Evaluation of the Tobii EyeX Eye tracking controller and Matlab toolkit for research

Agostino Gibaldi,Guido Maiello,Peter J Bex,Mauricio Vanegas

doi:10.3758/s13428-016-0762-9

Agostino Gibaldi, Guido Maiello + Show 2 more

Open Access

https://doi.org/10.3758/s13428-016-0762-9

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Abstract

The Tobii Eyex Controller is a new low-cost binocular eye tracker marketed for integration in gaming and consumer applications. The manufacturers claim that the system was conceived for natural eye gaze interaction, does not require continuous recalibration, and allows moderate head movements. The Controller is provided with a SDK to foster the development of new eye tracking applications. We review the characteristics of the device for its possible use in scientific research. We develop and evaluate an open source Matlab Toolkit that can be employed to interface with the EyeX device for gaze recording in behavioral experiments. The Toolkit provides calibration procedures tailored to both binocular and monocular experiments, as well as procedures to evaluate other eye tracking devices. The observed performance of the EyeX (i.e. accuracy < 0.6°, precision < 0.25°, latency < 50 ms and sampling frequency ≈55 Hz), is sufficient for some classes of research application. The device can be successfully employed to measure fixation parameters, saccadic, smooth pursuit and vergence eye movements. However, the relatively low sampling rate and moderate precision limit the suitability of the EyeX for monitoring micro-saccadic eye movements or for real-time gaze-contingent stimulus control. For these applications, research grade, high-cost eye tracking technology may still be necessary. Therefore, despite its limitations with respect to high-end devices, the EyeX has the potential to further the dissemination of eye tracking technology to a broad audience, and could be a valuable asset in consumer and gaming applications as well as a subset of basic and clinical research settings.

Highlights

Eye-tracking technology provides a unique source of information about how humans and animals visually explore the world
In order to allow users to exploit the full potential of the Tobii EyeX Controller, we implemented a calibration procedure that can be carried out both binocularly and monocularly with each eye, and we present an evaluation of the differences between the monocular and binocular calibration procedures
The Matlab Toolkit consists of four parts: 1) a client UDP (User Datagram Protocol) interface to connect Matlab with the Tobii server, 2) a set of basic connection functions for data transmission and reception, 3) a set of routines for standard use of the device, and 4) sample code provided to exemplify the usage of each function of the Toolkit in simple experiments in which we measure saccade, smooth pursuit, vergence and fixational eye movements

Summary

Introduction

Eye-tracking technology provides a unique source of information about how humans and animals visually explore the world. We are able to investigate the cognitive processes underlying visual experience (e.g. attention, preference, discrimination), as well as to quantify the low-level parameters of oculomotor control (e.g. response latency, kinematics of eye movements). For these reasons, eye tracking technology is increasingly employed in a broad variety of research fields, from neuroscience to psychology, and has important clinical applications. Eye tracking research required invasive and uncomfortable techniques such as scleral search coils (Robinson, 1963) or electro-oculography (Kaufman et al, 1993).

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