Game, set, matching umpire calls in tennis

Umpires at Wimbledon, Roland Garros, and Arthur Ashe Stadium might deserve a break, according to a new linkurl:study;http://journals.royalsociety.org/content/1172753827346768 published online this week in Proceedings of the Royal Society B. The study found that disputes over close calls during professional tennis matches arise because of double faults in the way information is processed in the brains of players and umpires. Nonetheless, both perceptions are remarkably accurate, though umpires are in the right most of the time. At next month's French Open, tennis balls will fly across the court at linkurl:speeds;http://www.the-scientist.com/2007/11/1/82/1/ of up to 150 mph. In such a fast-moving sport, arguments often erupt between players and umpires as to whether a ball bounces inside or outside the boundary lines. So in 2006, major tennis tournaments introduced a high-tech, ball-tracking system called linkurl:Hawk-Eye;http://www.hawkeyeinnovations.co.uk/ that can pinpoint the ball's position to within a tenth of an inch. Line calls are still made by umpires, but players are allowed to challenge an umpire's decision twice per set of play. "It occurred to me that the data collected as a by-product of Hawk-Eye is a perceptual experiment that could reveal something interesting about how decisions are made," said linkurl:George Mather,;http://www.lifesci.sussex.ac.uk/home/George_Mather/ a psychologist at the University of Sussex in England who led the study. Mather, who studies how humans perceive motion and is a huge Roger Federer fan, investigated 1473 challenges made by 246 players to test whether disputes occur because of perceptual linkurl:uncertainty,;http://www.the-scientist.com/article/display/14859/ or as a backhanded way for players to get ahead. He found that 94% of challenges occurred within about 4 inches of the line — a distance less than twice the diameter of the ball. Both players and umpires made mistakes, but only 40% of challenged line calls turned out to be incorrect. Advantage: umpires. Mather found a sharp peak in challenges the closer the ball landed to the boundary lines, which suggested that disputes occur because of minor linkurl:perceptual differences;http://www.the-scientist.com/article/home/53774/ between the brains of players and umpires, rather than because of gamesmanship or lapses in concentration. So Mather created a computer model in which a ball bounces, and theoretical players and umpires judge the ball's position — either in or out — but with a small amount of uncertainty that follows a simple bell-shaped curve. If the players and judges agree, then the simulation ends. But if they disagree, the player challenges the call, and the ball's true location is used to settle the dispute, just as Hawk-Eye does in real life. The model paralleled the data from actual matches with a high degree of accuracy, indicating that players' and umpires' brains make errors in predictable ways. "You can actually capture performance very accurately by introducing a bit of noise into the decision-making process," Mather told The Scientist. The study "took what we do in the dark rooms and labs and put it out into the real world," said linkurl:Saumil Patel;http://saumilresearch.org/ of the University of Texas Medical School at Houston, who was not involved in the study. He was surprised such a simple model could capture complicated neural processes when "more than half the brain is involved in these types of decisions." By treating the brain as a "black box" in the model, Patel said the ball was still in Mather's court to show "what areas of the brain are involved or what mechanisms are used to arrive at these judgments." Mather's model predicted that an umpire should only make a few perceptual mistakes per set; making the player's two challenges per set limit a pretty accurate one, according to the researcher. linkurl:Michael Wright;http://www.brunel.ac.uk/about/acad/sss/research/centres/cfcan/ccni_people/ccni_michael_wright of Brunel University in London, England, was impressed with this result, but wondered whether umpires' performances change over the course of a match. Mather's analysis was based on more than 1,000 decisions, Wright noted, but performance might wane over time because of exhaustion, or possibly even improve if umpires enter the linkurl:sweet spot;http://www.the-scientist.com/2005/3/28/30/1/ of attentiveness. Mather's analysis also grouped athletes of different skill levels together. But were top-ranking players like Roger Federer or the Williams sisters better at making line calls than others? Actually no, said Mather, adding that the grand slam explanation for the kinds of outbursts that made linkurl:John McEnroe;http://www.youtube.com/watch?v=v16tKIAddmQ&feature=related famous remains simple random fluctuations in perception.

Game, set, matching umpire calls in tennis

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