Question: what's studied by philosophers, psychologists, psychiatrists, anthropologists, physiologists, neurologists and linguists, affects everybody, and is one of the most complex and least understood behaviours known to man?

Answer: Laughter.

You might think the subject of laughter is simple - someone tells a joke, if it's funny, you laugh - but really, laughter is one of the few remaining great unknowns of human behaviour. Gelotology (the physiological study of laughter) is one of the least studied fields of science and in New Zealand and Australia there is not one registered gelotologist.

Part of the reason gelotology is such an obscure field is because, for years, researchers couldn't agree on a common definition of humour. The subject of laughter was also regarded by many as frivolous and unworthy of substantial analysis.

However, in recent years, European and American researchers have made significant headway into understanding the phenomenon and, as it turns out, may well get the last laugh.

If you've ever laughed so hard it hurt, it could mean you're unfit. Up to 80 muscles are used during a hearty laugh, the blood pressure rises, the heart beats faster and blood oxygen levels increase. In fact, a study released last year by German gelotologist Professor Gunther Sickl revealed that a one-minute guffaw has the same health benefits as a 45-minute gym workout. When the laughter stops, the blood pressure returns to normal and stress hormones are reduced - actually strengthening the immune system.

Other researchers have also found evidence that laughter really may be the best medicine. Laughter increases the production of Gamma-interferon (an antiviral protein) T-cells, which are key to immune response, and B-cells, which generate antibodies and help keep nasties at bay.

They also found that when laughter induces hiccupping or coughing, it helps to clear the respiratory tract by dislodging all kinds of gross stuff and increases the concentration of salivary immunoglobulin A, which helps kill any sickly bugs you may have inhaled.

It is not just the physical health benefits of laughter that have piqued researchers' interest though. Barbara Plester of Massey University's management and international business department has spent several years studying the effects of humour in the workplace and authored the paper, Taking the piss: Using banter at work.

Plester, who is one of only four New Zealand members of the International Society of Humour Studies (yes, there really is such a thing), says humour is multi-functioned. Plester has dedicated her masters and doctorate research to the study of workplace humour and believes it is one of the most fascinating, but complex, subjects around.

During her masters research, Plester spent time in three IT companies, observing the use of humour, and found that it was an essential coping strategy in high-pressure environments. Now she is looking at the role of workplace jokers and how humour can be a way of resisting managerial directives. "Often people stand up to management using humour because you can't tell the boss to piss off," she says.

While much of this may seem commonsensical, empirical research into laughter and humour is scarce and fragmented. Behavioural neurobiologist and gelotologist Robert Provine said it best in his 1996 American Scientist paper: "We know less about human laughter than we do about the calls and songs of some species of birds and nonhuman primates."

Though gelotology and the study of laughter are becoming more commonplace, for some it is a mystery best left uncovered. Famed children's author E.B. White had a point when he said: "Analysing humour is like dissecting a frog. Few people are interested and the frog dies of it."

* The average speaker laughs about 46 per cent more than the audience.

* Laughter is not exclusive to humans. Chimpanzees, apes and even rats have been found to make a laugh-like sound when tickled or during play.

* Women laugh more than men.

* Both men and women laugh more at men than they do at women.

* Less than 20 per cent of laughter is in response to a formal attempt at humour.

* Laughter consists of variations of short, vowel-like notes repeated every 210 milliseconds. Laughter can be of the "ha ha ha" variety or the "ho ho ho" type, but not a mixture of both.

* Children laugh an average of 400 times a day. Adults laugh only 17 times a day on average.

* The average baby begins to laugh at 4 months - approximately 3 months before the beginnings of talk.

* Some universities offer papers and courses specifically on humour. For example, Dartmouth College in America offers Rabbis, rogues and schlemiels: Jewish humour and its roots.