Tell a Pygmy a good joke and the probability is that he or she will drop to the floor and roll on the ground in side-slapping, uproarious laughter. The Dobuans of New Guinea, on the other hand, revile laughter and enjoy misery. Feuding Greenland Inuits resolve disputes by publicly humiliating themselves to see who gets laughed at the most and lower-caste Tamil men giggle when addressing someone from the upper caste to express humility.
Laughter is seriously complex. It can convey meaning more effectively than words and is a language in itself. After crying, laughter is the next big communicative milestone in human development and evolves from a baby's giggle into a social tool. But what is laughter, what is its purpose and are humans truly the only creatures with the ability to laugh? Not according to Professor of Psychology and Neuroscience Robert R Provine, a laughter expert whose studies of primate behaviour discovered that when chimpanzees play, they emit a panting noise which is interpreted by other chimps as a sign of safety. It signifies that the rough and tumble is harmless and lets the other chimps know that it is safe to join in. Provine believes that this play-panting is the starting block of human laughter and that it evolved into the 'ha-ha' sound we make after bipedalism gave humans the breath control needed for staggered exhalations.
According to other studies, apes are not the only animals to display laughter-like characteristics. Dr Jaak Panksepp specialises in studying animal emotions at Washington State University. Using high-frequency detector equipment, he recorded rats and discovered that they produce ultrasonic chirps, particularly when they appeared to be playfully interacting with each other. The more he studied the rats'behaviour, the more he began to ponder whether the chirping sounds had a purpose. Then he had an idea.
"One morning I came in and I said to one of the grad students: 'Let's go tickle some rats'," he explains.
"I picked up a rat and began to tickle it, moving my fingers rapidly all over the animal's body."
As he did this, he recorded the sound the rat made. It was the same noise as the chirps he had recorded previously but was louder and more consistent with a familiar, dynamic rhythm.
"I thought, 'My God, what if that sound is laughter?'," says Panksepp. He repeated the experiment with several rats and each time the noise he recorded was the same. And on several occasions, when the tickling stopped, the rat followed his hands, as if wanting more. Although the sounds the rats made showed all the characteristics of laughter, Panksepp is careful not to label it as such. "A lot of people don't like that word. Giving human qualities to animals is a no-no, since we are closer to the angels than the other creatures of the world," he says.
This reverential view of the humanness of laughter is mirrored in Aristotelian philosophy. The ancient Greek scholar believed that it is not speech, conscious thought, culture or opposable thumbs which separate us from the beasts; it's laughter. He wrote that when a baby emits its first laugh, it is transformed from a human into a human being, describing the process as "human ensouling".
From those first baby giggles, we begin to use laughter until it becomes a communicative Swiss Army knife which can be utilised to berate others or make them feel good. It can be used to make us popular and it can be used as an emotional release mechanism. While we are born with the physical ability to laugh, the capacity to utilise it as a social tool is something we learn. And in order to do this, we need to develop a sense of humour.
Stephanie Davies, the author of Laughology: The Science of Laughter and a behaviourist, is one of the country's pre-eminent laughter experts. A former stand-up comedian, she studied the science of laughter and founded Laughology, a unique enterprise which teaches individuals in the public and private sector how to enhance their potential through laughter and humour.
She explains the distinction between the two: "Laughter is a response; it's usually the outward manifestation of humour but doesn't always have to be about something which is funny. It can be used to fit in to a social situation or it can be a way of coping with a situation."
Humour, she says, is simply a system for processing information - so it changes in us all the time, depending on factors such as age and situation. "Different factors impact on how people develop a sense of humour," Davies says.
"A child knows that laughter is positive and learns that actions which get a laugh are positive. He or she will repeat those actions or mimic them from other people and start to develop an awareness of humour based on the reactions of those around them."
And while laughter has altered through evolution, humour has also evolved and continues to do so through cultural change. What was funny 30 years ago isn't always funny today, because our understanding of the world changes over time. In the 70s, the casual racism of television comedies such as Mind Your Language and It Ain't Half Hot Mum was perceived as funny because casual racism itself was acceptable. People were allowed to laugh at it. Today, society has evolved to understand that racism is not funny, so we are less likely to laugh.
For such an integral facet of humanity, the academic study of laughter and humour is still a relatively new field. Increasingly, however, experts are beginning to investigate the personal and social benefits of laughter.
