Testing Your Visual Acuity

Note: it may help to view this video full screen on a larger monitor, or to view the screen from closer than normal to get the full effect of the illusions.

Researchers at the University of Rochester's Center for Visual Science used some well-known illusions to test a hypothesis. What they found was that when objects in motion are seen in the peripheral vision, where the information is less clear, the human brain works a lot like a global positioning that is struggling with a weak signal.

When your phone's GPS has a strong signal, it's very good at locating where you are and where you're going, but when the signal is weak, it needs to use an algorithm, known as the Kalman Filter, to estimate your direction and position. With the weaker visual signal in the peripheral vision, the brain also uses the same algorithm to estimate where moving objects are, and in both cases, the results aren't always perfect.

These animations illustrate the concepts that the researchers were looking at, such as the "curveball illusion". This deals with the sudden, sharp break that batters perceive when a curveball is quickly approaching the plate and enters their peripheral vision. The actual motion of that pitch is a much more steady, gradual curve, but it's this imperfect processing of the information that happens in the brain that causes the illusion.

This research was conducted by Duje Tadin, associate professor of brain and cognitive sciences at the University of Rochester, as well as Oh-Sang Kwon, assistant professor at the Ulsan National Institute of Science and Technology, South Korea. The senior researcher was David C. Knill, professor of brain and cognitive sciences and associate director of the Center for Visual Science at the University of Rochester.

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[tomfieselmann]

I've played baseball, and currently softball, but while I'm an above average hitter (probably because of having played golf and tennis over the years, too), I have to admit that it is extremely rare when I actually SEE the contact between bat and ball, racquet and ball, and club and ball...  The activity is simply happens too fast, or the ball is travelling too fast for my eye and most everybody elses', too.  There are those who CAN see the spinning threads; John McEnroe and Rafa Nadal have said that they can see the spin via the seams - but not me, and, hey, my game's not too ba-a-ad.  I compensate by hitting "on top of the ball" to get UNDER the softball, and that usually lifts it well into deep outfield, but again it's compensation for lack of visual acuity.  This is a great video, thanks Rochester folks, and will help me prepare my hitters, and develop a strategy for my pitchers, as well.  Thanks again.

[SteadyRolling]

This argument reminds me of the folks who used to insist that a curve ball doesn't actually bend.  Finally, one of them had the courage to stand behind a tree to test his convictions.  Cutting to the chase:  He left the experiment with a few bruises.

Here are the two flaws with this study:

1.  Good batters don't watch a pitch with peripheral vision.  They turn their heads (and both eyes) towards the pitcher.

2.  Batters don't have any trouble hitting a curve ball which does not curve.  You'll see this a few times in every game and lot in games in Denver.  The ball is delivered with plenty of spin, but for whatever reason, it doesn't break.  This is called a "hanging curve".

No.  It's not the spin of the ball which fools the batter.  It is the fact that the ball breaks at the last moment.

[williamforrest]

I agree that the curveball isn't solved.  I agree that a hitter should look directly at the ball being hit.  Why look away?  This can be tested by using a uniformly white ball, so the spin can't be easily seen.  If the batting average goes up, then there's something to this theory..