Nav: Home

In game of tennis, seeing isn't always believing

October 27, 2008

A universal bias in the way people perceive moving objects means that tennis referees are more likely to make mistakes when they call balls "out" than when they call them "in," according to a new report in the October 28th issue of Current Biology, a Cell Press publication. Because recent rule changes allow professional tennis players to challenge the refs' calls, athletes could exploit the new findings to their advantage, according to researchers at the University of California, Davis.

Like all visual illusions, the new discovery provides visual neuroscientists with a window on how the brain processes information, explained David Whitney.

"The visual system faces a big challenge when trying to code the locations of objects so that we can perceive them," Whitney said. "Consider one of the difficulties: every time we move our eyes, the image on our retina moves. Even if our coffee cup is actually stationary on our desk, we move our eyes and head while reaching to pick it up so the image of the cup will move on our retina. This is a problem because the visual system is sluggish--it takes a hundred or more milliseconds for us to become aware of an image that strikes our retina. So, by the time we perceive an object like the coffee cup in one location, it will have already changed location as we move toward it. Our perception lags behind reality. The visual system has mechanisms that help alleviate this problem of living in the past, but these mechanisms are not perfect and occasionally result in visual illusions--like the misperception of tennis ball location we discovered."

Similar kinds of perceptual biases in the visual system had been documented before, but rarely in real-world situations. People consistently misperceive moving objects as shifted in the direction of their motion, so that at any moment they appear to be farther along their path than they are. Whitney said he realized it might be possible to study this in the context of tennis when he saw a referee call overturned by a player's challenge during a Wimbledon match.

On a tennis court, a ball could physically bounce in the court but be called out, or a ball could physically bounce out of the court but be called in. If tennis referees were bias-free, they would be equally likely to make each of these two kinds of errors. But because objects generally appear to be shifted in the direction of their motion, referees should incorrectly judge balls as being out more often.

Whitney's team confirmed that prediction. In a review of more than 4,000 randomly selected Wimbledon tennis points, the researchers uncovered 83 incorrect calls. Of those, 70 of the errors were of the type predicted.

Further study of the phenomenon in the laboratory confirmed that the refs' mistakes are not the result of poor refereeing. Rather, the errors are a general artifact of the way the human brain processes visual information about motion.

Indeed, the researchers said, tennis players and audience members surely make the same mistakes that refs do. The new findings suggest, however, that players could maximize their opportunity to challenge calls by focusing on balls that are called "out," since they are more likely to be incorrect.

The report also suggests that every shot in professional tennis should perhaps be reviewed by instant replay. "If that proves prohibitively time-consuming, the rules allowing players to challenge referee judgments should be scrutinized at least, in light of the current findings," they wrote. "If all else fails," they added, "perhaps professional tennis venues should follow the French, and universalize the clay court," where skid marks on the clay reduce reliance on the referees' motion perception.
-end-
The researchers include David Whitney, Nicole Wurnitsch, Byron Hontiveros, and Elizabeth Louie of The Center for Mind and Brain, University of California in Davis, California.

Cell Press

Related Visual System Articles:

Why visual perception is a decision process
A popular theory in neuroscience called predictive coding proposes that the brain produces all the time expectations that are compared with incoming information.
Visual impairment among women and dementia risk
Whether visual impairment is a risk factor for dementia was the focus of this observational study that included 1,000 older women who are participants in the Women's Health Initiative studies.
VR is not suited to visual memory?!
Toyohashi university of technology researcher and a research team at Tokyo Denki University have found that virtual reality (VR) may interfere with visual memory.
Dartmouth study finds conscious visual perception occurs outside the visual system
A Dartmouth study finds that the conscious perception of visual location occurs in the frontal lobes of the brain, rather than in the visual system in the back of the brain.
Learning to read boosts the visual brain
How does learning to read change our brain? Does reading take up brain space dedicated to seeing objects such as faces, tools or houses?
How brain rhythms organize our visual perception
Imagine that you are watching a crowded hang-gliding competition, keeping track of a red and orange glider's skillful movements.
Seeing it both ways: Visual perspective in memory
Think of a memory from your childhood. Are you seeing the memory through your own eyes, or can you see yourself, while viewing that child as if you were an observer?
Using visual imagery to find your true passions
You may think you know what you like -- how to spend your time or what profession to pursue.
VisiBlends, a new approach to disrupt visual messaging
To help non-professionals create visual blends for their news and PSAs, Columbia Engineering researchers have developed VisiBlends, a flexible, user-friendly platform that transforms the creative brainstorming activity into a search function, and enables a statistically higher output of visually blended images.
Why visual stimulation may work against Alzheimer's
MIT neuroscientists have found that using flickering light to stimulate gamma oscillations in the brain has widespread effects on neurons and immune cells called microglia.
More Visual System News and Visual System Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

TED Radio Wow-er
School's out, but many kids–and their parents–are still stuck at home. Let's keep learning together. Special guest Guy Raz joins Manoush for an hour packed with TED science lessons for everyone.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.