Daniel Wolpert On Why You Have A Brain

Daniel Wolpert is absolutely certain about one thing.  “We have a brain for one reason and one reason only, and that’s to produce adaptable and complex movements,” stated Wolpert, Director of the Computational and Biological Learning Lab at the University of Cambridge.  “Movement is the only way you have of affecting the world around you.”  After that assertive opening to his 2011 TED Talk, he reported that, despite this important purpose, we have a long way to go in understanding of how exactly the brain controls our movements.

Daniel Wolpert

The evidence for this is in how well we’ve learned to mimic our movements using computers and robots.  For example, take the game of chess.  Since the late 1990s, computer software has been playing competitive matches and beating human master players by using programmed tactics and sheer computing power to analyze possible moves.  However, Wolpert points out that a five-year-old child can outperform the best robot in actually moving chess pieces around the board.

From a sports context, think of a baseball batter at the plate trying to hit a fastball.  It seems intuitive to watch the ball, time the start of the swing, position the bat at the right height to intercept the ball and send it deep.  So, why is hitting a baseball one of the most difficult tasks in sports?  Why can’t we perform more consistently?

The problem is noise.  Not noise as in the sense of sound but rather the variability of incoming sensory feedback, in other words, what your eyes and ears are telling you.  In baseball, the location and speed of the pitch are never exactly the same, so the brain needs a method to adapt to this uncertainty.  To do this, we need to make inferences or beliefs about the world.


The secret to this calculation, says Wolpert, is Bayesian decision theory, a gift of 18th century English mathematician and minister, Thomas Bayes.  In this framework, a belief is measured between 0, no confidence in the belief at all, and 1, complete trust in the belief.  Two sources of information are compared to find the probability of one result given another.  In the science of movement, these two sources are data, in the form of sensory input, and knowledge, in the form of prior memories learned from your experiences.

Thomas Bayes

So, our brain is constantly doing Bayesian calculations to compute the probability that the pitch that our eyes tell us is a fastball is actually a fastball based on our prior knowledge.  Every hitter knows when this calculation goes wrong when our prior knowledge tells our brain so convincingly that the next pitch will be a fastball, it overrules the real-time sensory input that this is actually a nasty curve ball.  The result is either a frozen set of muscles that get no instructions from a confused brain or a swing that is way too early.

Our actions and movements become a never-ending cycle of predictions.  Based on the visual stimuli of the approaching baseball, we send a command to our muscles to swing at the pitch at a certain time.  We receive instant feedback from our eyes, ears and hands about our success or failure in hitting the ball, then log that experience in our memory.

Wolpert calls this process our “neural simulator” which constantly and subconsciously makes predictions of how our movements will influence our surroundings. “The fundamental idea is you want to plan your movements so as to minimize the negative consequence of the noise,” he explained.

We can get a sense of what its like to break this action-feedback loop.  Imagine a pitcher aiming at the catcher’s mitt, releasing the ball but then never being able to see where the pitch ended up.  The brain would not be able to store that action as a success or failure and the Bayesian algorithm for future predictions would be incomplete.

Try this experiment with a friend.  Pick up a heavy object, like a large book, and hold it underneath with your left hand.  If you now use your right hand to lift the book off of your left hand, you’ll notice that your left hand stays steady.  However, if your friend lifts the book off of your hand, your brain will not be able to predict exactly when that will happen.  Your left hand will rise up just a little after the book is gone, until your brain realizes it no longer needs to compensate for the book’s weight.  When your own movement removed the book, your brain was able to cancel out that action and predict with certainty when to adjust your left hand’s support.

“As we go around, we learn about statistics of the world and lay that down,” said Wolpert.  “But we also learn about how noisy our own sensory apparatus is and then combine those in a real Bayesian way.”

Our movements, especially in sports, are very complex and the brain to body communication pathways are still being discovered.  We’ll rely on self-proclaimed “movement chauvinists” like Daniel Wolpert to continue to map those routes.  In the meantime, you can still brag about the pure genius of your five-year-old hitting a baseball.

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Sports Science Gym Bag - 12-8-09

Wow, what are the odds that I lead off this week's Gym Bag with a Tiger Woods story?  Don't worry, this article has no mention of Escalades, golddiggers or mothers-in-law.  Plus, plenty of other great stuff from the sports science world.


