Home Field Advantage?

What’s Really Behind Home Field Advantage?

In almost every sport, everywhere on earth, the visiting team loses more often than not. You probably think you know why. and you’re probably wrong

by tobias j. moskowitz and l. jon wertheim Illustration by sean McCabe

or all the conventional sports wisdom that can be deconstructed, disproved or called into question, home team advantage is no myth. Indisputably, it exists—and it’s remarkably consistent. 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. The size of the advantage is remarkably stable in each sport too: The home team’s success rate has been almost exactly the same in the last decade as it was 50 and even 100 years ago. And home field advantage is the samewithin any sport, no matter where it is played. The home winning percentage in Arena Football is Fessentially the same as in the NFL. The home field advantage in the Not only do NBA is a virtual carbon copy of that in the WNBA. In professional soc- home teams cer, the sport with the greatest home field advantage, the host teams in win more often, but the three of Europe’s most popular leagues—England’s Premiership, Spain’s success rate in La Liga and Italy’s Serie A—win about 65% of the time. In 40 other soccer each sport has also remained leagues in 24 countries, the home field advantage hovers around 63%. consistent In the NBA an astounding 98.6% of teams fare better at home over the last than on the road. That means that in most seasons all NBA teams decade—and even the last have better home than road records. In hockey and soccer, more than century. 90% of the teams win more at home than on the road. Even in the

january 17, 2011 | Sports Illust r at eD

Sports Illustrated 01/17/2011 scorecast.l/o LEFT PAGE 64/1 of 2 Sports Illustrated 01/17/2011 scorecast.l/o righT PAGE 65/1 of 2 Version:33 01/09/2011 1108PM kerr hunt sun Version:33 01/09/2011 1108PM kerr hunt sun A.D./ext: Zamora/x0000 Statushere: 01/09/2011 08:23PM Liana Zamora A.D./ext: Zamora/x0000 Statushere: 01/09/2011 08:23PM Liana Zamora Revise comments: FINAL ART OK Revise comments: FINAL ART OK ±Local Read± ±Conference± ±Art Approval± ±HOLD:Updates/Checks ±HOLD:Art ±Local Read± ±Conference± ±Art Approval± ±HOLD:Updates/Checks ±HOLD:Art home field advantage

NFL and major league baseball, the leagues away teams won 316 (50.6%). In other words, each other—such as when the Lakers face with the lowest home winning percentages, for shootouts—held when you’d expect the the Clippers (who share their NBA arena), or more than 75% of teams do better at home. crowd to be especially involved—the NHL’s when the NHL’s Rangers play the Islanders:

It’s little wonder, then, that leagues reward significant home ice advantageevaporates . The designated home teams have the exact P ma zu previous spread: spread: previous the best teams in the regular season with In the NFL we could look at punters and same advantage they do in all the other games ress.com ( ress.com home field advantage in the playoffs—it’s kickers. But it turns out that yards per punt they host. Likewise, road teams don’t lose a hell of an incentive to win those dreary are identical for home and visiting punters more often when they travel greater distances. F r a ncesco ncesco a r midseason games. There is also considerable (about 41.5 yards). Likewise, field goal suc- In baseball, too, in games involving teams y t i/Get a Pill l Pa economic incentive for home teams to win as cess from the same distance and extra-point from the same metro area (interleague play often as possible. The better the home team accuracy are identical for kickers at home between the Cubs and White Sox, Yankees T plays, the more likely fans are to buy tickets and on the road (about 72%). Of course, and Mets, Dodgers and Angels, Giants and Gre i); t ot

and hats and T-shirts and renew their luxury- you could question whether punters and A’s), the home teams win at exactly the same I ma g g

suite leases; the more likely corporations are kickers have the ball long enough to be af- rate at which they normally do. The fact that ( es

N el son ( son el

to buy sponsorships; and the more likely local fected by a rabid crowd. O.K., then, let’s take home field advantage has been remarkably S achin achin television networks are to bid for rights fees. quarterbacks. Extreme crowd noise might be constant over the last century—it was virtu- A T ndy ndy

