Robert Watts and Terry Bahill
W.H. Freeman
Published Date

A Book Review by: Paul Harris, OD  

This book was recommended to me by an attendee of the Sports Vision course and I found it extremely insightful into not just the visual aspects of baseball but anything that involves a ball of any sort.  The book helped to dissolve many of the misconceptions that have existed relative to curve balls or the possibility of a “rising” fastball.  The physics of curve balls and the paths they travel and the science of how a rotating ball, from baseballs to golf balls to soccer balls, was described in easy to understand concepts.  The flow of air around a baseball is much like the flow of air over and under a wing.  The rotation of the stitches creates differential points of where the flow shifts from laminar flow to turbulent flow.  The asymmetry in this creates lateral forces that act to move the ball away from the simple hyperbolic arcs that would exist secondary to gravity only.  It is these asymmetric forces that are the basis for these shifts and Watts and Bahill do a great job explaining them.

Here are some facts about an 80-mile an hour curve ball.  It moves 2.1 feet laterally during its 60 feet 6 inch path.  Only .52 feet of that occurs in the first half of the path to the plate.  •It moves 0.058 feet in the first 10 feet. •It moves 1.45 feet in the last 10 feet!  They also explain a little about knuckle balls.  Knuckle balls with very low spin rates, for example, 3 rpm, has typical lateral displacement of 2 feet. The distance a knuckle ball moves is independent of velocity.  Thus, it is better to throw a knuckle ball fast as it will still have all that lateral movement occurring in a shorter period of time.

•In discussing some of the earlier studies on eye movements to track baseball they cite work that suggested three increasingly more complex strategies for tracking the baseball:

  • Track the ball with only eye movements, and fall behind in the last 10 feet.
  • Track the ball with head movements and smooth pursuit eye movements and fall behind in the last 5 feet.
  • Track the ball over the first part of its trajectory with smooth pursuit eye movement, make a saccadic eye movement to a predicted point ahead of the ball, continue to follow it with peripheral vision, and finally, at the end of the ball’s flight, resume smooth pursuit tracking with the ball’s image on the fovea.

Here are a few interesting quotes from the text.

  • Batters do not use vergence eye movements.
  • Head movement: “The professional made tracking head movements between 10 and 20 degrees, which were probably small enough to go unnoticed by their coach.  What the batter does not want to do is to allow rotations of the body to drag the head along.”
  • Coaches should say, “Don’t let your body move your head, but it’s okay to move your head to track the ball.”

As Pete Rose used to say, “See the ball, hit the ball.”  Well its not quite that easy! “Now, if the batter is to hit the ball, he must predict where it will be when it crosses the plate.  We say that he creates a mental model of the pitch.  The batter uses the mental model to predict the flight of the pitch.”

And what about the rising fastball?  “The illusion of the rising fastball is the result of the batter’s mistake in formulating his mental model.  It is most likely that the batter’s perceived jump is the result of his perspective and his underestimation of the speed of the pitch for his mental model.”

Watts and Bahill conceptualize three different phases involved in hitting a baseball.

  • •In the first third of the ball’s flight the batter forms his mental model of the ball’s trajectory.
  • •In the middle third, he observes differences between the actual trajectory and his mental model, updates his mental model, and finalizes his swing.
  • •In the last third, he observes errors in his mental model so that he can track the next pitch better.

And what are the qualities of a superstar? The success of the good players is due to faster smooth pursuit eye movements, a good ability to suppress the vestibulo-ocular reflex, and the occasional use of an anticipatory saccade.


There is a great deal more in this book that is of value.  I highly recommend it for those of you that are sports enthusiasts or who will work with athletes.

Available from Amazon