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Published: August 16, 2008

If you are betting on Olympic tae kwon do, you may do well to consider the color of the fighter’s protective gear. A German study has found that referees consistently favor the fighter wearing red, although the researchers say they are not sure why.

In Olympic tae kwon do, one competitor wears a blue helmet and chest protector, the other red. The referee awards 1 point for delivering attacks to the chest protector with feet or fist, and 2 for a blow to the head, permitted only with the foot. Knocking down an opponent gains additional points, and points can be deducted for prohibited moves.

The study, published in the August issue of Psychological Science, involved 42 experienced tae kwon do referees. Researchers presented them with video excerpts from sparring rounds of five pairs of male competitors of similar abilities and asked them to referee the matches. In each video, one competitor wore red protective gear while the other wore blue. The referees awarded competitors wearing red an average of 13 percent more points.

Next, the researchers digitally reversed the colors of the protective gear, and showed the clips again. The number of points awarded increased for the competitor whose equipment was now changed to red and decreased for the one altered to appear blue — even though the referees were watching the same matches. Neither the sex of the referee (29 men were in the group) nor the order of presentation of the clips made any difference; only the color of the gear did.

Would red uniforms have the same effect in other sports?

“Referees have an important role in combat sports,” said Norbert Hagemann, the lead author of the study and a sports psychologist at the University of Münster, “but the input of referees is not as strong in sports like soccer or baseball.

“Previous studies have found the same phenomenon in boxing and wrestling, but it is strongest in tae kwon do.”

Hagemann said the athletes themselves could be affected by the color the opponent is wearing. But this study looked only at the effect on the referee.

“We show experimentally that the referees have a significant influence,” he said.