When are stimuli actually sent to the user's machine?

veskerm

Crossposting from the JATOS topic:

I am working on an online response-time experiment (made using Opensesame and OSWeb) where the subject is shown approximately 50 photographs (1 per trial), and had a question: are all the stimuli sent to the user's machine during the initial loading stage of the experiment, or are they sent at the moment when the corresponding trial comes up?

My thinking is that if all the stimuli pictures are loaded at the outset, then a higher number of concurrent users would increase the initial loading stage (which is not too crucial), but should not impact the timing of the experiment too much once its in progress. On the other hand if the stimuli are sent on a trial by trial basis then a larger number of concurrent users might throw off the timing within the experiment, which would be a bigger problem for my experiment. Therefore, depending on when the stimuli are actually sent, I may have to gate the number of concurrent participants.

Thank in advance!

sebastiaan

Hi @veskerm ,

are all the stimuli sent to the user's machine during the initial loading stage of the experiment (…)?

Yes! All the stimuli are included in the file pool, and this loaded at startup into the browser of the participant. Afterwards, the only communication between the browser and the JATOS server involves sending data back to the server.

So, as you correctly say, in terms of experiment timing (aside from the initial loading stage), the number of simultaneous participants doesn't matter.

Cheers!

Sebastiaan

veskerm

Thank you for the response Sebastiaan! I participated in the workshop a couple of weeks ago, but only thought of this question after it was over :)