A UCSB researcher recently discovered that by age four, humans can accurately size up a potential opponent’s fighting skills with a single glance.

Aaron Sell, a postgraduate fellow at UCSB’s Center for Evolutionary Psychology, has found that humans can determine a male’s fighting ability by gauging a man’s upper-body strength — a characteristic the study deemed the most important variable in close hand-on-hand combat.

According to Sell, it is crucial for animals to possess the ability to judge the fighting skills of other males in order to avoid situations in which they will suffer bodily harm as the weaker combatant. The study was designed to verify if there is a similar ability within humans, he said.

“Our hypothesis was that humans should be good at this [as well],” Sell said.

The results of the study conclude that both males and females can accurately estimate the upper-body strength of males using only a picture of the individual’s face. The assessment was even more accurate when given a full body picture. However, Sell noted that the study found that neither males nor females were very accurate in estimating the upper-body strength of females.

“Archeological evidence has shown that males have been in more combat than women,” Sell said. “… Even in modern America rates of homicide are nine to one done by males. Ancestrally, men were more likely to be engaged in combat [compared to] women.”

Also, the study’s results confirmed that there was a correlation between the upper body strength of men and how attractive female test subjects found them, Sell said.

“Women were good at estimating male strength, but not female,” Sell said. “[This is so] females could find strong men.”

The study was done in four parts, and contained data from UCSB students, members of the Tsimane tribe in Bolivia and herder-horticulturalists in the Andes. Upper-body strength measurements were taken using weight machines to produce comparative data.

According to Sell, muscularity was better perceived than body size by participants in the study, while height and weight did not factor into strength estimation.

For the future, Sell plans to continue studying human strength and his newest research suggests fighting ability does not derive from education or cultural associations.

“Early results show children as young as four can do this as well,” Sell said, “… The ability to measure fighting ability is not through media relations, cultural beliefs or socialization.”

Additionally, Sell said the fighting stances and facial expressions males use for intimidation before a fight are currently under study.