Alternating trial type, use random trials once each


Attached is a SuperLab experiment in which I am trying to randomly present 24 pictures (half with an audio startle probe) and 23 ITIs (with 12 having audio startle probes). The startle onsets are also random, and I am having difficulty presenting the correct number trials for each condition. For example, when looking at the saved log file, I am seeing a number of PictureStartles that is different than 12.

Any help would be greatly appreciated. (I have not included the picture files for copyright reasons; I hope this is not an issue.)

Todd (6.56 KB)

The structure of your experiment can be greatly simplified by using a Trial Variable of type “Number” to randomize the startle onsets. Once the Trial Variable is set (click on the Experiment menu, then Trial Variable), you can use it in the Event Editor’s input tab by choosing a variable time limit. This will eliminate the need to randomize events within a trial and will allow you to simplify the design a bit.