London, Jul 2 (IANS): Scientists have tried to explain how human beings recognise faces of their own kind at first glance -- be it a nice waitress in the coffee shop around the corner, the bus driver or colleagues at the office -- but not those of other species.

Monkeys also possess the remarkable ability to differentiate faces of group members and to extract the relevant information about the individual directly from the face.

With the help of the so-called Thatcher illusion, scientists of the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, have examined how people and macaque monkeys recognise faces and process the information in the brain.

They found out that both species perceive the faces of their kin immediately while the faces of the other species are processed in a different way.

"From an early age on we are accustomed to the faces of other humans: a long nose, the swing of the lips or the bushy eyebrows...," explains Christoph Dahl, researcher at the Max Planck Institute for Biological Cybernetics.

It is similar in monkeys. They learn to recognise the features of their fellow monkeys (so called conspecifics) and can grasp the identity of every group member quickly.

"However in humans, as well as in macaque monkeys, this principle only works with individuals of the same kind," says Dahl.

Even though the recognition of conspecific faces is achieved by means of holistic processing, the separate parts such as mouth, nose and eyes as well as the facial proportions are still important, said a Max Planck release.

"Although we look at the eyes first our neural functions still grasp the whole picture," said Dahl.