THE BOOK--Playing The Percentages In Baseball

I don’t understand the idea from the summary ... I’ll have to read the paper. 

Specifically, what angle is it that we measure the acceleration of?  The angle from eye to ball? 

Is the idea that if you’re positioned exactly right, the angle from eye to ball will change only with constant velocity?  That doesn’t seem to make sense ... obviously, it’s going to start by increasing off the bat, then decreasing to the glove.  If it changes direction, it must be accelerating.

Guess I’ll check out the paper later.

What’s not clear to me from reading the summary is whether this also explains how some outfielders get good jumps on the ball. I remember watching Andruw Jones back when he was good and he seemed to get an incredible jump on the ball. This is a purely subjective impression but he seemed to start moving at the instant the ball was hit. Was he just so good that he got a general idea where the ball was going to go by the angle it came off of the bat? It might be interesting if they could test some good fielding major league outfielders. Their skills might be different, i.e., better, than amateurs.

Any acceptible theory on how an outfielder catches fly balls would have answer two questions for me.  First, why is it possible to judge the distance a fly ball will travel almost instantaneously on balls hit not right at you. And second why is it extremely difficult to judge the distance of balls that are hit right at you.  I can’t tell whether the theory that this paper concludes is correct can answer those questions or not.  I also can’t tell whether their virtual model of fly ball flight contains accelerations due to spin induced magnus forces which also complicate fly ball landing location predictions for outfielders.

Anyone who gets a good jump off the ball is going off the pitch location, swing timing and swing speed, not the initial trajectory, which comes too late to explain a good jump.  An experienced fielder with good vision can see the pitch and the bat converging, and make a very good estimate of the initial direction and the quality of contact. 

For more support to this, watch a good fielder move even when a pitch is missed, or fouled off:  obviously if a good jump came off a read of the initial trajectory, the fielder would not move on “swing-and-misses”, but in fact they do…

Peter, for your first question, I say experience along with some visual processing, as well as aural processing/experience.  Pro outfielders have fielded thousands upon thousands of fly balls, and know what a solidly struck ball looks like and sounds like, and know where they are on the field, so they can make an initial move that is correct almost all the time. 

The exception seems to be for balls hit straight at them, particularly in center field (in the corners, even balls hit right at you usually have some side spin / hook or slice that “breaks the spell” that a liner straight at you induces. 

My idea on the liners straight at you is that the magnitude of the visual and aural clues are reduced, in relation to what a fielder needs to make the “in or out” decision, such that they sometimes make the wrong decision - although as anyone who watches baseball could tell you, when they do err, pro outielders always realize their mistake a fraction of a second later, but that fraction is often enough to doom the fielder to missing the catch.

Greg - My wording in Post #3 was poor.  I played the outfield for over 30 years in amateur baseball and softball, and even I began moving before the ball was hit.  That’s why I am skeptical of this study.  I wasn’t asking the questions in Post #3 because I felt I needed answers, I was just saying that any study on how outfielders accomplish getting to the right landing spot has to provide answers to those questions and as far as I can tell the conclusions of this study do not.

Peter,

Sure, I figured you had your own ideas, too, and were wondering if the study was going to address those points. 

I think they could perhaps state a bit more clearly that they are talking about tracking/adjustments made while the ball is in the air, and setting aside any pre-contact motion or visual/aural/other processing by the fielder…

My understanding of the paper is that they did not come up with a new theory of how outfielders track fly balls.  They provided experimental evidence that confirms the theory of outfielder fly ball tracking that Chapman introduced in 1968.

I’d be curious to hear Alan Nathan’s take on this paper.  I know that his 2008 paper on pop-up tracking assumed Chapman’s 1968 OAC theory as the baseline for typical fly ball tracking and showed how that tracking method becomes problematic for high pop-ups.
http://webusers.npl.illinois.edu/~a-nathan/pob/AJP-Aug2008.pdf

Getting a good jump on the ball apparently depends on accoustics—the “crack of the bat.” Here’s an article by Adair about this.

http://www.acoustics.org/press/141st/adair.html

In agreement with Peter Jensen, more from observation than playing:  an outfielder uses all his senses, including hearing (cf. Adair’s article), and getting a jump means paying attention to the pitcher’s and hitter’s tendencies, the base-out situation, the count, the elements (wind, sun location, the cut and dryness of the grass), the catcher’s setup, etc. Further an outfielder chooses an initial location before the pitch is thrown and may also “shade” his stance or lean in a particular way.

He can’t just be reactive to the flight of the ball.

Re Mike (#8):  In our paper, we simply assumed that the OAC tracking method was valid and examined the consequences of using that method for our “paradoxical popups.” Mike McBeath, one of the co-authors, is the real expert on how people (and dog!) track projectiles.  I will have to read the new paper carefully (I have not done that yet) and go back and read McBeath’s critique of it that he sent me a couple of weeks ago.

There’s a good, readable summary of this sort of work in the Psychology of Baseball by Stadler.  Less current (though only a few years old), but talks about the competing models.  Link to the book in my name.
-j