Washington, Oct 28 : Tennis referees are very likely to make mistakes when they call balls "out" than when they call them "in", mainly because of the inherent bias in people perceiving moving objects, according to a new report.
As it turns out, the study by researchers at the University of California, Davis, might just support the recent rule changes allowing professional tennis players to challenge the referees' calls, thus helping them in exploiting the new findings to their advantage.
David Whitney, a member of the research team, said that just like all visual illusions, the new discovery provides visual neuroscientists with a window on how the brain processes information.
"The visual system faces a big challenge when trying to code the locations of objects so that we can perceive them," said Whitney.
He added: "Our perception lags behind reality. The visual system has mechanisms that help alleviate this problem of living in the past, but these mechanisms are not perfect and occasionally result in visual illusions-like the misperception of tennis ball location we discovered."
People have a tendency to misperceive moving objects as shifted in the direction of their motion, so that at any moment they appear to be farther along their path than they are.
Whitney decided to study the misconception in the context of tennis when he saw a referee call overturned by a player's challenge during a Wimbledon match.
On a tennis court, a ball could physically bounce in the court but be called out, or a ball could physically bounce out of the court but be called in.
Tennis referees would be equally likely to make each of these two kinds of errors, only if they were completely bias-free. But as objects generally appear to be shifted in the direction of their motion, referees should incorrectly judge balls as being out more often.
And the researchers confirmed that prediction- in a review of more than 4,000 randomly selected Wimbledon tennis points, 83 incorrect calls were uncovered.
They later confirmed that the refs' mistakes are not the result of poor refereeing, but they attributed it to the errors in the visual information about motion processed by human brain.
In fact, according to the researchers, tennis players and audience members make the same mistakes that refs do.
However, the new findings suggest that players could maximize their opportunity to challenge calls by focusing on balls that are called "out," since they are more likely to be incorrect.
The report also suggests that every shot in professional tennis should perhaps be reviewed by instant replay.
"If that proves prohibitively time-consuming, the rules allowing players to challenge referee judgments should be scrutinized at least, in light of the current findings," wrote the authors.
They added; "If all else fails, perhaps professional tennis venues should follow the French, and universalize the clay court," where skid marks on the clay reduce reliance on the referees' motion perception.
The study was published in the recent issue of Current Biology, a Cell Press publication.