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Which gaze position does eyetracker.sample() return?

we wrote a drift check via an inline script and it seems to work just fine. Still, we are wondering how the (x,y) tuple from eyetracker.sample() is calculated? It's just one pair of coordinates, even if we track both eyes. So we guessed that it is either the left's or right eye's position. Or does it calculate an average gaze position by incorporating both eye positions?
We weren't able to find anything regarding that specific topic neither in the opensesame documentation nor on the pygaze sites.
Best wishes,


  • Hi Christina,

    This depends on the eye tracker. What eye tracker are you using?


  • edited May 2018

    Hi Christina,

    To provide a general response to this:

    EyeLink: Monocular, whether it's the right or left eye depends on which eye you're recording (you can set this in the EyeLink UI interface).

    EyeTribe: The mean of both eyes if both eyes are available, the left eye if only the left eye is available, the right eye if only the right eye is available, and missing. Note that this is based on the EyeTribe's own avgx and avgy variables, which I think also go through a smoothing process. (This is done by the EyeTribe's software, which we don't have direct insight into.)

    GazePoint (OpenGaze API): Average of both if both eyes are available, and left/right if only that eye is available. Note that this is based on the 'best available point-of-regard' (variable BPOGX and BPOGY in the OpenGaze API), which is computed within the GazePoint software.

    SensoMotoric Instruments (SMI): Monocular. It takes either the right or the left eye, depending on which one you're tracking.

    Tobii (new Pro SDK): Depends on your settings. When you're tracking either the left OR the right eye, it returns that eye's position. If you're doing binocular tracking, it returns the average of both eyes if both eyes are available, or the left/right eye depending on which is available.

    Tobii-legacy (old SDK): Monocular. It gives you the left eye, unless you've specifically set it to return the right eye.

  • As far as I remember, for binocular SMI trackers (x, y) returns an averaged position as well. (Just providing a specific note to @Edwin's great general response).

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