That the home field advantage exists is expected to distract visiting quarterbacks, ally the same in MLB from 1903 to ’09 as it r); a lk endu D a rvish); rvish); a D

undeniable. But why does it exist? but actually it doesn’t seem to. In fact, visiting was from 2003 to ’09—suggests that teams Winslo lton); a It’s not for the reasons you might think. teams pass slightly better than home teams. jetting on chartered flights have no more E L l a ine ine a l In baseball the closest we can come to success than the teams that traveled to games u o

[ Myth #1 ] C

measuring the crowd’s influence is to exam- in Pullmans. a p T w oz zol a ( a zol oz hom

Home teams win because their crowds ine the pitcher. Not his ball-strike count— Nor does travel play much of a role in the T o p w son/

boost players’ performance influenced, as it is, by the batter, the umpire NFL’s home field advantage. Teams play nson/ A le x x le It’s reasonable to think that you play better and the game situation—but his velocity, only one game per week and in fact usually A P ( P A P ( P L O

when you’re cheered, your favorite songs movement and placement. Data from the depart for a game a few days in advance to Jackson); ren au vechkin); Jeff Jeff vechkin); T blare on the P.A. system and your pregame MLB.com technology Pitch f/x, tracking acclimate themselves. As in the other sports, om B introduction is accompanied by fireworks. more than two million pitches over the last when nearby teams play—Raiders versus dy); a r But fans’ influence on the players is actually three years, show that major league pitchers 49ers, Giants versus Jets, Ravens versus D Z u o eleva nsk y/Get t y y t y/Get nsk eleva

pretty small. How do we know this? One of are as accurate at home as they are on the Redskins—the home field advantage holds D g avid avid the problems with testing the effect of crowd road, throwing a ball within the strike zone firm at its normal level. mes/ Ja R support is that almost every feat in team 44.3% of the time at home and 44.5% of the o g I con con sports is a function of not only the player and time on the road. They also throw with the [ Myth #3 ] y t ers/Get SMI

the crowd but also the player’s teammates, same velocity—87 mph on average when I Home teams win because ( ma R od Windsor); Windsor); od g I ma the defender, the defender’s teammates and the ball crosses the plate—and movement. they benefit from a kinder, gentler schedule ( es g K the referee. How do we isolate the crowd ef- We can also use the Pitch f/x data to help In the NBA the vast majority of back-to-back ( es y le le y I

fect? We need to look at an area of the game gauge whether playing at home has any im- games are played by visiting teams, which is el a sr S in g divorced from all the other factors, such as pact on batters. The data show that when a exhausting for the players. Could that help B ler); John W. W. John ler); r a d d a r D a

free throws. Free throws are an isolated in- player swings at a pitch, in or out of the strike create home court advantage? Yes. Of the 20 gg M n a teraction between one player—the shooter— zone, his probability of hitting the ball is ex- or so back-to-back games NBA teams play ); A g ndre and the crowd that is trying to distract him. actly the same at home and away. Hey-batter- each season, an average of 14 are on the ( in T M im im w c

Over the last two decades in the NBA, batter-batter-swing? Sorry. He’s going to do it road. By our calculations, teams win only D Y L n u ono tes/ at encompassing more than 23,000 games, just as well whether you’re chattering or not. 36% of those 14 games. That translates into Geor m); incecu g f a the free throw percentage of visiting teams one or two additional games that teams lose ( h P/Get t y y t P/Get Myth #2 K has been 75.9%, and that of home teams has [ ] each season on the road. obe B g been . . . 75.9%. Are these shooting percent- Home teams win because the rigors It’s not just back-to-back games, either. nt); rya e e I ma H l nd/ a oll ages any different at different points in the of travel doom visitors Home teams generally have more off days g es (Way ne ne (Way es L

game—say, during the fourth quarter or in The rigors of the road exist, of course, but within the same time span, such as the last / Gene is lu

