, tense, happy, tricked by someone, or simply because someone else is laughing or crying.
Doris Bergen, professor of educational psychology at Miami University in Oxford, Ohio, says that while laughter is an innate characteristic, our reasons for laughing vary at different ages. Children, for example, laugh unconditionally while adults laugh for some reason or purpose.
Babies start giggling as a result of physical interaction from games such as peekaboo. Even at that early age, a baby laughs if she anticipates her father approaching her, but watches him tumbling and falling down.
When children get to preschool age, they begin understanding riddling patterns. They laugh at riddle-telling, regardless of whether they understand the point of the riddle.
Young children are estimated to laugh over 300 times a day - a reason why they seem to have more obvious fun than adults who average 20 times daily.
Not so long ago, laughter was considered an unsocial, sinister behavior. In the eighteenth century, Lord Chesterfield, writing to his son, said, ". . . there is nothing so illiberal, and so ill-bred, as audible laughter."
According to Oliver Goldsmith, laughter was the expression of "the vacant mind" and John Ray likened it as "the hiccup of a fool."
Today we have come a long way. Laughter is accepted as a natural, social behaviour. In fact, having a good sense of humour is regarded as a thoroughly desirable attribute by almost all of us, including human resource managers.
Recent surveys indicate that laughter can enhance the quality of our conversations and productivity. It makes people feel closer to each other.
In his book, Laughter: A Scientific Investigation, Provine says that laughter is the oil in the social machine, helping human interactions run more smoothly.
Provine reveals laughter is 30 times less likely to occur when a person is alone than when a person is with others.
We tend to think of laughter as being tee-hee or ha-ha or ho-ho sorts of sounds, but studies conducted by Vanderbilt psychologist Jo-Anne Bachorowski and Cornell psychologist Michael Owren indicate otherwise: laughers produce many different kinds of sounds, including grunts and snorts.
Bachorowski and Owren studied the way 97 young adults laugh in different kind of social pairings as they watched humorous scenes from films such as When Harry Met Sally or Monty Python and the Holy Grail.
In their research, published in the September 2000 issue of the Journal of the Acoustical Society of America, the investigators found interesting gender differences in laughter sounds, with males tending to grunt and snort more often than females.
Women produced more musical laughter than men. These song-like laughs are "voiced," meaning that they involve the vocal folds, the tissues in the larynx involved in producing vowels and related sounds.
On average, men and women produced the same number of laughs, but men tended to laugh a "bit longer" than women.
A person's laughter was found to be dependent on the sex of his or her companion. When paired with friends of either sex, men laughed significantly more than men who were tested alone or with a male or female stranger.
Women, one the other hand, produced more laughs in the company of a male friend than females tested alone, with a female friend, or with a male stranger.
Laughter is greatly influential. In a study presented at the 138th Acoustic Society of America meeting, Bachorowski and Owren studied the impact that laughter sounds have on emotional responses in listeners.
In a quite room, undergraduate students listened to a set of 70 laughs over headphones. Fifty of the laughs (25 produced by males and 25 by females) were voiced. The remaining 20 laughs (10 produced by males and 10 by females) were unvoiced, sounding more like pants or cackles.
The students were asked to rate the laugh samples in terms of their friendliness, sexiness, how interested they would be in meeting the laugher, whether they thought the laugh should be included in a laugh track, and the extent to which it elicited a positive emotional response.
Regardless of the rating scheme, the researchers found that listeners were more likely to rate comparatively stereotypical, song-like laughs more positively than the other types.
"These results support the notion that one important function of laugh acoustics is to influence the emotional responses of listeners," the researchers conclude.
The science of laughter is in its infancy, but one thing is clear: laughter is good you.
Laughter stimulates our endocrine system, including the pituitary gland. The pituitary gland, in turn, stimulates release of endorphins and enkephalins, natural painkillers that are chemical cousins to opiates such as morphine and heroin.
Dr. Lee S. Berk, at Loma Linda University School of Medicine and Public Health in California, and endocrinologist Stanley Tan studied groups of average adults and found that both arms of the immune system got a boost out of laughter.
Participants faced a solid hour of videos of comedians, while a control group sat quietly out of earshot. The researchers took blood samples at 10-minute intervals before, during and after the laughter workout.
The laughter group showed increases in the good hormones - such as endorphins and neurotransmitters, and decreased levels of the stress hormones - such as cortisol and adrenaline.
Laughter also creates an increase in the number and activity level of natural killer cells, which attack virus-infected cells and some types of cancer cells. Laughter can also keep allergies at bay. According to a report in the Journal of the American Medical Association, Dr. Hajime Kimata of Unitika Central Hospital, Japan, studied the effects of laughter on patients allergic to dust mites, cedar pollen and cat dander.
Skin prick tests using a commercial allergen were performed on 26 patients before and after they viewed the Charlie Chaplin comedy Modern Times. During the same procedure, a control group watched a video featuring weather information.
The results showed that allergic reactions of comedy watchers were reduced for four hours after the screening. In contrast, there was no effect on allergic responses of weather watchers.
Laughter, along with an active sense of humour, may also help protect against heart attacks, according to a study by cardiologists at the University of Maryland Medical Center in Baltimore.
The researchers found that people with heart disease were 40 per cent less likely to laugh in a variety of situations compared to people of the same age without heart disease.
An old saying puts laughter in its true perspective and spirit: "He who laughs, lasts."