Scorecasting (25 page)

So how much of the home court advantage in the NBA is due to referee bias? If we attribute the differences in free throw attempts to referee bias, this would account for 0.8 points per game. That alone accounts for almost one-fourth of the NBA home court advantage of 3.4 points per game. If we gave credit to the referees for the more ambiguous turnover differences and computed the value of those turnovers, this would also capture another quarter of the home team’s advantage. Attributing some of the other foul differences to the referees and adding the effects of those fouls (other than free throws) on the game, this brings the total to about three-quarters of the home team’s advantage. And remember, scheduling in the NBA explained about 21 percent of the home team’s success, as well. That adds up to nearly all of the NBA home court advantage.

Long story short, referee bias could well be the
main reason
for home court advantage in basketball. And if the refs call turnovers and fouls in the home team’s favor, we can assume they make other biased calls in favor of the home team that we cannot see or measure.

What about the NHL? By now you can probably guess what we found. Home teams in
hockey get 20 percent fewer penalties called on them and receive fewer minutes in the box per penalty. (In other words, home teams are not just penalized less often but penalized for less severe violations.) The net result is that on average per game, home teams get two and a half more minutes of power play opportunities—a one-man advantage during which goals often are scored—than away teams. That is a
huge
advantage. To provide some perspective, the average NHL team succeeds in scoring a goal during a two-minute power play about 20 percent of the time. So if you take the power play advantage and multiply it by the 20 percent success rate (per two minutes), this gives the home team a 0.25-goal advantage per game. The average point differential between home and away teams in the NHL is 0.30 goals per game, so this alone accounts for more than 80 percent of the home ice advantage in hockey.

But is the penalty difference driven by refereeing bias? Repeating the same exercise we conducted for the NBA, we looked at more ambiguous calls—holding, hooking, cross-checking, boarding, tripping—and found that these penalties in particular went the home team’s way. Less ambiguous calls such as too many men on the ice, illegal equipment, delay of game from sending the puck into the stands, and fighting had much less home team bias. Again, this is consistent with officiating bias—and not with tired or sloppy play from visiting teams.

Also, don’t forget the shootout results we discussed earlier. Remember, in a shootout we found no home ice advantage. Not coincidentally, this is the only part of the game in which the referee essentially plays no role.

The fact that we can identify an officiating bias toward the home team is unsettling—that this may be the chief reason home field
advantage exists in every sport is
very
unsettling. But
why
are officials biased toward the home team?

First let’s be clear: Is there a conspiracy afoot in which officials are somehow
instructed
to rule in favor of the home team, especially since the league has an economic incentive to boost home team wins? Almost unquestionably no. We’re convinced that the vast majority of, if not all, officials are upstanding professionals, uncorrupted and incorruptible, consciously doing their best to ensure fairness. All things considered, they do a remarkable job.

They are not, however, immune to human psychology, and that’s where we think the explanation for home team bias resides. Despite fans’ claims to the contrary, referees are, finally, human. Psychology finds that social influence is a powerful force that can affect human behavior and decisions
without the subjects even being aware of it
. Psychologists call this influence
conformity because it causes the subject’s opinion to conform to a group’s opinion. This influence can come from social pressure or from an ambiguous situation in which someone seeks information from a group.

In 1935, the psychologist
Muzafer Sherif conducted a study about conformity, using a small point of light in an otherwise dark or featureless environment. Because of the way the human eye works, the light appears to move, but the amplitude of the movements is undefined—individual observers set their own frames of reference to judge amplitude and direction. Therefore, each individual saw the “movement” differently and to differing degrees.

When participants were asked individually to estimate how far the light had moved, as one would expect, they gave widely varying answers. Then they were retested in groups of three. The composition of the group was manipulated; testers put together two
people whose estimate of the light movement when alone was very similar and one person whose estimate was very different. Each person in the group had to say aloud how far he or she thought the light had moved. Sherif found that over numerous trials, the group converged on a common estimate. The subject whose estimate of movement had been vastly different from that of the other two in the group came to conform to the majority view.

