Fun with Science Club®


			Are mistakes by referees not always their fault? Carrie Straight 06.01.01 Football (soccer for people from the United States) is a very competitive sport worldwide. Spectators usually get upset when they see the assistant referee makes a bad call. Some scientists were trying to figure out why the assistant referees tended to make errors when calling players offside during football matches. A referee calls offside when an offensive player is closer to the goal than any of the defenders (except the goalkeeper or netminder) when a teammate passes them the ball. They set up an experiment using two teams and three professional assistant referees. One of the three referees wore a light-weight camera. The referees judged 200 offside situations. The referees made 40 mistakes, wither wrongly calling a player offside or not calling a player offside when they should have. At first, the researchers predicted that the referee’s mistakes happened when they looked from the passer to the receiver. By looking at the film footage, the researchers found out that the referee did not move his head as the ball moved and therefore was not distracted. In over half of the trials the referee was farther down the field than the last defender, giving them a good view of the play. By drawing out the positions of the players when an offside occurred, the researchers decided that it must be the viewpoint of the referee that causes them to make the mistake. They decided that when players are on the far side of the field and an offensive player is on the far side of the last defensive player, the referees where more likely to call an offside foul when none had occurred. Through their diagrams, the researchers predicted when referees would make mistakes depending on the position of the players. After making the predictions, they watched 200 videotaped football matches and documented when errors occurred. The errors on the videotaped football matches followed the predictions. The viewpoint of the referee causes him/her to make mistakes in judging offside and there is not much the referee can do about it.


			Oudejans, Raôul R. D., Raymond Verheijen, Frank C. Bakker, Jeroen C. Gerrits, Marten Steinbrückner, and Peter J. Beek. 2000. Errors in judging ‘offside’ in football. Nature 404: 33.