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How to trouble shoot when online experiment gets stuck only for few participants

Hey everyone,

I’m now running an experiment online. It is a large experiment including presentation of videos and images. I tried to compress the videos and images to my best ability and use format of videos that should not be problematic as suggested by others Media formats suitable for online studies — PsychoPy v2021.2

The experiment ran just fine for most participants (it usually takes ~5min to load the whole experiment). However, for about 5 out 30 participants, it got stuck at some point or some of the videos failed to be loaded. This happened regardless of the internet speed and the browser they used. Sometimes the problems got fixed when they load it again on a different day, sometimes not.

Could anyone give me some hints on how I should troubleshoot this problem? I normally asked these participants their internet speed, how long it took them to load the experiment, the browser and computer system they used. Thanks a lot!

Hi There,

This is something that we need to test still (I encountered this in my own experiment - but only for when the task was run on mobile phones, for that reason I instructed all participants to use laptops and chrome where possible). If possible, can you track what trial number the crash usually occurs on? If it is predictable, perhaps the task could be split in two?

My suspicion is that the videos are clogging up the browser memory (which would also be why it ran ok other days, if the browser cache had time to clear!) - one possible solution you could test is if you can ask participants to clear their browser cache beforehand? (but I know that is not always ideal or possible).

I’de be interested to hear feedback on what type of device it occurs on, what browser, what trial number and how large each video is.

Hopefully we can debug this!

Hi Becca–Thanks so much for the suggestion! I will try to gather more information if this keeps happening for other participants (I’m thinking for future online studies whether adding a short survey at the end will be better)! I think it’s a good idea to ask them to clear their browser cache if they run into problem.