Sports fans around the world can rely on one fact about their sport: the home team wins more often than the visiting team. A 2011 Sports Illustrated article concludes: "Home field advantage is no myth. Indisputably, it exists …. Across all sports and at all levels, from Japanese baseball to Brazilian soccer to the NFL, the team hosting a game wins more often than not." What explains this fact?

A wealth of evidence disputes the most common theories behind home team advantage. For instance, thousands of cheering or jeering fans didn't change a team's performance. On a number of statistics—such as pitch velocity in baseball or free throw percentage in basketball (which over two decades was 75.9 percent for home and visiting teams)—home field advantage didn't make a difference. Their research also eliminated other likely theories based on the rigors of travel for the visiting team or the home team's familiarity with their field, rink, or court.

So what drives home field advantage? According to the authors of the article, "Officials' bias is the most significant contribution to home field advantage." In short, the refs don't like to get booed. So when the game gets close, they call fewer fouls or penalties against the home team; or they call more strikes against visiting batters. Larger and louder fans really do influence the calls from the officials. The refs naturally (and often unconsciously) respond to the pressure from the crowd. Then they try to please the angry fans and make the calls that will lessen the pain of crowd disapproval. In the end, the refs' people-pleasing response can have an impact on the final result of the game.