Data not saving from iPhone Safari on Cognition.run despite using on_data_update and save()

[shahdiya30]

Hi all,

I’m running a jsPsych 6.3 experiment via Cognition.run. I’ve used on_data_update and save(jsPsych.data.get().json()) after every trial, and even added manual calls to save() before jsPsych.finishTrial() inside a custom plugin. Despite that, data does not save at all when users exit mid-experiment on iPhone Safari.
What I’ve tried:

Saving via on_data_update (with/without setTimeout)

Calling save() manually inside plugin trial endings

Using document.visibilitychange and pagehide events

Everything works perfectly on desktop. But on iOS Safari, closing the tab causes all data to be lost.

Is this a known Cognition limitation on iPhone?
Is there a workaround or alternative save strategy that works reliably on mobile?

Any help would be hugely appreciated!

Thanks so much,
Diya

[kurokida]

Hi, Diya,

A long time ago, I also experienced the similar situation; iPhone data wasn't saved. In my case, I wasn't using Cognition, so this issue might be unrelated to Cognition. I'm sorry, but since it happened quite a while ago, I don't remember the details. Updating jsPsych to version 7 or higher might resolve the issue.

Best,
Daiichiro

[shahdiya30]

Hi Daiichiro,

Thank you for your response! Yes, I might try to switch to a higher version of jsPsych, but it was a bit time consuming to switch over the code since the experiment is a bit detailed, but I might see if that works. Thanks!