Horizontal and Vertical Eye and Head Movements during a Baseball Swing THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Tyler William Persson Graduate Program in Vision Science The Ohio State University 2013 Master's Examination Committee: Nicklaus Fogt, O.D., Ph.D., Advisor Heather Chandler, Ph.D Andrew Hartwick, O.D., Ph.D. Copyright by Tyler William Persson 2013 Abstract The purpose of this experiment was to observe and classify the head and eye movements of experienced baseball players when they are trying to hit a baseball. More specifically, it was designed to determine if players track deep into the pitch trajectory when attempting to hit, and if they use a similar tracking strategy when taking a pitch. We hypothesized that the batsmen would utilize two separate tracking methods, one for taking and another for swinging. Subjects were tested using a pitching machine called the Flamethrower under two separate conditions, in one condition they were instructed to “track the ball like you are taking a pitch”, and in the second condition they were instructed to “swing at the pitches like you would in batting practice”. Tennis balls were pitched from a distance of 56.3 feet from the batter at a measured velocity of approximately 75 miles per hour. Eye movements were recorded with the ISCAN infrared eye tracker and horizontal head rotations were recorded with the 3DM-GX1 head tracker and the Flock of Birds head tracker. All head and eye recordings were temporally synchronized with each other and with ball position using software. Two subjects were enrolled in the study. Each subject viewed 50 pitches under the “take” condition and 40 pitches under the “swing” condition. A total of 180 pitches were successfully recorded and both subjects were able to track a tennis ball in both testing conditions. Thus, 180 pitches were analyzed. ii Mean gaze errors for both trials indicated that the subjects were able to accurately track the pitched tennis balls for a majority of the ball’s flight path under each testing condition. Inter- subject comparison revealed the subjects exhibited similar tracking strategies in each condition, although one subject appeared to have less variability with his head and eye movements. Both subjects utilized different tracking strategies for taking versus swinging. In the “take” condition, the subjects used fast head and eye movements to produce a tracking lead, in an apparent effort to view the balls when they cross the plate. This observation agrees with previous reports in the literature for a proposed “optimum learning strategy” for successful hitting. In the “swing” condition the subjects used head and eye movements to track the balls late in the pitch trajectory. However, the head and eye movements in the “swing” condition were significantly decreased in both magnitude and amplitude compared to the “take” condition. Overall, these results indicate that the subjects tracked the balls both horizontally and vertically late in the pitch trajectory when swinging at the pitch. The reason for this is unknown, but indicates tracking with one’s gaze plays an integral role in hitting. That role is yet to be defined, and can only be postulated without further studies. iii Dedication This document is dedicated to my brother, Preston Earl Persson. iv Acknowledgments I would like to thank Dr. Fogt for all of the time and effort he has invested in me and this study. Most importantly, working with him has facilitated me to strive to be a lifelong learner, a more thorough researcher, and a more competent clinician. I would also like to thank my parents, Preston and Mary Persson, and Marie Schaefer. They have always supported me emotionally and physically through all of my endeavors. v Vita May 2003 .......................................................Williston Senior High School May 2008 .......................................................B.A. Chemistry, Minot State University May 2013 ......................................................O.D., The Ohio State University May 2013 ......................................................M.S., The Ohio State University Fields of Study Major Field: Vision Science vi Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iv Acknowledgments............................................................................................................... v Vita ..................................................................................................................................... vi Fields of Study ................................................................................................................... vi Table of Contents .............................................................................................................. vii List of Tables ..................................................................................................................... xi List of Figures .................................................................................................................. xiii Chapter 1: Introduction ...................................................................................................... 1 1.1: Pitch Dynamics ........................................................................................................ 1 1.2: Gaze Tracking in Baseball/Previous Studies ........................................................... 2 1.3: Why Study Gaze Tracking? ..................................................................................... 7 1.4: Summary of Gaze Tracking in Baseball ................................................................ 12 1.5: Aims of the Study................................................................................................... 12 Chapter 2: Methods ........................................................................................................... 14 vii 2.1: Subject Enrollment and Eligibility ......................................................................... 14 2.2: Pitching Machine ................................................................................................... 14 2.3: Ball Location .......................................................................................................... 15 2.3a: Linear ball location ........................................................................................... 15 2.3b: Flamethrower accuracy/Vertical ball location .................................................. 19 2.3c: Summary of ball location measurements .......................................................... 21 2.4: Eye and Head Movement Monitoring .................................................................... 21 2.4a: Monitoring eye movements .............................................................................. 21 2.4b: Monitoring head movements ............................................................................ 23 2.4c: Summary of data recording .............................................................................. 25 2.5: Translation Error of Flock of Birds ........................................................................ 26 2.6: Study Construct ...................................................................................................... 28 Chapter 3: Results ............................................................................................................. 31 3.1: Data Analysis ......................................................................................................... 31 3.1a: Synchronization of those data from the Ascension Flock of Birds data and those data from the analog-to-digital converter ......................................................... 31 3.1b: Eye values ......................................................................................................... 34 3.1c: Gaze values ....................................................................................................... 35 3.2: Head Movement Behavior ..................................................................................... 35 viii 3.2a: Horizontal head rotation ................................................................................... 35 3.2b: Vertical head rotation ....................................................................................... 38 3.2c: Head tilt ............................................................................................................ 40 3.3: Eye Movement Behavior ........................................................................................ 40 3.3a: Horizontal eye rotation ..................................................................................... 40 3.3b: Vertical eye rotation ......................................................................................... 43 3.4: Gaze Position ......................................................................................................... 45 3.4a: Horizontal gaze position ................................................................................... 45 3.4b: Vertical gaze position ....................................................................................... 49 3.5: Success Rate ..........................................................................................................