When loaded with too many pictures, the experiment seems to have difficulty to initialize

I am trying to build a simple lexical decision task, that is, judging whether the presented stimuli is true or false. To have a better control over the visual size, I made all stimuli into pictures (in all for about seven hundred some pictures) and put all these pictures together with the .py file in the same path. The name of each picture is listed in excel, which is later added to the loop.
The experiment can run, but it seems to have difficulty to initialize. Firstly, when I press to run, there will be circle running and indicating there is no response. But if I take patience to wait, it works to start. Then after viewing the instruction, it moves to the loop, it freezes for a while again (I press the intended space bar to continue but nothing changes for a while). After about a few seconds, it changes but the first trial runs very fast (not as what I design). starting from the second trial, things turn normal.
I thought it might be due to the large number of images. but I do not know how to handle it with the builder mode.
if anyone has ever met with similar problems before?

Hello anne235

well, the browser downloads your ~700 pictures first before starting the experiment. This may take a while.
At the moment, I have no idea why the first trial seems to run faster than the following trials. It might be due to loading the image? Hard to tell without access to the code or experiment.

If you want evenly space word and pseudoword stimuli you could use a monospaced font instead of a proportional font.

If you want evenly large stimuli on each screen your participants are using, you need an extra routine, see:

Best wishes Jens

Hello, Jens,
Thanks a lot for reply. I find the cause minutes ago. It is not due to the large number of pictures but because of the oversized excel file… When preparing the material, I paste and reorganize the excel file for so many times that it grows… I now paste the material to a brand-new excel and add it to the loop, the experiment stops freezing.
The oversized excel file also causes problem when builders try to create variables from the file so it takes a long time to add. If others have similar issues, they may learn my lesson.
Thanks a lot anyway!
Best wishes Anne