overtime, when the score is tied? No. Even in they don’t underpin the home court advan- three days, the last week or even the last two C a l l a R Sp

close games, when home fans are trying their tage. Why? Consider what happens when weeks. All this takes its toll on visitors. We ooney) ort ort f a

hardest to distract the opponents and exhort teams from the same or a nearby city play estimate that about 21% of the NBA’s home y t P/Get M . This page: gina houseman (book jacke (book houseman gina page: This . the home team, the percentages are identical. court advantage is attributable to scheduling. ( edia L What about other sports? In hockey Scheduling is less of an issue in baseball; I ma Excerpted from scorecasting: ndon a g

there’s a rough equivalent to free throws: the The Hidden Influences Behind teams play in three- and four-game series. ( es How Sports Are Played and Games L shootout, in which each team chooses three When teams travel, they stay put in the D ionel ionel Are Won, by Tobias J. Moskowitz n); onova players to shoot one-on-one at the goalie. In and L. Jon Wertheim. Copyright visiting city, and the consecutive games

from 2005–06 (when the shootout was in- arrangement with Crown Archetype, letes. And in the NFL, the one league that ( yodo I stituted to settle ties at the end of overtime) an imprint of the Crown Publishing unapologetically strives for parity, there is ma g

Group, a division of Random Y o/ t u to ’08–09, home teams won 308 (49.4%) and House Inc., New York. no evidence of scheduling bias. )

Sports Illust r at eD | january 17, 2011

Sports Illustrated 01/17/2011 scorecast.l/o LEFT PAGE 66/1 of 2 Version:33 01/09/2011 1108PM kerr hunt sun A.D./ext: Zamora/x0000 Statushere: 01/09/2011 08:23PM Liana Zamora Revise comments: FINAL ART OK ±Local Read± ±Conference± ±Art Approval± ±HOLD:Updates/Checks ±HOLD:Art home field advantage

