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# Tobii 150 Spectrum and PyGaze

I am running a series of eye tracker experiments in OpenSesame to investigate cognitive effort by means of checking the variability of the pupil size across conditions, first, in a AX-CPT and, after, in a Simon task. Howver, I am facing some problems and would like to ask for advice/help.

1) When we run the experiments sometimes I get this error:

Detenido

El experimento no pudo terminar de forma normal por la siguiente razón:

Unexpected error

Details

item-stack: experiment[run].pygaze_init[run]

exception type: AttributeError

exception message: TobiiProTracker instance has no attribute 't0'

time: Thu Mar 28 17:03:00 2019

Traceback (also in debug window)

File "C:\Program Files (x86)\OpenSesame\lib\site-packages\libqtopensesame\misc\process.py", line 157, in run

exp.run()

File "C:\Program Files (x86)\OpenSesame\lib\site-packages\libopensesame\experiment.py", line 456, in run

self.items.execute(self.var.start)

File "C:\Program Files (x86)\OpenSesame\lib\site-packages\libopensesame\item_store.py", line 103, in execute

self.run(name)

File "C:\Program Files (x86)\OpenSesame\lib\site-packages\libopensesame\item_store.py", line 122, in run

self[name].run()

File "C:\Program Files (x86)\OpenSesame\lib\site-packages\libopensesame\sequence.py", line 51, in run

self.experiment.items.run(_item)

File "C:\Program Files (x86)\OpenSesame\lib\site-packages\libopensesame\item_store.py", line 122, in run

self[name].run()

File "C:\Program Files (x86)\OpenSesame\share\opensesame_plugins\pygaze_init\pygaze_init.py", line 227, in run

self.experiment.pygaze_eyetracker.calibrate()

File "C:\Program Files (x86)\OpenSesame\lib\site-packages\pygaze\_eyetracker\libtobii.py", line 299, in calibrate

self.start_recording()

File "C:\Program Files (x86)\OpenSesame\lib\site-packages\pygaze\_eyetracker\libtobii.py", line 192, in start_recording

if not self.t0 and self._write_enabled:

AttributeError: TobiiProTracker instance has no attribute 't0'

Does anyone know what this error means? It does not appear all the time though, but I think this indicates that there is something wrong in the experiment.

2) Another problem is that the calibration phase does not happen in the same way all the time. That is, sometimes, pygaze does not ask to confirm the calibration and after the first calibration period it skips directly to the experiment. Also, the eye tracker sample rate varies drastically and sometimes it is super low (like 4 Hz for instance instead of ~150hz).

3) As you know, when we run an experiment using Open Sesame and PyGaze we get two output files: one with the behavior results (open sesame file) and the other with the eye tracker results (pygaze file). Is there any easy way to integrate both files? For example, adding variable to the pygaze logfile so I can link my conditions with the pupil size information?

Patricia

• Hi Patricia,

This sounds like a Tobii-specific problem. Would you mind opening a new issue on GitHub via the link below, and tag the Tobii developers @grebdems and @pedrotari7, please?

Point 2 might well be related to the same underlying issue.

As for point 3, you can use a pygaze_log item to log whatever you want to the gaze data file :)

Good luck!

Edwin

• Hi Edwin,

I am a colleague of Patricia, working on the same project. We still get the attribute 't0' error that Patricia describes in point 1. I opened an issue on GitHub, and also contacted Tobii support. From Tobii support, they say it does not seem to be an eyetracker error, but rather a PyGaze error (or an issue that arises when integrating PyGaze and OpenSesame), as 't0' is defined within PyGaze, and not by the eyetracker software.

Would you have any insight into why this error occurs and whether it could be "programmed away"?

Thank you very much.

Paula