# Images sometimes not appearing on a trial - attention capture task

**URL:** <https://discourse.psychopy.org/t/images-sometimes-not-appearing-on-a-trial-attention-capture-task/45147>\
**Category:** Online experiments\
**Tags:** timing, online, images, pavlovia\
**Created:** [July 4, 2025, 12:16pm UTC](https://discourse.psychopy.org/t/images-sometimes-not-appearing-on-a-trial-attention-capture-task/45147 "2025-07-04T12:16:13Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![kerblooee](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/kerblooee/32/11489_2.png) [@kerblooee](https://discourse.psychopy.org/u/kerblooee)\
**Post date:** [July 5, 2025, 9:23am UTC](https://discourse.psychopy.org/t/images-sometimes-not-appearing-on-a-trial-attention-capture-task/45147/5 "2025-07-05T09:23:57Z")

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I did as you suggested and changed the stop time to “duration”=.05, and now I am seeing stimuli on top of each other that should be appearing in succession. I will try the frames next, but I’ve had issues with lags using frames before (which makes sense if the experiment is dropping frames a lot).

If anyone has found success consistently presenting rapid visual stimuli on Pavlovia I’d love to hear some tips! One option that is not ideal is to instruct participants not to have any other processes / applications running in the background while they do the task, but for an online study that is putting a lot of responsibility on the participant. So if there’s anything I can do from my end that would be optimal.

Edit: I found this other thread that suggested extending fixation time between trials- actually, my issue only occurs on main experiment trials, not practice trials - the difference is that the practice trials have an extra feedback screen at the end. I think this will be the solution!:

> [@Online Frame Issues & Variability](https://discourse.psychopy.org/t/online-frame-issues-variability/29066):
>
> Hi, I’m trying to run an experiment online and am running into frame timing issues. Specifically, there are several stimuli (a combination of images and fixation crosses) that need to appear on screen for precise and small intervals of time \<500ms. When I run the experiment locally, the timing is all as intended. When run online, however, a few issues crop-up. For instance, in most cases, the stimuli don’t seem to be appearing at all. I’d think that there was an issue with the build that prevent…

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