Sydney, Aug 29 (IANS): Do you know what is the most common facial feature when you get angry at someone? It is lowered eyebrow.

Also include thinned lips and flared nostrils as researchers have identified the origin and purpose of the facial expression for anger that is universal.

“The expression is cross-culturally universal and even congenitally blind children make this same face without ever having seen one,” said lead author Aaron Sell from school of criminology at Griffith University in Australia.

The “anger expression” employs seven distinct muscle groups that contract in a highly stereotyped manner.

The researchers sought to understand why evolution chose those particular muscle contractions to signal the emotional state of anger.

Using computer-generated faces, they demonstrated that each of the individual components of the anger face made those computer-generated people appear physically stronger.

“We hypothesised that the anger face evolved its specific form because it delivers something more for the expresser. Each element is designed to help intimidate others by making the angry individual appear more capable of delivering harm if not appeased,” Sell explained.

“The function of the anger face is intimidation, just like a frog will puff itself up or a baboon will display its canines,” added Leda Cosmides, a professor of psychology at University of California Santa Barbara.

These threat displays - like those of other animals - consist of exaggerations of cues of fighting ability, Sell continued.

“So a man will puff up his chest, stand tall and morph his face to make himself appear stronger,” he noted.

The findings appeared online in the journal Evolution and Human Behavior.