You may believe that race is something not so obvious, but adult brains are so keen in detecting race, sex and age that we can correctly determine those traits from nothing more than a black-and-white silhouette, new experiments show.

"It's surprising how much information the silhouette provides," said lead researcher Nicolas Davidenko, a cognitive psychologist at Stanford University.

"We rarely have to identify a person in a silhouette, yet in the experiment, people can do that without difficulty. The way that our brains process faces seems so flexible that our minds can even assign people to social and biological categories drawing only on views that occur less commonly in our daily lives-including black-and-white profiles."

In 70 % of the cases, people could correctly identify the sex of the person in the black and white profiles.

In the same time, in 68 % of the cases, people could determine the right age, to within 10 years.

Men were identified more easily than women and people gave 8-year greater estimations than the real age of the people.
"These biases might be due to the lack of hair on the silhouettes, which were cropped to show only a facial profile. This could make them seem bald in some cases, a trait common to males and generally older people," said Davidenko,

The team, who employed a collection of 400 face profiles, also discovered that people were 85 % correct in guessing a person's race from the black-and-white profiles.

Researchers often look at traits like eyes, nose and mouth when investigating face recognition, while the new investigation reveals other traits of the face as being, as well, main characters employed to recognize a face.

The brow width, chin length of chin and nose protrusion were linked to a more masculine appearance, while other traits were linked to feminine faces.

"I hope other researchers will use this mathematically controlled method. It provides an easy to use tool that makes research more quantitative," said Davidenko.