Randomizing without replacement?

I am making an experiment in which a trial consists of a picture followed by two rating screens (each asking for a rating of the picture). What I would like is to tell Superlab to choose a picture at random from a list/folder and then present each of the two rating screens. For as many trials as I have, I would like Superlab to continue to do this without replacement. That is, continually dip back into the folder for a picture (but not one seen previously) followed by the presentation of the two rating screens.

Is randomization for each trial --but without replacement across trials – possible?


This is precisely what stimulus lists are for. With stimulus lists, you would only create one trial, instead of creating many trials. You point your variable event at a stimulus list, and then SuperLab will create (at runtime) multiple trials based on your template. Anything you put in the template will be presented in each of the copies of the original trial.

Randomization is then done at the block level–you’ll randomize the trials within the block. When done with stimulus lists, it’s always done without replacement. (Randomization with replacement is possible, but tricky, since it isn’t a provided option.)

I hope this helps to get you pointed in the right direction.