THE eyes are the window to the soul, it is said. Now scientists have found that the patterns in someone’s iris may give important clues about their personality, ranging from how warm and trusting they are to whether they are impulsive or neurotic.

The researchers argue that eyes and personality may be linked because the genes responsible for the development of the iris also play a role in shaping part of the frontal lobe of the brain, which influences personality. The scientists have not studied possible applications for their work, but other experts believe they could be used in fields such as screening job candidates, psychoanalysis or even airport security.

“Our results suggest people with different iris features tend to develop along different personality lines,” said Mats Lars-son, a behavioural scientist who led the study at Orebro University in Sweden.

“Tissue differences in the iris can be used as a biomarker that reflect genetic differences among people.”

The structure of lines, dots and colour in everyone’s iris is different. The British government is already testing the use of computerised photographs of the iris as part of the “biometric” passports and identity cards, due to be introduced from 2009.

Previous research has explored eye colour and personality. In addition, iridology, a form of alternative medicine, claims certain parts of the iris represent parts of the body. Few have studied its links with personality.

For the new study, which is awaiting publication in the journal Biological Psychology, scientists at Orebro and at the Karolin-ska Institute in Stockholm analysed the eyes of 428 people and tested their personalities.

They looked at three features of the iris: the crypts, wavy threads that radiate from the pupil; furrows, the lines curving round the outer edge formed when the pupils dilate and contract; and the dots of pigment.

The results show people with densely packed crypts were more warm-hearted, responsive to their inner feelings and likely to sympathise with others.

While crypts were linked to emotions, furrows — both in their numbers and how far round the eye they extend — were more associated with urges. People with more furrows found it less easy to control cravings and were more impulsive.

While the links between crypts and furrows were significant, the scientists found no strong links between pigment dots and personality traits.

The researchers argue that as much as 90% of the differences in people’s irises are due to genetic variation and they are particularly interested in one gene called Pax6, which helps to set the formation of the iris in embryos. Other research has shown that a mutation in this gene is linked to impulsiveness and poor social skills.

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