Experiment with video stimuli goes blank after 4 trials

PennController for IBEX Forums Support Experiment with video stimuli goes blank after 4 trials

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    I’m trying to run a relatively simple experiment that asks participants to watch a video and then rate it on a Likert scale. The videos are all hosted on a external website.

    The experiment works smoothly for exactly 4 trials. Then, I hit a “resources preloading” page, which takes longer than the initial preload, and eventually get stuck on a blank page with just a progress bar on it.

    Here is the demo link:

    I have taken the following troubleshooting steps:
    – removing randomization
    – renaming conditions (to remove any called “control”)
    – changing all conditions to just one name
    – combinations of the above

    None of these steps have gotten me beyond 4 trials — although the trials I see before it hits the problem may be different, it is always exactly 4 trials. Given my troubleshooting, it doesn’t seem related to the conditions or randomization — please help!

    Thank you so much, from a struggling PhD student 🙂



    Unfortunately I cannot efficiently troubleshoot your study right now, because my connection is extremely slow and downloading even a single video takes forever (so I keep hitting the “resources preloading” page before every single trial)

    Did you check that every single URL in your CSV file points to a valid file? Does the problem persist if you consolidate your video files in a single zip archive?



    Hi again,

    I was able to test your experiment on a better connection. It does look like the browser starts fetching (partial) data from four videos from your server, but after that all requests stall. Because this doesn’t happen across all experiments on the farm, the issue must lie at least partly in how your server is configured to respond to the requests for video files that the farm sends it

    Unfortunately, I cannot tell what server configuration controls that behavior, but I strongly encourage you to explore the zip file method, which will fetch all the video files from a single request to your server, and see if the problem persists


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