A computer-generated male face, made from an average of 32 males.

Credit: University of Regensburg

SYDNEY: Our ability to judge the health, education level and character traits of others just by looking at their faces is an innate skill, common across cultures.

Isolated Amazonian tribe members could accurately assess facial cues that correspond to traits related to reproductive success, a team of American scientists report in the journal PLoS One.

"Our results suggest that the ability to judge people's traits based on facial features is an evolutionary specialisation of human beings," said Eduardo Undurraga, lead author of the study from Brandeis University in Waltham, Massachusetts.

New cross-cultural research

"The face contains important information about a person," said Undurraga. This area has been studied extensively, however until now most previous studies of this sort have only considered members of Western industrialised societies.

Participants in the study belonged to the Tsimane (pronounced 'cheeMAU- Nay') tribe, an indigenous group of Bolivia who have been the subject of a multi-year investigation on how economic development and globalisation affect culture and wellbeing.

"Doing this kind of research with non-Western participants requires long-term commitment and rigorous field-work," said Undurraga. Undurraga and his colleagues had to learn the complexities of Tsimane's society and language.

Rating traits from facial photographs

The researchers asked 40 females and 40 males 16-25 years of age to look at 93 facial photographs of other Tsimane' males.

The participants rated how they perceived the health, dominance, knowledge and sociability of each face.

The participants' interpretations of the photographs were compared with data collected about the men in the images, and adjusted according to whether they found the faces familiar.

Objectively measuring traits

Researchers objectively measured the four traits, for example, health was measured using recent illnesses and knowledge by competency in ethnobotany, language and arithmetic.

According to the researchers, the ability to recognise such attributes in a partner should result in stronger offspring.

Men and women both did well at assessing most of the traits, but notably, the women were better than the men at judging health cues in the photos.