Friedman Lee, Hanson Timothy, Komogortsev Oleg V
Texas State University, San Marcos, Texas, USA.
Medtronic Fridley, Minnesota, USA.
J Eye Mov Res. 2021 Oct 28;14(3). doi: 10.16910/jemr.14.3.4. eCollection 2021.
This paper is a follow-on to our earlier paper (7), which focused on the multimodality of angular offsets. This paper applies the same analysis to the measurement of spatial precision. Following the literature, we refer these measurements as estimates of device precision, but, in fact, subject characteristics clearly affect the measurements. One typical measure of the spatial precision of an eye-tracking device is the standard deviation (SD) of the position signals (horizontal and vertical) during a fixation. The SD is a highly interpretable measure of spread if the underlying error distribution is unimodal and normal. However, in the context of an underlying multimodal distribution, the SD is less interpretable. We will present evidence that the majority of such distributions are multimodal (68-70% strongly multimodal). Only 21-23% of position distributions were unimodal. We present an alternative method for measuring precision that is appropriate for both unimodal and multimodal distributions. This alternative method produces precision estimates that are substantially smaller than classic measures. We present illustrations of both unimodality and multimodality with either drift or a microsaccade present during fixation. At present, these observations apply only to the EyeLink 1000, and the subjects evaluated herein.
本文是我们早期论文（7）的后续研究，早期论文聚焦于角度偏移的多模态。本文将同样的分析应用于空间精度的测量。参照文献，我们将这些测量称为设备精度的估计值，但实际上，受试者的特征显然会影响测量结果。眼动追踪设备空间精度的一种典型测量方法是注视期间位置信号（水平和垂直）的标准差（SD）。如果潜在误差分布是单峰且正态的，那么标准差是一种对离散程度具有高度可解释性的度量。然而，在潜在多峰分布的情况下，标准差的可解释性较差。我们将给出证据表明，大多数此类分布是多峰的（68 - 70%为强多峰）。只有21 - 23%的位置分布是单峰的。我们提出了一种适用于单峰和多峰分布的测量精度的替代方法。这种替代方法产生的精度估计值比传统测量方法小得多。我们展示了在注视期间存在漂移或微扫视情况下的单峰和多峰情况的示例。目前，这些观察结果仅适用于EyeLink 1000以及本文所评估的受试者。
