Eyelink recording slows down the experiment

SINE

Hi,

I am running an experiment which needs high temporal precision. In particular, following the presentation of a mask, this should disappear as soon as participants provide a keyboard response. This works very well when I use the simple dummy mode, without therefore recording with the Eyelink. However, when I use Eyelink, following the keyboard response, the masks take considerably longer before disappearing from the screen (I would say around 200-300ms). Is this normal? I suspect that also the other stimuli that I am presenting might be lasting on the screen slightly longer because of the Eyelink recording.

Thanks for any help you might provide!

eduard

Hi SINE,

If you have the record and stop items in the trial loop, that is normal indeed. These two items need some extra time to communicate with the eye tracker. To prevent that delay, you need to move them outside the items between which you need accurate timing, i.e. before and after the trial_loop. But be aware that if you do that, you might need to include log messages within each trial, to make sure that you can distinguish different events within the trial.

Hope this helps,

Eduard

Edwin

To be honest, this type of delay sounds like there is a huge amount of logging going on. Are you recording all your variables to the EDF? You might want to not do so, and instead only log the relevant stuff.