US mini logoHome | A-Z Index | People | Reference | Contact us

Press release

  • 16 April 2008

Science uncovers the ins and outs of tennis line calls

To the point: A Hawk-Eye tennis match adjudication

To the point: A Hawk-Eye tennis match adjudication

Research from the University of Sussex could help to take the tantrums out of Centre Court clashes at Wimbledon this summer.

Players who challenge decisions by line judges are often accused of resorting to gamesmanship: officials who are challenged are also seen as inept in their decision making. In fact, analysis of line call challenges by psychologist Professor George Mather shows that both players and line judges are remarkably accurate in their decisions - up to a point.

Professor Mather, who studies motion perception in laboratory-based experiments, says: "I was intrigued to discover how line call errors measured up against laboratory data. Lab studies show that observers tend to perceive moving objects slightly ahead of their actual position.

"I could find no evidence, however, in the line call data of the kind of constant error reported in the lab. In fact, performance was remarkably good. Line judges and players can locate the bounce position of a ball moving at up to 50 metres per second to within just a few centimetres. The analysis did show, however, that some errors are inevitable, due to limitations in perceptual processing in the brain."

Professor Mather's study, published in the journal Proceedings of the Royal Society B today (Weds 16 April 2008), suggests that tennis players could therefore be justified in making full use of their right to challenge line judges' decisions.

To test his theory, Professor Mather analysed electronic line call data and records of challenges by individual players from the Association of Tennis Professionals for 15 tournaments during 2006 and 2007. He says: "While watching tennis on TV it occurred to me that Hawk-Eye [the electronic line call adjudicator used when line calls are disputed] data should allow us to work out the factors that influence line calls and challenges.

"When a ball bounces very close to a court line, the brain is unable to locate its position with sufficient precision to reach a correct decision on every occasion, so both players and line judges make some errors. Line judges, however, are more accurate than players. Nevertheless, both players and judges are remarkably accurate."

Analysis also threw up other insights - a widely differing number of challenges made by individual players. Professor Mather says: "One player in the top ten made only seven challenges in 15 tournaments, while another made 52. But the analysis indicated that a certain proportion of line call errors are inevitable, so players should make full use of the challenges available.

Professor Mather concludes: "Line calls on base and service lines are more difficult than those on side and centre lines, which is useful for both officials and players to know."

Given the margin of line call errors, Professor Mather also thinks that the three line call challenges players are allowed to make per set "seems fair".

Notes for editors

'Perceptual uncertainty and line-call challenges in professional tennis', by Professor George Mather, is published online in Proceedings of the Royal Society B today (Wednesday 16 April 2008).


The Royal Society, the national academy of science of the UK and the Commonwealth, is an independent charitable body, deriving its status from 1,400 Fellows and Foreign Members. It influences science policy and debates scientific issues with the public. For further details see


For further information about Professor Mather's research into motion perception and visual illusions, see


Image provided courtesy of Hawk-Eye Innovations. See:


University of Sussex Press officers: Maggie Clune and Jacqui Bealing. Tel: 01273 678 888 or email

Useful links

Site maintained by: Web team Disclaimer | Feedback