Webcam eye tracking close to laboratory standards: Comparing a new webcam-based system and the EyeLink 1000

Abstract

This paper aims to compare a new webcam-based eye-tracking system, integrated into the Labvanced platform for online experiments, to a ``gold standard'' lab-based eye tracker (EyeLink 1000 - SR Research). Specifically, we simultaneously recorded data with both eye trackers in five different tasks, analyzing their real-time performance. These tasks were a subset of a standardized test battery for eye trackers, including a Large Grid task, Smooth Pursuit eye movements, viewing natural images, and two Head Movements tasks (roll, yaw). The results show that the webcam-based system achieved an overall accuracy of 1.4 degrees, and a precision of 1.1 degrees (standard deviation (SD) across subjects), an error of about 0.5 degrees larger than the EyeLink system. Interestingly, both accuracy (1.3 degrees) and precision (0.9 degrees) were slightly better for centrally presented targets, the region of interest in many psychophysical experiments. Remarkably, the correlation of raw gaze samples between the EyeLink and webcam-based was at about 90% for the Large Grid task and about 80% for Free View and Smooth Pursuit. Overall, these results put the performance of the webcam-based system roughly on par with mobile eye-tracking devices (Ehinger et al. PeerJ, 7, e7086, 2019; Tonsen et al., 2020) and demonstrate substantial improvement compared to existing webcam eye-tracking solutions (Papoutsaki et al., 2017).