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Non-slip timing for fMRI with variable ISI/ITI

Dear PsychoPy community,

I know that there have been a number of posts to the forum regarding this issue, but I haven’t seen any real satisfactory answers in the past few years. I’m hoping that by now someone may have come up with a good workaround that they would be able to share.

We have a task that will be run while participants are undergoing fMRI. Some of the routines have fixed start and end points, and others are variable (i.e., the ISI and ITI reference variables in a spreadsheet because these need to be jittered for appropriate fMRI design). We also have a routine that contains a choice screen in which participants make a decision. This is to be presented for a max of 4 seconds, but should end when participants enter their choice. We are adding the remaining time to the subsequent ISI and have implemented this with some code routines.

Clearly, there are a number of moving parts here, and I know that if routines do not have a specific start and end time, that builder doesn’t automatically apply non-slip timing. However, has anyone (the developers or anyone in the community) figured out a way to implement non-slip timing for routines with variable lengths of presentation? I have seen many posts about this and no real solutions… Any suggestions would be incredibly appreciated.


Can anyone offer a solution to this sort of issue? Any guidance at all would be much appreciated.

Hi @melanieziur,

How about the approach suggested by @Arboc here?