Health - Faces reveal physical strength

WASHINGTON: Misjudging physical strength of a would-be opponent might have potentially deadly consequences - at least for our ancestors.


A study conducted by University of California, Santa Barbara (UCSB) scientists has found that a mechanism within the brain enables people to determine accurately the fighting ability of men around them.

"Assessing fighting ability was important for our ancestors, and the characteristic that the mind implicitly equates with fighting ability is upper body strength," said Aaron Sell, a postdoctoral fellow at UCSB's Centre for Evolutionary Psychology and the paper's co-author.

Sell conducted the study with Leda Cosmides and John Tooby, professor of psychology and anthropology, respectively; Michael Gurven, an associate professor of anthropology and graduate students Daniel Sznycer and Christopher von Rueden.

The study consisted of four sections, each of which asked the test subjects to assess the physical strength of individuals based on photographs of their faces, their bodies, or both, according to an UCSB press release.

Subjects were asked to rate the fighting ability of the people in the photographs on a scale of one to seven. When the photographs depicted men whose strength had been measured precisely on weight-lifting machines, the researchers found an almost perfect correlation between perceptions of fighting ability and perceptions of strength.

They also found that perceptions of strength and fighting ability reflected the target's actual strength, as measured on weight-lifting machines at the gym. In other sections of the study, the researchers showed that this result extended far beyond the gym.

Both men and women accurately judge men's strength, whether those men are drawn from a general campus population, a hunter-horticulturalist group in Bolivia, or a group of herder-horticulturalists living in the Argentinian Andes.

Leg strength was measured along with upper body strength in both the US and Bolivian populations, but the results showed that perceptions of men's strength and fighting ability reflect upper body strength, not that of legs. "That makes sense," said Cosmides.

"If, for example, you're trying to lift something really heavy, or run a long distance, your lower body - your legs - will also be significant. But for fighting at close quarters, it's the upper body that really matters."

In men, this mechanism is a barometer for measuring potential threats and determining how aggressive or submissive they should be when facing a possible enemy.

For women, the mechanism helps identify males who can adequately protect them and their children. Men have a lot more experience with rough and tumble play and direct experience with fighting, yet women are just as good at assessing these variables.

The study appears in the current issue of the Proceedings of the Royal Society.