In college sports, by contrast, there’s abun- looked at the most obvious case—“hitter- sity of Chicago, Luis Garicano and Canice dant evidence. College boosters might claim friendly” ballparks versus “pitcher-friendly” Prendergast, to study the officials’ conduct. that the exceptionally high home winning ballparks—and found that teams in hitters’ Examining 750 matches from La Liga, the percentage in NCAA sports is a consequence parks, presumably stacked with sluggers, researchers determined that in close matches of rabid school spirit, but what really drives it don’t outhit their visitors by more than teams in which the home team was ahead, the ref- is the scheduling of weak opponents early in in pitchers’ parks outhit theirs. We also found erees reduced the extra time significantly. In the season. We found that schedule padding that teams from hitters’ ballparks hit no close games in which the home team was accounts for roughly half of the home team better on the road than teams from pitchers’ behind, the referees lengthened the injury advantage in college football. If we adjust for parks. That is, the Rockies (hitters’ park) hit time. If the home team was ahead by a goal the quality of teams—or look at in-conference as well as the Mets (pitchers’ park) when at the end of regulation, the average injury games, for which the conferences and not each team plays the Cardinals in St. Louis. time was barely two minutes, but if the home the big schools set the schedule—home win- Nor do deception and “dark arts”—sign team was behind by a goal, the average injury ning percentage drops from 64% to 57%. stealing, groundskeeping shenanigans, lock- time was four minutes. Sure enough, when Amazingly, that 57% is almost the same rate er room sabotage—help explain baseball’s the score was tied the average injury time at which home teams win in the NFL and home advantage. At one time they might was right around three minutes. Arena Football. have, but because of standardized league What happened when the home team was So scheduling bias gets us only so far. It rules, surveillance technology and stiff pun- significantly ahead or behind? There was no accounts for half of the home field advan- ishments for cheating, it would be hard to bias at all. The extra time was roughly the tage in college football and basketball and pull off this kind of skulduggery today. same whether the home team was ahead by partially explains the home field advantage two goals or more or behind by two goals in the NBA and the NHL. In baseball, soccer [ the big question ] or more. This makes sense. A referee has to and the NFL, however, it doesn’t provide So what really drives home field advantage? balance the benefit of any favoritism with any explanation at all. Every sports fan believes that officials make its costs: harm to his reputation, media bad calls against his or her team. The home scrutiny and potential reprimands. If the [ Myth #4 ] crowd voices this displeasure the loudest, extra time wasn’t going to affect the game’s Home teams benefit from emitting cries that range from the pass- outcome, why stretch or condense it, right? unique “home” characteristics ably clever (“Ref, if you had one more eye, This wasn’t unique to Spain. Researchers An NBA court is an NBA court, and an you’d be a Cyclops!”) to the troglodytic (“You found the same injury-time bias in the Pre- NHL rink is an NHL rink. The games are suck!”). We’ve found that officialsare biased, mier League, Serie A, Germany’s Bundesliga, played indoors, in climate-controlled envi- but not against the louts screaming epithets the Scottish league and MLS. Soccer referees ronments. In the NFL, however, the climate at them. They’re biased for them—and the also award more penalties in favor of the and playing conditions can vary immensely. bigger the crowd, the worse the bias. In fact, home team. Looking at more than 15,000 Is the league’s home field advantage influ- officials’ bias is the most significant contribu- matches in the Premier League, La Liga and enced by teams tailoring their rosters to tor to home field advantage. Serie A, we found that home teams receive the weather? Let’s start by determining how to measure many fewer red and yellow cards. Suddenly No. Much as broadcasters talk about those referee bias. We looked for a component of a it isn’t so surprising that the home team in poor Dolphins faltering on the redundantly sport that the refs control and that isn’t influ- soccer wins nearly 63% of its games. “frozen tundra” in Green Bay, climate is large- enced by players. We found it in soccer. But But surely U.S. sports wouldn’t be subject ly irrelevant in the NFL. After studying data if it hadn’t been for a diligent grandmother to the same referee bias. from nearly 6,000 games be- in Spain religiously record- tween 1985 and 2009, we found ing years of Sunday-evening [ Or would they? ] that cold-weather teams are no matches, we might not have Let’s start with baseball more likely to win at home when discovered this bias at all. It turns out that the most significant dif- the weather is brutally cold, nor much as In soccer the referee has ference between home and away teams is are warm-weather teams more broadcasters discretion over the addition that home teams strike out less and walk likely to win at home when the of extra time, referred to as more—a lot more—per plate appearance. Balls temperature is awfully hot. talk about the “stoppage time,” at the end and strikes are the domain of the home plate What about baseball? After of the game to make up for umpire. Could he be biased toward the home all, not only do the playing con- “frozen tundra” suspensions of play for in- team? This would explain the differences ditions vary, but each stadium juries, penalties and substi- in strikeouts and walks despite the lack of is also unique. Don’t the home of green tutions. Using handwritten any difference in hitting and pitching. But players get an advantage from notes that his elderly mother walks and strikeouts are not the right sta- being more familiar with their bay, climate had made while watching tistics to measure, because some walks are ballparks’ idiosyncrasies? What matches in her living room, intentional and many strikes occur when a about the notion that baseball is largely Natxo Palacios-Huerta, a pro- batter swings and misses or fouls off a ball. teams win more games at home irrelevant in fessor at the London School of Those don’t require any judgment on the part because they tailor their rosters Economics, joined with two of the umpire. A better metric is called balls to their fields’ dimensions? We the nfl. colleagues from the Univer- (eliminating intentional walks) and strikes—

