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N. F. Fogt, J. Young, A. Zimmerman; The Influence of Instructions on Ocular Gaze Tracking of Baseballs. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2531.
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© ARVO (1962-2015); The Authors (2016-present)
To determine what influence tracking instructions have on gaze tracking behavior during a baseball pitch. This information is useful in optimizing the tracking behavior of baseball batters.
Data were gathered from 23 subjects (age <29). 4 of these subjects had baseball experience at the high school level or above. Subjects viewed 100 tennis balls thrown from a pitching machine at about 80mph. 8 subjects were told to call out numbers (0-8) and the color of these numbers (red or black) written on the balls (Group 1). 8 subjects were told to track the balls all the way to home plate (Group 2). 7 subjects were told to do what they would normally do if they were batting a ball (Group 3). Head movements were recorded with a magnetic tracker, eye movements were recorded with a video tracker, and ball position was measured using lasers and photocells. A computer program was used to synchronize these data.
594 pitches from Group 1, 499 pitches from Group 2, and 555 pitches from Group 3 were analyzed. Mean gaze errors, mean head movements, and mean eye movements at 5.83 feet from the batter were determined. The mean gaze error (negative indicates lagging behind the ball) was -8.95±7.10deg (Group 1), -8.46±6.92deg (Group 2), and -4.61±13.66deg (Group 3). The mean of the absolute values of gaze error was 10.45±4.63deg (Group 1), 9.85±4.73deg (Group 2), and 11.89±8.13deg (Group 3). The mean head movement was 4.73±5.10deg (Group 1), 3.05±4.19deg (Group 2), and 8.59±11.90deg (Group 3). The mean eye movement was 0.70±4.38deg (Group 1), 2.88±6.02deg (Group 2), and 1.18±5.92deg (Group 3). The mean gaze error was significantly smaller for Group 3 compared to Groups 1 and 2. The mean of the absolute value of gaze errors was significantly smaller for Groups 1 and 2 compared to Group 3. Mean head movements were significantly different for all groups. Mean eye movements were significantly larger for Group 2 compared to the other groups.
Gaze tracking behavior depended on the tracking instructions. Mean gaze errors overall were smallest for Group 3, but the standard deviation of these gaze errors was very high and the mean absolute errors were higher for this group. Group 3 individuals also had the largest mean head movements. Group 2 individuals on average used a nearly equal combination of eye and head movements in tracking the ball, while individuals in Groups 1 and 3 on average used primarily head movements to track the ball. The larger head movements (and smaller eye movements) of Group 3 were correlated with smaller mean tracking errors. However, these larger head movements were correlated with less precise tracking so from pitch to pitch, tracking errors were substantial.
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