Quantitative comparison of a mobile and a stationary video-based eye-tracker

Vision represents the most important sense of primates. To understand visual processing, various different methods are employed, e.g. electrophysiology, psychophysics or eye tracking. For the latter, researchers recently began to step outside the artificial environments of laboratory setups towards the more natural conditions we usually face in the real world. This approach was enabled by sophisticated video-based mobile eye-trackers. Yet, their mobility and light weight often comes at an expense of reduced performance and accuracy, compared to the stationary eye-trackers, which nowadays are considered a gold standard in vision science.

In order to get a better understanding of the advantages and limitations of both eye-tracking techniques, we quantitatively compared one of the most advanced mobile eye-trackers available, the EyeSeeCam (ESC, sampling at 230 Hz), with a commonly used laboratory eye-tracker, the EyeLink II (ELII, sampling at 500 Hz). We aimed to investigate whether or not fully mobile eye-trackers are capable of providing adequate data to allow for a direct comparison with data recorded with stationary eye-trackers. Therefore, we recorded three different, commonly used eye movements, i.e. fixation, saccades and smooth pursuit eye movements, with both eye trackers in successive standardized paradigms in a laboratory setting with eight human subjects.

Despite major technical differences, the values of most eye movement parameters were not statistically different between both systems. Differences could only be found in overall gaze accuracy and for time critical parameters like saccade duration, for which a higher sample frequency is especially useful. Although, the stationary ELII system proved to be superior, especially at a single subject or even at a single trial basis, the ESC showed a similar performance for averaged parameters across trials and subjects. We conclude that modern high-performance mobile eye-trackers are well suited to provide reliable oculomotor data at the required spatial and temporal resolution.

Here we provide the raw data recorded with both eye trackers in eights human subjects in the three different, commonly used, oculomotor tasks.