Millisecond Forums

Hi there,

I was trying to capture the time between when a stimulus was presented until the stimulus was replaced by another stimulus, for e.g. the stimulus gdg_67soa below.

<trial pic_67soa>
/ stimulustimes = [
0 = fixation_cross;
1000 = gdg_67soa;
1067 = mask1;
1127 = mask2;
1187 = mask3;
1247 = mask4;
1307 = mask5;
]
/ timeout = parameters.fixationduration + 67 + (5 * 60)
/branch = [surveypage.word_generation]
/ ontrialbegin = [
values.trial_start = script.elapsedtime
]
/ontrialend = [
values.img_num = picture.gdg_67soa.currentvalue;
values.img_file = picture.gdg_67soa.currentitem;
values.soa = 67;
values.est_soa = script.elapsedtime - values.trial_start - 1000 - (5 * 60)
]
/ recorddata = true
</trial>

Here I am storing the elapsed time when the trial begins and derived the stimulus presentation time (for gdg_67soa) by using 
script.elapsedtime - values.trial_start - 1000 - (5 * 60)

I compared the derived values with the intended stimulustimes (67ms) - it is way over - double or more.

However, when I turn on the /audit = true, the time seems to be very close to 67ms - this leads me to think that my derivation above could be wrong, and might include any lag that I haven't factor in. I also try /pretrialpause but it does not seem to reduce the estimation.

Any comments would be much appreciated.

Thanks!