I'm sorry. I don't know what I did wrong the first time but now it's working. I do have one additional problem now, however. It's my understanding that the trial interval specified wouldn't occur until after the 2000 ms is up. I would like each stimulus to appear 2000 ms following the previous (400 ms stimulus, 1600 ms blank screen, 400 ms stimulus, etc). However, since I would like to record responses during that 1600 ms blank screen, it seems that I will have to add more time between trials for the trial interval. Is this correct?