The facial expressions that we exhibit when we are happy, sad or angry are actually inherited, says a new study.

Gili Peleg and colleagues of University of Haifa, Israel, analysed the facial expressions of 21 volunteers who had been blind from birth along with those of their relatives, reported the online edition of BBC.

They interviewed the participants, asking them to recount experiences of when they were happy, sad, angry and disgusted, and recorded their mannerisms while doing so. They also analysed expressions when they were in deep concentration and shocked them to witness their expressions of surprise.

When the researchers compared the results, they discovered that even though the blind volunteers had never seen their relatives’ faces, their facial expressions were extremely alike.

“We have found that facial expressions are typical to families – a kind of facial expression ‘signature’,” said Peleg. She said the results of the study suggested that facial expressions had an evolutionary basis.

Our next step is to find the exact genes that influence facial expression.” This could have an impact on autism research, where facial expressions are central to the disorder, she added.