People with blue eyes have one thing in common

If you have lighter eyes you're more likely to be egocentric, competitive and skeptical.

However, if you're the opposite, you're more likely to be sympathetic and altruistic.

This is according to a 2010 Australian study, published in Current Biology, which looked at personality characteristics and eye colouration in people of North European ancestry.

The authors wrote that there was an evolutionary explanation for this:

The rare-color advantage of light eyed females, is likely to increase the chance of being noticed by a male.

Moreover, competitive personality traits (such as wanting to beat others and being sceptical of others’ intentions) secure the long-term commitment necessary for self and offspring survival.

Whilst some may argue that it is unlikely that a male would choose a disagreeable female we argue that mating is not the sole choice of males and that the disagreeable traits of competitive women are directed primarily at other female competition rather than towards males.

In short, they say you're more likely to be gritty and self-preserving if you have brown eyes, because your eyes aren't as pretty.

It's not the only finding that links eye colour to other characteristics.

Scientists at Orebro University in Sweden studied over 400 subjects to see if personality traits were linked to Iris patterns. They found that eye colour is linked to the same genes that form our frontal lobes - thus people who share similar irises are likely to share some behaviours.

Dr Anthony Fallone of Edniburgh University concluded in 1991 that dark-eyed students performed significantly better in time-limited intelligence tests in a study of over 100 people. He told the Daily Mail:

The eye is so closely linked neurologically to the brain that you might call it the only part of our brain you can see from the outside.

It seems to hold vital clues to our brain function.

Another study found that type 1 diabetes is associated more with people with blue eyes - in Lazio and Sardinia, among people with type 1 diabetes 21 per cent had blue eyes, compared to 9 per cent of the general population.

Who knew your eyes could tell you so much?

HT Forbes

More: It's official: Blue is the most attractive eye colour