The Scientist

The attire of competitors playing combat sports at the 2004 Olympic Games is the unlikely subject of a sparring session between biologists in Nature this week, as scientists argue whether the theories of evolutionary psychology can explain why teams wearing certain colors are more likely to win. In the red corner are scientists who argue there are evolutionary explanations for why red teams often win. In the blue corner, scientists say blue teams can win, too, and red and blue teams are likely more often victorious because white-wearing teams are easier to see, and therefore anticipate.

Previous research has suggested that the color of team uniforms can influence the players wearing them—for instance, players who wear black tend to be more aggressive. In May, 2005, Russell Hill and Robert Barton from Durham University, UK, took it a step further. They released an analysis of the results of combat sports -- boxing, tae kwon do, Greco-Roman wrestling and freestyle wrestling -- at the Athens Olympics, showing that contestants who had been randomly assigned red outfits were more likely to beat those wearing blue. As reported in The Scientist, they interpreted the findings as evidence that humans are predisposed biologically and culturally to associate red with dominance and aggression.

Red coloration is widely used by male animals to attract mates and intimidate rivals, they argued. Hill told The Scientist that male zebra finches fitted with red leg bands are particularly attractive to females, suggesting that red clothing might also augment aggressive human signals, such as our tendency to flush red when angry.

Now, Candy Rowe of the UK's University of Newcastle and colleagues offer a different explanation. From the same Olympics, they studied judo uniforms, a sport in which neither competitor wears red. This week, they report in Nature that competitors wearing blue had an edge over those in white, and suggest that both sets of results can be explained by the influence of different colors on the visibility of opponents – opponents in white are easier to see and, therefore, beat -- and not evolutionary psychology.

"There's a lot of merit to both proposals," said Geoffrey Miller, an evolutionary psychologist at the University of New Mexico, Albuquerque, who was involved in neither study. He added that he is impressed that Hill and Barton found an effect of color in male, but not female, competitors, a finding that appears to support their evolutionary model.

Roland Carlstedt, chair of the American Board of Sport Psychology, who has already criticized the design of Hill and Barton's original study, is equally scathing of the new one. "Non-parametric and post-hoc retrospective analyses are at the lowest level in the evidence hierarchy," he told The Scientist. "They could easily have tested their theories in an experimental manner, rather than speculate about it…that's what should be getting into Nature."

And not all bookmakers took stock in the findings, either. After Hill and Barton's original study, a spokesperson for William Hill, one of the world's largest betting companies (and no relation to Russell Hill) told TheScientist the findings wouldn't change the way odds are calculated, and rattled off a number of recent matches that would seem to disprove Hill and Barton's report.

In a response to Rowe et al's work, also published this week, Hill and Barton defend their theory, arguing that blue is used as a signal of "long-term developmental vigor" in species such as mandrills, and may, therefore, also confer psychological advantages compared with paler colors.

But Rowe is concerned that other animals – dominant silverback gorillas, for example - could also bolster the evolutionary interpretation had white been found to carry an advantage over blue. "Evolutionary psychology has often been criticized for building stories around data sets without considering the alternatives," she said.

Rowe agreed with criticisms that experiments are required to test the effects of different colored outfits on detection and reaction times of opponents. And Hill noted that he and Barton plan to measure the effects of outfit color on competitors' levels of testosterone, which mediates aggressive displays in other animals.