SuperLab 4.0.3 includes quite a few timing improvements, most of which are on the Mac, but a few of which are on Windows.
SuperLab Pro 2 on Windows did not synchronize with the monitor’s refresh rate. SuperLab Pro 1 on the Mac did synchronize in 256 colors. SuperLab 4 does synchronize with your monitor’s refresh. Therefore, it’s important to know what your refresh rate is on your monitor when picking the times you request of SuperLab.
Here’s a small list:
Not many of these refresh rates are conducive to a 20ms exposure. Specifically, 20ms is 1/50th of a second, so any refresh rate you pick should be a multiple of 50 (that is 100Hz, 150Hz, 200Hz, but please don’t pick 50Hz for the sake of the people sitting in front of the screen).
I just ran through this a few times on my own to double-check exactly what SuperLab does so I can tell you. The time limit that you are specifying is not the time that the stimulus is on the screen. This time is the amount of time that SuperLab stops and waits before moving on. In the case of RSVP, here’s what happens:
1st refresh - draw buffer to screen (stimulus)
n refreshes - take your time limit, round it up to the nearest refresh, and insert it here
1 more refresh - erase stimulus
Therefore, the amount of time it will take is the amount you specified rounded up to the nearest refresh plus two more refreshes–one to draw the stimulus, and one to erase the stimulus. The amount of time the stimulus would be on the screen would be your time rounded up plus one refresh. The amount of time you specify for your blank interval will depend on your refresh rate, but it should be definitely be a bit less than 80ms if you want your stimuli to appear every 100ms.
The information above I determined from a new obscure and undocumented 4.0.3 feature. SuperLab can now provide you with very detailed information about what happens when you run an experiment. This is still a work-in-progress, but the basics are available now. If you launch SuperLab from a DOS prompt with the “–verbose” flag, you will get a report after you finish running your experiment. This is not intended for data collection, but rather as an experimenter’s debugging tool. Instead of launching from a DOS prompt, you can also create a shortcut and then add " --verbose" to the end of the Target name in the shortcut’s properties. My target looks like this:
“C:\Program Files\SuperLab 4.0\SuperLab.exe” --verbose
Many things were improved with SuperLab 4.0.3 with respect to timing; it may not look it on the surface, but it’s a pretty hefty improvement over 4.0.2.