One of the best documented examples of the effect laughter can have on health involves the writer Norman Cousins, who was diagnosed with a debilitating spinal disease and given a one in 500 chance of survival in 1964. Rather than stay in hospital, he checked into a hotel where he took large doses of vitamin C and devised a treatment programme consisting of positive behaviours such as laughter, love and joy.
He watched as much comedy as he could, including episodes of Candid Camera and Marx Brothers movies and found that over time, laughter stimulated chemicals in his body which allowed him several hours of pain-free sleep. He continued the treatment until, eventually, his disease went into remission and he was able to return to work.
He wrote: "I made the joyous discovery that 10 minutes of genuine belly laughter had an anaesthetic effect and would give me at least two hours of pain-free sleep."
Since then, numerous scientists have conducted tests with similar results. The University of Maryland, for example, conducted a study where people were shown funny movies to gauge the effect on cardiac health. The results, presented at the American College of Cardiology, showed that laughter appeared to cause the inner lining of blood vessels - the endothelium - to dilate, thus increasing blood flow.
And yet the healing power of laughter is nothing new. Ancient Greeks believed human health was governed by the equilibrium of four key liquids in the body. These liquids, 'the four humours', affected emotions and physicians sent patients to the hall of comedians to be entertained as part of the healing process. The benefits of humour are even referenced in the Bible (Book of Proverbs 17.22), where it states: "A cheerful heart does good medicine, but a broken spirit makes you sick".
Throughout the centuries, court jesters were hired by royals to relieve stress: biologically, laughter reduces stress hormones such as cortisol and increases health-enhancing hormones such as endorphins. It also increases the number of antibody-producing cells and enhances the effectiveness of T cells, leading to a stronger immune system.
As well as benefits for the individual, laughter and humour can also help heal communities. In a pioneering project in an underprivileged part of Bradford, Davies has used principles from her Laughology model to promote resilience and help people cope in difficult situations. Along with other public agencies, she has helped train a team of community 'champions' to become more positively engaged in their community.
She explains: "There is a happiness debate going on in the country at the moment and in an ideal world it would be great if we were all happy all of the time but we are not, we are human beings and it is healthy to be sad."
What really counts, she thinks, is the way people cope with difficulties. Her theory is that the more resilient we are, the more likely we are to be happy.
"The Bradford project is about creating resilient communities through a series of thinking skills which we teach people," she says. "The real key to happiness on a society level is to enable people to be more resilient and to feel more supported by one another and to have friendlier communities." Laughology aims to get people to remember 'laughter triggers' - funny memories - to help them feel positive. The theory goes, this process has an impact on emotions and a person's emotional responses to situations. "If we laugh we feel better about a situation, if we see something in a different way and find the humour in it we can almost take a mental step back from it and not be so negatively emotionally involved," Davies expounds.
But can laughter really be spread through society? It is certainly contagious. Researchers at the University College of London found that the brain responds to the sound of laughter by preparing the muscles in the face to laugh and smile. Our predisposition to laugh when others laugh was a behavioural trait exploited in live recorded US sitcoms where the audiences were often seeded with paid extras picked specifically for their infectious laughs.
In very rare cases, this infection can reach epidemic levels, as it did in 1962 in Tanzania when there was a recorded outbreak of hysteria near the village of Kashasha on the western coast of Lake Victoria. The epidemic began with one girl laughing hysterically in a classroom in a boarding school for girls and spread throughout the building. The school was forced to close down and the students were sent home. The epidemic then spread to villages where some of the affected girls lived. In April and May in one village, 217 people had laughing attacks. In addition to hysterical laughter, symptoms included pain, fainting, respiratory problems, rashes, attacks of crying and random screaming. In total, 14 schools were shut down and 1,000 people were affected.
The most plausible explanation for the epidemic appears to be that it was a form of mass hysteria in reaction to the nation's seismic shift to independence which happened at the same time and which instilled a new religion, political culture and way of life on the populace. While there was nothing funny about the Tanzanian outbreak, it did show that laughter can be contagious on a grand scale. If contagious laughter can be spread community-wide, the suggestion is that so, too, can good humour. And in these difficult times, a feel-good injection like that would be no laughing matter.
How to laugh...the Marathi way
The 40 million speakers of Marathi, in western India, have a considerable vocabulary for laughter
Khudukhudu: The soft, pleasant laughter of an infant
Phidiphid: Vulgar and obscene laughter
Hyahya: Superficial, polite laughter
Khadakhada: Loud laughter of an infant
Khaskhas: Mild, appreciative laughter
Khokho: Loud, uproarious laughter
Khikhi: Horse-like laughter
Phisphis: Derogatory laughter