Eyetracking output file timestamps

[Anissa Neal]

Hello!

I’ve been running an eyetracking experiment, and am having trouble interpreting the results of the output (the one generated by the PHP script).

Here is a link to the experiment: https://farm.pcibex.net/r/vLDtTt/
Much of the code also comes from Mieke Slim: https://github.com/MiekeSlim/PCIbex_VisualWorld

The scripts generate an .csv output file, but I am having trouble determining what time point in the eyetracking files lines up with when code in PCIbex is being run. One concern I have is that on two separate lines, I call.start() on the eyetracking (“tracker”) element, but only call .stop() once.

Here is a sample of what the recorded eye movements are, as I have only two quadrants (Left and Right).

Participant trial times _Left _Ys _Right _Xs
a001 51 0 0 383 1 940
a001 51 57 0 452 1 884
a001 51 106 0 524 1 885

I am just basically confused and concerned and trying to figure out what the time stamp of 0 here is above!

Thanks so much for any help!

[Jeremy]

Hi,

You are not supposed to call start on an EyeTracker element that’s already started. When .log is called on the EyeTracker element, lines are added to the results file, including one line that tells you when .start was executed and reporting the corresponding timestamp. Then you can use the times column from the .csv output file to calculate when each gaze estimate was recorded (EventTime + times). For example, the value of 0 in your sample simply corresponds to the tracker’s start timestamp (not sure which of the two starts though, but you can determine that using the timestamps of print on the Left and Right Canvas elements, since you print those between the tracker’s first and second starts). Comparing those values with the timestamps reported in your results file for other events, such as audio start/stop, will give you an idea of where the participant was looking during the unfolding of the event in the trial

Jeremy

[Author]

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