Refs choke on whistles when the home team commits a foul

Here in North Carolina, for many sports fans, it's considered common knowledge that basketball referees don't call fouls against Duke. The reasons for the supposed bias vary from racism, to payoffs from wealthy alums, to the intimidating atmosphere at Duke's legendary Cameron Indoor Stadium, but nearly everyone in the state who's not a Duke fan seems to believe that the rich northerners at Duke University get all sorts of unfair advantages.

That said, accusations of bias in sports officials aren't limited to the Atlantic Coast Conference. Studies on home field advantage in Major League Baseball in the 1970s found that the advantage increased with larger crowds. Perhaps crowds intimidate or otherwise influence the officials, no matter what the sport.

A later study found that basketball refs call fewer fouls against star players in home games compared to away games, adding further fuel to the debate. Yet not all cheering is good: another study found that home teams commit more fouls when the crowd exhibits antisocial behavior such as booing or chanting taboo words. But when a group of researchers led by A.M. Nevill observed that no controlled study of officiating had been made, they sought to remedy it by showing game videos to English football (soccer) referees.

The videos showed 47 critical plays from an English Premier League match between the home Liverpool team and Leicester City. Each clip showed the entire contested play and six seconds of the aftermath, up to the point when the referee either called a penalty or let the teams play on. Twenty-two referees watched a video with crowd noise from the game but no other commentary; the other 18 officials saw a completely silent video. In each case, the referees were allowed to call a foul on either team, no foul, or "uncertain," which they knew in a game situation would result in a non-call. Here are the results:

Referees who saw the video with sound called significantly fewer fouls against the home team than those who saw a silent video. Interestingly, they didn't call fouls any differently against the away team, regardless of whether the soundtrack was playing. The referees in the "sound" condition matched calls made during the actual game nearly exactly.

Nevill's team made a further analysis of the referees to see if years of experience mattered: perhaps more experienced officials would be better at filtering out crowd noise. They found that while more experienced officials called fewer fouls overall, they still were affected by crowd noise just as much as those with less experience.

The reduction in number of fouls may seem small -- just 15 percent fewer fouls were called against the home team with crowd noise compared to the silent video -- but this number corresponds quite closely with the overall home field advantage in the Premier League, where the home team wins 63.9 percent of the time -- about 13.9 percent more than chance levels. (But see also our report on the influence of testosterone levels and the home field advantage.)

So does Duke University get an unfair advantage due to the home court? This study doesn't answer that question, but it does suggest that officials may give all home teams with cheering crowds a substantial advantage.

Nevill, A.M., Balmer, N.J., & Williams, A.M. (2002). The influence of crowd noise and experience on refereeing decisions in football. Psychology of Sport and Exercise, 3, 261-272.