Art of the smile

The Royal College of Art's exhibition of 33,000 images of smiles celebrates one of the most powerful human actions.

With such a notion in mind, more than 35,000 examples of the human smile have been assembled at the Royal College of Art (RCA) in Kensington, west London, to form the world's largest photographic exhibition.

The exhibition opens today and runs until Monday. It comprises digital images uploaded by the public on to the website of the computer giant Hewlett Packard. The company has given 25p for each one to the children's charity NCH. Behind each image there is a different story.

The beaming faces of a group of underprivileged Welsh schoolchildren are the result of a visit and a gift of rugby balls from the England international Martin Johnson. More than 7,000 smiles were donated from revellers at this year's Glastonbury Festival - despite the rain. Then there are the proud faces of new fathers, clutching their soggy, just-born babies. There are smiling brides and grooms, engagement parties, birthdays and holidays. Some of those portrayed are even smiling as they work.

Scientists say the smile is a vital signal of attraction and a precursor of reproduction - that most basic human instinct of them all. In the medial orbitofrontal cortex, the pleasure and reward section of the brain, an attractive human face triggers a chemical response.

This is strongest when the face is looking directly at us. And it is strongest of all when it is accompanied by a smile. The response has even been called the moment when we first begin to fall in love.

The psychologist Dr David Lewis said: "The powerful emotions triggered when someone important in our lives smiles at us and we smile back changes our brain chemistry. It creates what is termed a 'halo effect', which helps us to remember other happy events more vividly, feel more optimistic, more positive and more motivated".

One recent survey even suggested that a smile from a friend was more treasured than sex with a lover as the source of a short-term high. Other studies have shown that smiling can help people to cope with pain, it can also increase their ability to deal with extremes of hot and cold. As the first step on the road to laughter, smiles are also central in what doctors believe is a medicine of mirth - the positive cardiovascular effect linked to a good old chuckle.

Perhaps, then, it is no surprise that in this often grim-faced world there are now courses on how to smile. They run alongside the plethora of happiness workshops and humour seminars run by the burgeoning number of alternative therapists.

And if you still remain unconvinced on the benefits, as the back of any good matchbox would have once told you, it takes 42 muscles to frown and just 17 to smile.