MAD saccade: statistically robust saccade threshold estimation via the median absolute deviation

Keywords: Saccades, median absolute deviation, MAD, eye tracking, head-free viewing

Abstract

Saccade detection is a critical step in the analysis of gaze data. A common method for saccade detection is to use a simple threshold for velocity or acceleration values, which can be estimated from the data using the mean and standard deviation. However, this method has the downside of being influenced by the very signal it is trying to detect, the outlying velocities or accelerations that occur during saccades. We propose instead to use the median absolute deviation (MAD), a robust estimator of dispersion that is not influenced by outliers. We modify an algorithm proposed by Nyström and colleagues, and quantify saccade detection performance in both simulated and human data. Our modified algorithm shows a significant and marked improvement in saccade detection - showing both more true positives and less false negatives – especially under higher noise levels. We conclude that robust estimators can be widely adopted in other common, automatic gaze classification algorithms due to their ease of implementation.

Author Biographies

Benjamin Voloh, Vanderbilt University

Department of Psychology, Vanderbilt University

Marcus R Watson, York University

Post-doctoral Fellow

Department of Biology

York University

Seth Konig, Vanderbilt University

Post-doctoral Fellow

Department of Psychology

Vanderbilt University

Thilo Womelsdorf, Vanderbilt University

Associate Professor

Department of Psychology

Vanderbilt University

Published
02-12-2019
How to Cite
Voloh, B., Watson, M. R., Konig, S., & Womelsdorf, T. (2020). MAD saccade: statistically robust saccade threshold estimation via the median absolute deviation. Journal of Eye Movement Research, 12(8). https://doi.org/10.16910/jemr.12.8.3
Section
Articles