In every trial of my fMRI experiment (made with Builder), subjects would hear a sound (of various durations between trials) and would then be asked to press a key to give a rating (through a rating-scale component). Typically, RTs would be expected to be between 0.5 and 2s.
I have noticed two critical problems with how this experiment’s data was recorded, as per its output XLS file:
- the RT corresponding to the rating component is always shown as zero, for all trials:
What could be the cause of this? I don’t think there is anything peculiar about how the experiment is programmed that would explain it. For instance, below is the timing of the rating component, meant to appear after a sound has finished playing, and to stay active for a given number of seconds.
- As a sanity check, I computed the difference (time lapsed) between the start- and stop time of the sound component (or rather of the image component time-locked to it, since the soundphrase.stopped column for some reason only contains ‘None’ values). While for most trials this difference is (as expected) equal to the stimulus duration (as measured for each WAV file), for other trials it is not; for those trials, the computed difference is always (up to 1s) shorter than the stimulus duration. This difference does not increase with trial number (as the run progresses), instead it simply seems to be greater for the longer stimuli. Because of this problem, in my fMRI GLM analysis, I don’t know whether to enter the actual stimulus duration or the duration psychoPy indicates the sound was on for.
I attach the XLS file, which demonstrates the problems described above. The critical columns for problem 1 are X and AG, and for problem 2, E to G. I can also upload the psyexp file, although I’d rather not make it public here.
outputProblems.xlsx (69.9 KB)
My guess is that this has to do with psychoPy’s long-standing issue with non-slip timing, which here I’ve had to use because of the variable stimulus durations. As per this older post, the intended duration is in my case known at the start of the routine, but even so there might be a slip-timing issue. But it’s strange then that the sound duration discrepance does not accumulate with time, as would be expected for such an issue; and also that RT columns are simply 0, which suggests rather a programming issue.
Am I right that this data set is compromised in terms of RTs and possibly all other timing parameters? Fortunately, this was just a pilot, but it would of course be absolutely critical to know what went wrong here, so as to avoid ruining a later full fMRI experiment. Thanks in advance to the psychoPy team for any help that they may hopefully be able to offer here!!
OS (e.g. Win10): Win10
PsychoPy version (e.g. 1.84.x): 3.2.4