The Tiger Woods Effect

 Success is intimidating. When we compete against someone who's supposed to be better than us, we start to get nervous, and then we start to worry, and then we start to make stupid mistakes. That, at least, is the lesson of a new working paper by Jennifer Brown, a professor at the Kellogg school.
Brown demonstrated this psychological flaw by analyzing data from every player in every PGA tournament from 1999 to 2006. The reason she chose golf is that Tiger Woods is an undisputed superstar, the most intimidating competitor in modern sports. (In 2007, Golf Digest noted that Woods finished with 19.62 points in the World Golf Ranking, more than twice as many as his closest rival. This meant that "he had enough points to be both No. 1 and No. 2.") Brown also notes that "golf is an excellent setting in which to examine tournament theory and superstars in rank-order events, since effort relates relatively directly to scores and performance measures are not confounded by team dynamics." In other words, every golfer golfs alone...

Vince Young
The underlying assumption of the Wonderlic test is that players who are better at math and logic problems will make better decisions in the pocket. At first glance, this seems like a reasonable conjecture. No other position in sports requires such extreme cognitive talents. A successful quarterback will need to memorize hundreds of offensive plays and dozens of different defensive formations. They'll need to spend hours studying game tape of their opponents so that, when they're on the field, they can put that knowledge to use. In many instances, quarterbacks are even responsible for changing the play at the line of scrimmage. They are like a coach with shoulder pads...

UN calls for football tax to fund education for poor children 
The United Nations today launches an appeal to FIFA football leagues, including the Premier League, to place a small levy on sponsorship revenues that would help get 2 million children in poor countries into school over the next five years...

Pushing Past the Pain of Exertion
LAST November, Kara Goucher ran the ING New York City Marathon, her first 26.2-mile race. Even though she was an Olympian who had placed 10th in the 10,000 meter race in 2008 in Beijing — running the equivalent of 6.2 miles — she felt fear.  “I was really scared I wouldn’t be able to handle the pain for that long,” said Ms. Goucher, 31, who had never run more than 18 miles at a time before training for the marathon. “Now I was asking myself to run eight miles farther, a lot faster. It was daunting.”

Coaching and science: What's the big deal and who cares for the science?
"As promised, today begins a series of posts on coaching and science, and how the science can be, should be, and sometimes is, and often is not, applied to athlete preparation. Obviously, it comes with an endurance focus, but there's no reason why sprint coaches and team sport coaches can also not glean some information from this.
This is a series that was inspired by my visit to the US Olympic Center in Colorado Springs. I was lucky enough to be invited there by Prof Randy Wilber of the USOC, who had organized a symposium on altitude training. The symposium brought together scientists, coaches, athletes and mangers from 22 different countries, and included 32 Olympic athletes, and numerous sporting codes, Summer and Winter Olympics among them..."

Belichick had the numbers on his side
Among the countless criticisms hurled at Patriots coach Bill Belichick for his decision to go for it on fourth down Sunday night, former Colts coach Tony Dungy summed up the most popular when, speaking on NBC, he said, “You have got to play the percentages and punt the ball.’’ What Dungy did not realize, though, is that “the percentages’’ dictated that Belichick do exactly what he did...

Short Heels and Long Toes: A Surprising Recipe for Speed
Track coaches have long claimed that the best sprinters are born, not made. Now, new research on the biomechanics of sprinting suggests that at least part of elite athletes’ impressive speed comes from the natural shape of their foot and ankle bones.
Using ultrasound imaging, researchers compared the feet of 12 top college sprinters with those of 12 mere mortals. Surprisingly, the athletes had particularly short heels and longer-than-average toes — features that actually put them at a mechanical disadvantage when running.
“What we found is that sprinters actually had less mechanical advantage than the non-sprinter subjects that we tested,” said biomechanics researcher Stephen Piazza of Penn State University, co-author of the study published Friday in the Journal of Experimental Biology. “This was surprising to us because we expected that sprinters needed all the help they could get.”

The Fastest Man On No Legs

In an ironic twist, Oscar Pistorius' disability has now been shown to be an unfair advantage. The South African sprinter, who races with two prosthetic lower legs, has been the subject of a see-saw legal battle trying to determine if his carbon fiber, crescent-shaped manufactured legs give him an unfair advantage.