68 | Sports Illust r at eD | january 17, 2011

Sports Illustrated 01/17/2011 scorecast.l/o LEFT PAGE 68/1 of 2 Version:34 01/10/2011 301 PM kerr hunt sun A.D./ext: Zamora/x0000 Statushere: 01/09/2011 08:23PM Liana Zamora Revise comments: FINAL ART OK ±Local Read± ±Conference± ±Art Approval± ±HOLD:Updates/Checks ±HOLD:Art home field advantage

pitches that don’t involve swings parks where umpires were not replay challenges, which were instituted by the batter. It turns out that home teams being monitored. We also found in 1999 and were followed by a decline in home batters receive far fewer something surprising. When the home team success rate from 58.5% strikes per called pitch than are more QuesTec was watching them, (1985–98) to 56% (1999–2008). Coincidence? away batters do. umpires called more strikes We can start by looking at turnovers. Before It’s even more apparent when likely to be and fewer balls on home team instant replay home teams enjoyed more we look at called strikes and batters. In short, when umpires than an 8% edge in turnovers, losing the balls at different points in the successful knew they were being moni- ball far less often than road teams. When game. A wizard sabermetri- tored, the advantage swung to replay challenges came along, the turnover cian, Tom Tango, devised the when the visiting team. advantage was cut in half! Leverage Index to measure the stealing a If QuesTec is our smoking We can also distinguish between fum- relative importance of game gun in the case to prove um- bles lost and fumbles retained. The home situations. A leverage index base and pires’ home team bias, Pitch team does not fumble less often than the of 1 is the average situation; f/x provides the ballistic sup- away team, but before replay challenges the an index of 2 means the situa- turning a port. We found that pitches home team lost fewer fumbles than the away tion is twice as crucial. For ex- in the exact same location are team. After instant replay this advantage ample, down by four runs with double play. called differently for home miraculously disappeared. In close games, two outs and nobody on in the and away batters. According when referees’ decisions really matter, home bottom of the ninth, the game to data we examined on ter- teams enjoyed a healthy 12% advantage in isn’t in much doubt, and the leverage index is minal pitches—ones that result in either a recovering fumbles before instant replay was 0.1—one tenth as crucial as the average situ- strikeout or a walk—516 more strikeouts are installed. Afterward, that edge also vanished. ation. Down by one run in the bottom of the called on away teams and 195 more walks If away teams are indeed getting more ninth with two outs and the bases loaded, the are awarded to home teams over the course bad calls than home teams, we should see leverage index is 10.9, almost 11 times more of a season thanks to umpire bias. And this more of their calls being overturned on crucial than the average situation. doesn’t take into account errant calls made instant replay. And they are. We looked at Using the index, we found that when the earlier in the pitch count that could confer an the results of nearly 1,300 instant-replay game is not in much doubt, the home team ad- even greater advantage for the home team. challenges from 2005 to ’09 and found that vantage in receiving fewer called strikes and Calculating the value of a walk and a away teams are more successful in overturn- more balls goes away. But the called-strike strikeout in various game situations, we found ing calls than home teams are, if only by a advantage for home teams grows considerably that each home team gains 7.3 runs per sea- modest margin (37% versus 35%). as the game situation gets more important. son thanks to the plate umpire. Cumulatively, These statistics are misleading, though, Now let’s look at other calls that fall under home teams outscore their visitors by only because referees are less likely to make bi- the domain of the umpires, such as stolen 10.5 runs in a season. Thus more than two ased judgments when the game is no longer bases and double plays. We found that home thirds of the home field advantage comes by in doubt. So what happens if the home team teams are more likely to be successful when virtue of the home plate umpire’s bad calls. is behind? Then its challenges are success- stealing a base and when turning a double We can’t expect umpires to be perfect, and ful 28.4% of the time, while challenges by play. In addition the success rates of home in fact they call strikes and balls correctly the away team are successful 40.0% of the teams in scoring from second base on a single 85.6% of the time, according to QuesTec. time. Thus away teams seem to get more or from third on an out—typically close plays But the errors they do make don’t seem to than their fair share of bad calls when they at the plate—are much higher than they are be random. They favor the home team. are winning, which is when bad calls would for their visitors in high-leverage situations. be most valuable to the home team. But the most damning evidence of umpire [ now, football ] Could referee bias explain a large part of bias comes, ironically, from an attempt by the Is it the same in the NFL? the home field advantage in football? Abso- major leagues to police it. A digital technology For evidence of official bias in the nation’s lutely. Again we see a dramatic reduction in called Umpire Information System (UIS), most popular sports league, it makes sense the home team’s edge when instant replay from QuesTec, was introduced in 2001 to to start with penalties. Home teams receive is introduced. Yet instant replay affords monitor the accuracy of umpires. According to fewer penalties than away teams (about half each team only three incorrect challenges MLB, QuesTec was installed in six ballparks a penalty less per game) and are penalized per game and is limited to certain circum- in the first year; by the time it was discon- fewer yards per call. Of course, this does not stances. Clearly other calls are not being tinued in 2008, 11 parks had the technology. prove officials are biased. Away teams might challenged that could go the home team’s With two cameras positioned at field level and commit more fouls and play more sloppily way, such as penalties. The fact that home two in the upper deck, QuesTec tracked where or more aggressively. But when we look at teams in football have better offensive stats the ball crossed the plate. We compared all more crucial situations in the NFL, we find could be the result of getting more favorable pitches, about 5.5 million of them, from 2002 that the penalty bias is exaggerated. The calls and fewer penalties and committing to ’08 in stadiums using QuesTec versus those more valuable penalties, those which result fewer turnovers. If you play at home and without it. What did we find? Called strikes in first downs, also favor the home team. sense that you’re less likely to get called for and balls went the home team’s way only The most compelling evidence of referee a penalty, you may be more inclined to block in stadiums without QuesTec—that is, ball- influence in the NFL comes from instant- more aggressively or challenge a receiver.

