The art of speaking without saying a word: what's in a smile?

The original Pretty Woman, Julia Roberts, has the best smile of all time, according to research by smile, the internet bank.

Eighteen years after her starring role as down-on-her-luck prostitute Vivian Ward almost half (47%) of the great British public voted for Julia as having the most beautiful and genuine smile around.

Surprisingly, second in the poll was ‘Mr Nasty' Simon Cowell (25%) with his ultra white smile and who has apparently turned over a new leaf for this year's X-Factor auditions. Meanwhile, America Ferrera, known for her role as Ugly Betty and who sweeped three awards in last week's Hispanic Awards came third, with one in five (21%) of the 3,000 polled voting for her smile full of braces.

Leonardo Da Vinci's portrait of the Mona Lisa, perhaps the most famous painting in the history of art, gained 5 per cent of the vote to take fourth place in the poll of the best smile, while fifth place went to another star of the big screen George Clooney with 2 per cent.

Psychologist, Donna Dawson said: "There are many different kinds of smiles, but the 'true', genuine, spontaneous smile is one where the mouth spreads in a relaxed way across the face and the eyes sparkle or soften, depending on the context and meaning of the smile.

At the other end of the scale, clothes horse and super WAG Victoria Beckham tops the list of the worst fake ‘smilers' with over a third (38 %) of the vote due her constant sullen look. She is followed by the current President of the USA, George Bush in second place; with more than 1 in 4 people (26%) clearly not trusting his ‘what-me-worry?' grin.

The former ‘Princess of Pop', Britney Spears came third (17%) and our very own former Prime Minister, Tony Blair took fourth spot (14%). Queen Supreme, Diana Ross concluded the list of worst fake smiles with five per cent of the vote.

According to scientists, although fake smiles often look very similar to genuine smiles, they are actually slightly different, because they are brought about by different muscles, which are controlled by different parts of the brain.

Donna Dawson adds: "False smiles involve only the mouth: if you were to cover up the mouth of a 'false smile' in a photograph, you would see that the eyes appear to be 'dead' and expressionless."

Paul Hemingway, Head of Campaign Marketing at smile said: "Smiling: the art of speaking without saying a word differs from person to person. It is interesting to see from our ‘what's in a smile?' survey that two politicians figure in the worst fake smile category - the next question to ask is do people really trust them? It seems that we all believe in the celebrity mega-watt smile is much more trustworthy."