The British scientists theorized that the home team’s hormonal surge is an evolutionary holdover, related to animal species’ territoriality -- that is, the tendency to vigorously defend their ranging area against intruders. Indeed, some studies have shown that animals defending their turf tend to have a home-field advantage, even if they are smaller than the intruders.
Sports fans seem to believe pretty strongly in the notion that they can influence the game by creating visual or aural distractions. The spectators at NBA arenas, for example, often flutter streamers and wave colorful objects behind the backboard while an opposing player is shooting free throws.
Whether such distractions work on highly trained, focused professional athletes is a matter for debate.
Moskowitz and Wertheim report that NBA visiting teams shot exactly the same free-throw percentage over the past 20 years -- 75.9 percent -- that home teams achieved. And in deadlocked NHL games decided by shootouts, in which each team gets to pick three players to shoot one-on-one at the other team’s goalie, visiting teams’ 50.6 percent winning rate was actually higher than the 49.6 percent that home teams managed.
Those examples aside, a deeper dig into individual athletes’ statistics shows that even among the most talented, being on the road does seem to affect performance negatively.
Miami Heat superstar LeBron James, for example, is slightly less accurate from the field when away (.542) than he is at home (.592) and makes a lower percentage of free throws (.714 vs. 785). He also tends to make slightly more turnovers (3.3 away, vs. 2.7 at home). While those are slight differences, in a close game they could mean the difference between victory and defeat.
Part of the explanation, Jamieson says, may be that playing in front of an unfriendly crowd can cause subtle but possibly significant degradation of the complex skills that athletes have developed through extensive practice. It’s not the distractions, necessarily, but the crowd’s jeering when a player makes a mistake.
The negative feedback, he says, can raise a player’s stress level, and cause a player to try to compensate by concentrating on specific parts of his baseball swing or his basketball jump shot. When players do that rather than simply performing the entire skill as practiced, it’s a recipe for disaster, he says.
“When you do performance monitoring -- that is, trying to do something carefully so that you don’t do it poorly -- you’re basically trying not to lose. Instead of thinking about winning, you’re trying to avoid being booed.”
There’s also evidence that officials are influenced psychologically by the home crowd’s emotional response to plays.
A 2007 study by Harvard University researcher Ryan Boyko, which looked at 5,000 English Premier League soccer matches involving 50 different referees, found that away teams tended to score fewer goals and give away more penalties, which suggests that officials made calls in home teams’ favor.
Boyko also found that the effect was less pronounced when officials were more experienced, suggesting that they developed a resistance to the crowd’s psychological influence over time. Even so, Boyko calculated that for every additional 10,000 people in the stadium, the home team’s advantage increased by 0.1 goals.
Sports psychologist Hatfield, however, noted that not every individual athlete benefits from home field advantage.
Star players may benefit from familiarity with the stadium and feed off the energy of the crowd, he said, but less-skilled and less-experienced players actually may perform worse at home, because of anxiety about meeting the home crowd's expectations.
"If an athlete isn't a seasoned veteran," Hatfield said, "he may actually play better on the road."