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Play's direction of motion may bias soccer referees


While watching the World Cup final between Spain and the Netherlands, which featured more penalty cards than points scored, a friend asked me, "How do the referees determine if the foul play merits a yellow or red card?"

I explained that, despite FIFA's guidelines for disciplining players, referees' decisions are often subjective. For example, findings published last week in PLoS ONE suggest that referees are more likely to call a foul when they see the direction of play moving from right to left, or leftward. According to a University of Pennsylvania release:

In a study of twelve members of the University of Pennsylvania's varsity soccer teams (all native English speaking), researchers found that participants called approximately three more fouls when images of soccer plays where viewed from right-to-left (66.5 fouls) compared to mirror images moving left-to-right (63.3 fouls). Participants were statistically more likely to call a foul when seeing a right-to-left attack.

Scientists intend to review World Cup footage to further determine how the direction of play could influence a referee's judgment. It will be interesting to see if such research finally convinces FIFA to implement instant replay.

Photo by NathanF

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