It is called “football crowd disorder” in the academic literature. On the street, it’s known simply as hooliganism. The melees at international soccer matches are infamous for the intensity of violence. Among the worst was the rioting that killed 39 fans at Belgium’s Heysel Stadium during a 1985 match between English and Italian clubs. To keep public order, many countries flood big games with police in full riot gear. But the hard-line display of uniforms, helmets and batons often has the opposite effect, acting as a spark that incites disturbances.

Social scientists who study hooligan chaos think they have found a better way to keep the peace. Last year Clifford Stott of the University of Liverpool in England and his colleagues published in Psychology, Public Policy, and Law a paper that relates a giant experiment at the Euro2004 championship finals. There Portuguese security adopted the researchers’ recommendation to institute low-profile, nonaggressive tactics—the most visible of which was to leave the riot gear behind for police officers closest to fans. “We had a working hypothesis that predicted what would happen, but we had never had an entire European nation implement a style of policing based on our predictions,” Stott says.

The Portuguese deployed on average seven police near every 100 fans during high-risk matches as compared with one officer for every two fans at Euro2000 in the Netherlands and Belgium. One English fan among the 150,000 at Euro2004 was arrested for violent offenses as against nearly 1,000 of the English contingent at Euro2000. (Stott’s team tracked the English spectators closely because fans of that nation are so intimately associated with soccer hooliganism.)

The laissez-faire style, the team contends, did not alienate fans in the same way that legions of police in riot gear do. Shows of force, it seems, tend to antagonize crowds, especially if police display favoritism, as in the case of a 2001 match in Rome when the officers stood by while Italian fanatics pelted Manchester United aficionados with full plastic bottles.

Stott and his colleagues are now involved in a European Union–sponsored project to implement these policing methods in almost all member countries. If they are successful, European fans would feel the sting only of their team’s loss, rather than that of tear gas.