January 26, 2013
Researchers Find No Association Between Facial Shape And Aggression
April Flowers for redOrbit.com - Your Universe Online
An international research group, led by the University of Barcelona, has found there is no evidence to support the association between facial shape and aggression in men. The study, published in a recent issue of PLOS ONE, sampled almost 5,000 individuals from 94 worldwide populations.
The team, which includes Rolando GonzÃ¡lez JosÃ©, from the Patagonic National Centre (CENPAT-CONICET) and Jorge GÃ³mez ValdÃ©s, from the National Autonomous University of Mexico, rejects the hypotheses that associate facial shape with antisocial and criminal behaviors. The idea of such an association reached its height in the mid-19th century and has lately been revitalized. The large sample size — 4,960 individuals — allowed the team to get a global estimation of facial shape and develop an accurate analysis tool, taking into consideration distinguishing traits. The research model is based on the study of fWHR — facial width-to-height ratio — as a possible predictor of aggressive behaviors in males.
Professor Mireia Esparza, from the Anthropology Section of the Department of Animal Biology of the University of Barcelona says, “fWHR was used for two main reasons: on one hand, it is a good indicator of face shape and, on the other hand, it was used in those previous studies which established a correlation between higher fWHR scores and aggression. By this way, we were able to compare results without any bias caused by the use of any other indicator."
Esparza reconstructed the genealogies of the Hallstatt population using biodemographic data for the skulls studied, and to estimate the fitness of each individual analyzed.
The results of this study support previous research, which did not prove any relation between fWHR and aggression.
“This study goes more deeply”, remarks Mireia Esparza. “The methodology used is based on craniofacial measurements and 2D and 3D cranial landmark coordinates, so it provides us with more accurate results than other previous studies based on photograph[ic] analysis. Moreover, our research used a large sample of about 5,000 individuals from 94 worldwide populations, so we were able to carry out inter and intra-population comparisons.”
“Finally, two specific databases, one sample of male prisoners of the Mexico City Federal Penitentiary and one the skulls from the catholic church of Hallstatt, Austria, enabled a deeper analysis. The Hallstatt database was used to estimate the correlation among life history parameters, such as fitness or reproductive success, and skull shape traits; this sample has been essential to yield that there is not significant correlation between fWHR and male fitness in this population. The Mexican database demonstrated that fWHR is not significantly greater on those males involved in aggressive crimes in comparison with the general population."
Rolando GonzÃ¡lez JosÃ© and Jorge GÃ³mez ValdÃ©s state, “the social and political implications that this kind of non-contrasted adaptive hypotheses could have, may increase racial prejudices, discrimination and intolerance."
The study also focused on sexual dimorphism and fWHR, proving there is, again, no correlation. Males who present higher fWHR values — wide faces in comparison with their height — do not have a greater reproductive success. The authors conclude that if males displaying higher fWHR scores achieved better fitness values, a process of sexual selection focused on fWHR would be triggered.
“Our study proves that there is not statistical association between fWHR and male fitness, and that facial shape is not a good predictor of behavior”, concludes Esparza.