At first I thought that BGR values (identified as "RBG" in the documentation, but as BGR in the samples) superseded the WGR values (likewise, identified as "RWG" in the documentation). That is, I thought that DirectRT would randomize blocks of trials using BGR values first, then use WGR values to randomize with the BGR defined blocks.
But that simple rule doesn't appear to be the case. Consider this series of trials:
block trial bgr wgr
1 1 1 1
1 2 1 2
1 3 1 1
1 4 1 2
2 5 2 1
2 6 2 2
2 7 2 1
2 8 2 2
The sequence of trials doesn't follow the pattern I'd expected: I expected to get either trials 1-4 or 5-8, followed by the other four trials. That's not what happens.
Could someone explain how DirectRT combines these two parameters to determine randomization order?
Thank You!