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Problem Tobii X3-120 with Pygaze(Opensesame). PupilSizeRight/Left =-1 2times over every 3

I have tried to run an experiment in Opensesame with pygaze. I have a Tobii X3-120.

I notice this problem when I open the output file:

Every 3 measure, PupilSizeRight/Left have value "-1" for 2 times. I attach the image of the top of the data file.  The rest of the file looks the same

Do you have any suggestion?




  • Hi Paolo,

    Usually that indicates missing data. I'll admit that it's a bit weird, considering that the pupil validity is 1, and normal gaze samples seem to be coming through.

    If it keeps happening in good calibrations that produce good gaze samples without a pupil size indication, you might want to check with Tobii directly. (The data is streamed from their tracker and application.)



  • Dear Edwin, thank you for your reply. I tried also on another computer, same results.

    I will try to contact the Tobii support.

    Best regards,


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