At a code level, what the isTrials flag achieves is it adds in the line thisExp.nextEntry() which essentially causes an advance in the data file to the next line. The outcomes of that extra line depend on context:
- Applied to a blocks loop (around trials) this has the effect of controlling whethere there’s an extra line
- Applied to an inner loop of say, stimuli (looping within a single trial) it indeed does what @Michael says, resulting in a factorial combination
- Applied to a separate loop, which sounds like @wakecarter is using, it should determine whether the data appear on one-line-per-iteration or whether the the data will be inserted just with the final value of the loop integrated into the first line of the next (trials) loop
@TParsons is currently looking into whther the issue is with the Builder code ouptuts (not honoring the isTrials flag during script compile, in which case we can fix it in psychoPY) or whether our outputs are correct but something about psychoJS is then overriding the code (needs Alain’s help)