ASU Curtain of Distraction: Has Arizona State University discovered the holy grail of free-throw distraction?

Has ASU Discovered the Holy Grail of Free-Throw Distraction?

Has ASU Discovered the Holy Grail of Free-Throw Distraction?

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The stadium scene.
Feb. 17 2015 8:51 PM

Curtains Up

Is ASU’s bizarre new technique the holy grail of free-throw distraction?

ASU Curtain of Distraction
You never know what awaits behind Arizona State’s Curtain of Distraction.

Photo illustration by Slate. Photos by Ethan Miller/Getty Images; Gary Null/NBC/NBCU Photo Bank via Getty Images; Thinkstock.

A couple of weeks ago, I got an unexpected note from a radio producer in Phoenix. She wanted me to comment on the city’s local college basketball team, the Arizona State Sun Devils, whose fans had worked out a novel way to distract opponents at the free-throw line. “They put up a curtain,” she wrote, “and when an opposing team goes up to make a free throw they pull it back and hijinks ensue.” Did I think this ploy might work?

Daniel Engber Daniel Engber

Daniel Engber is a columnist for Slate.

I did not, and said as much during my interview. But in the past few days, ASU’s “Curtain of Distraction” has been gaining credibility, and even some full-fledged quantitative nerds now argue that it works. For the first time in recent memory, the notion of “free-throw defense”—that a home team’s fans might rattle opposing players into missing shots—is being treated as something other than a quirky sideshow. Arizona State supporters say their method even helped them upset Arizona, their much higher-ranked rival in the Pac-12, on Feb. 7. But after looking at the data, I’m still a bit suspicious. Even if the curtain did work on the college level, it would never translate to the NBA.

First, a note about my qualifications, and why that radio producer chose to speak with me: In the tiny, undeveloped field of free-throw distractology, I may be among the nation’s leading experts. Ten years ago, I noticed that home-team fans at basketball games were taking the wrong approach to unnerving opposing free-throw shooters. The people sitting right behind the backboard would try to break a player’s concentration by waving noodles or banging ThunderStix together. From my student research into motor psychophysics, I knew that this random, uncoordinated motion could be easily ignored; to the players, it’s white noise. So I wrote an email to the Dallas Mavericks’ owner, Mark Cuban, and suggested that he have the Dallas fans wave their ThunderStix in unison. In theory, this could produce in free-throw shooters the illusion of drifting to one side, which might then elicit a compensatory movement as they shot the ball. Cuban liked my idea and for a few glorious games during the 2004­–05 season, he put it to the test against the best basketball players in the world.

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In the end, the “coherent motion” tactic didn’t seem to work. Nor does anything else: When I compared all the NBA players’ aggregate free-throw percentages at home and on the road, they came out the same, down to a fraction of a percentage point. That suggests that no matter how the fans might try to sway opposing teams—with sticks, or horns, or signs, or funny semi-nude dances—nothing makes a difference. Pro athletes are unflappable.

But the fans of Arizona State think they’ve made a breakthrough. Instead of waving sticks, they drape a curtain on a frame of PVC pipes, then whip it open to announce surreal, disturbing skits: A pair of fans start making out while wearing unicorn heads and tutus, or they start twerking in their underwear and animal masks. The scenes are sometimes improvised, and sometimes planned ahead; they’re always strange and shocking. But were they effective?

It seemed unlikely until I saw an article on the front page of the New York Times by economist and sports-statistics wonk Justin Wolfers. The story has a graph showing how the free-throw rate of Arizona State’s opponents dropped once its fans introduced the Curtain of Distraction for the 2013–14 season. During the three years prior, visiting opponents made about 70 percent of their free throws; in the one and half seasons since, they’ve made just 61 percent.

Wolfers also found that Arizona State’s opponents had not gotten any worse against other teams, so this didn’t seem to be a matter of the school’s facing weaker competition. Also, visitors’ stats only seemed to be affected at the free-throw line; their field-goal percentage has not taken a hit since 2013. “Statistics can never fully prove a causal link,” wrote Wolfers, “but this case is pretty strong.”

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Still, the numbers seemed a little odd. As Wolfers points out, opposing players only face the Curtain of Distraction during the second half, when they’re shooting on the basket in front of Arizona State’s rambunctious student fans. Indeed, he notes that opponents’ second-half free-throw rate dropped from 75 percent in the 2012–13 season to 60 percent in the games since then. Austin Tymins of the Harvard Sports Analysis Collective estimated that the visiting teams’ lowered accuracy—60.6 percent in the second half this season, versus 68.6 percent in the first—should result in a 1.41 points per game home advantage for ASU.

