Yamamoto Hiroyuki, Shinya Masahiro, Kudo Kazutoshi
a Graduate School of Arts and Sciences , The University of Tokyo , Tokyo , Japan.
b Graduate School of Interdisciplinary Information Studies , The University of Tokyo , Tokyo , Japan.
J Mot Behav. 2019;51(2):141-150. doi: 10.1080/00222895.2018.1440523. Epub 2018 Mar 6.
This study aimed to investigate whether the isotropy bias (estimating one's own motor variance as an approximately circular distribution rather than a vertically elongated distribution) arises in tennis players for the estimation of the two-dimensional variance for forehand strokes in tennis (Experiment 1), as well as the process underlying the isotropy bias (Experiment 2). In Experiment 1, 31 tennis players were asked to estimate prospectively their distribution of ball landing positions. They were then instructed to hit 50 forehand strokes. We compared the eccentricity of the ellipse calculated from estimated and observed landing positions. Eccentricity was significantly smaller in the estimated ellipse than in the observed ellipse. We assumed that the isotropy bias for the estimated ellipse comes from the process of variance estimation. In Experiment 2, nine participants estimated the 95% confidence interval of 300 dots. Eccentricity was significantly smaller in their estimated ellipses than it was in the ellipses for the dots, though the magnitude of bias decreased for the estimation of dots. These results suggest that the isotropy bias in tennis ball landing position includes the bias of recognizing landing position and the bias of estimating the ellipse confidence interval from the recognized landing position.
本研究旨在调查网球运动员在估计网球正手击球二维方差时是否会出现各向同性偏差（将自身运动方差估计为近似圆形分布而非垂直拉长分布）（实验1），以及各向同性偏差背后的过程（实验2）。在实验1中，31名网球运动员被要求前瞻性地估计球的落点分布。然后他们被指示打出50次正手击球。我们比较了根据估计落点位置和观察落点位置计算出的椭圆离心率。估计椭圆的离心率显著小于观察椭圆的离心率。我们认为估计椭圆的各向同性偏差来自方差估计过程。在实验2中，9名参与者估计了300个点的95%置信区间。他们估计椭圆的离心率显著小于点的椭圆的离心率，尽管点估计的偏差幅度有所减小。这些结果表明，网球落点位置的各向同性偏差包括落点位置识别偏差和从识别出的落点位置估计椭圆置信区间的偏差。