More important, when interviewed afterward, the subject whose initial estimate had been very different now
believed
his or her initial estimate was wrong. That is, that subject did not succumb to social pressure and state something he or she didn’t believe; his or her actual perception of the light’s movement had changed. The experiment demonstrated that when placed in an ambiguous situation, a person will look to others for guidance or additional information to help make the “right” decision.

After the Sherif study,
Solomon Asch, a pioneer of social psychology, conducted an experiment in which he asked participants to look at two cards and decide which line (A, B, or C) on the card on the right in the following illustration was most like the line on the card on the left.

The answer, you probably guessed, is C. The participants, though, were asked to make this assessment in a group setting. Asch had put one unwitting subject in a room with seven confederates, or actors. The actors were told in advance how to respond.
Each person in the room gave his or her answer, and the “real” participant offered his or her answer second to last. In most of the cases, the subject yielded to the majority at least once, even though he or she suspected it was wrong.

Asked why they readily conformed to the group even though they felt the answer was wrong, most participants said that they did not really believe their answer; rather, they went along with the others for fear of being ridiculed or thought “peculiar.” A few, however, said that they really did believe the group’s answers were correct. Asch also found that subjects felt enormous stress when making these decisions; giving a response that was at odds with the majority caused anxiety, even though they knew they were right.

The takeaway here is that human beings conform for two reasons: (1) because they want to fit in with the group and (2) because they believe the group is better informed than they are. Makes sense, right? If you are asked to make a decision and are unsure of your answer, wouldn’t you look for other cues and signals to improve that answer? And don’t you accord weight to people’s answers by the confidence with which they provide them? After a difficult test in school, who hasn’t polled other classmates for the answer to a question, paying particular attention to the responses of the known “A” students?

Now, back to referees. When humans are faced with enormous pressure—say, making a crucial call with a rabid crowd yelling, taunting, and chanting a few feet away—it is natural to want to alleviate that pressure. By making snap-judgment calls in favor of the home team, referees, whether they consciously appreciate it or not, are relieving some of that stress. They may also be taking a cue from the crowd when trying to make the right call, especially in an uncertain situation. They’re not sure whether that tailing 95-mph fastball crossed the strike zone, but again, even if it’s subconsciously, the crowd’s reaction may provide a useful signal that changes their perception.

If beliefs are being changed by the environment, as psychology
shows, referees aren’t necessarily consciously favoring the home team but are doing what they believe is right. It’s just that their perceptions have been altered. In trying to make the right call, they are conforming to a larger group’s opinion, swayed by tens of thousands of people witnessing the exact same play they did. As the saying goes in psychology, “I’ll see it when I believe it.” Referees, it’s safe to assume, do not intend this favoritism. They’re probably not even aware of it. But it is a natural human response.

Remember, too, that on top of the anxiety caused by passionate and sometimes angry fans, the refs receive stress from their supervisors and superiors. In a variety of ways—some subtle, some not—officials must take in cues that the league has an economic incentive for home teams to do well. If your boss sent a subtle but unmistakable message that Outcome A was preferable to Outcome B, when you were forced to make a difficult, uncertain, and quick decision, how would you be inclined to act?

Let’s look at our previous results on referees through the lens of psychology and our understanding of the human propensity to conform. The extra injury time in soccer? It is probably a response to social pressure, that is, the desire to please the crowd—and in some cases preserve personal safety. The strike-ball discrepancy in baseball and similar disparities in fouls and turnovers in basketball, along with penalties and turnovers in football and hockey, may also be the result of “informational conformity” in the face of social pressure—using the crowd as a cue to resolve an uncertain or ambiguous situation.

If this is true, psychology suggests that both the crowd size and the uncertainty or ambiguity of the situation should make a difference. Home team favoritism therefore should be greater the larger and more relevant the crowd and the more ambiguous the situation. We’ve already shown in a variety of ways how the more ambiguous the call—whether it is a 90-mph pitch on the corner of the strike zone in baseball, a fumbled football, a two- or three-step move without dribbling in basketball, or a questionable check in hockey—the more severe the home advantage.