How good you are at telling what someone is thinking or feeling from just their eyes is partly down to genetics. David Long

The eyes are the window to the soul, but how good you are at looking through that window is at least partly down to your genes.

Some people are better than others at reading how people are feeling and what they are thinking just from their eyes. The largest study on the genetics of empathy has found several genes that appear to be behind this skill.

The study, published in the journal Molecular Psychiatry, looked at the genomes of 90,000 people across the world. Many of these participants were clients of the genetics company 23andMe. As well as having their genome analysed, they also took the 'Reading the Mind in the Eyes' test. They looked at pictures of people's eyes and had to identify the emotion they were expressing to test their levels of empathy.

Women were slightly better than men at the eye test, the study found, with a small but consistent advantage across populations. However, the genes responsible weren't located on the X-chromosome, of which women have two of but men have only one.

"One potential hypothesis is that these genes might be influenced by genes on the X- chromosome, so sex-specific hormones could be interacting with them," study author Varun Warrier of the University of Cambridge told IBTimes UK.

Several genes associated with performance on the eye test were located on chromosome 3. One in particular stood out, called Leucine Rich Neuronal 1 (LRRN1).

"This is the most exciting gene we found," Warrier said.

This gene is most highly expressed in the brain, in a region called the dorsal striatum. Previous research has shown that people who have damage to the dorsal striatum perform worse in empathy tests. This study suggests a role for LRRN1 in the dorsal striatum that could contribute to this function.

Link to anorexia

Several conditions have been linked to the capacity to cognitive empathy. People who tend to score more highly on the test are also slightly more likely to have anorexia.

"The genes that contribute to performance in the eye test also increase the risk for anorexia nervosa, but this risk is very small," Warrier said.

Exactly how this risk is linked to anorexia is not clear, he said. However, further research could eventually lead to better informed treatments and interventions for the condition.

"This line of research is interesting because we are looking at underlying traits that contribute to differences or strengths in psychiatric conditions," Warrier said.

"This might help us understand on the genetic level how some conditions are different from others and how they might be linked."