I have a question about randomization and stimulus lists.
I know that if I do not present stimuli randomly (that is, if I don’t randomize in the block), I can pair two items from two different stimulus lists, and that pairing will always be the same. If I do randomize in the block, I get a randomization of each stimulus list, but lose the consistent pairings.
What I want to do is always have the same sound and same picture paired, but randomize the order of presentation of the sounds and pictures.
That is, I want to pair (P1,S1), (P2,S2), etc. and then randomize the order of those pairings. Does this make any sense? Can SuperLab handle this or do I need to randomize by hand?
You need to create two stimulus lists, one for the pictures and the other for sounds. The order of the items in the lists is important because that’s what will determine the pairing.
In your trial, you will need two events: one for the sound and the other for the picture. Both events need to get the sound and picture files from the stimulus lists.
Now, all you need to do is randomize at the block level. This will randomize trials but the two events within each trial will remain the same. To form a good idea of how SuperLab does this at run time, click on the Experiment menu and select Expand Events That Use Lists. This will open a new window where the events that use lists have been converted to events that use the individual files.
Note: I suggest that you do not make changes to the “expanded” experiment because they will not be included in the original one, the one that uses lists.
I hope this helps.