An explanation for why some people always seem to have a 'sour' expression on their face may have been found.
Researchers from the University of Portsmouth found that some people have fewer facial muscles than others.
Everyone has a core system of five muscles in the face that enables them to express certain emotions, such as anger, happiness, surprise or fear. However, there may be as many as 19 muscles in the face, but not everyone has all of them.
According to Dr Bridget Waller from the university's Centre of Emotional Study, everyone can master the basic facial expressions, but there are also individual variations on those expressions.
"Some less common expressions are unique to some people," said Waller.
She and her team studied the facial muscles of corpses.
The risorius muscle, which experts believe enables a person to express extreme fear, only occurs in two thirds of the population.
According to Waller, actors don't have to worry, because another muscle can be used to create the same expression.
A person can also learn to master a certain expression by practicing in front of the mirror.
"There is a lot of asymmetry in the face and the left side usually has more expression than the right," concluded Waller.
-(Anesca Smith, Die Burger, June 2008)
Smiles written in the genes