Ever wonder how a batter knows when to swing at a pitch coming toward him, sometimes at more than 90 miles per hour?  Former Yankees catcher Yogi Berra pondered that question, once asking "How can you think and hit at the same time?" 

Yogi Berra might be interested to know that a team of researchers at UC-Berkeley has come up with the answer to his question, which is that you can't, because there isn't time for both. But you don't have to think about it, because the brain does it automatically.  

Here's how:  Start with the premise that the brain is a lot slower than a speeding baseball. What to do if you are up to bat?  Turns out, our wondrous brains actually perceive speeding objects further along in their trajectories than seen by the eye, giving the batter time to swing at the pitch. 

So far so good, but a baseball traveling at 90 mph is slow compared to an ace tennis serve that might reach 160 mph. What then? The brain comes to the rescue here, too.  In the split second that it takes a tennis ball to travel from the racket of the server to the other side of the net, there is a lot of work to be done. The eye must find the ball, the sensory cells in the eye must determine its speed and rush the information to the brain. The brain, in turn, will send messages to the muscles of the arms and legs to respond.  Problem is, by this time the information is already out of date.  In other words, by the time the brain "catches up" with all that data, a lightening fast tennis serve would already put the ball 10 to 15 feet closer than the image in the eye. 

But we know that tennis players manage to hit the ball in spite of all that, so how do they do it?  The experiments conducted by the research team show that as soon as the brain knows that something is in motion, it pushes the moving object forward along its trajectory, creating an accurate measure of where the object really is. 

How did they arrive at their conclusions? It's complicated, but this is what I got out of the explanation:  a region in the back of the brain, called area V5, computes information about movement and projects where it thinks the moving object (such as a baseball or tennis ball) should  be, rather than where the eye sees it. To demonstrate this, experiments were conducted with volunteers viewing flashing lights against a moving background while their brains were being scanned with a functional MRI. It is called the "flash-drag effect" -- a two part visual illusion. 

If all this is over your head, you are not alone!  (But I'm willing to take their word for it.) And here's something else:  Not only do such tests help explain how altered trajectories -- like back-spins in tennis and late-breaking baseball pitches -- can fool us, they have implications for other, far more important situations than sports, such as when we are trying to cross a street in front of a speeding car. 

It isn't hard to see that a better understanding of the way the brain processes information about moving objects would be useful in diagnosing and treating some disorders that involve impaired motion perception.  When that perception is impaired in people it means they have trouble accurately predicting the location of objects, and find it difficult to perform even simple tasks like pouring a cup of coffee without spilling it or crossing a road safely.  

As one member of the research team put it, "The brain does not work in real time." 

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