Lower free throws through science

Foul Play
How a Slate scientist changed the NBA forever-or at least a week.
By Daniel Engber
Posted Thursday, Jan. 6, 2005, at 4:01 PM PT



If you're a scientist, you don't get many opportunities to work in
professional basketball. I don't have any illusions about my chances of
becoming a player, a head coach, or the Phoenix gorilla. But I have held out
a tiny bit of hope that some day I'd be able to use my grad-school education
to help some woebegone franchise shut down opposing free-throw shooters.
Last week, my dream came true.

In today's NBA, there's no subtlety to free-throw defense. Hometown crowds
try to unnerve enemy shooters with rally towels, pompoms, clackers, rhythmic
chants, balloons, and signs that say "BRICK." It doesn't take a scientist to
see how poorly this stuff works. In the 2003-2004 NBA season, free-throw
percentages at home and on the road were identical to within one-twentieth
of 1 percent. One hundred ninety-four players shot free throws better at
home; 192 did better on the road.

Undeterred by the facts, NBA teams hand out special distracting equipment to
fans behind the backboards. Some get foam "wiggle sticks," or "thunder
sticks"-those long, skinny white balloons you wave in the air and smack
together. Others get signs with particularly distracting words printed on
them. These tools might be effective, but they don't come with instructions.
That's where the staff neuroscientist comes in.

Last week, I wrote to the NBA owner I deemed most likely to consider
applying the scientific method to free-throw shooting, Mark Cuban of the
Dallas Mavericks. I told Cuban that the assumption that waving balloons
wildly will produce the biggest distraction is just plain wrong. Given how
the brain perceives motion, randomly moving balloons aren't very
off-putting. When you see a lot of little objects moving crazily back and
forth, all the different motion signals that get sent to the brain cancel
each other out. In the mind of a free-throw shooter, a crowd of people
waving wiggle sticks looks like a snowy TV screen. This sort of white noise
might make it harder to see the rim, but the stats show that isn't a big
deal for the pros.

But what if the waving balloons didn't cancel each other out? If fans behind
the backboard waved their balloons from side to side in unison, opposing
players would perceive a field of background motion. When we see a moving
background, we tend to assume that we're the ones moving and that the
background is staying put. If everything on my desk suddenly drifted to the
right, I would probably assume that my chair had rolled to the left. And if
I were at the free-throw line as the world drifted to the right, my shooting
motion would automatically compensate for what I perceived to be my own
motion to the left. David Whitney, a visual psychophysicist at the
University of California-Davis,* recently described this phenomenon in the
lab. The results, published in Nature ("The influence of visual motion on
fast reaching movements to a stationary object"), showed that a field of
background motion can bias hand movements in the direction of that motion.

A few hours after I wrote Cuban that first e-mail, I got an answer. "I love
using science to gain an advantage," he wrote. He said he'd give the plan a
try.

But how do you go about getting a bunch of unruly, brawl-inciting NBA fans
to flap their sticks in unison? I had suggested that a human conductor might
do the trick. At schools like Duke University and the University of Texas,
student cheerleaders lead similar organized distractions, where everyone
waves their arms together in one direction. If Cuban could get someone in
the stands to conduct the thunder sticks, the plan might work.


The Mavericks sprang into action at their next opportunity. During last
week's game against the Celtics, three members of the Mavs' "Hoop Troop"
worked the crowd behind the backboard. Boston shot 18 for 30 from the line,
or 60 percent, about 20 percent below their season average. The Mavericks
kept up their suddenly stout free-throw defense in the next game, holding
the Bucks to 17 for 27 from the charity stripe-63 percent. But in the game
after, on Wednesday night, the Lakers were seemingly undeterred by Hoop
Troop staffers waving big red arrows to direct the crowd's stick movements:
They shot 21 for 27, or 78 percent, pretty much the league average. In
total, though, the project has been a success. Mavericks opponents have shot
8 percent below the league average since adopting my strategy. More
important, Dallas has yet to lose a game.

An 8 percent effect may not seem like a big deal, but even a tiny decrease
in shooting percentages can change the course of a season. Last year, the
Cleveland Cavaliers missed out on a playoff berth by just one game. I went
through their home box scores and figured out that even a 3 percent decrease
in their opponents' free-throw shooting would have gotten the Cavs a chance
at the playoffs.

The league rules on the legality of the kind of coordinated behavior that I
suggested are a bit ambiguous. While almost anything goes in college, from
the tie-dyed T-shirts and giant swirlies displayed by Wake Forest students
to the posters of near-naked women used elsewhere, all pro teams must follow
a set of guidelines on "End Zone Distractions." According to the NBA
Operations Manual, fans may not wield anything designed to create optical
illusions or that might affect a player's ability to perceive depth-specific
(and somewhat arbitrary) examples include pinwheels, umbrellas, and laser
pointers. Balloons and wiggle sticks are explicitly permitted, so long as
they're deployed by fans and not team employees. There's a special exception
to this last rule for team mascots. If Cuban had the Mavs Man and his
horse-friend Champ steer the crowd rather than three Mavericks employees,
he'd almost certainly be in the clear.

An idea that would surely test the rules comes from David Whitney, the
scientist who published the visual-motion study in Nature. Whitney suggests
that it would be easy to create an improved version of the thunder stick
that becomes more noticeable when waved in one direction. One such device
might work by hanging LEDs inside a hollow tube with holes in it. When swung
to the right, the LEDs would be visible through the holes, creating spots of
light that would vanish when the stick went back to the left. As hundreds of
fans shook the sticks wildly, the shooter would see something that looked
like a flurry of snow drifting in one direction.

I'm sad to say that my success as a basketball scientist was short-lived. A
mere three games into this bold new era, I got fired. "It failed miserably
last night," Cuban e-mailed me the day after the Lakers game. "I think our
early success was random." I can't help but wonder if the Mavericks are
giving up too soon. Slate's photographer told me that the Hoop Troop's
movements weren't even timed to the shooting of the basketball. If I'd been
the guy leading the crowd, we would have done things right.

Daniel Engber is a writer in Washington, D.C.

Article URL: http://slate.msn.com/id/2111939/


--
-Fred

np: http://www.audioscrobbler.com/user/freeloosedirt/