Long loading time of images (Prolific study)

[Eliane Roy]

Hi Minno Group

I recently launched a study collecting data on Prolific, and participants are reporting many issues with how the tasks including images load. Specifically, the loading takes a very long time and in some situations, stops loading. I am thinking this has to do with the file size of the images which may be too large for some slower internet connections, which then times out the session.

One thing I did to try and fix this is to reduce the file size of all pictures involved in the study, so it loads better. This change will come into effect after the deployment on Thursday, October 27th. Still, I was wondering if this issue had occurred to others, and if so what was the solution?

Here is the showfile link: https://app-prod-03.implicit.harvard.edu/implicit/showfiles.jsp?user=eroy&study=contest_jbt_round3

Here is the data collection link: https://implicit.harvard.edu/implicit/Launch?study=/user/jaxt/contest_jbt_round3/contest_jbt_round3.expt.xml

Thank you!

Eliane

[Yoav Bar-Anan]

Hi Eliane, 

The link you provided does not point to a study. 

If it did, I would have examined whether you are using the preloadImages API function in the manager file to preload the images, and whether the file names you are giving that function are the correct names.

Yoav

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[Eliane Roy]

Hi Yoav, 

Thank you for the quick reply! Here is the correct link.

However, I did not know this function existed, so I can confirm that I am not using this function. I will consult the documentation you pointed to and add it to my study.

Thank you!

Eliane

[Yoav Bar-Anan]

Great. 

Remember that the preloadImages function does not know to add the mediaURL or baseURL, so you will need to add it when you construct the image names for that function. 

Here is an example for using the function. 

And a more simple example (loading 36 images, named pos1.jpg to pos18.jpg and neg1.jpg to neg18.jpg):

    //Preload images
    var photos = [];
    var iPhoto;
    for (iPhoto = 1; iPhoto <= 18; iPhoto++)
    {
        photos.push(global.mediaURL + 'pos'+iPhoto+'.jpg');
        photos.push(global.mediaURL + 'neg'+iPhoto+'.jpg');
    }

    API.addSettings('preloadImages', photos);

When using the preloadImages API function I recommend opening the Developer tools (in Chrome: More tools->Developer tools or Ctrl-Shift I). Sometimes the image urls are constructed wrong, and then you will see error printings reporting that the image was not found.

Yoav

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