Now, two sports scientists have published new research showing that the legs, known as "Cheetahs," make him 15-20 percent faster, equal to 10 seconds over a 400 meter race, then he otherwise would be with natural legs.

In 2008, the Court of Arbitration for Sport (CAS) overturned a competition ban placed on Pistorius from the International Association of Athletics Federations (IAAF), track and field's governing body. Seven scientists produced research that refuted the IAAF's contentions and Pistorius was cleared in time to try for a spot on the Beijing Olympic squad. He just missed making that team by .7 seconds, but is now training for the 2012 London games. He did go on the win three gold medals in the 2008 Paralympics.

Pistorius, known as the Blade Runner, was born without fibula bones in his lower legs, resulting in a double amputation at the age of 11 months. At age 18, he won the 200m race at the 2004 Summer Paralympics, followed by a gold medal in the 2005 South African championships against able-bodied competitors.

Of course, when the discussion is about steroids, blood doping or even corked bats, the athlete becomes the villian. For the "fastest man on no legs," as Pistorius is often called, there are mixed opinions, ranging from those that champion the rights and progress of disabled athletes to those that want to preserve the perceived "level playing field" and integrity of the sport.

Supporting the CAS appeal, seven scientists showed that the IAAF's research (which held that Pistorius should not compete) was not valid. However, according to two of the scientists, Peter Weyand of Southern Methodist University in Dallas and Matthew Bundle of the University of Wyoming, they were careful not to imply that there was no advantage. "We are pleased to finally be able to go public with conclusions that the publishing process has required us to keep confidential until now. We recognized that the blades provide a major advantage as soon as we analyzed the critical data more than a year and a half ago," said Weyand and Bundle in a statement.

They explain that all of the group's research did not become public at the CAS hearing because, first, the CAS only asked them to refute the earlier research based on different logic and, second, the long timeline of the peer-review process of academic research just now made it possible to publish.

Specifically, what Weyand and Bundle found was that the lightweight blades weigh less than half of what a comparable human lower leg would, allowing Pistorius to swing his leg 15.7 percent faster than the average of five former 100m world record holders. They used high-speed motion cameras to compare leg speed and gait. "Even in comparison to those male sprinters with the most extreme adaptations for speed in recorded human history, Oscar Pistorius has limb repositioning times that are literally off the charts," Bundle said. "Usain Bolt is considered somewhat freakish because he outruns his opponents by 2-4 percent. At top speed, Oscar Pistorius repositions his limbs 15 percent more rapidly than six of the most recent world record holders in the 100 meter dash, including Usain Bolt."

In addition, because of how the Cheetahs, from Icelandic manufacturer Ossur, position his upper body, he can leave each "foot" on the ground longer, generating more force with each stride. "He repositions his limbs so fast that he doesn't need to get his body back up into the air so high like other sprinters, and that lowers the force he needs to generate," Weyand told Sports Illustrated. "The muscular forces he has to generate are less than half of what an intact sprinter has to generate to go the same speed."

Their research was part of a Point-Counterpoint feature in the current online edition of the Journal of Applied Physiology. In the Counterpoint reply, led by Hugh Herr of MIT, the remaining five scientists contend that studying just one double amputee does not provide enough evidence that the Cheetah legs will consistently provide an advantage. "The notion that lightweight prostheses are the only reason for Pistorius' rapid swing times ignores that he has had many years to train and adapt his neuromuscular system to using prostheses," the authors write.

The published research should not cause the CAS to reconsider and, as of now, Pistorius is still eligible to compete for a spot in London. He seems to be keeping all of this debate in perspective, "When people ask me what it's like having artificial legs, I reply, 'I don't know. What's it like having real legs?'" He adds, "Some people view themselves as disabled because they have one or two disabilities. But what about the millions and millions of abilities they have?"

Sports Science Weekly Gym Bag - 10-28-09

Welcome to a World Series edition of the Weekly Sports Science Gym Bag, a collection of some of the best stuff I've found in the last week.  A few more baseball stories are included, while you watch the Yankees lose in 6 games!

