![]() 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. 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. I can also upload the psyexp file, although I’d rather not make it public here. The critical columns for problem 1 are X and AG, and for problem 2, E to G. I attach the XLS file, which demonstrates the problems described above. 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. This difference does not increase with trial number (as the run progresses), instead it simply seems to be greater for the longer stimuli. 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. 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).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. 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. the RT corresponding to the rating component is always shown as zero, for all trials:.I have noticed two critical problems with how this experiment’s data was recorded, as per its output XLS file: ![]() ![]() Typically, RTs would be expected to be between 0.5 and 2s. 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).
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