But the closer you look at these half-by-half breakdown numbers, the more they seem mysterious. Along with Slate’s Josh Levin, I reviewed the data from last year, the only full season so far during which Sun Devils fans worked the curtain. When we considered just those games, the effect disappeared (or even flipped): Opponents shot 58.9 percent in the first halves of games while visiting Arizona State during the 2013–14 season, and they improved to 60.1 percent in the second halves. When we combined all the games from that season with the current one, the net effect turned out positive but very small: Visiting teams do drop off in free-throw accuracy after halftime, but by only 1.3 percent.

I called Wolfers and asked how this could be. If the curtain of distraction really works, then why would opposing players shoot just as poorly in the first half as in the second? (Were the skits somehow distracting them from behind their backs?) He proposed that I was using the wrong baseline: Instead of comparing free-throw rates in the first and second half, I ought to compare free-throw rates from the second halves of games before and after the curtain of distraction came into effect. Why? According to Wolfers, opposing players tend to have an advantage while shooting free throws in the second half, even as they’re staring down a horde of feisty home-team fans.

To buttress this idea, Wolfers pointed me to a recent study of the Big Ten Conference, which found that, over the 2009–10 and 2010–11 seasons, visiting teams’ free-throw percentages increased by 2.6 percent on average from the first half to the second. If this turned out to be a general feature of college basketball (I could not personally find any NCAA-wide study), then it would be a curious fact. Wolfers hinted at one explanation: Research on the NBA has found that players improve their accuracy with successive free throws in a single trip to the line, by more than 4 percent per shot. It could be that the act of shooting helps to calibrate the shooter’s motion and make it smoother for his next attempt. By the same logic, it’s possible that free throws taken in the second half would benefit from the shooter’s having gone through his motions in the first.

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If free-throw shooting normally improves in the second half, then Wolfers’ data make more sense, intuitively. Before Arizona State’s fans started putting up the curtain of distraction, the team’s opponents shot much better in the second half than the first. Then came the amorous unicorns and the twerking donkeys, which, according to the Wolfers’ theory, rattled opposing players just enough to strip them of their second-half edge.

I’d still like to know why Arizona State’s visitors had such a pronounced second-half edge in the year before the fans put up their curtain, though. Wolfers’ data put it at something like a boost of 8 or 9 percent between halves, much higher than the mean 2.6-percent margin from the Big Ten study. If the Sun Devils’ baseline free-throw defense were distorted for any reason, then the benefits of the curtain would get puffed up. To know if free-throw distraction really works, for ASU or any other team, it would be nice to find all the best “free-throw defense” teams in the country and then to aggregate their first-half/second-half splits.

Numbers aside, I’m also left wondering why the Arizona State curtain should be so much more effective than other forms of fan distraction. At the NBA level, spectator shenanigans don’t work at all. In college, they might be having a small effect. Wolfers put together a dataset of 25,000 games and compared the free-throw rates of Division I teams when they were playing at home, at another team’s home arena, and in a neutral site. As a rule, he found that college teams shoot slightly worse in front of a hostile crowd, by a little more than 1 percent. But there’s no way to know if that difference comes from fan behavior behind the backboard, or from any other aspect of playing on the road.

In any case, lots of teams have tried to make their own distractological innovations:

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Maryland fans hold up Bridget Riley–style patterns to hurt the shooters’ eyes; Arizona uses swirlies; Utah State has a really fat guy; Duke once had someone dancing in a Speedo; and it seems like everyone is using giant heads.* So have the Arizona State fans really hit on something so new and disruptive—a curtain rod—that it beats out all these prior methods of distraction? And if the curtain rod is better than the swirlies and the big-heads, is it really so much better that we’d expect to see a quantum leap in efficacy—from almost nothing to several percentage points per game?

If a distraction works at all, whether it’s the curtain or any other gimmick, it may apply only to the least skilled opponents. I’m guessing that it functions like the full-court press on defense—a strategy that overcomes any team below a minimum threshold of competence. That would explain why home-away splits in free-throw percentage exist in college but not the NBA, and also why Wolfers finds a smaller split for better college teams. It could also explain why a marginal shooter like North Carolina guard Jackie Manuel missed two shots when confronted by Speedo Guy in 2003: “It was kind of hard to focus on my free throws,” he told ESPN.

Then again, Manuel might have missed those free throws even without a bathing suit in the arena. He was a career 58 percent free throw shooter at UNC, so missing two in a row would not have been so unexpected. That’s the irony of free-throw distraction: All those dancing unicorns and teddy bears make it hard to figure out when something works and when it doesn’t.

*Correction, Feb. 18, 2015: This article originally misstated that Utah has a really fat guy. It’s Utah State. (Return.)