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On/Off latency for starting/stopping recording eyetracker data

Hi everyone,

I was just wondering if anyone knows of the kind of latencies one can expect when using the pygaze_start_recording and pygaze_stop_recording items in experimental trials?

To give some background: I'm looking at some simple visual search tasks and want to record eye movement during the trials. I would expect the 'active' part of the trials (i.e. when the participant is searching for the target) to only last a couple of seconds at the most, and just wondered whether my method of recording the ET data was reasonable?

The order of events for a trial is basically:

show fixation point -> remove fixation point -> start_pygaze_recording -> show stimuli -> wait for keypress -> stop_pygaze_recording -> record_keypress -> show mask

I know I could actually figure the timings out myself but I don't have access to the eye tracker at the moment. Any thoughts very welcome!

BWs

Neon

Comments

  • Hi Neon,

    It depends. In my experiments, it took usually around 450 ms to start/stop a recording. Other people found other delays. But if you are interested in the exact numbers, you should test it yourself (take the time before and after starting/stopping and compare).

    Given your idea, I'd recommend to start the recording before the trials begins and end after the trial is over. In order to still know which data in the ed file corresponds to the relevant part of the trial, you can send log messages to the eyetracker, saying something like exp.pygaze_eyetracker.log('Show stimuli').

    Hope this helps.
    Eduard

  • Thanks, @eduard for that. Yes, I'd concluded this myself so will proceed that way.

    Best wishes,

    Neon

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