Eye-tracking
Eye-tracking is conducted using the Tobii Pro Spectrum systems.
The laboratory houses two Tobii Pro Spectrum systems (in rooms 405G and 405F).
- This system is a screen-based eye tracker capturing gaze data at speeds up to 1200 Hz. This high-performance research system provides superior data quality and is designed for extensive research into behavior and eye movements – from fixation-based studies to micro-saccades. It combines video-based pupil- and corneal reflection eye tracking with dark and bright pupil illumination modes.
- Two cameras capture stereo images of both eyes for robust accurate measurement of eye gaze and eye position in 3D space, as well as pupil diameter. Sampling frequencies range between 60-1200 Hz with precision and accuracy between 0.01-0.06°(RMS), and 0.3°, respectively. The system provides binocular eye tracking with total system latency of less than 3 frames and a blink recovery time of 1 frame. The dual-camera, relative to one camera, system gives a more accurate data calculation and the best level of precision and robustness for head movement.
- The hardware is combined with Tobii Pro Lab software which provides a visual user interface and software features that efficiently guide and support the researcher through all phases of an eye tracking experiment – from test design and recording to analysis. The Tobii Pro Lab facilitates the combination of eye tracking with biometric data streams, like EEG, GSR, and ECG. For co-registration with other data sources, the software allows for a TTL marker at every stimulus onset to ensure precise data synchronization.
- The Tobi Pro specifications
Interfacing with the eyetrackers and collecting data
To interface with the you have multiple options:
- Using the software provided with the Tobii Pro System known as the Tobii Pro Lab software. It is similar in use to E-Prime and PsychoPy and user-friendly (see here for manual).
- Code up your experiments in either MATLAB (with Psychtoolbox) or use Python (with in-line code or PsychoPy). The Human Neuroscience Lab recommends employing the Tobi Pro Software Developer Kit (SDK). Feel free to contact Dr. Preston Thakral for assistance or templates.
For example, in the Human Neuroscience Lab we have interfaced the Tobii-Pro Spectrum with PsychoPy. Linked here is a sample experiment in PsychoPy that has the necessary code to interface with the Tobii system (with calibration/validation). It is a source memory task with the Snodgrass-Corwin object stimuli. The eyetracking data is outputted as an HDF5 file, which can be opened in MATLAB or a viewer. Here is a link describing the output of the HDF5 file