title: Human's cognitive ability to assess facial cues from photographs: a study of sexual selection in the Bolivian Amazon.
abstract: BACKGROUND
  Evolutionary theory suggests that natural selection favors the evolution of cognitive abilities which allow humans to use facial cues to assess traits of others. The use of facial and somatic cues by humans has been studied mainly in western industrialized countries, leaving unanswered whether results are valid across cultures.
  
  
  RESULTS
  Our objectives were to test (i) if previous finding about raters' ability to get accurate information about an individual by looking at his facial photograph held in low-income non western rural societies and (ii) whether women and men differ in this ability. To answer the questions we did a study during July-August 2007 among the Tsimane', a native Amazonian society of foragers-farmers in Bolivia. We asked 40 females and 40 males 16-25 years of age to rate four traits in 93 facial photographs of other Tsimane' males. The four traits were based on sexual selection theory, and included health, dominance, knowledge, and sociability. The rating scale for each trait ranged from one (least) to four (most). The average rating for each trait was calculated for each individual in the photograph and regressed against objective measures of the trait from the person in the photograph. We found that (i) female Tsimane' raters were able to assess facial cues related to health, dominance, and knowledge and (ii) male Tsimane' raters were able to assess facial cues related to dominance, knowledge, and sociability.
  
  
  CONCLUSIONS
  Our results support the existence of a human ability to identify objective traits from facial cues, as suggested by evolutionary theory.
authors.affiliation: Heller School for Social Policy and Management, Brandeis University, Waltham, Massachusetts, United States of America. eundurra@brandeis.edu
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Undurraga
authors.forename: Dan T A
authors.initials: DT
authors.lastname: Eisenberg
authors.forename: Oyunbileg
authors.initials: O
authors.lastname: Magvanjav
authors.forename: Ruoxue
authors.initials: R
authors.lastname: Wang
authors.forename: William R
authors.initials: WR
authors.lastname: Leonard
authors.forename: Thomas W
authors.initials: TW
authors.lastname: McDade
authors.forename: Victoria
authors.initials: V
authors.lastname: Reyes-García
authors.forename: Colleen
authors.initials: C
authors.lastname: Nyberg
authors.forename: Susan
authors.initials: S
authors.lastname: Tanner
authors.forename: Tomás
authors.initials: T
authors.lastname: Huanca
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Godoy
mesh_terms: D001838:Bolivia; D003071:Cognition; D005145:Face; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D010781:Photography; D012641:Selection, Genetic; D019529:Sexuality