The Overmanager: Why the New York Yankees' Joe Girardi is too smart for his own good
To play in the NFL, you have to make a show of going to college. To play in the NBA, you have to get through high school. To sign a contract with a major league baseball team, all you have to do is convince someone you're 16, provided you weren't born in a country with inconvenient labor laws. Perhaps this goes some way toward explaining both the high reverence in which the intellectual is held in baseball and the low standards necessary to qualify as one...

Running To The Right Beat
With the Fall marathon season in full swing, thousands of runners are gearing up for the big day.  Just as important as their broken-in shoes and heart rate monitor is their source of motivation, inspiration and distraction: their tunes.  Several recent studies try to chase down the connection between our ears and our feet...

Phys Ed: Do More Bicyclists Lead to More Injuries?
Recently, surgeons and emergency room physicians at the Rocky Mountain Regional Trauma Center in Denver noticed a troubling trend. They seemed to be seeing cyclists with more serious injuries than in years past. Since many of the physicians at the hospital, a Level I trauma center serving the Denver metropolitan area, were themselves cyclists, they wondered if their sense of things was accurate.  So the doctors began gathering data on all cycling-related trauma admittances at the hospital and dividing them into two blocks, one covering 1995-2000 and the other 2001-6...

Football
In light of a recent post on the difficulty of changing our decision-making habits - even when we're aware that our habits are biased and flawed - I thought it might be interesting to look at two examples from professional football. Why sports? Given the intense competitive pressure in the NFL - there's a thin line between victory and ignominy - you'd expect head coaches to have corrected many of their decision-making mistakes, especially once those mistakes have been empirically demonstrated. But you'd be wrong. 
Consider some research done by David Romer, an economist at UC Berkeley, who published a 2001 paper entitled "Do Firms Maximize? Evidence From Professional Football". The question Romer was trying to answer is familiar to every NFL fan: what to do on 4th down? Is it better to bring on the kicking team for a punt or field-goal attempt? Under what conditions should coaches risk going for it?

Missed Kicks Make Brain See Smaller Goal Post
Flubbing a field goal kick doesn’t just bruise your ego — new research shows it may actually change how your brain sees the goal posts.  In a study of 23 non-football athletes who each kicked 10 field goals, researchers found that players’ performance directly affected their perception of the size of the goal: After a series of missed kicks, athletes perceived the post to be taller and more narrow than before, while successful kicks made the post appear larger-than-life.  Professional athletes have long claimed that their perception changes when they’re playing well — they start hitting baseballs as large as grapefruits, or aiming at golf holes the size of a bucket — but many scientists have been slow to accept that performance can alter visual perception...  

Baseball: Head-first Slide Is Quicker
Base running and base stealing would appear to be arts driven solely by a runner's speed, but there's more than mere gristle, bone and lung power to this facet of baseball -- lots of mathematics and physics are at play. Who gets there faster, the head-first slider or the feet-first?

Pump your arms to speed up your legs, thanks to “neural coupling”
“Keep pumping your arms!” That’s one of those canonical pieces of advice that it seems every coach gives to his or her runners. The idea is that, late in a run or race when your legs are burning and you’re starting to slow down, if you keep moving arms briskly, your legs will follow. It’s a nice idea — it’s always good to have some concrete piece of advice that you can hang onto when it seems like the world is about to explode. But does it work?
Unfortunately, I don’t know. But in the course of researching a completely different topic today, I stumbled on an interesting piece of research by Daniel Ferris, a University of Michigan researcher who’s best known for his research into assisted movement using robotic exoskeletons. The paper, which appeared in the journal Exercise and Sport Science Reviews back in 2006, is called “Moving the arms to activate the legs.” The full text is available here...

The Human Body Is Built for Distance
Does running a marathon push the body further than it is meant to go?  The conventional wisdom is that distance running leads to debilitating wear and tear, especially on the joints. But that hasn’t stopped runners from flocking to starting lines in record numbers.  Last year in the United States, 425,000 marathoners crossed the finish line, an increase of 20 percent from the beginning of the decade, Running USA says. Next week about 40,000 people will take part in the New York City Marathon. Injury rates have also climbed, with some studies reporting that 90 percent of those who train for the 26.2-mile race sustain injuries in the process...