january 17, 2011 | Sports Illust r at eD | 71

Sports Illustrated 01/17/2011 scorecast.l/o righT PAGE 71/1 of 2 Version:34 01/10/2011 301 PM kerr hunt sun A.D./ext: Zamora/x0000 Statushere: 01/09/2011 08:23PM Liana Zamora Revise comments: FINAL ART OK ±Local Read± ±Conference± ±Art Approval± ±HOLD:Updates/Checks ±HOLD:Art home field advantage

[ the reason ] of play. In those stadiums the referees are by the home team were less likely to be called why officials favor the home team more removed from the fans. Guess what? fouls. The referees who viewed the tackles First, let’s be clear: There is no evidence The bias that refs exhibit for the home team in silence showed no bias. that officials are instructed to rule in favor is cut in half. Not only that, but the referees watching of the home team. We believe that the vast What about the extra walks awarded with sound also reported more anxiety and majority, if not all, of them are upstanding to home teams and the extra strikeouts uncertainty regarding their calls, consis- professionals doing their best to be fair. All called on away teams by home plate um- tent with the stress they felt from the crowd. things considered, they do a remarkable job. pires? These also occur predominantly in Imagine how much more intense that stress They are not, however, immune to social high-attendance games. The highest fifth would have been if they were on the actual pressure, and that’s where we think the ex- of attended games account for about half field of play. planation for home team bias lies. Referees of the entire strikeout and walk advantage But perhaps the most persuasive evi- are, ultimately, human. In test after test, psy- given to home teams each season. dence for the effect of crowds on referees chologists have found that social influence In the NBA crowd size also affects the occurred when no fans were present. On has a powerful effect on people’s behavior and home-away differences, particularly with Feb. 2, 2007, supporters of two soccer clubs decisions—without their even being aware of it. more ambiguous calls. Traveling is whistled in Italy—Catania and Palermo—clashed Psychologists call this influence conformity, 15% less often against home than away play- with each other and police. Following the because it causes an individual’s opinion to ers, but at the most attended games the episode, the Italian government forced conform to a group’s opinion. In other words, home team is 28% less likely to be called teams with deficient security standards to when humans are under enormous stress— for traveling. And even in the NFL, in which play their home games without any specta- say, making a crucial call with a rabid crowd most games are sold out, the home-away tors. Two economists (and soccer fanatics) yelling a few feet away—it is natural for them discrepancies in penalties and turnovers from Sweden, Per Pettersson-Lidbom and to want to alleviate it. Making snap judg- increase with crowd size. In virtually every Mikael Priks, collected data from 21 soccer ments in favor of the home team is one way sport the home advantage is significantly matches that were played before empty to do that. Umpires also may be taking cues larger when the crowd is bigger. bleachers. What they found was amazing. from the crowd when they’re uncertain. They In the least attended games in each sport, When teams played without spectators, don’t know whether that tailing 95-mph fast- conversely, the home field advantage all but the home bias in favorable calls dropped ball crossed the strike zone, but the crowd’s vanishes. In baseball, if you look at the 20% by 23% in fouls, 26% in yellow cards and reaction may change their perception. of games that are least