Brain Makes Tennis Call Error More Likely
http://www.sciam.com/podcast/episode.cf ... e-08-10-27
The eyes often don’t have it. Tennis referees, for example, sometimes mess up when calling a ball in or out. And a new study finds that refs are much more likely to make a mistake by calling a good ball out than by calling a bad ball in. The research is in the October 28th issue of the journal Current Biology.
It takes at least a tenth of a second for us to become aware of an image striking the retina. So we all have to construct our perception of moving objects. And the way the brain works, we consistently think something has gone slightly further than it really has. It’s not surprising then that we misjudge the position of hundred-mile-an-hour tennis balls.
When researcher David Whitney saw a call overturned during Wimbledon, he decided to check out referee error rates. He reviewed videos of more than 4,000 randomly selected tennis points, and found 83 incorrect calls. Seventy of the 83 were the type predicted. So players contesting calls are better off asking for reviews on their own shots called out than their opponent’s called in.
—Steve Mirsky
On challenging referees in Grand Slams
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Re: On challenging referees in Grand Slams
Tennis refs are people, too: Visual illusion to blame for all those bad calls
Jordan Lite
http://www.sciam.com/blog/60-second-sci ... 2008-10-27
Flummoxed by those wrong "out" calls tennis referees make? Blame it on the brain's sluggish visual-processing system: It makes the ump — and all humans — likely to perceive moving objects as farther along in their trajectory than they actually are, a new study says.
The glitch produces a visual illusion that makes refs' erroneous calls overwhelmingly more likely to be on balls they call "out" than on ones they judge as "in," according to new research in today's Current Biology. Because the brain is constantly playing catch up with visual reality, it can become particularly taxed in situations in which an object is moving extremely quickly or unpredictably; in the case of a bouncing tennis ball, the brain may perceive it as landing beyond where it actually did.
"This is not a problem with referees," says study co-author David Whitney, a vision scientist at the Center for Mind and Brain at the University of California, Davis. "It’s a consequence of human visual processing … a visual illusion caused by a mechanism that allows the system to localize a moving object."
The problem involves a 100 millisecond-lag between the moment an object appears on the retina, the part of the eye that translates light into images, and when our brains make us aware of that object. "To compensate, the visual system takes the image and shifts it forward and allows us to perceive it in a more physically accurate position so we can live in the present," Whitney says. That trick "works great for continuously moving systems, but if something changes abruptly, there can be mistakes; the visual system has a hard time with that abrupt change."
In Whitney's study, three scientists independently reviewed video and instant replay of 4,457 randomly selected points from the 2007 Wimbledon championships. Of the 83 calls that the video and instant replay showed were wrong, 70 were "out" calls. The scientists found the same bias when they reviewed player challenges in this year's Wimbledon: 69 percent of those calls were judged by refs as being out when they were really in.
Players could use the findings to strategize about which calls to challenge (they should object more often to those called "out" than "in," Whitney says). The results are also likely to apply in other sports in which the visual localization process plays a make-or-break role, such as synchronized diving — in which athletes quickly change positions — or baseball, Whitney says. "When a ball is thrown to first base there's a perceptual challenge there: Does the ball hit the glove first or the foot hit the base first?" he says. "The visual system may be taxed to its limit."
Jordan Lite
http://www.sciam.com/blog/60-second-sci ... 2008-10-27
Flummoxed by those wrong "out" calls tennis referees make? Blame it on the brain's sluggish visual-processing system: It makes the ump — and all humans — likely to perceive moving objects as farther along in their trajectory than they actually are, a new study says.
The glitch produces a visual illusion that makes refs' erroneous calls overwhelmingly more likely to be on balls they call "out" than on ones they judge as "in," according to new research in today's Current Biology. Because the brain is constantly playing catch up with visual reality, it can become particularly taxed in situations in which an object is moving extremely quickly or unpredictably; in the case of a bouncing tennis ball, the brain may perceive it as landing beyond where it actually did.
"This is not a problem with referees," says study co-author David Whitney, a vision scientist at the Center for Mind and Brain at the University of California, Davis. "It’s a consequence of human visual processing … a visual illusion caused by a mechanism that allows the system to localize a moving object."
The problem involves a 100 millisecond-lag between the moment an object appears on the retina, the part of the eye that translates light into images, and when our brains make us aware of that object. "To compensate, the visual system takes the image and shifts it forward and allows us to perceive it in a more physically accurate position so we can live in the present," Whitney says. That trick "works great for continuously moving systems, but if something changes abruptly, there can be mistakes; the visual system has a hard time with that abrupt change."
In Whitney's study, three scientists independently reviewed video and instant replay of 4,457 randomly selected points from the 2007 Wimbledon championships. Of the 83 calls that the video and instant replay showed were wrong, 70 were "out" calls. The scientists found the same bias when they reviewed player challenges in this year's Wimbledon: 69 percent of those calls were judged by refs as being out when they were really in.
Players could use the findings to strategize about which calls to challenge (they should object more often to those called "out" than "in," Whitney says). The results are also likely to apply in other sports in which the visual localization process plays a make-or-break role, such as synchronized diving — in which athletes quickly change positions — or baseball, Whitney says. "When a ball is thrown to first base there's a perceptual challenge there: Does the ball hit the glove first or the foot hit the base first?" he says. "The visual system may be taxed to its limit."