Sgttoolbox: Utility for controlling SimpleGazeTracker from Psychtoolbox

Eye movement analysis is effective for investigating visual perception and cognition. The cost of conducting eye movement studies has decreased as a result of the recent release of low-cost commercial and open-source eye trackers. However, synchronizing visual stimulus presentation with eye movement recording is still difficult, particularly if the eye tracker does not come with a practical application programming interface. This paper introduces a Matlab/Octave toolbox named Sgttoolbox, which works in conjunction with the widely used experiment control library Psychtoolbox to control a cross-platform open-source eye tracker named SimpleGazeTracker, which is an eye-tracking application of GazeParser software. Hardware and software requirements for Sgttoolbox and its main functions are described. A test of temporal accuracy showed that eye movement sampling frequency was stable when stimulus presentation and recording were performed on a single PC, although better performance was obtained when presentation and recording were performed on separate PCs. Transferring the latest eye position from SimpleGazeTracker to Psychtoolbox script takes 2 to 4 ms on average, which causes a delay in drawing multiple visual stimuli when recording and stimulus presentation were performed on a single PC. When such a transfer delay is not importnat, Sgttoolbox would be a good choice for Psychtoolbox users who wish to conduct eye-tracking studies.