attended, the home 70% in red cards. The players, on the other In that case umpires aren’t consciously field advantage is only 50.7%. In the NBA the hand, performed the same whether or not favoring the home team; they are doing what least attended games are won by the home there was a crowd. they believe is right. In trying to make the team only 55% of the time and the most at- In the end referee bias explains not only right call, they conform to a larger group’s tended games 69% of the time. In the NHL the home field advantage but also why the opinion, swayed by thousands of people wit- the home team wins only 52% of the time in home team’s success rate hasn’t changed in nessing the exact same play they did. the lowest attended games but 60% of the more than a century. Although sports have Let’s look at our previous results on ref- time in the highest attended games. And in altered their rules—raising and lowering erees through the lens of psychology and European soccer the home team wins 57% the pitcher’s mound, introducing a shot our understanding of the human propensity of the time in the lowest attended games clock and the three-point line—the official’s to conform. The stoppage time in soccer? It and an astonishing 78% of the time in the role in the game hasn’t changed much. Um- probably reflects the ref’s desire to please highest attended matches. pires still call balls and strikes; referees still the crowd—and in some cases preserve Still not convinced by the call fouls and penalties; and his safety. The strike-ball discrepancy in psychological explanation for they are still human beings, baseball and disparities in fouls and turn- referee bias? Consider a study none of them immune from overs in hoops, hockey and football may performed in 2001. Research- human psychology. Although also be the result of what psychologists call ers made videos of soccer umpires we will never be able to mea- “informational conformity” in the face of matches, focusing on tackles, aren’t sure or test all the decisions social pressure, using the crowd as a cue and showed them to two groups an official makes, if we can see to resolve uncertainty. of referees. The first group consciously that some of them are biased If this is true, psychology suggests that was shown the tackles with in favor of the home team, it’s the larger and more passionate the crowd the crowd noise audible. The favoring the likely that other judgments is, and the more ambiguous the situation second group was shown the we can’t see are also going the is, the greater the home favoritism should same tackles with the crowd home team; home team’s way. Think of the be. Recall the original study of La Liga. The noise muted. The referees who father who comes home early authors found that the bias in regard to stop- watched with the crowd noise they are from work and catches his page time was greater when the crowd was were much more likely to call teenage daughter kissing her larger. But even more interesting was a study the tackles with the crowd. doing what boyfriend. He’s upset about the conducted in Germany, where many soccer That is, tackles against the they believe kiss, but he’s more upset about stadiums have running tracks that act as home team were more likely what else she might be doing moats, separating the stands from the field to be called fouls, and tackles is right. when he isn’t looking. ±

72 | Sports Illust r at eD | january 17, 2011

Sports Illustrated 01/17/2011 scorecast.l/o LEFT PAGE 72/1 of 2 Version:34 01/10/2011 301 PM kerr hunt sun A.D./ext: Zamora/x0000 Statushere: 01/09/2011 08:23PM Liana Zamora Revise comments: FINAL ART OK ±Local Read± ±Conference± ±Art Approval± ±HOLD:Updates/Checks ±HOLD:Art